From 257f167f913dfb364da5b847c0055892bb0c981d Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Thu, 3 Jul 2025 17:45:41 +0200
Subject: [PATCH 01/36] feat(rum): Add initial config and API

---
 internal-api/build.gradle                     |   1 +
 .../main/java/datadog/trace/api/Config.java   |   4 +
 .../trace/api/rum/ContentTypesCache.java      |  45 ++++
 .../java/datadog/trace/api/rum/RumConfig.java | 198 ++++++++++++++++++
 .../datadog/trace/api/rum/RumInjector.java    |  18 ++
 5 files changed, 266 insertions(+)
 create mode 100644 internal-api/src/main/java/datadog/trace/api/rum/ContentTypesCache.java
 create mode 100644 internal-api/src/main/java/datadog/trace/api/rum/RumConfig.java
 create mode 100644 internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java

diff --git a/internal-api/build.gradle b/internal-api/build.gradle
index fbf1916a4af..424873f75be 100644
--- a/internal-api/build.gradle
+++ b/internal-api/build.gradle
@@ -244,6 +244,7 @@ dependencies {
   api project(':dd-trace-api')
   api libs.slf4j
   api project(':components:context')
+  api project(':components:json')
   api project(':components:yaml')
   api project(':components:cli')
   api project(":utils:time-utils")
diff --git a/internal-api/src/main/java/datadog/trace/api/Config.java b/internal-api/src/main/java/datadog/trace/api/Config.java
index 6534d8f870c..3140a95d547 100644
--- a/internal-api/src/main/java/datadog/trace/api/Config.java
+++ b/internal-api/src/main/java/datadog/trace/api/Config.java
@@ -1190,6 +1190,10 @@ public static String getHostName() {
 
   private final int stackTraceLengthLimit;
 
+  // RUM config -- start
+  // TODO
+  // RUM config -- end
+
   // Read order: System Properties -> Env Variables, [-> properties file], [-> default value]
   private Config() {
     this(ConfigProvider.createDefault());
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/ContentTypesCache.java b/internal-api/src/main/java/datadog/trace/api/rum/ContentTypesCache.java
new file mode 100644
index 00000000000..59c439c7173
--- /dev/null
+++ b/internal-api/src/main/java/datadog/trace/api/rum/ContentTypesCache.java
@@ -0,0 +1,45 @@
+package datadog.trace.api.rum;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/*
+ * Cache for ContentTypes answers
+ */
+public class ContentTypesCache {
+  static final short MAX_ITEMS = 1_000;
+  private final Map<String, Boolean> map;
+
+  /*
+   * Constructs a new ContentTypes cache for the provided types
+   *
+   * @param contentTypes the list of ContentTypes it will store answers for
+   */
+  public ContentTypesCache(String[] contentTypes) {
+    this.map = new HashMap<>();
+    for (String contentType : contentTypes) {
+      this.map.put(contentType, true);
+    }
+  }
+
+  public boolean contains(String headerValue) {
+    return this.map.computeIfAbsent(headerValue, this::shouldProcess);
+  }
+
+  private boolean shouldProcess(String headerValue) {
+    Boolean typeAllowed = this.map.get(getContentType(headerValue));
+    return typeAllowed != null && typeAllowed;
+  }
+
+  private String getContentType(String headerValue) {
+    // multipart/* are expected to contain boundary unique values
+    // let's abort early to avoid exploding the cache
+    // additionally, if the cache is already too big, let's also abort
+    if (this.map.size() > MAX_ITEMS || headerValue.startsWith("multipart/")) {
+      return null;
+    }
+    // RFC 2045 defines optional parameters always behind a semicolon
+    int semicolon = headerValue.indexOf(";");
+    return semicolon != -1 ? headerValue.substring(0, semicolon) : headerValue;
+  }
+}
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumConfig.java b/internal-api/src/main/java/datadog/trace/api/rum/RumConfig.java
new file mode 100644
index 00000000000..f9e241f7bca
--- /dev/null
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumConfig.java
@@ -0,0 +1,198 @@
+package datadog.trace.api.rum;
+
+import static java.util.Locale.ROOT;
+
+import datadog.json.JsonWriter;
+import datadog.trace.api.Config;
+import java.util.HashMap;
+import java.util.Map;
+import javax.annotation.Nullable;
+
+public class RumConfig {
+  private static final String DEFAULT_SITE = "datadoghq.com";
+  private static final String GOV_CLOUD_SITE = "ddog-gov.com";
+  private static final Map<String, String> REGIONS = new HashMap<>();
+
+  static {
+    REGIONS.put("datadoghq.com", "us1");
+    REGIONS.put("us3.datadoghq.com", "us3");
+    REGIONS.put("us5.datadoghq.com", "us5");
+    REGIONS.put("datadoghq.eu", "eu1");
+    REGIONS.put("ap1.datadoghq.com", "ap1");
+  }
+
+  /** RUM application ID */
+  public final String applicationId;
+  /** The client token provided by Datadog to authenticate requests. */
+  public final String clientToken;
+  /** The Datadog site to which data will be sent (e.g., `datadoghq.com`). */
+  public final String site;
+  /** The name of the service being monitored. */
+  @Nullable public final String service;
+  /** The environment of the service (e.g., `prod`, `staging` or `dev). */
+  @Nullable public final String env;
+  /** SDK major version. */
+  public int majorVersion;
+  /** The version of the service (e.g., `0.1.0`, `a8dj92`, `2024-30`). */
+  @Nullable public final String version;
+  /** Enables or disables the automatic collection of users actions (e.g., clicks). */
+  @Nullable public final Boolean trackUserInteractions;
+  /** Enables or disables the collection of resource events (e.g., loading of images or scripts). */
+  @Nullable public final Boolean trackResources;
+  /** Enables or disables the collection of long task events. */
+  @Nullable public final Boolean trackLongTask;
+  /** The privacy level for data collection. */
+  @Nullable public final PrivacyLevel defaultPrivacyLevel;
+  /** The percentage of user sessions to be tracked (between 0.0 and 100.0). */
+  @Nullable public final Float sessionSampleRate;
+  /**
+   * The percentage of tracked sessions that will include Session Replay data (between 0.0 and
+   * 100.0).
+   */
+  @Nullable public final Float sessionReplaySampleRate;
+
+  public static RumConfig from(Config config) {
+    // TODO
+    return null;
+  }
+
+  RumConfig(
+      String applicationId,
+      String clientToken,
+      @Nullable String site,
+      @Nullable String service,
+      @Nullable String env,
+      int majorVersion,
+      @Nullable String version,
+      @Nullable Boolean trackUserInteractions,
+      @Nullable Boolean trackResources,
+      @Nullable Boolean trackLongTask,
+      @Nullable PrivacyLevel defaultPrivacyLevel,
+      @Nullable Float sessionSampleRate,
+      @Nullable Float sessionReplaySampleRate) {
+    if (applicationId == null || applicationId.isEmpty()) {
+      throw new IllegalArgumentException("Invalid application id: " + applicationId);
+    }
+    this.applicationId = applicationId;
+    if (clientToken == null || clientToken.isEmpty()) {
+      throw new IllegalArgumentException("Invalid client token: " + clientToken);
+    }
+    this.clientToken = clientToken;
+    if (site == null || site.isEmpty()) {
+      this.site = DEFAULT_SITE;
+    } else if (validateSite(site)) {
+      this.site = site;
+    } else {
+      throw new IllegalArgumentException("Invalid site: " + site);
+    }
+    this.service = service;
+    this.env = env;
+    if (majorVersion != 5 && majorVersion != 6) {
+      throw new IllegalArgumentException("Invalid major version: " + majorVersion);
+    }
+    this.majorVersion = majorVersion;
+    this.version = version;
+    this.trackUserInteractions = trackUserInteractions;
+    this.trackResources = trackResources;
+    this.trackLongTask = trackLongTask;
+    if (sessionSampleRate != null && (sessionSampleRate < 0f || sessionSampleRate > 100f)) {
+      throw new IllegalArgumentException("Invalid session sample rate: " + sessionSampleRate);
+    }
+    this.sessionSampleRate = sessionSampleRate;
+    if (sessionReplaySampleRate != null
+        && (sessionReplaySampleRate < 0f || sessionReplaySampleRate > 100f)) {
+      throw new IllegalArgumentException(
+          "Invalid session replay sample rate: " + sessionReplaySampleRate);
+    }
+    this.sessionReplaySampleRate = sessionReplaySampleRate;
+    this.defaultPrivacyLevel = defaultPrivacyLevel;
+  }
+
+  private static boolean validateSite(String site) {
+    for (String key : REGIONS.keySet()) {
+      if (key.equals(site)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  public String getSnippet() {
+    return "<script>\n"
+        + "(function(h,o,u,n,d) {\n"
+        + "  h=h[d]=h[d]||{q:[],onReady:function(c){h.q.push(c)}}\n"
+        + "  d=o.createElement(u);d.async=1;d.src=n\n"
+        + "  n=o.getElementsByTagName(u)[0];n.parentNode.insertBefore(d,n)\n"
+        + "})(window,document,'script','"
+        + getCdnUrl()
+        + "','DD_RUM')\n"
+        + "window.DD_RUM.onReady(function() {\n"
+        + "  window.DD_RUM.init("
+        + jsonPayload()
+        + ");\n"
+        + "});\n"
+        + "</script>\n";
+  }
+
+  private String getCdnUrl() {
+    if (!GOV_CLOUD_SITE.equals(this.site)) {
+      return "https://www.datadoghq-browser-agent.com/datadog-rum-v" + this.majorVersion + ".js";
+    }
+    return "https://www.datadoghq-browser-agent.com/"
+        + REGIONS.get(this.site)
+        + "/v"
+        + this.majorVersion
+        + "/datadog-rum.js";
+  }
+
+  private String jsonPayload() {
+    try (JsonWriter writer = new JsonWriter()) {
+      writer.beginObject();
+      writer.name("application_id").value(this.applicationId);
+      writer.name("client_token").value(this.clientToken);
+      if (this.site != null) {
+        writer.name("site").value(this.site);
+      }
+      if (this.service != null) {
+        writer.name("service").value(this.service);
+      }
+      if (this.env != null) {
+        writer.name("env").value(this.env);
+      }
+      if (this.version != null) {
+        writer.name("version").value(this.version);
+      }
+      if (this.trackUserInteractions != null) {
+        writer.name("track_user_interactions").value(this.trackUserInteractions);
+      }
+      if (this.trackResources != null) {
+        writer.name("track_resources").value(this.trackResources);
+      }
+      if (this.trackLongTask != null) {
+        writer.name("track_long_task").value(this.trackLongTask);
+      }
+      if (this.defaultPrivacyLevel != null) {
+        writer.name("default_privacy_level").value(this.defaultPrivacyLevel.toJson());
+      }
+      if (this.sessionSampleRate != null) {
+        writer.name("session_sample_rate").value(this.sessionSampleRate);
+      }
+      if (this.sessionReplaySampleRate != null) {
+        writer.name("session_replay_sample_rate").value(this.sessionReplaySampleRate);
+      }
+      return writer.toString();
+    } catch (Exception e) {
+      throw new IllegalStateException("Fail to generate config payload", e);
+    }
+  }
+
+  public enum PrivacyLevel {
+    ALLOW,
+    MASK,
+    MASK_USER_INPUT;
+
+    public String toJson() {
+      return toString().toLowerCase(ROOT);
+    }
+  }
+}
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
new file mode 100644
index 00000000000..b854c3ea804
--- /dev/null
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
@@ -0,0 +1,18 @@
+package datadog.trace.api.rum;
+
+public final class RumInjector {
+
+  private static volatile String snippet;
+
+  private static volatile RumConfig config;
+
+  public static boolean isEnabled() {
+    // Check lazy config init
+    // TODO Config.isRumEnabled()? + valid config
+    return false;
+  }
+
+  public static String getSnippet() {
+    return null;
+  }
+}

From 5e734e3a3e46387f9cecb536874e836dc0dbc266 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 06:59:17 +0200
Subject: [PATCH 02/36] feat(rum): Iterating on initial config and API

---
 .../datadog/trace/api/ConfigDefaults.java     |  5 ++
 .../datadog/trace/api/config/RumConfig.java   | 20 ++++++
 .../main/java/datadog/trace/api/Config.java   | 68 ++++++++++++++++++-
 .../datadog/trace/api/rum/RumInjector.java    | 36 ++++++++--
 ...{RumConfig.java => RumInjectorConfig.java} | 33 +++------
 5 files changed, 130 insertions(+), 32 deletions(-)
 create mode 100644 dd-trace-api/src/main/java/datadog/trace/api/config/RumConfig.java
 rename internal-api/src/main/java/datadog/trace/api/rum/{RumConfig.java => RumInjectorConfig.java} (87%)

diff --git a/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java b/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
index a6d5888e76f..c3656cd3251 100644
--- a/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
+++ b/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
@@ -240,6 +240,11 @@ public final class ConfigDefaults {
   static final boolean DEFAULT_TELEMETRY_LOG_COLLECTION_ENABLED = true;
   static final int DEFAULT_TELEMETRY_DEPENDENCY_RESOLUTION_QUEUE_SIZE = 100000;
 
+  static final boolean DEFAULT_RUM_ENABLED = false;
+  static final int DEFAULT_RUM_MAJOR_VERSION = 6;
+  static final float DEFAULT_RUM_SESSION_SAMPLE_RATE = 100f;
+  static final float DEFAULT_RUM_SESSION_REPLAY_SAMPLE_RATE = 100f;
+
   static final boolean DEFAULT_SSI_INJECTION_FORCE = false;
   static final String DEFAULT_INSTRUMENTATION_SOURCE = "manual";
 
diff --git a/dd-trace-api/src/main/java/datadog/trace/api/config/RumConfig.java b/dd-trace-api/src/main/java/datadog/trace/api/config/RumConfig.java
new file mode 100644
index 00000000000..51d90fd31c4
--- /dev/null
+++ b/dd-trace-api/src/main/java/datadog/trace/api/config/RumConfig.java
@@ -0,0 +1,20 @@
+package datadog.trace.api.config;
+
+public final class RumConfig {
+  public static final String RUM_ENABLED = "rum.enabled";
+  public static final String RUM_APPLICATION_ID = "rum.application.id";
+  public static final String RUM_CLIENT_TOKEN = "rum.client.token";
+  public static final String RUM_SITE = "rum.site";
+  public static final String RUM_SERVICE = "rum.service";
+  public static final String RUM_ENVIRONMENT = "rum.environment";
+  public static final String RUM_MAJOR_VERSION = "rum.major.version";
+  public static final String RUM_VERSION = "rum.version";
+  public static final String RUM_TRACK_USER_INTERACTION = "rum.track.user.interaction";
+  public static final String RUM_TRACK_RESOURCES = "rum.track.resources";
+  public static final String RUM_TRACK_LONG_TASKS = "rum.track.long.tasks";
+  public static final String RUM_DEFAULT_PRIVACY_LEVEL = "rum.default.privacy.level";
+  public static final String RUM_SESSION_SAMPLE_RATE = "rum.session.sample.rate";
+  public static final String RUM_SESSION_REPLAY_SAMPLE_RATE = "rum.session.replay.sample.rate";
+
+  private RumConfig() {}
+}
diff --git a/internal-api/src/main/java/datadog/trace/api/Config.java b/internal-api/src/main/java/datadog/trace/api/Config.java
index 3140a95d547..b40d229cf87 100644
--- a/internal-api/src/main/java/datadog/trace/api/Config.java
+++ b/internal-api/src/main/java/datadog/trace/api/Config.java
@@ -118,6 +118,10 @@
 import static datadog.trace.api.ConfigDefaults.DEFAULT_REMOTE_CONFIG_POLL_INTERVAL_SECONDS;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_REMOTE_CONFIG_TARGETS_KEY;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_REMOTE_CONFIG_TARGETS_KEY_ID;
+import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_ENABLED;
+import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_MAJOR_VERSION;
+import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_SESSION_REPLAY_SAMPLE_RATE;
+import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_SESSION_SAMPLE_RATE;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_SCOPE_DEPTH_LIMIT;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_SCOPE_ITERATION_KEEP_ALIVE;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_SECURE_RANDOM;
@@ -461,6 +465,20 @@
 import static datadog.trace.api.config.RemoteConfigConfig.REMOTE_CONFIG_TARGETS_KEY;
 import static datadog.trace.api.config.RemoteConfigConfig.REMOTE_CONFIG_TARGETS_KEY_ID;
 import static datadog.trace.api.config.RemoteConfigConfig.REMOTE_CONFIG_URL;
+import static datadog.trace.api.config.RumConfig.RUM_APPLICATION_ID;
+import static datadog.trace.api.config.RumConfig.RUM_CLIENT_TOKEN;
+import static datadog.trace.api.config.RumConfig.RUM_DEFAULT_PRIVACY_LEVEL;
+import static datadog.trace.api.config.RumConfig.RUM_ENABLED;
+import static datadog.trace.api.config.RumConfig.RUM_ENVIRONMENT;
+import static datadog.trace.api.config.RumConfig.RUM_MAJOR_VERSION;
+import static datadog.trace.api.config.RumConfig.RUM_SERVICE;
+import static datadog.trace.api.config.RumConfig.RUM_SESSION_REPLAY_SAMPLE_RATE;
+import static datadog.trace.api.config.RumConfig.RUM_SESSION_SAMPLE_RATE;
+import static datadog.trace.api.config.RumConfig.RUM_SITE;
+import static datadog.trace.api.config.RumConfig.RUM_TRACK_LONG_TASKS;
+import static datadog.trace.api.config.RumConfig.RUM_TRACK_RESOURCES;
+import static datadog.trace.api.config.RumConfig.RUM_TRACK_USER_INTERACTION;
+import static datadog.trace.api.config.RumConfig.RUM_VERSION;
 import static datadog.trace.api.config.TraceInstrumentationConfig.ADD_SPAN_POINTERS;
 import static datadog.trace.api.config.TraceInstrumentationConfig.AXIS_PROMOTE_RESOURCE_NAME;
 import static datadog.trace.api.config.TraceInstrumentationConfig.CASSANDRA_KEYSPACE_STATEMENT_EXTRACTION_ENABLED;
@@ -618,6 +636,8 @@
 import datadog.trace.api.iast.telemetry.Verbosity;
 import datadog.trace.api.naming.SpanNaming;
 import datadog.trace.api.profiling.ProfilingEnablement;
+import datadog.trace.api.rum.RumInjectorConfig;
+import datadog.trace.api.rum.RumInjectorConfig.PrivacyLevel;
 import datadog.trace.bootstrap.config.provider.CapturedEnvironmentConfigSource;
 import datadog.trace.bootstrap.config.provider.ConfigProvider;
 import datadog.trace.bootstrap.config.provider.SystemPropertiesConfigSource;
@@ -1190,9 +1210,8 @@ public static String getHostName() {
 
   private final int stackTraceLengthLimit;
 
-  // RUM config -- start
-  // TODO
-  // RUM config -- end
+  private final boolean rumEnabled;
+  private final RumInjectorConfig rumInjectorConfig;
 
   // Read order: System Properties -> Env Variables, [-> properties file], [-> default value]
   private Config() {
@@ -2677,9 +2696,40 @@ PROFILING_DATADOG_PROFILER_ENABLED, isDatadogProfilerSafeInCurrentEnvironment())
     this.stackTraceLengthLimit =
         configProvider.getInteger(STACK_TRACE_LENGTH_LIMIT, defaultStackTraceLengthLimit);
 
+    this.rumEnabled = configProvider.getBoolean(RUM_ENABLED, DEFAULT_RUM_ENABLED);
+    this.rumInjectorConfig = parseRumConfig(configProvider);
+
     log.debug("New instance: {}", this);
   }
 
+  private static RumInjectorConfig parseRumConfig(ConfigProvider configProvider) {
+    String applicationId = configProvider.getString(RUM_APPLICATION_ID);
+    String clientToken = configProvider.getString(RUM_CLIENT_TOKEN);
+    if (applicationId == null || clientToken == null) {
+      return null;
+    }
+    try {
+      return new RumInjectorConfig(
+          applicationId,
+          clientToken,
+          configProvider.getString(RUM_SITE),
+          configProvider.getString(RUM_SERVICE),
+          configProvider.getString(RUM_ENVIRONMENT),
+          configProvider.getInteger(RUM_MAJOR_VERSION, DEFAULT_RUM_MAJOR_VERSION),
+          configProvider.getString(RUM_VERSION),
+          configProvider.getBoolean(RUM_TRACK_USER_INTERACTION),
+          configProvider.getBoolean(RUM_TRACK_RESOURCES),
+          configProvider.getBoolean(RUM_TRACK_LONG_TASKS),
+          configProvider.getEnum(RUM_DEFAULT_PRIVACY_LEVEL, PrivacyLevel.class, null),
+          configProvider.getFloat(RUM_SESSION_SAMPLE_RATE, DEFAULT_RUM_SESSION_SAMPLE_RATE),
+          configProvider.getFloat(
+              RUM_SESSION_REPLAY_SAMPLE_RATE, DEFAULT_RUM_SESSION_REPLAY_SAMPLE_RATE));
+    } catch (IllegalArgumentException e) {
+      log.warn("Unable to configure RUM injection", e);
+      return null;
+    }
+  }
+
   /**
    * Converts a list of packages in Jacoco exclusion format ({@code
    * my.package.*,my.other.package.*}) to list of package prefixes suitable for use with ASM ({@code
@@ -4912,6 +4962,14 @@ public int getCloudPayloadTaggingMaxTags() {
     return cloudPayloadTaggingMaxTags;
   }
 
+  public boolean isRumEnabled() {
+    return this.rumEnabled;
+  }
+
+  public RumInjectorConfig getRumInjectorConfig() {
+    return this.rumInjectorConfig;
+  }
+
   private <T> Set<T> getSettingsSetFromEnvironment(
       String name, Function<String, T> mapper, boolean splitOnWS) {
     final String value = configProvider.getString(name, "");
@@ -5592,6 +5650,10 @@ public String toString() {
         + cloudResponsePayloadTagging
         + ", experimentalPropagateProcessTagsEnabled="
         + experimentalPropagateProcessTagsEnabled
+        + ", rumEnabled="
+        + rumEnabled
+        + ", rumInjectorConfig="
+        + rumInjectorConfig.jsonPayload()
         + '}';
   }
 }
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
index b854c3ea804..4b880f6a252 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
@@ -1,18 +1,40 @@
 package datadog.trace.api.rum;
 
-public final class RumInjector {
+import datadog.trace.api.Config;
 
+public final class RumInjector {
+  private static volatile boolean initialized = false;
+  private static volatile boolean enabled;
   private static volatile String snippet;
 
-  private static volatile RumConfig config;
-
+  /**
+   * Check whether RUM injection is enabled and ready to inject.
+   *
+   * @return {@code true} if enabled, {@code otherwise}.
+   */
   public static boolean isEnabled() {
-    // Check lazy config init
-    // TODO Config.isRumEnabled()? + valid config
-    return false;
+    if (!initialized) {
+      Config config = Config.get();
+      boolean rumEnabled = config.isRumEnabled();
+      RumInjectorConfig injectorConfig = config.getRumInjectorConfig();
+      if (rumEnabled && injectorConfig != null) {
+        enabled = true;
+        snippet = injectorConfig.getSnippet();
+      } else {
+        enabled = false;
+        snippet = null;
+      }
+      initialized = true;
+    }
+    return enabled;
   }
 
+  /**
+   * Get the HTML snippet to inject RUM SDK
+   *
+   * @return The HTML snippet to inject, {@code null} if RUM injection is disabled to inject.
+   */
   public static String getSnippet() {
-    return null;
+    return snippet;
   }
 }
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumConfig.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
similarity index 87%
rename from internal-api/src/main/java/datadog/trace/api/rum/RumConfig.java
rename to internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
index f9e241f7bca..66b350c2b46 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumConfig.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
@@ -3,12 +3,11 @@
 import static java.util.Locale.ROOT;
 
 import datadog.json.JsonWriter;
-import datadog.trace.api.Config;
 import java.util.HashMap;
 import java.util.Map;
 import javax.annotation.Nullable;
 
-public class RumConfig {
+public class RumInjectorConfig {
   private static final String DEFAULT_SITE = "datadoghq.com";
   private static final String GOV_CLOUD_SITE = "ddog-gov.com";
   private static final Map<String, String> REGIONS = new HashMap<>();
@@ -44,19 +43,14 @@ public class RumConfig {
   /** The privacy level for data collection. */
   @Nullable public final PrivacyLevel defaultPrivacyLevel;
   /** The percentage of user sessions to be tracked (between 0.0 and 100.0). */
-  @Nullable public final Float sessionSampleRate;
+  public final float sessionSampleRate;
   /**
    * The percentage of tracked sessions that will include Session Replay data (between 0.0 and
    * 100.0).
    */
-  @Nullable public final Float sessionReplaySampleRate;
+  public final float sessionReplaySampleRate;
 
-  public static RumConfig from(Config config) {
-    // TODO
-    return null;
-  }
-
-  RumConfig(
+  public RumInjectorConfig(
       String applicationId,
       String clientToken,
       @Nullable String site,
@@ -68,8 +62,8 @@ public static RumConfig from(Config config) {
       @Nullable Boolean trackResources,
       @Nullable Boolean trackLongTask,
       @Nullable PrivacyLevel defaultPrivacyLevel,
-      @Nullable Float sessionSampleRate,
-      @Nullable Float sessionReplaySampleRate) {
+      float sessionSampleRate,
+      float sessionReplaySampleRate) {
     if (applicationId == null || applicationId.isEmpty()) {
       throw new IllegalArgumentException("Invalid application id: " + applicationId);
     }
@@ -95,12 +89,11 @@ public static RumConfig from(Config config) {
     this.trackUserInteractions = trackUserInteractions;
     this.trackResources = trackResources;
     this.trackLongTask = trackLongTask;
-    if (sessionSampleRate != null && (sessionSampleRate < 0f || sessionSampleRate > 100f)) {
+    if (sessionSampleRate < 0f || sessionSampleRate > 100f) {
       throw new IllegalArgumentException("Invalid session sample rate: " + sessionSampleRate);
     }
     this.sessionSampleRate = sessionSampleRate;
-    if (sessionReplaySampleRate != null
-        && (sessionReplaySampleRate < 0f || sessionReplaySampleRate > 100f)) {
+    if (sessionReplaySampleRate < 0f || sessionReplaySampleRate > 100f) {
       throw new IllegalArgumentException(
           "Invalid session replay sample rate: " + sessionReplaySampleRate);
     }
@@ -145,7 +138,7 @@ private String getCdnUrl() {
         + "/datadog-rum.js";
   }
 
-  private String jsonPayload() {
+  public String jsonPayload() {
     try (JsonWriter writer = new JsonWriter()) {
       writer.beginObject();
       writer.name("application_id").value(this.applicationId);
@@ -174,12 +167,8 @@ private String jsonPayload() {
       if (this.defaultPrivacyLevel != null) {
         writer.name("default_privacy_level").value(this.defaultPrivacyLevel.toJson());
       }
-      if (this.sessionSampleRate != null) {
-        writer.name("session_sample_rate").value(this.sessionSampleRate);
-      }
-      if (this.sessionReplaySampleRate != null) {
-        writer.name("session_replay_sample_rate").value(this.sessionReplaySampleRate);
-      }
+      writer.name("session_sample_rate").value(this.sessionSampleRate);
+      writer.name("session_replay_sample_rate").value(this.sessionReplaySampleRate);
       return writer.toString();
     } catch (Exception e) {
       throw new IllegalStateException("Fail to generate config payload", e);

From dde7164cb6eb557a08ed832719dfab0697bd2c79 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 07:46:51 +0200
Subject: [PATCH 03/36] fix(rum): Fix config print

---
 internal-api/src/main/java/datadog/trace/api/Config.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/internal-api/src/main/java/datadog/trace/api/Config.java b/internal-api/src/main/java/datadog/trace/api/Config.java
index b40d229cf87..56a55be4204 100644
--- a/internal-api/src/main/java/datadog/trace/api/Config.java
+++ b/internal-api/src/main/java/datadog/trace/api/Config.java
@@ -5653,7 +5653,7 @@ public String toString() {
         + ", rumEnabled="
         + rumEnabled
         + ", rumInjectorConfig="
-        + rumInjectorConfig.jsonPayload()
+        + (rumInjectorConfig == null ? "null" : rumInjectorConfig.jsonPayload())
         + '}';
   }
 }

From bb22e1ac0cfac43044708a429f1a3a0b7ea605b6 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 08:32:45 +0200
Subject: [PATCH 04/36] fix(rum): Remove content type support as only
 "text/html" is supported

---
 .../trace/api/rum/ContentTypesCache.java      | 45 -------------------
 1 file changed, 45 deletions(-)
 delete mode 100644 internal-api/src/main/java/datadog/trace/api/rum/ContentTypesCache.java

diff --git a/internal-api/src/main/java/datadog/trace/api/rum/ContentTypesCache.java b/internal-api/src/main/java/datadog/trace/api/rum/ContentTypesCache.java
deleted file mode 100644
index 59c439c7173..00000000000
--- a/internal-api/src/main/java/datadog/trace/api/rum/ContentTypesCache.java
+++ /dev/null
@@ -1,45 +0,0 @@
-package datadog.trace.api.rum;
-
-import java.util.HashMap;
-import java.util.Map;
-
-/*
- * Cache for ContentTypes answers
- */
-public class ContentTypesCache {
-  static final short MAX_ITEMS = 1_000;
-  private final Map<String, Boolean> map;
-
-  /*
-   * Constructs a new ContentTypes cache for the provided types
-   *
-   * @param contentTypes the list of ContentTypes it will store answers for
-   */
-  public ContentTypesCache(String[] contentTypes) {
-    this.map = new HashMap<>();
-    for (String contentType : contentTypes) {
-      this.map.put(contentType, true);
-    }
-  }
-
-  public boolean contains(String headerValue) {
-    return this.map.computeIfAbsent(headerValue, this::shouldProcess);
-  }
-
-  private boolean shouldProcess(String headerValue) {
-    Boolean typeAllowed = this.map.get(getContentType(headerValue));
-    return typeAllowed != null && typeAllowed;
-  }
-
-  private String getContentType(String headerValue) {
-    // multipart/* are expected to contain boundary unique values
-    // let's abort early to avoid exploding the cache
-    // additionally, if the cache is already too big, let's also abort
-    if (this.map.size() > MAX_ITEMS || headerValue.startsWith("multipart/")) {
-      return null;
-    }
-    // RFC 2045 defines optional parameters always behind a semicolon
-    int semicolon = headerValue.indexOf(";");
-    return semicolon != -1 ? headerValue.substring(0, semicolon) : headerValue;
-  }
-}

From 1bf99a1d1848566c95880828ed140d47766dc840 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 10:17:39 +0200
Subject: [PATCH 05/36] feat(rum): Add smoke tests

---
 dd-smoke-tests/rum/build.gradle               |  7 +++
 .../rum/AbstractRumServerSmokeTest.groovy     | 38 ++++++++++++++++
 dd-smoke-tests/rum/tomcat-9/build.gradle      | 26 +++++++++++
 .../main/java/com/example/HelloServlet.java   | 28 ++++++++++++
 .../src/main/java/com/example/Main.java       | 34 +++++++++++++++
 .../rum/tomcat9/Tomcat9RumSmokeTest.groovy    | 43 +++++++++++++++++++
 settings.gradle                               |  2 +
 7 files changed, 178 insertions(+)
 create mode 100644 dd-smoke-tests/rum/build.gradle
 create mode 100644 dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
 create mode 100644 dd-smoke-tests/rum/tomcat-9/build.gradle
 create mode 100644 dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
 create mode 100644 dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
 create mode 100644 dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy

diff --git a/dd-smoke-tests/rum/build.gradle b/dd-smoke-tests/rum/build.gradle
new file mode 100644
index 00000000000..f5a54e7985a
--- /dev/null
+++ b/dd-smoke-tests/rum/build.gradle
@@ -0,0 +1,7 @@
+apply from: "$rootDir/gradle/java.gradle"
+
+description = 'appsec-smoke-tests'
+
+dependencies {
+  api project(':dd-smoke-tests')
+}
diff --git a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
new file mode 100644
index 00000000000..6fa39dcf792
--- /dev/null
+++ b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
@@ -0,0 +1,38 @@
+package datadog.smoketest.rum
+
+import datadog.smoketest.AbstractServerSmokeTest
+import okhttp3.Response
+import spock.lang.Shared
+
+class AbstractRumServerSmokeTest extends AbstractServerSmokeTest {
+
+
+
+  @Shared
+  protected String[] defaultRumProperties = [
+    "-Ddd.appsec.enabled=${System.getProperty('smoke_test.appsec.enabled') ?: 'true'}",
+    "-Ddd.profiling.enabled=false",
+    // TODO: Remove once this is the default value
+    "-Ddd.api-security.enabled=true",
+    "-Ddd.appsec.waf.timeout=300000",
+    "-DPOWERWAF_EXIT_ON_LEAK=true",
+    // disable AppSec rate limit
+    "-Ddd.appsec.trace.rate.limit=-1"
+  ] + (System.getProperty('smoke_test.appsec.enabled') == 'inactive' ?
+    // enable remote config so that appsec is partially enabled (rc is now enabled by default)
+    [
+      '-Ddd.remote_config.url=https://127.0.0.1:54670/invalid_endpoint',
+      '-Ddd.remote_config.poll_interval.seconds=3600'
+    ]:
+    ['-Ddd.remote_config.enabled=false']
+  )
+
+
+  static void assertRumInjected(Response response) {
+    assert response.header('x-datadog-rum-injected') == '1' : 'RUM injected header missing'
+    def content = response.body().toString()
+    assert content.contains('https://www.datadoghq-browser-agent.com') : 'RUM script not injected'
+  }
+
+
+}
diff --git a/dd-smoke-tests/rum/tomcat-9/build.gradle b/dd-smoke-tests/rum/tomcat-9/build.gradle
new file mode 100644
index 00000000000..2c4d856c541
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-9/build.gradle
@@ -0,0 +1,26 @@
+plugins {
+  id 'com.gradleup.shadow'
+}
+
+apply from: "$rootDir/gradle/java.gradle"
+description = 'RUM Tomcat 9 Smoke Tests'
+
+dependencies {
+  implementation 'org.apache.tomcat.embed:tomcat-embed-core:9.0.88'
+  implementation 'org.apache.tomcat.embed:tomcat-embed-jasper:9.0.88'
+  implementation 'javax.servlet:javax.servlet-api:4.0.1'
+
+  testImplementation project(':dd-smoke-tests:rum')
+}
+
+jar {
+  manifest {
+    attributes('Main-Class': 'com.example.Main')
+  }
+}
+
+tasks.withType(Test).configureEach {
+  dependsOn "shadowJar"
+
+  jvmArgs "-Ddatadog.smoketest.rum.tomcat9.shadowJar.path=${tasks.shadowJar.archiveFile.get()}"
+}
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
new file mode 100644
index 00000000000..e86b58e65c2
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
@@ -0,0 +1,28 @@
+package com.example;
+
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+
+public class HelloServlet extends HttpServlet {
+    @Override
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+        resp.setContentType("text/html;charset=UTF-8");
+        resp.getWriter().write(
+                "<!DOCTYPE html>" +
+                "<html lang=\"en\">" +
+                "<head>" +
+                "    <meta charset=\"UTF-8\">" +
+                "    <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">" +
+                "    <title>Hello Servlet</title>" +
+                "</head>" +
+                "<body>" +
+                "    <h1>Hello from Tomcat 9 Servlet!</h1>" +
+                "    <p>This is a demo HTML page served by Java servlet.</p>" +
+                "</body>" +
+                "</html>"
+        );
+    }
+}
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
new file mode 100644
index 00000000000..ce614550a82
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
@@ -0,0 +1,34 @@
+package com.example;
+
+import org.apache.catalina.Context;
+import org.apache.catalina.startup.Tomcat;
+
+import java.io.File;
+
+public class Main {
+  public static void main(String[] args) throws Exception {
+    int port = 8080;
+    if (args.length == 1) {
+      port = Integer.parseInt(args[0]);
+    }
+
+    Tomcat tomcat = new Tomcat();
+    tomcat.setPort(port);
+
+    // Setup base directory
+    tomcat.setBaseDir(".");
+
+    // Add webapp context
+    String contextPath = "/";
+    String docBase = new File(".").getAbsolutePath();
+    Context context = tomcat.addContext(contextPath, docBase);
+
+    // Add servlet programmatically
+    context.addServletContainerInitializer((c, ctx) -> {
+      ctx.addServlet("helloServlet", new HelloServlet()).addMapping("/hello");
+    }, null);
+
+    tomcat.start();
+    tomcat.getServer().await();
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
new file mode 100644
index 00000000000..25bfe66de87
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
@@ -0,0 +1,43 @@
+package datadog.smoketest.rum.tomcat9
+
+import datadog.smoketest.rum.AbstractRumServerSmokeTest
+import datadog.trace.api.Platform
+import okhttp3.Request
+import okhttp3.Response
+
+class Tomcat9RumSmokeTest extends AbstractRumServerSmokeTest {
+
+
+  @Override
+  ProcessBuilder createProcessBuilder() {
+    String jarPath = System.getProperty('datadog.smoketest.rum.tomcat9.shadowJar.path')
+
+    List<String> command = []
+    command.add(javaPath())
+    command.addAll(defaultJavaProperties)
+    command.addAll(defaultRumProperties)
+    if (Platform.isJavaVersionAtLeast(17)) {
+      command.addAll((String[]) ['--add-opens', 'java.base/java.lang=ALL-UNNAMED'])
+    }
+    command.addAll(['-jar', jarPath, Integer.toString(httpPort)])
+    ProcessBuilder processBuilder = new ProcessBuilder(command)
+    processBuilder.directory(new File(buildDirectory))
+    return processBuilder
+  }
+
+  void 'test RUM SDK injection'() {
+    given:
+    def url = "http://localhost:${httpPort}/hello"
+    def request = new Request.Builder()
+      .url(url)
+      .get()
+      .build()
+
+    when:
+    Response response = client.newCall(request).execute()
+
+    then:
+    response.code() == 200
+    assertRumInjected(response)
+  }
+}
diff --git a/settings.gradle b/settings.gradle
index cc17a3de79f..c414abaf11e 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -153,6 +153,8 @@ include ':dd-smoke-tests:quarkus-native'
 include ':dd-smoke-tests:sample-trace'
 include ':dd-smoke-tests:ratpack-1.5'
 include ':dd-smoke-tests:resteasy'
+include ':dd-smoke-tests:rum'
+include ':dd-smoke-tests:rum:tomcat-9'
 include ':dd-smoke-tests:spring-boot-3.0-native'
 include ':dd-smoke-tests:spring-boot-2.4-webflux'
 include ':dd-smoke-tests:spring-boot-2.5-webflux'

From 8814d867cbe195e37bf6630e52edc6de7c291f6a Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 11:26:39 +0200
Subject: [PATCH 06/36] feat(rum): Add smoke tests

---
 .../rum/AbstractRumServerSmokeTest.groovy     | 41 ++++++-------------
 .../main/java/com/example/HelloServlet.java   |  3 +-
 .../src/main/java/com/example/Main.java       | 11 +++--
 3 files changed, 19 insertions(+), 36 deletions(-)

diff --git a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
index 6fa39dcf792..9144ccdde39 100644
--- a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
+++ b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
@@ -5,34 +5,19 @@ import okhttp3.Response
 import spock.lang.Shared
 
 class AbstractRumServerSmokeTest extends AbstractServerSmokeTest {
-
-
-
-  @Shared
-  protected String[] defaultRumProperties = [
-    "-Ddd.appsec.enabled=${System.getProperty('smoke_test.appsec.enabled') ?: 'true'}",
-    "-Ddd.profiling.enabled=false",
-    // TODO: Remove once this is the default value
-    "-Ddd.api-security.enabled=true",
-    "-Ddd.appsec.waf.timeout=300000",
-    "-DPOWERWAF_EXIT_ON_LEAK=true",
-    // disable AppSec rate limit
-    "-Ddd.appsec.trace.rate.limit=-1"
-  ] + (System.getProperty('smoke_test.appsec.enabled') == 'inactive' ?
-    // enable remote config so that appsec is partially enabled (rc is now enabled by default)
-    [
-      '-Ddd.remote_config.url=https://127.0.0.1:54670/invalid_endpoint',
-      '-Ddd.remote_config.poll_interval.seconds=3600'
-    ]:
-    ['-Ddd.remote_config.enabled=false']
-  )
-
-
-  static void assertRumInjected(Response response) {
-    assert response.header('x-datadog-rum-injected') == '1' : 'RUM injected header missing'
-    def content = response.body().toString()
-    assert content.contains('https://www.datadoghq-browser-agent.com') : 'RUM script not injected'
-  }
+    @Shared
+    protected String[] defaultRumProperties = [
+            "-Ddd.rum.enabled=true",
+            "-Ddd.rum.application.id=appid",
+            "-Ddd.rum.client.token=token"
+    ]
+
+
+    static void assertRumInjected(Response response) {
+        assert response.header('x-datadog-rum-injected') == '1': 'RUM injected header missing'
+        def content = response.body().toString()
+        assert content.contains('https://www.datadoghq-browser-agent.com'): 'RUM script not injected'
+    }
 
 
 }
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
index e86b58e65c2..dff7dec2ebc 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
@@ -1,6 +1,5 @@
 package com.example;
 
-import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -8,7 +7,7 @@
 
 public class HelloServlet extends HttpServlet {
     @Override
-    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
         resp.setContentType("text/html;charset=UTF-8");
         resp.getWriter().write(
                 "<!DOCTYPE html>" +
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
index ce614550a82..434bf83efa5 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
@@ -1,12 +1,12 @@
 package com.example;
 
+import java.io.File;
 import org.apache.catalina.Context;
+import org.apache.catalina.LifecycleException;
 import org.apache.catalina.startup.Tomcat;
 
-import java.io.File;
-
 public class Main {
-  public static void main(String[] args) throws Exception {
+  public static void main(String[] args) throws LifecycleException {
     int port = 8080;
     if (args.length == 1) {
       port = Integer.parseInt(args[0]);
@@ -14,12 +14,11 @@ public static void main(String[] args) throws Exception {
 
     Tomcat tomcat = new Tomcat();
     tomcat.setPort(port);
-
-    // Setup base directory
+    tomcat.getConnector(); // This is required to make Tomcat start
     tomcat.setBaseDir(".");
 
     // Add webapp context
-    String contextPath = "/";
+    String contextPath = "";
     String docBase = new File(".").getAbsolutePath();
     Context context = tomcat.addContext(contextPath, docBase);
 

From a1f0a77a943a865f41e33e2ab49634ca70caf7d3 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 11:27:49 +0200
Subject: [PATCH 07/36] feat(rum): Add smoke tests

---
 .../main/java/com/example/HelloServlet.java   | 38 +++++++++----------
 .../src/main/java/com/example/Main.java       |  8 ++--
 2 files changed, 24 insertions(+), 22 deletions(-)

diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
index dff7dec2ebc..d88c4774078 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
@@ -1,27 +1,27 @@
 package com.example;
 
+import java.io.IOException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
-import java.io.IOException;
 
 public class HelloServlet extends HttpServlet {
-    @Override
-    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
-        resp.setContentType("text/html;charset=UTF-8");
-        resp.getWriter().write(
-                "<!DOCTYPE html>" +
-                "<html lang=\"en\">" +
-                "<head>" +
-                "    <meta charset=\"UTF-8\">" +
-                "    <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">" +
-                "    <title>Hello Servlet</title>" +
-                "</head>" +
-                "<body>" +
-                "    <h1>Hello from Tomcat 9 Servlet!</h1>" +
-                "    <p>This is a demo HTML page served by Java servlet.</p>" +
-                "</body>" +
-                "</html>"
-        );
-    }
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    resp.setContentType("text/html;charset=UTF-8");
+    resp.getWriter()
+        .write(
+            "<!DOCTYPE html>"
+                + "<html lang=\"en\">"
+                + "<head>"
+                + "    <meta charset=\"UTF-8\">"
+                + "    <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">"
+                + "    <title>Hello Servlet</title>"
+                + "</head>"
+                + "<body>"
+                + "    <h1>Hello from Tomcat 9 Servlet!</h1>"
+                + "    <p>This is a demo HTML page served by Java servlet.</p>"
+                + "</body>"
+                + "</html>");
+  }
 }
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
index 434bf83efa5..a69a8701d89 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
@@ -23,9 +23,11 @@ public static void main(String[] args) throws LifecycleException {
     Context context = tomcat.addContext(contextPath, docBase);
 
     // Add servlet programmatically
-    context.addServletContainerInitializer((c, ctx) -> {
-      ctx.addServlet("helloServlet", new HelloServlet()).addMapping("/hello");
-    }, null);
+    context.addServletContainerInitializer(
+        (c, ctx) -> {
+          ctx.addServlet("helloServlet", new HelloServlet()).addMapping("/hello");
+        },
+        null);
 
     tomcat.start();
     tomcat.getServer().await();

From f941b4a69bc354486ac07d11e005d75620f4b2e9 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 11:29:02 +0200
Subject: [PATCH 08/36] feat(rum): Add smoke tests

---
 .../rum/AbstractRumServerSmokeTest.groovy     | 24 +++++++++----------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
index 9144ccdde39..27d2b03ecdf 100644
--- a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
+++ b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
@@ -5,19 +5,17 @@ import okhttp3.Response
 import spock.lang.Shared
 
 class AbstractRumServerSmokeTest extends AbstractServerSmokeTest {
-    @Shared
-    protected String[] defaultRumProperties = [
-            "-Ddd.rum.enabled=true",
-            "-Ddd.rum.application.id=appid",
-            "-Ddd.rum.client.token=token"
-    ]
-
-
-    static void assertRumInjected(Response response) {
-        assert response.header('x-datadog-rum-injected') == '1': 'RUM injected header missing'
-        def content = response.body().toString()
-        assert content.contains('https://www.datadoghq-browser-agent.com'): 'RUM script not injected'
-    }
+  @Shared
+  protected String[] defaultRumProperties = [
+    "-Ddd.rum.enabled=true",
+    "-Ddd.rum.application.id=appid",
+    "-Ddd.rum.client.token=token"
+  ]
 
 
+  static void assertRumInjected(Response response) {
+    assert response.header('x-datadog-rum-injected') == '1': 'RUM injected header missing'
+    def content = response.body().toString()
+    assert content.contains('https://www.datadoghq-browser-agent.com'): 'RUM script not injected'
+  }
 }

From fe2006cd7c653e293498be8eded1ca9132106483 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Fri, 4 Jul 2025 11:56:28 +0200
Subject: [PATCH 09/36] Add RUM injection for servlet 3

---
 .../buffer/InjectingPipeOutputStream.java     | 90 +++++++++++++++++++
 .../decorator/HttpServerDecorator.java        |  1 +
 .../InjectingPipeOutputStreamTest.groovy      | 23 +++++
 .../RumHttpServletResponseWrapper.java        | 84 +++++++++++++++++
 .../servlet3/Servlet3Advice.java              | 12 ++-
 .../servlet3/Servlet3Instrumentation.java     |  2 +
 .../servlet3/WrappedServletOutputStream.java  | 57 ++++++++++++
 .../src/test/groovy/JettyServlet3Test.groovy  | 86 ++++++++++++++++--
 .../datadog/trace/api/rum/RumInjector.java    | 37 +++++++-
 9 files changed, 382 insertions(+), 10 deletions(-)
 create mode 100644 dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
 create mode 100644 dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy
 create mode 100644 dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
 create mode 100644 dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java

diff --git a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
new file mode 100644
index 00000000000..f5d7d60404d
--- /dev/null
+++ b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
@@ -0,0 +1,90 @@
+package datadog.trace.bootstrap.instrumentation.buffer;
+
+import java.io.FilterOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.function.Consumer;
+
+/**
+ * A circular buffer that holds n+1 bytes and with a lookbehind buffer of n bytes. The first time
+ * that the latest n bytes matches the marker, a content is injected before.
+ */
+public class InjectingPipeOutputStream extends FilterOutputStream {
+  private final byte[] lookbehind;
+  private int pos;
+  private boolean bufferFilled;
+  private final byte[] marker;
+  private final byte[] contentToInject;
+  private boolean found = false;
+  private int matchingPos = 0;
+  private final Consumer<Void> onContentInjected;
+
+  /**
+   * @param downstream the delegate output stream
+   * @param marker the marker to find in the stream
+   * @param contentToInject the content to inject once before the marker if found.
+   */
+  public InjectingPipeOutputStream(
+      final OutputStream downstream,
+      final byte[] marker,
+      final byte[] contentToInject,
+      final Consumer<Void> onContentInjected) {
+    super(downstream);
+    this.marker = marker;
+    this.lookbehind = new byte[marker.length + 1];
+    this.pos = 0;
+    this.contentToInject = contentToInject;
+    this.onContentInjected = onContentInjected;
+  }
+
+  @Override
+  public void write(int b) throws IOException {
+    if (found) {
+      out.write(b);
+      return;
+    }
+    lookbehind[pos] = (byte) b;
+    pos = (pos + 1) % lookbehind.length;
+
+    if (marker[matchingPos++] == b) {
+      if (matchingPos == marker.length) {
+        found = true;
+        out.write(contentToInject);
+        if (onContentInjected != null) {
+          onContentInjected.accept(null);
+        }
+        drain((pos + 1) % lookbehind.length, marker.length);
+        return;
+      }
+    } else {
+      matchingPos = 0;
+    }
+
+    if (!bufferFilled) {
+      bufferFilled = pos == lookbehind.length - 1;
+    }
+
+    if (bufferFilled) {
+      super.write(lookbehind[(pos + 1) % lookbehind.length]);
+    }
+  }
+
+  private void drain(int from, int size) throws IOException {
+    while (size-- > 0) {
+      super.write(Character.valueOf((char) lookbehind[from]));
+      from = (from + 1) % lookbehind.length;
+    }
+  }
+
+  @Override
+  public void close() throws IOException {
+    if (!found) {
+      if (bufferFilled) {
+        drain((pos + 2) % lookbehind.length, marker.length - 1);
+      } else {
+        drain(0, pos);
+      }
+    }
+    super.close();
+  }
+}
diff --git a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpServerDecorator.java b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpServerDecorator.java
index 33e2ed2ebd8..fa712db6ceb 100644
--- a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpServerDecorator.java
+++ b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/decorator/HttpServerDecorator.java
@@ -57,6 +57,7 @@ public abstract class HttpServerDecorator<REQUEST, CONNECTION, RESPONSE, REQUEST
 
   public static final String DD_SPAN_ATTRIBUTE = "datadog.span";
   public static final String DD_DISPATCH_SPAN_ATTRIBUTE = "datadog.span.dispatch";
+  public static final String DD_RUM_INJECTED = "datadog.rum.injected";
   public static final String DD_FIN_DISP_LIST_SPAN_ATTRIBUTE =
       "datadog.span.finish_dispatch_listener";
   public static final String DD_RESPONSE_ATTRIBUTE = "datadog.response";
diff --git a/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy b/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy
new file mode 100644
index 00000000000..d01b38d3a1e
--- /dev/null
+++ b/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy
@@ -0,0 +1,23 @@
+package datadog.trace.bootstrap.instrumentation.buffer
+
+import spock.lang.Specification
+
+class InjectingPipeOutputStreamTest extends Specification {
+  def 'should filter a buffer and inject if found #found'() {
+    setup:
+    def downstream = new ByteArrayOutputStream()
+    def piped = new OutputStreamWriter(new InjectingPipeOutputStream(downstream, marker.getBytes("UTF-8"), contentToInject.getBytes("UTF-8"), null),
+    "UTF-8")
+    when:
+    try (def closeme = piped) {
+      piped.write(body)
+    }
+    then:
+    assert downstream.toByteArray() == expected.getBytes("UTF-8")
+    where:
+    body                                      | marker            | contentToInject         | found | expected
+    "<html><head><foo/></head><body/></html>" | "</head>"         | "<script>true</script>" | true  | "<html><head><foo/><script>true</script></head><body/></html>"
+    "<html><body/></html>"                    | "</head>"         | "<something/>"          | false | "<html><body/></html>"
+    "<foo/>"                                  | "<longerThanFoo>" | "<nothing>"             | false | "<foo/>"
+  }
+}
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
new file mode 100644
index 00000000000..389bf77eddf
--- /dev/null
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
@@ -0,0 +1,84 @@
+package datadog.trace.instrumentation.servlet3;
+
+import datadog.trace.api.rum.RumInjector;
+import java.io.IOException;
+import java.io.PrintWriter;
+import javax.servlet.ServletOutputStream;
+import javax.servlet.http.HttpServletResponse;
+import javax.servlet.http.HttpServletResponseWrapper;
+
+public class RumHttpServletResponseWrapper extends HttpServletResponseWrapper {
+  private ServletOutputStream outputStream;
+  private PrintWriter printWriter;
+  private boolean shouldInject;
+
+  public RumHttpServletResponseWrapper(HttpServletResponse response) {
+    super(response);
+  }
+
+  @Override
+  public ServletOutputStream getOutputStream() throws IOException {
+    if (!shouldInject) {
+      return super.getOutputStream();
+    }
+    if (outputStream == null) {
+      String encoding = getCharacterEncoding();
+      if (encoding == null) {
+        encoding = "UTF-8";
+      }
+      outputStream =
+          new WrappedServletOutputStream(
+              super.getOutputStream(),
+              RumInjector.getMarker(encoding),
+              RumInjector.getSnippet(encoding),
+              this::onInjected);
+    }
+    return outputStream;
+  }
+
+  @Override
+  public PrintWriter getWriter() throws IOException {
+    if (!shouldInject) {
+      return super.getWriter();
+    }
+    if (printWriter == null) {
+      printWriter = new PrintWriter(getOutputStream());
+    }
+    return printWriter;
+  }
+
+  @Override
+  public void setContentLength(int len) {
+    // don't set it since we don't know if we will inject
+  }
+
+  @Override
+  public void reset() {
+    this.outputStream = null;
+    this.printWriter = null;
+    this.shouldInject = false;
+    super.reset();
+  }
+
+  @Override
+  public void resetBuffer() {
+    this.outputStream = null;
+    this.printWriter = null;
+    this.shouldInject = false;
+    super.resetBuffer();
+  }
+
+  public void onInjected(Void ignored) {
+    try {
+      setHeader("x-datadog-rum-injected", "1");
+    } catch (Throwable ignored2) {
+    }
+  }
+
+  @Override
+  public void setContentType(String type) {
+    if (type != null && type.contains("html")) {
+      shouldInject = true;
+    }
+  }
+}
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Advice.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Advice.java
index b4f1a5ad164..8ed6322fe4d 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Advice.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Advice.java
@@ -4,6 +4,7 @@
 import static datadog.trace.bootstrap.instrumentation.api.Java8BytecodeBridge.spanFromContext;
 import static datadog.trace.bootstrap.instrumentation.decorator.HttpServerDecorator.DD_DISPATCH_SPAN_ATTRIBUTE;
 import static datadog.trace.bootstrap.instrumentation.decorator.HttpServerDecorator.DD_FIN_DISP_LIST_SPAN_ATTRIBUTE;
+import static datadog.trace.bootstrap.instrumentation.decorator.HttpServerDecorator.DD_RUM_INJECTED;
 import static datadog.trace.bootstrap.instrumentation.decorator.HttpServerDecorator.DD_SPAN_ATTRIBUTE;
 import static datadog.trace.instrumentation.servlet3.Servlet3Decorator.DECORATE;
 
@@ -15,6 +16,7 @@
 import datadog.trace.api.DDTags;
 import datadog.trace.api.GlobalTracer;
 import datadog.trace.api.gateway.Flow;
+import datadog.trace.api.rum.RumInjector;
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
 import datadog.trace.instrumentation.servlet.ServletBlockingHelper;
 import java.security.Principal;
@@ -30,7 +32,7 @@ public class Servlet3Advice {
   @Advice.OnMethodEnter(suppress = Throwable.class, skipOn = Advice.OnNonDefaultValue.class)
   public static boolean onEnter(
       @Advice.Argument(value = 0, readOnly = false) ServletRequest request,
-      @Advice.Argument(value = 1) ServletResponse response,
+      @Advice.Argument(value = 1, readOnly = false) ServletResponse response,
       @Advice.Local("isDispatch") boolean isDispatch,
       @Advice.Local("finishSpan") boolean finishSpan,
       @Advice.Local("contextScope") ContextScope scope) {
@@ -41,7 +43,13 @@ public static boolean onEnter(
     }
 
     final HttpServletRequest httpServletRequest = (HttpServletRequest) request;
-    final HttpServletResponse httpServletResponse = (HttpServletResponse) response;
+    HttpServletResponse httpServletResponse = (HttpServletResponse) response;
+
+    if (RumInjector.isEnabled() && httpServletRequest.getAttribute(DD_RUM_INJECTED) == null) {
+      httpServletRequest.setAttribute(DD_RUM_INJECTED, Boolean.TRUE);
+      httpServletResponse = new RumHttpServletResponseWrapper(httpServletResponse);
+      response = httpServletResponse;
+    }
 
     Object dispatchSpan = request.getAttribute(DD_DISPATCH_SPAN_ATTRIBUTE);
     if (dispatchSpan instanceof AgentSpan) {
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Instrumentation.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Instrumentation.java
index a7dc4f28368..d7732045329 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Instrumentation.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Instrumentation.java
@@ -52,6 +52,8 @@ public String[] helperClassNames() {
       packageName + ".Servlet3Decorator",
       packageName + ".ServletRequestURIAdapter",
       packageName + ".FinishAsyncDispatchListener",
+      packageName + ".RumHttpServletResponseWrapper",
+      packageName + ".WrappedServletOutputStream",
       "datadog.trace.instrumentation.servlet.ServletBlockingHelper",
     };
   }
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
new file mode 100644
index 00000000000..fbafb01cdc0
--- /dev/null
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
@@ -0,0 +1,57 @@
+package datadog.trace.instrumentation.servlet3;
+
+import datadog.trace.bootstrap.instrumentation.buffer.InjectingPipeOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.function.Consumer;
+import javax.servlet.ServletOutputStream;
+import javax.servlet.WriteListener;
+
+public class WrappedServletOutputStream extends ServletOutputStream {
+  private final OutputStream filtered;
+  private final ServletOutputStream delegate;
+
+  public WrappedServletOutputStream(
+      ServletOutputStream delegate,
+      byte[] marker,
+      byte[] contentToInject,
+      Consumer<Void> onInjected) {
+    this.filtered = new InjectingPipeOutputStream(delegate, marker, contentToInject, onInjected);
+    this.delegate = delegate;
+  }
+
+  @Override
+  public void write(int b) throws IOException {
+    filtered.write(b);
+  }
+
+  @Override
+  public void write(byte[] b) throws IOException {
+    filtered.write(b);
+  }
+
+  @Override
+  public void write(byte[] b, int off, int len) throws IOException {
+    filtered.write(b, off, len);
+  }
+
+  @Override
+  public void flush() throws IOException {
+    filtered.flush();
+  }
+
+  @Override
+  public void close() throws IOException {
+    filtered.close();
+  }
+
+  @Override
+  public boolean isReady() {
+    return delegate.isReady();
+  }
+
+  @Override
+  public void setWriteListener(WriteListener writeListener) {
+    delegate.setWriteListener(writeListener);
+  }
+}
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/test/groovy/JettyServlet3Test.groovy b/dd-java-agent/instrumentation/servlet/request-3/src/test/groovy/JettyServlet3Test.groovy
index 61a255e1f0d..2ed349c5402 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/test/groovy/JettyServlet3Test.groovy
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/test/groovy/JettyServlet3Test.groovy
@@ -3,6 +3,7 @@ import datadog.trace.agent.test.base.HttpServer
 import datadog.trace.agent.test.naming.TestingGenericHttpNamingConventions
 import datadog.trace.api.iast.InstrumentationBridge
 import datadog.trace.api.iast.sink.ApplicationModule
+import datadog.trace.api.rum.RumInjector
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan
 import datadog.trace.bootstrap.instrumentation.api.Tags
 import datadog.trace.instrumentation.servlet3.AsyncDispatcherDecorator
@@ -20,6 +21,7 @@ import javax.servlet.AsyncListener
 import javax.servlet.Servlet
 import javax.servlet.ServletException
 import javax.servlet.annotation.WebServlet
+import javax.servlet.http.HttpServlet
 import javax.servlet.http.HttpServletRequest
 import javax.servlet.http.HttpServletResponse
 
@@ -167,8 +169,8 @@ abstract class JettyServlet3Test extends AbstractServlet3Test<Server, ServletCon
   Map<String, Serializable> expectedExtraErrorInformation(ServerEndpoint endpoint) {
     if (endpoint.throwsException) {
       ["error.message": "${endpoint.body}",
-        "error.type": { it == Exception.name || it == InputMismatchException.name },
-        "error.stack": String]
+        "error.type"   : { it == Exception.name || it == InputMismatchException.name },
+        "error.stack"  : String]
     } else {
       Collections.emptyMap()
     }
@@ -233,6 +235,77 @@ class JettyServlet3TestSync extends JettyServlet3Test {
   }
 }
 
+class JettyServlet3SyncRumInjectionForkedTest extends JettyServlet3TestSync {
+
+  static class RumServlet extends HttpServlet {
+    private final String mimeType
+
+    RumServlet(String mime) {
+      this.mimeType = mime
+    }
+
+    @Override
+    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+      resp.setContentType(mimeType)
+      try (def writer = resp.getWriter()) {
+        writer.println("\n" +
+        "<!doctype html>\n" +
+        "<html>\n" +
+        "  <head>\n" +
+        "    <title>This is the title of the webpage!</title>\n" +
+        "  </head>\n" +
+        "  <body>\n" +
+        "    <p>This is an example paragraph. Anything in the <strong>body</strong> tag will appear on the page, just like this <strong>p</strong> tag and its contents.</p>\n" +
+        "  </body>\n" +
+        "</html>")
+      }
+    }
+  }
+
+  static class HtmlRumServlet extends RumServlet {
+    HtmlRumServlet() {
+      super("text/html")
+    }
+  }
+
+  static class XmlRumServlet extends RumServlet {
+    XmlRumServlet() {
+      super("text/xml")
+    }
+  }
+
+  @Override
+  protected void configurePreAgent() {
+    super.configurePreAgent()
+    injectSysConfig("rum.enabled", "true")
+    injectSysConfig("rum.application.id", "test")
+    injectSysConfig("rum.client.token", "secret")
+  }
+
+  @Override
+  protected void setupServlets(ServletContextHandler servletContextHandler) {
+    super.setupServlets(servletContextHandler)
+    addServlet(servletContextHandler, "/gimme-html", HtmlRumServlet)
+    addServlet(servletContextHandler, "/gimme-xml", XmlRumServlet)
+  }
+
+  def "test rum injection in head for mime #mime"() {
+    setup:
+    def request = new okhttp3.Request.Builder().url(server.address().resolve("gimme-$mime").toURL())
+      .get().build()
+    when:
+    def response = client.newCall(request).execute()
+    then:
+    assert response.code() == 200
+    assert response.body().string().contains(new String(RumInjector.getSnippet("UTF-8"), "UTF-8")) == expected
+    assert response.header("x-datadog-rum-injected") == (expected ? "1" : null)
+    where:
+    mime   | expected
+    "html" | true
+    "xml"  | false
+  }
+}
+
 
 class JettyServlet3SyncV1ForkedTest extends JettyServlet3TestSync implements TestingGenericHttpNamingConventions.ServerV1 {
 
@@ -260,6 +333,7 @@ class JettyServlet3TestAsync extends JettyServlet3Test {
 class JettyServlet3ASyncV1ForkedTest extends JettyServlet3TestAsync implements TestingGenericHttpNamingConventions.ServerV1 {
 
 }
+
 class JettyServlet3TestFakeAsync extends JettyServlet3Test {
 
   @Override
@@ -586,16 +660,16 @@ class IastJettyServlet3ForkedTest extends JettyServlet3TestSync {
     client.newCall(request).execute()
 
     then:
-    1 *  appModule.onRealPath(_)
-    1 *  appModule.checkSessionTrackingModes(_)
+    1 * appModule.onRealPath(_)
+    1 * appModule.checkSessionTrackingModes(_)
     0 * _
 
     when:
     client.newCall(request).execute()
 
     then: //Only call once per application context
-    0 *  appModule.onRealPath(_)
-    0 *  appModule.checkSessionTrackingModes(_)
+    0 * appModule.onRealPath(_)
+    0 * appModule.checkSessionTrackingModes(_)
     0 * _
   }
 
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
index 4b880f6a252..25e337f67ec 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
@@ -1,12 +1,35 @@
 package datadog.trace.api.rum;
 
 import datadog.trace.api.Config;
+import datadog.trace.api.cache.DDCache;
+import datadog.trace.api.cache.DDCaches;
+import java.util.function.Function;
 
 public final class RumInjector {
   private static volatile boolean initialized = false;
   private static volatile boolean enabled;
   private static volatile String snippet;
 
+  private static final String MARKER = "</head>";
+  private static final DDCache<String, byte[]> SNIPPET_CACHE = DDCaches.newFixedSizeCache(16);
+  private static final DDCache<String, byte[]> MARKER_CACHE = DDCaches.newFixedSizeCache(16);
+  private static final Function<String, byte[]> SNIPPET_ADDER =
+      charset -> {
+        try {
+          return snippet.getBytes(charset);
+        } catch (Throwable t) {
+          return null;
+        }
+      };
+  private static final Function<String, byte[]> MARKER_ADDER =
+      charset -> {
+        try {
+          return MARKER.getBytes(charset);
+        } catch (Throwable t) {
+          return null;
+        }
+      };
+
   /**
    * Check whether RUM injection is enabled and ready to inject.
    *
@@ -34,7 +57,17 @@ public static boolean isEnabled() {
    *
    * @return The HTML snippet to inject, {@code null} if RUM injection is disabled to inject.
    */
-  public static String getSnippet() {
-    return snippet;
+  public static byte[] getSnippet(String encoding) {
+    if (!isEnabled()) {
+      return null;
+    }
+    return SNIPPET_CACHE.computeIfAbsent(encoding, SNIPPET_ADDER);
+  }
+
+  public static byte[] getMarker(String encoding) {
+    if (!isEnabled()) {
+      return null;
+    }
+    return MARKER_CACHE.computeIfAbsent(encoding, MARKER_ADDER);
   }
 }

From 2ac167a7eac2f54d01df0f91385d28e0b0442f86 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Fri, 4 Jul 2025 12:11:12 +0200
Subject: [PATCH 10/36] fix rum injection smoke test

---
 .../rum/AbstractRumServerSmokeTest.groovy     |  2 +-
 .../main/java/com/example/HelloServlet.java   | 30 ++++++++++---------
 2 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
index 27d2b03ecdf..dade3311a41 100644
--- a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
+++ b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
@@ -15,7 +15,7 @@ class AbstractRumServerSmokeTest extends AbstractServerSmokeTest {
 
   static void assertRumInjected(Response response) {
     assert response.header('x-datadog-rum-injected') == '1': 'RUM injected header missing'
-    def content = response.body().toString()
+    def content = response.body().string()
     assert content.contains('https://www.datadoghq-browser-agent.com'): 'RUM script not injected'
   }
 }
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
index d88c4774078..5639cb65677 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
@@ -1,6 +1,7 @@
 package com.example;
 
 import java.io.IOException;
+import java.io.PrintWriter;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -9,19 +10,20 @@ public class HelloServlet extends HttpServlet {
   @Override
   protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
     resp.setContentType("text/html;charset=UTF-8");
-    resp.getWriter()
-        .write(
-            "<!DOCTYPE html>"
-                + "<html lang=\"en\">"
-                + "<head>"
-                + "    <meta charset=\"UTF-8\">"
-                + "    <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">"
-                + "    <title>Hello Servlet</title>"
-                + "</head>"
-                + "<body>"
-                + "    <h1>Hello from Tomcat 9 Servlet!</h1>"
-                + "    <p>This is a demo HTML page served by Java servlet.</p>"
-                + "</body>"
-                + "</html>");
+    try (final PrintWriter writer = resp.getWriter()) {
+      writer.write(
+          "<!DOCTYPE html>"
+              + "<html lang=\"en\">"
+              + "<head>"
+              + "    <meta charset=\"UTF-8\">"
+              + "    <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">"
+              + "    <title>Hello Servlet</title>"
+              + "</head>"
+              + "<body>"
+              + "    <h1>Hello from Tomcat 9 Servlet!</h1>"
+              + "    <p>This is a demo HTML page served by Java servlet.</p>"
+              + "</body>"
+              + "</html>");
+    }
   }
 }

From c389b7767fdcc597dd17d25246da4babf0b8be3f Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Fri, 4 Jul 2025 12:26:43 +0200
Subject: [PATCH 11/36] fix javadoc

---
 .../instrumentation/buffer/InjectingPipeOutputStream.java        | 1 +
 1 file changed, 1 insertion(+)

diff --git a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
index f5d7d60404d..ea3322103f7 100644
--- a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
+++ b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
@@ -23,6 +23,7 @@ public class InjectingPipeOutputStream extends FilterOutputStream {
    * @param downstream the delegate output stream
    * @param marker the marker to find in the stream
    * @param contentToInject the content to inject once before the marker if found.
+   * @param onContentInjected callback called when and if the content is injected.
    */
   public InjectingPipeOutputStream(
       final OutputStream downstream,

From 01f6aaeee17956416184ab513e27ad4417a6509f Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Fri, 4 Jul 2025 13:53:30 +0200
Subject: [PATCH 12/36] Add benchmark

---
 .../InjectingPipeOutputStreamBenchmark.java   | 60 +++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java

diff --git a/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java b/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java
new file mode 100644
index 00000000000..2432469949c
--- /dev/null
+++ b/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java
@@ -0,0 +1,60 @@
+package datadog.trace.bootstrap.instrumentation.buffer;
+
+import static java.util.concurrent.TimeUnit.MICROSECONDS;
+import static java.util.concurrent.TimeUnit.SECONDS;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.PrintWriter;
+import java.net.URL;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+import org.apache.commons.io.IOUtils;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+@State(Scope.Benchmark)
+@Warmup(iterations = 1, time = 30, timeUnit = SECONDS)
+@Measurement(iterations = 2, time = 30, timeUnit = SECONDS)
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(MICROSECONDS)
+@Fork(value = 1)
+public class InjectingPipeOutputStreamBenchmark {
+  private static final List<String> htmlContent;
+  private static final byte[] marker;
+  private static final byte[] content;
+
+  static {
+    try (InputStream is = new URL("https://www.google.com").openStream()) {
+      htmlContent = IOUtils.readLines(is, StandardCharsets.UTF_8);
+    } catch (IOException ioe) {
+      throw new RuntimeException(ioe);
+    }
+    marker = "</head>".getBytes(StandardCharsets.UTF_8);
+    content = "<script/>".getBytes(StandardCharsets.UTF_8);
+  }
+
+  @Benchmark
+  public void withPipe() throws Exception {
+    try (final PrintWriter out =
+        new PrintWriter(
+            new InjectingPipeOutputStream(new ByteArrayOutputStream(), marker, content, null))) {
+      htmlContent.forEach(out::println);
+    }
+  }
+
+  @Benchmark
+  public void withoutPipe() throws Exception {
+    try (final PrintWriter out = new PrintWriter(new ByteArrayOutputStream())) {
+      htmlContent.forEach(out::println);
+    }
+  }
+}

From 486ee57a404676a54de372d69c9690754c7fdbba Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Fri, 4 Jul 2025 14:11:44 +0200
Subject: [PATCH 13/36] avoid linkage issues with earlier servlet specs

---
 .../servlet3/WrappedServletOutputStream.java  | 36 ++++++++++++++++---
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
index fbafb01cdc0..32323a1cfff 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
@@ -1,8 +1,10 @@
 package datadog.trace.instrumentation.servlet3;
 
 import datadog.trace.bootstrap.instrumentation.buffer.InjectingPipeOutputStream;
+import datadog.trace.util.MethodHandles;
 import java.io.IOException;
 import java.io.OutputStream;
+import java.lang.invoke.MethodHandle;
 import java.util.function.Consumer;
 import javax.servlet.ServletOutputStream;
 import javax.servlet.WriteListener;
@@ -11,6 +13,18 @@ public class WrappedServletOutputStream extends ServletOutputStream {
   private final OutputStream filtered;
   private final ServletOutputStream delegate;
 
+  private static final MethodHandle IS_READY_MH = getMh("isReady");
+  private static final MethodHandle SET_WRITELISTENER_MH = getMh("setWriteListener");
+
+  private static final MethodHandle getMh(final String name) {
+    try {
+      return new MethodHandles(ServletOutputStream.class.getClassLoader())
+          .method(ServletOutputStream.class, name);
+    } catch (Throwable ignored) {
+      return null;
+    }
+  }
+
   public WrappedServletOutputStream(
       ServletOutputStream delegate,
       byte[] marker,
@@ -45,13 +59,27 @@ public void close() throws IOException {
     filtered.close();
   }
 
-  @Override
   public boolean isReady() {
-    return delegate.isReady();
+    if (IS_READY_MH == null) {
+      return false;
+    }
+    try {
+      return (boolean) IS_READY_MH.invoke(delegate);
+    } catch (Throwable e) {
+      // how to sneaky throw?
+      throw new RuntimeException(e);
+    }
   }
 
-  @Override
   public void setWriteListener(WriteListener writeListener) {
-    delegate.setWriteListener(writeListener);
+    if (SET_WRITELISTENER_MH == null) {
+      return;
+    }
+    try {
+      SET_WRITELISTENER_MH.invoke(delegate, writeListener);
+    } catch (Throwable e) {
+      // how to sneaky throw?
+      throw new RuntimeException(e);
+    }
   }
 }

From 2a55b6932d695a613e63cb055f9c84bc9415c613 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 15:22:44 +0200
Subject: [PATCH 14/36] feat(rum): Improve smoke test to add more cases

---
 .../rum/AbstractRumServerSmokeTest.groovy     |  6 +++++
 .../{HelloServlet.java => HtmlServlet.java}   |  2 +-
 .../src/main/java/com/example/Main.java       |  3 ++-
 .../src/main/java/com/example/XmlServlet.java | 25 +++++++++++++++++++
 .../rum/tomcat9/Tomcat9RumSmokeTest.groovy    | 20 +++++++++++++--
 5 files changed, 52 insertions(+), 4 deletions(-)
 rename dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/{HelloServlet.java => HtmlServlet.java} (95%)
 create mode 100644 dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/XmlServlet.java

diff --git a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
index dade3311a41..0f9247348fd 100644
--- a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
+++ b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
@@ -18,4 +18,10 @@ class AbstractRumServerSmokeTest extends AbstractServerSmokeTest {
     def content = response.body().string()
     assert content.contains('https://www.datadoghq-browser-agent.com'): 'RUM script not injected'
   }
+
+  static void assertRumNotInjected(Response response) {
+    assert response.header('x-datadog-rum-injected') == null: 'RUM header unexpectedly injected'
+    def content = response.body().toString()
+    assert !content.contains('https://www.datadoghq-browser-agent.com'): 'RUM script unexpectedly injected'
+  }
 }
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HtmlServlet.java
similarity index 95%
rename from dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
rename to dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HtmlServlet.java
index 5639cb65677..ed7283ec81e 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HelloServlet.java
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/HtmlServlet.java
@@ -6,7 +6,7 @@
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-public class HelloServlet extends HttpServlet {
+public class HtmlServlet extends HttpServlet {
   @Override
   protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
     resp.setContentType("text/html;charset=UTF-8");
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
index a69a8701d89..96a5f07cd87 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
@@ -25,7 +25,8 @@ public static void main(String[] args) throws LifecycleException {
     // Add servlet programmatically
     context.addServletContainerInitializer(
         (c, ctx) -> {
-          ctx.addServlet("helloServlet", new HelloServlet()).addMapping("/hello");
+          ctx.addServlet("htmlServlet", new HtmlServlet()).addMapping("/html");
+          ctx.addServlet("xmlServlet", new HtmlServlet()).addMapping("/xml");
         },
         null);
 
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/XmlServlet.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/XmlServlet.java
new file mode 100644
index 00000000000..15bb275acac
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/XmlServlet.java
@@ -0,0 +1,25 @@
+package com.example;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+public class XmlServlet extends HttpServlet {
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    resp.setContentType("application/xml;charset=UTF-8");
+    try (PrintWriter out = resp.getWriter()) {
+      out.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
+      out.println("<response>");
+      out.println("    <status>success</status>");
+      out.println("    <message>RUM injection test</message>");
+      out.println("    <data>");
+      out.println("        <item id=\"1\">Test Item 1</item>");
+      out.println("        <item id=\"2\">Test Item 2</item>");
+      out.println("    </data>");
+      out.println("</response>");
+    }
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
index 25bfe66de87..d12563deead 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
+++ b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
@@ -25,9 +25,9 @@ class Tomcat9RumSmokeTest extends AbstractRumServerSmokeTest {
     return processBuilder
   }
 
-  void 'test RUM SDK injection'() {
+  void 'test RUM SDK injection on html'() {
     given:
-    def url = "http://localhost:${httpPort}/hello"
+    def url = "http://localhost:${httpPort}/html"
     def request = new Request.Builder()
       .url(url)
       .get()
@@ -40,4 +40,20 @@ class Tomcat9RumSmokeTest extends AbstractRumServerSmokeTest {
     response.code() == 200
     assertRumInjected(response)
   }
+
+  void 'test RUM SDK injection skip on supported mime type'() {
+    given:
+    def url = "http://localhost:${httpPort}/xml"
+    def request = new Request.Builder()
+      .url(url)
+      .get()
+      .build()
+
+    when:
+    Response response = client.newCall(request).execute()
+
+    then:
+    response.code() == 200
+    assertRumNotInjected(response)
+  }
 }

From ce2c14125d584e114078950096bb6cf8033f14d2 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 15:40:31 +0200
Subject: [PATCH 15/36] feat(rum): Add remote config and fix json encoding

---
 .../datadog/trace/api/ConfigDefaults.java     |  2 -
 .../datadog/trace/api/config/RumConfig.java   |  1 +
 .../main/java/datadog/trace/api/Config.java   | 19 ++++----
 .../trace/api/rum/RumInjectorConfig.java      | 45 +++++++++++++------
 4 files changed, 40 insertions(+), 27 deletions(-)

diff --git a/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java b/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
index c3656cd3251..3f79a2b9cb3 100644
--- a/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
+++ b/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
@@ -242,8 +242,6 @@ public final class ConfigDefaults {
 
   static final boolean DEFAULT_RUM_ENABLED = false;
   static final int DEFAULT_RUM_MAJOR_VERSION = 6;
-  static final float DEFAULT_RUM_SESSION_SAMPLE_RATE = 100f;
-  static final float DEFAULT_RUM_SESSION_REPLAY_SAMPLE_RATE = 100f;
 
   static final boolean DEFAULT_SSI_INJECTION_FORCE = false;
   static final String DEFAULT_INSTRUMENTATION_SOURCE = "manual";
diff --git a/dd-trace-api/src/main/java/datadog/trace/api/config/RumConfig.java b/dd-trace-api/src/main/java/datadog/trace/api/config/RumConfig.java
index 51d90fd31c4..b8cf85e017c 100644
--- a/dd-trace-api/src/main/java/datadog/trace/api/config/RumConfig.java
+++ b/dd-trace-api/src/main/java/datadog/trace/api/config/RumConfig.java
@@ -15,6 +15,7 @@ public final class RumConfig {
   public static final String RUM_DEFAULT_PRIVACY_LEVEL = "rum.default.privacy.level";
   public static final String RUM_SESSION_SAMPLE_RATE = "rum.session.sample.rate";
   public static final String RUM_SESSION_REPLAY_SAMPLE_RATE = "rum.session.replay.sample.rate";
+  public static final String RUM_REMOTE_CONFIGURATION_ID = "rum.remote.configuration.id";
 
   private RumConfig() {}
 }
diff --git a/internal-api/src/main/java/datadog/trace/api/Config.java b/internal-api/src/main/java/datadog/trace/api/Config.java
index 56a55be4204..7ed894265ee 100644
--- a/internal-api/src/main/java/datadog/trace/api/Config.java
+++ b/internal-api/src/main/java/datadog/trace/api/Config.java
@@ -120,8 +120,6 @@
 import static datadog.trace.api.ConfigDefaults.DEFAULT_REMOTE_CONFIG_TARGETS_KEY_ID;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_ENABLED;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_MAJOR_VERSION;
-import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_SESSION_REPLAY_SAMPLE_RATE;
-import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_SESSION_SAMPLE_RATE;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_SCOPE_DEPTH_LIMIT;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_SCOPE_ITERATION_KEEP_ALIVE;
 import static datadog.trace.api.ConfigDefaults.DEFAULT_SECURE_RANDOM;
@@ -471,6 +469,7 @@
 import static datadog.trace.api.config.RumConfig.RUM_ENABLED;
 import static datadog.trace.api.config.RumConfig.RUM_ENVIRONMENT;
 import static datadog.trace.api.config.RumConfig.RUM_MAJOR_VERSION;
+import static datadog.trace.api.config.RumConfig.RUM_REMOTE_CONFIGURATION_ID;
 import static datadog.trace.api.config.RumConfig.RUM_SERVICE;
 import static datadog.trace.api.config.RumConfig.RUM_SESSION_REPLAY_SAMPLE_RATE;
 import static datadog.trace.api.config.RumConfig.RUM_SESSION_SAMPLE_RATE;
@@ -2702,16 +2701,14 @@ PROFILING_DATADOG_PROFILER_ENABLED, isDatadogProfilerSafeInCurrentEnvironment())
     log.debug("New instance: {}", this);
   }
 
-  private static RumInjectorConfig parseRumConfig(ConfigProvider configProvider) {
-    String applicationId = configProvider.getString(RUM_APPLICATION_ID);
-    String clientToken = configProvider.getString(RUM_CLIENT_TOKEN);
-    if (applicationId == null || clientToken == null) {
+  private RumInjectorConfig parseRumConfig(ConfigProvider configProvider) {
+    if (this.rumEnabled) {
       return null;
     }
     try {
       return new RumInjectorConfig(
-          applicationId,
-          clientToken,
+          configProvider.getString(RUM_APPLICATION_ID),
+          configProvider.getString(RUM_CLIENT_TOKEN),
           configProvider.getString(RUM_SITE),
           configProvider.getString(RUM_SERVICE),
           configProvider.getString(RUM_ENVIRONMENT),
@@ -2721,9 +2718,9 @@ private static RumInjectorConfig parseRumConfig(ConfigProvider configProvider) {
           configProvider.getBoolean(RUM_TRACK_RESOURCES),
           configProvider.getBoolean(RUM_TRACK_LONG_TASKS),
           configProvider.getEnum(RUM_DEFAULT_PRIVACY_LEVEL, PrivacyLevel.class, null),
-          configProvider.getFloat(RUM_SESSION_SAMPLE_RATE, DEFAULT_RUM_SESSION_SAMPLE_RATE),
-          configProvider.getFloat(
-              RUM_SESSION_REPLAY_SAMPLE_RATE, DEFAULT_RUM_SESSION_REPLAY_SAMPLE_RATE));
+          configProvider.getFloat(RUM_SESSION_SAMPLE_RATE),
+          configProvider.getFloat(RUM_SESSION_REPLAY_SAMPLE_RATE),
+          configProvider.getString(RUM_REMOTE_CONFIGURATION_ID));
     } catch (IllegalArgumentException e) {
       log.warn("Unable to configure RUM injection", e);
       return null;
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
index 66b350c2b46..c1d1ca6c8bb 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
@@ -43,12 +43,14 @@ public class RumInjectorConfig {
   /** The privacy level for data collection. */
   @Nullable public final PrivacyLevel defaultPrivacyLevel;
   /** The percentage of user sessions to be tracked (between 0.0 and 100.0). */
-  public final float sessionSampleRate;
+  @Nullable public final Float sessionSampleRate;
   /**
    * The percentage of tracked sessions that will include Session Replay data (between 0.0 and
    * 100.0).
    */
-  public final float sessionReplaySampleRate;
+  @Nullable public final Float sessionReplaySampleRate;
+  /** The remote configuration identifier. */
+  @Nullable public final String remoteConfigurationId;
 
   public RumInjectorConfig(
       String applicationId,
@@ -62,8 +64,9 @@ public RumInjectorConfig(
       @Nullable Boolean trackResources,
       @Nullable Boolean trackLongTask,
       @Nullable PrivacyLevel defaultPrivacyLevel,
-      float sessionSampleRate,
-      float sessionReplaySampleRate) {
+      @Nullable Float sessionSampleRate,
+      @Nullable Float sessionReplaySampleRate,
+      @Nullable String remoteConfigurationId) {
     if (applicationId == null || applicationId.isEmpty()) {
       throw new IllegalArgumentException("Invalid application id: " + applicationId);
     }
@@ -89,16 +92,23 @@ public RumInjectorConfig(
     this.trackUserInteractions = trackUserInteractions;
     this.trackResources = trackResources;
     this.trackLongTask = trackLongTask;
-    if (sessionSampleRate < 0f || sessionSampleRate > 100f) {
+    if (sessionSampleRate != null && (sessionSampleRate < 0f || sessionSampleRate > 100f)) {
       throw new IllegalArgumentException("Invalid session sample rate: " + sessionSampleRate);
     }
     this.sessionSampleRate = sessionSampleRate;
-    if (sessionReplaySampleRate < 0f || sessionReplaySampleRate > 100f) {
+    if (sessionReplaySampleRate != null
+        && (sessionReplaySampleRate < 0f || sessionReplaySampleRate > 100f)) {
       throw new IllegalArgumentException(
           "Invalid session replay sample rate: " + sessionReplaySampleRate);
     }
     this.sessionReplaySampleRate = sessionReplaySampleRate;
     this.defaultPrivacyLevel = defaultPrivacyLevel;
+    this.remoteConfigurationId = remoteConfigurationId;
+    if (this.remoteConfigurationId == null
+        && (this.sessionSampleRate == null || this.sessionReplaySampleRate == null)) {
+      throw new IllegalArgumentException(
+          "Either remote configuration id or both session and session replay sample rates must be set");
+    }
   }
 
   private static boolean validateSite(String site) {
@@ -141,8 +151,8 @@ private String getCdnUrl() {
   public String jsonPayload() {
     try (JsonWriter writer = new JsonWriter()) {
       writer.beginObject();
-      writer.name("application_id").value(this.applicationId);
-      writer.name("client_token").value(this.clientToken);
+      writer.name("applicationId").value(this.applicationId);
+      writer.name("clientToken").value(this.clientToken);
       if (this.site != null) {
         writer.name("site").value(this.site);
       }
@@ -156,19 +166,26 @@ public String jsonPayload() {
         writer.name("version").value(this.version);
       }
       if (this.trackUserInteractions != null) {
-        writer.name("track_user_interactions").value(this.trackUserInteractions);
+        writer.name("trackUserInteractions").value(this.trackUserInteractions);
       }
       if (this.trackResources != null) {
-        writer.name("track_resources").value(this.trackResources);
+        writer.name("trackResources").value(this.trackResources);
       }
       if (this.trackLongTask != null) {
-        writer.name("track_long_task").value(this.trackLongTask);
+        writer.name("trackLongTask").value(this.trackLongTask);
       }
       if (this.defaultPrivacyLevel != null) {
-        writer.name("default_privacy_level").value(this.defaultPrivacyLevel.toJson());
+        writer.name("defaultPrivacyLevel").value(this.defaultPrivacyLevel.toJson());
+      }
+      if (this.sessionSampleRate != null) {
+        writer.name("sessionSampleRate").value(this.sessionSampleRate);
+      }
+      if (this.sessionReplaySampleRate != null) {
+        writer.name("sessionReplaySampleRate").value(this.sessionReplaySampleRate);
+      }
+      if (this.remoteConfigurationId != null) {
+        writer.name("remoteConfigurationId").value(this.remoteConfigurationId);
       }
-      writer.name("session_sample_rate").value(this.sessionSampleRate);
-      writer.name("session_replay_sample_rate").value(this.sessionReplaySampleRate);
       return writer.toString();
     } catch (Exception e) {
       throw new IllegalStateException("Fail to generate config payload", e);

From 9d43968709b32c7cb9d585af6261cb386c0266c7 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 16:44:47 +0200
Subject: [PATCH 16/36] feat(rum): Add more smoke tests

---
 .../rum/AbstractRumServerSmokeTest.groovy     | 32 +++++++++++++++++
 dd-smoke-tests/rum/tomcat-10/build.gradle     | 25 +++++++++++++
 .../main/java/com/example/HtmlServlet.java    | 29 +++++++++++++++
 .../src/main/java/com/example/Main.java       | 36 +++++++++++++++++++
 .../src/main/java/com/example/XmlServlet.java | 25 +++++++++++++
 .../rum/tomcat10/Tomcat10RumSmokeTest.groovy  | 23 ++++++++++++
 .../rum/tomcat9/Tomcat9RumSmokeTest.groovy    | 32 -----------------
 settings.gradle                               |  1 +
 8 files changed, 171 insertions(+), 32 deletions(-)
 create mode 100644 dd-smoke-tests/rum/tomcat-10/build.gradle
 create mode 100644 dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/HtmlServlet.java
 create mode 100644 dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/Main.java
 create mode 100644 dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/XmlServlet.java
 create mode 100644 dd-smoke-tests/rum/tomcat-10/src/test/groovy/datadog/smoketest/rum/tomcat10/Tomcat10RumSmokeTest.groovy

diff --git a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
index 0f9247348fd..7ee362ea605 100644
--- a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
+++ b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
@@ -1,6 +1,7 @@
 package datadog.smoketest.rum
 
 import datadog.smoketest.AbstractServerSmokeTest
+import okhttp3.Request
 import okhttp3.Response
 import spock.lang.Shared
 
@@ -12,6 +13,37 @@ class AbstractRumServerSmokeTest extends AbstractServerSmokeTest {
     "-Ddd.rum.client.token=token"
   ]
 
+  void 'test RUM SDK injection on html'() {
+    given:
+    def url = "http://localhost:${httpPort}/html"
+    def request = new Request.Builder()
+            .url(url)
+            .get()
+            .build()
+
+    when:
+    Response response = client.newCall(request).execute()
+
+    then:
+    response.code() == 200
+    assertRumInjected(response)
+  }
+
+  void 'test RUM SDK injection skip on unsupported mime type'() {
+    given:
+    def url = "http://localhost:${httpPort}/xml"
+    def request = new Request.Builder()
+            .url(url)
+            .get()
+            .build()
+
+    when:
+    Response response = client.newCall(request).execute()
+
+    then:
+    response.code() == 200
+    assertRumNotInjected(response)
+  }
 
   static void assertRumInjected(Response response) {
     assert response.header('x-datadog-rum-injected') == '1': 'RUM injected header missing'
diff --git a/dd-smoke-tests/rum/tomcat-10/build.gradle b/dd-smoke-tests/rum/tomcat-10/build.gradle
new file mode 100644
index 00000000000..fd084160e73
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-10/build.gradle
@@ -0,0 +1,25 @@
+plugins {
+  id 'com.gradleup.shadow'
+}
+
+apply from: "$rootDir/gradle/java.gradle"
+description = 'RUM Tomcat 10 Smoke Tests'
+
+dependencies {
+  implementation 'org.apache.tomcat.embed:tomcat-embed-core:10.1.13'
+  implementation 'org.apache.tomcat.embed:tomcat-embed-jasper:10.1.13'
+  implementation 'jakarta.servlet:jakarta.servlet-api:5.0.0'
+
+  testImplementation project(':dd-smoke-tests:rum')
+}
+
+jar {
+  manifest {
+    attributes('Main-Class': 'com.example.Main')
+  }
+}
+
+tasks.withType(Test).configureEach {
+  dependsOn "shadowJar"
+  jvmArgs "-Ddatadog.smoketest.rum.tomcat10.shadowJar.path=${tasks.shadowJar.archiveFile.get()}"
+}
diff --git a/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/HtmlServlet.java b/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/HtmlServlet.java
new file mode 100644
index 00000000000..31a3c0825d9
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/HtmlServlet.java
@@ -0,0 +1,29 @@
+package com.example;
+
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.io.PrintWriter;
+
+public class HtmlServlet extends HttpServlet {
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    resp.setContentType("text/html;charset=UTF-8");
+    try (final PrintWriter writer = resp.getWriter()) {
+      writer.write(
+          "<!DOCTYPE html>"
+              + "<html lang=\"en\">"
+              + "<head>"
+              + "    <meta charset=\"UTF-8\">"
+              + "    <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">"
+              + "    <title>Hello Servlet</title>"
+              + "</head>"
+              + "<body>"
+              + "    <h1>Hello from Tomcat 9 Servlet!</h1>"
+              + "    <p>This is a demo HTML page served by Java servlet.</p>"
+              + "</body>"
+              + "</html>");
+    }
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/Main.java b/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/Main.java
new file mode 100644
index 00000000000..96a5f07cd87
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/Main.java
@@ -0,0 +1,36 @@
+package com.example;
+
+import java.io.File;
+import org.apache.catalina.Context;
+import org.apache.catalina.LifecycleException;
+import org.apache.catalina.startup.Tomcat;
+
+public class Main {
+  public static void main(String[] args) throws LifecycleException {
+    int port = 8080;
+    if (args.length == 1) {
+      port = Integer.parseInt(args[0]);
+    }
+
+    Tomcat tomcat = new Tomcat();
+    tomcat.setPort(port);
+    tomcat.getConnector(); // This is required to make Tomcat start
+    tomcat.setBaseDir(".");
+
+    // Add webapp context
+    String contextPath = "";
+    String docBase = new File(".").getAbsolutePath();
+    Context context = tomcat.addContext(contextPath, docBase);
+
+    // Add servlet programmatically
+    context.addServletContainerInitializer(
+        (c, ctx) -> {
+          ctx.addServlet("htmlServlet", new HtmlServlet()).addMapping("/html");
+          ctx.addServlet("xmlServlet", new HtmlServlet()).addMapping("/xml");
+        },
+        null);
+
+    tomcat.start();
+    tomcat.getServer().await();
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/XmlServlet.java b/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/XmlServlet.java
new file mode 100644
index 00000000000..8f8399bb408
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/XmlServlet.java
@@ -0,0 +1,25 @@
+package com.example;
+
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.io.PrintWriter;
+
+public class XmlServlet extends HttpServlet {
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    resp.setContentType("application/xml;charset=UTF-8");
+    try (PrintWriter out = resp.getWriter()) {
+      out.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
+      out.println("<response>");
+      out.println("    <status>success</status>");
+      out.println("    <message>RUM injection test</message>");
+      out.println("    <data>");
+      out.println("        <item id=\"1\">Test Item 1</item>");
+      out.println("        <item id=\"2\">Test Item 2</item>");
+      out.println("    </data>");
+      out.println("</response>");
+    }
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-10/src/test/groovy/datadog/smoketest/rum/tomcat10/Tomcat10RumSmokeTest.groovy b/dd-smoke-tests/rum/tomcat-10/src/test/groovy/datadog/smoketest/rum/tomcat10/Tomcat10RumSmokeTest.groovy
new file mode 100644
index 00000000000..54a07fe3f3e
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-10/src/test/groovy/datadog/smoketest/rum/tomcat10/Tomcat10RumSmokeTest.groovy
@@ -0,0 +1,23 @@
+package datadog.smoketest.rum.tomcat10
+
+import datadog.smoketest.rum.AbstractRumServerSmokeTest
+import datadog.trace.api.Platform
+
+class Tomcat10RumSmokeTest extends AbstractRumServerSmokeTest {
+  @Override
+  ProcessBuilder createProcessBuilder() {
+    String jarPath = System.getProperty('datadog.smoketest.rum.tomcat10.shadowJar.path')
+
+    List<String> command = []
+    command.add(javaPath())
+    command.addAll(defaultJavaProperties)
+    command.addAll(defaultRumProperties)
+    if (Platform.isJavaVersionAtLeast(17)) {
+      command.addAll((String[]) ['--add-opens', 'java.base/java.lang=ALL-UNNAMED'])
+    }
+    command.addAll(['-jar', jarPath, Integer.toString(httpPort)])
+    ProcessBuilder processBuilder = new ProcessBuilder(command)
+    processBuilder.directory(new File(buildDirectory))
+    return processBuilder
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
index d12563deead..e504bfca648 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
+++ b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
@@ -24,36 +24,4 @@ class Tomcat9RumSmokeTest extends AbstractRumServerSmokeTest {
     processBuilder.directory(new File(buildDirectory))
     return processBuilder
   }
-
-  void 'test RUM SDK injection on html'() {
-    given:
-    def url = "http://localhost:${httpPort}/html"
-    def request = new Request.Builder()
-      .url(url)
-      .get()
-      .build()
-
-    when:
-    Response response = client.newCall(request).execute()
-
-    then:
-    response.code() == 200
-    assertRumInjected(response)
-  }
-
-  void 'test RUM SDK injection skip on supported mime type'() {
-    given:
-    def url = "http://localhost:${httpPort}/xml"
-    def request = new Request.Builder()
-      .url(url)
-      .get()
-      .build()
-
-    when:
-    Response response = client.newCall(request).execute()
-
-    then:
-    response.code() == 200
-    assertRumNotInjected(response)
-  }
 }
diff --git a/settings.gradle b/settings.gradle
index c414abaf11e..3cfd335e31e 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -155,6 +155,7 @@ include ':dd-smoke-tests:ratpack-1.5'
 include ':dd-smoke-tests:resteasy'
 include ':dd-smoke-tests:rum'
 include ':dd-smoke-tests:rum:tomcat-9'
+include ':dd-smoke-tests:rum:tomcat-10'
 include ':dd-smoke-tests:spring-boot-3.0-native'
 include ':dd-smoke-tests:spring-boot-2.4-webflux'
 include ':dd-smoke-tests:spring-boot-2.5-webflux'

From a80904410e1a60a623d9bd298e4bef7479652913 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 17:02:07 +0200
Subject: [PATCH 17/36] fix(rum): Fix config

---
 internal-api/src/main/java/datadog/trace/api/Config.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/internal-api/src/main/java/datadog/trace/api/Config.java b/internal-api/src/main/java/datadog/trace/api/Config.java
index 7ed894265ee..82108612c29 100644
--- a/internal-api/src/main/java/datadog/trace/api/Config.java
+++ b/internal-api/src/main/java/datadog/trace/api/Config.java
@@ -2702,7 +2702,7 @@ PROFILING_DATADOG_PROFILER_ENABLED, isDatadogProfilerSafeInCurrentEnvironment())
   }
 
   private RumInjectorConfig parseRumConfig(ConfigProvider configProvider) {
-    if (this.rumEnabled) {
+    if (!this.rumEnabled) {
       return null;
     }
     try {

From a0bae01df3bacd9c7cbf72d7a899a96e25ffd9a3 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 17:02:24 +0200
Subject: [PATCH 18/36] fix(rum): Fix smoke tests

---
 dd-smoke-tests/rum/tomcat-10/build.gradle | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/dd-smoke-tests/rum/tomcat-10/build.gradle b/dd-smoke-tests/rum/tomcat-10/build.gradle
index fd084160e73..11052e3edb2 100644
--- a/dd-smoke-tests/rum/tomcat-10/build.gradle
+++ b/dd-smoke-tests/rum/tomcat-10/build.gradle
@@ -2,12 +2,16 @@ plugins {
   id 'com.gradleup.shadow'
 }
 
+ext {
+  minJavaVersionForTests = JavaVersion.VERSION_11
+}
+
 apply from: "$rootDir/gradle/java.gradle"
 description = 'RUM Tomcat 10 Smoke Tests'
 
 dependencies {
-  implementation 'org.apache.tomcat.embed:tomcat-embed-core:10.1.13'
-  implementation 'org.apache.tomcat.embed:tomcat-embed-jasper:10.1.13'
+  implementation 'org.apache.tomcat.embed:tomcat-embed-core:10.1.42'
+  implementation 'org.apache.tomcat.embed:tomcat-embed-jasper:10.1.42'
   implementation 'jakarta.servlet:jakarta.servlet-api:5.0.0'
 
   testImplementation project(':dd-smoke-tests:rum')
@@ -19,6 +23,17 @@ jar {
   }
 }
 
+java {
+  toolchain {
+    languageVersion = JavaLanguageVersion.of(11)
+  }
+}
+tasks.withType(JavaCompile).configureEach {
+  setJavaVersion(it, 11)
+  sourceCompatibility = JavaVersion.VERSION_11
+  targetCompatibility = JavaVersion.VERSION_11
+}
+
 tasks.withType(Test).configureEach {
   dependsOn "shadowJar"
   jvmArgs "-Ddatadog.smoketest.rum.tomcat10.shadowJar.path=${tasks.shadowJar.archiveFile.get()}"

From 42e3e6bdb31548229ea119501621347b403f0610 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Fri, 4 Jul 2025 17:02:34 +0200
Subject: [PATCH 19/36] feat(rum): Add more smoke tests

---
 .../rum/AbstractRumServerSmokeTest.groovy     | 12 +++---
 dd-smoke-tests/rum/tomcat-11/build.gradle     | 40 +++++++++++++++++++
 .../main/java/com/example/HtmlServlet.java    | 29 ++++++++++++++
 .../src/main/java/com/example/Main.java       | 36 +++++++++++++++++
 .../src/main/java/com/example/XmlServlet.java | 25 ++++++++++++
 .../rum/tomcat11/Tomcat11RumSmokeTest.groovy  | 23 +++++++++++
 .../rum/tomcat9/Tomcat9RumSmokeTest.groovy    |  2 -
 settings.gradle                               |  1 +
 8 files changed, 160 insertions(+), 8 deletions(-)
 create mode 100644 dd-smoke-tests/rum/tomcat-11/build.gradle
 create mode 100644 dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/HtmlServlet.java
 create mode 100644 dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/Main.java
 create mode 100644 dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/XmlServlet.java
 create mode 100644 dd-smoke-tests/rum/tomcat-11/src/test/groovy/datadog/smoketest/rum/tomcat11/Tomcat11RumSmokeTest.groovy

diff --git a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
index 7ee362ea605..1431c541ed4 100644
--- a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
+++ b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
@@ -17,9 +17,9 @@ class AbstractRumServerSmokeTest extends AbstractServerSmokeTest {
     given:
     def url = "http://localhost:${httpPort}/html"
     def request = new Request.Builder()
-            .url(url)
-            .get()
-            .build()
+      .url(url)
+      .get()
+      .build()
 
     when:
     Response response = client.newCall(request).execute()
@@ -33,9 +33,9 @@ class AbstractRumServerSmokeTest extends AbstractServerSmokeTest {
     given:
     def url = "http://localhost:${httpPort}/xml"
     def request = new Request.Builder()
-            .url(url)
-            .get()
-            .build()
+      .url(url)
+      .get()
+      .build()
 
     when:
     Response response = client.newCall(request).execute()
diff --git a/dd-smoke-tests/rum/tomcat-11/build.gradle b/dd-smoke-tests/rum/tomcat-11/build.gradle
new file mode 100644
index 00000000000..fd2a4049237
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-11/build.gradle
@@ -0,0 +1,40 @@
+plugins {
+  id 'com.gradleup.shadow'
+}
+
+ext {
+  minJavaVersionForTests = JavaVersion.VERSION_17
+}
+
+apply from: "$rootDir/gradle/java.gradle"
+description = 'RUM Tomcat 11 Smoke Tests'
+
+dependencies {
+  implementation 'org.apache.tomcat.embed:tomcat-embed-core:11.0.8'
+  implementation 'org.apache.tomcat.embed:tomcat-embed-jasper:11.0.8'
+  implementation 'jakarta.servlet:jakarta.servlet-api:6.0.0'
+
+  testImplementation project(':dd-smoke-tests:rum')
+}
+
+jar {
+  manifest {
+    attributes('Main-Class': 'com.example.Main')
+  }
+}
+
+java {
+  toolchain {
+    languageVersion = JavaLanguageVersion.of(17)
+  }
+}
+tasks.withType(JavaCompile).configureEach {
+  setJavaVersion(it, 17)
+  sourceCompatibility = JavaVersion.VERSION_17
+  targetCompatibility = JavaVersion.VERSION_17
+}
+
+tasks.withType(Test).configureEach {
+  dependsOn "shadowJar"
+  jvmArgs "-Ddatadog.smoketest.rum.tomcat11.shadowJar.path=${tasks.shadowJar.archiveFile.get()}"
+}
diff --git a/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/HtmlServlet.java b/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/HtmlServlet.java
new file mode 100644
index 00000000000..31a3c0825d9
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/HtmlServlet.java
@@ -0,0 +1,29 @@
+package com.example;
+
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.io.PrintWriter;
+
+public class HtmlServlet extends HttpServlet {
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    resp.setContentType("text/html;charset=UTF-8");
+    try (final PrintWriter writer = resp.getWriter()) {
+      writer.write(
+          "<!DOCTYPE html>"
+              + "<html lang=\"en\">"
+              + "<head>"
+              + "    <meta charset=\"UTF-8\">"
+              + "    <meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\">"
+              + "    <title>Hello Servlet</title>"
+              + "</head>"
+              + "<body>"
+              + "    <h1>Hello from Tomcat 9 Servlet!</h1>"
+              + "    <p>This is a demo HTML page served by Java servlet.</p>"
+              + "</body>"
+              + "</html>");
+    }
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/Main.java b/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/Main.java
new file mode 100644
index 00000000000..96a5f07cd87
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/Main.java
@@ -0,0 +1,36 @@
+package com.example;
+
+import java.io.File;
+import org.apache.catalina.Context;
+import org.apache.catalina.LifecycleException;
+import org.apache.catalina.startup.Tomcat;
+
+public class Main {
+  public static void main(String[] args) throws LifecycleException {
+    int port = 8080;
+    if (args.length == 1) {
+      port = Integer.parseInt(args[0]);
+    }
+
+    Tomcat tomcat = new Tomcat();
+    tomcat.setPort(port);
+    tomcat.getConnector(); // This is required to make Tomcat start
+    tomcat.setBaseDir(".");
+
+    // Add webapp context
+    String contextPath = "";
+    String docBase = new File(".").getAbsolutePath();
+    Context context = tomcat.addContext(contextPath, docBase);
+
+    // Add servlet programmatically
+    context.addServletContainerInitializer(
+        (c, ctx) -> {
+          ctx.addServlet("htmlServlet", new HtmlServlet()).addMapping("/html");
+          ctx.addServlet("xmlServlet", new HtmlServlet()).addMapping("/xml");
+        },
+        null);
+
+    tomcat.start();
+    tomcat.getServer().await();
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/XmlServlet.java b/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/XmlServlet.java
new file mode 100644
index 00000000000..8f8399bb408
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/XmlServlet.java
@@ -0,0 +1,25 @@
+package com.example;
+
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.io.PrintWriter;
+
+public class XmlServlet extends HttpServlet {
+  @Override
+  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
+    resp.setContentType("application/xml;charset=UTF-8");
+    try (PrintWriter out = resp.getWriter()) {
+      out.println("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
+      out.println("<response>");
+      out.println("    <status>success</status>");
+      out.println("    <message>RUM injection test</message>");
+      out.println("    <data>");
+      out.println("        <item id=\"1\">Test Item 1</item>");
+      out.println("        <item id=\"2\">Test Item 2</item>");
+      out.println("    </data>");
+      out.println("</response>");
+    }
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-11/src/test/groovy/datadog/smoketest/rum/tomcat11/Tomcat11RumSmokeTest.groovy b/dd-smoke-tests/rum/tomcat-11/src/test/groovy/datadog/smoketest/rum/tomcat11/Tomcat11RumSmokeTest.groovy
new file mode 100644
index 00000000000..993b69dbe66
--- /dev/null
+++ b/dd-smoke-tests/rum/tomcat-11/src/test/groovy/datadog/smoketest/rum/tomcat11/Tomcat11RumSmokeTest.groovy
@@ -0,0 +1,23 @@
+package datadog.smoketest.rum.tomcat11
+
+import datadog.smoketest.rum.AbstractRumServerSmokeTest
+import datadog.trace.api.Platform
+
+class Tomcat11RumSmokeTest extends AbstractRumServerSmokeTest {
+  @Override
+  ProcessBuilder createProcessBuilder() {
+    String jarPath = System.getProperty('datadog.smoketest.rum.tomcat11.shadowJar.path')
+
+    List<String> command = []
+    command.add(javaPath())
+    command.addAll(defaultJavaProperties)
+    command.addAll(defaultRumProperties)
+    if (Platform.isJavaVersionAtLeast(17)) {
+      command.addAll((String[]) ['--add-opens', 'java.base/java.lang=ALL-UNNAMED'])
+    }
+    command.addAll(['-jar', jarPath, Integer.toString(httpPort)])
+    ProcessBuilder processBuilder = new ProcessBuilder(command)
+    processBuilder.directory(new File(buildDirectory))
+    return processBuilder
+  }
+}
diff --git a/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
index e504bfca648..8555fb773b9 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
+++ b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
@@ -2,8 +2,6 @@ package datadog.smoketest.rum.tomcat9
 
 import datadog.smoketest.rum.AbstractRumServerSmokeTest
 import datadog.trace.api.Platform
-import okhttp3.Request
-import okhttp3.Response
 
 class Tomcat9RumSmokeTest extends AbstractRumServerSmokeTest {
 
diff --git a/settings.gradle b/settings.gradle
index 3cfd335e31e..34585048c17 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -156,6 +156,7 @@ include ':dd-smoke-tests:resteasy'
 include ':dd-smoke-tests:rum'
 include ':dd-smoke-tests:rum:tomcat-9'
 include ':dd-smoke-tests:rum:tomcat-10'
+include ':dd-smoke-tests:rum:tomcat-11'
 include ':dd-smoke-tests:spring-boot-3.0-native'
 include ':dd-smoke-tests:spring-boot-2.4-webflux'
 include ':dd-smoke-tests:spring-boot-2.5-webflux'

From 4f0b6466160368c5289502ab2c20456ef24a535d Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Mon, 7 Jul 2025 09:00:20 +0200
Subject: [PATCH 20/36] feat(rum): Simplify config to remove dynamic init

RUM injection remote config is not dynamic as other products
---
 .../RumHttpServletResponseWrapper.java        |  6 +-
 .../servlet3/Servlet3Advice.java              |  2 +-
 .../datadog/trace/api/rum/RumInjector.java    | 96 +++++++++++--------
 3 files changed, 63 insertions(+), 41 deletions(-)

diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
index 389bf77eddf..826b38355d1 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
@@ -8,12 +8,14 @@
 import javax.servlet.http.HttpServletResponseWrapper;
 
 public class RumHttpServletResponseWrapper extends HttpServletResponseWrapper {
+  private final RumInjector rumInjector;
   private ServletOutputStream outputStream;
   private PrintWriter printWriter;
   private boolean shouldInject;
 
   public RumHttpServletResponseWrapper(HttpServletResponse response) {
     super(response);
+    this.rumInjector = RumInjector.get();
   }
 
   @Override
@@ -29,8 +31,8 @@ public ServletOutputStream getOutputStream() throws IOException {
       outputStream =
           new WrappedServletOutputStream(
               super.getOutputStream(),
-              RumInjector.getMarker(encoding),
-              RumInjector.getSnippet(encoding),
+              rumInjector.getMarker(encoding),
+              rumInjector.getSnippet(encoding),
               this::onInjected);
     }
     return outputStream;
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Advice.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Advice.java
index 8ed6322fe4d..2ffacb26bea 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Advice.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/Servlet3Advice.java
@@ -45,7 +45,7 @@ public static boolean onEnter(
     final HttpServletRequest httpServletRequest = (HttpServletRequest) request;
     HttpServletResponse httpServletResponse = (HttpServletResponse) response;
 
-    if (RumInjector.isEnabled() && httpServletRequest.getAttribute(DD_RUM_INJECTED) == null) {
+    if (RumInjector.get().isEnabled() && httpServletRequest.getAttribute(DD_RUM_INJECTED) == null) {
       httpServletRequest.setAttribute(DD_RUM_INJECTED, Boolean.TRUE);
       httpServletResponse = new RumHttpServletResponseWrapper(httpServletResponse);
       response = httpServletResponse;
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
index 25e337f67ec..36b84d62ac1 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
@@ -4,23 +4,11 @@
 import datadog.trace.api.cache.DDCache;
 import datadog.trace.api.cache.DDCaches;
 import java.util.function.Function;
+import javax.annotation.Nullable;
 
 public final class RumInjector {
-  private static volatile boolean initialized = false;
-  private static volatile boolean enabled;
-  private static volatile String snippet;
-
+  private static final RumInjector INSTANCE = new RumInjector(Config.get());
   private static final String MARKER = "</head>";
-  private static final DDCache<String, byte[]> SNIPPET_CACHE = DDCaches.newFixedSizeCache(16);
-  private static final DDCache<String, byte[]> MARKER_CACHE = DDCaches.newFixedSizeCache(16);
-  private static final Function<String, byte[]> SNIPPET_ADDER =
-      charset -> {
-        try {
-          return snippet.getBytes(charset);
-        } catch (Throwable t) {
-          return null;
-        }
-      };
   private static final Function<String, byte[]> MARKER_ADDER =
       charset -> {
         try {
@@ -30,44 +18,76 @@ public final class RumInjector {
         }
       };
 
+  private final boolean enabled;
+  private final String snippet;
+
+  private final DDCache<String, byte[]> snippetCache;
+  private final DDCache<String, byte[]> markerCache;
+  private final Function<String, byte[]> snippetAdder;
+
+  RumInjector(Config config) {
+    boolean rumEnabled = config.isRumEnabled();
+    RumInjectorConfig injectorConfig = config.getRumInjectorConfig();
+    // If both RUM is enabled and injector config is valid
+    if (rumEnabled && injectorConfig != null) {
+      this.enabled = true;
+      this.snippet = injectorConfig.getSnippet();
+      this.snippetCache = DDCaches.newFixedSizeCache(16);
+      this.markerCache = DDCaches.newFixedSizeCache(16);
+      this.snippetAdder =
+          charset -> {
+            try {
+              return snippet.getBytes(charset);
+            } catch (Throwable t) {
+              return null;
+            }
+          };
+    } else {
+      this.enabled = false;
+      this.snippet = null;
+      this.snippetCache = null;
+      this.markerCache = null;
+      this.snippetAdder = null;
+    }
+  }
+
+  public static RumInjector get() {
+    return INSTANCE;
+  }
+
   /**
-   * Check whether RUM injection is enabled and ready to inject.
+   * Checks whether RUM injection is enabled and ready to inject.
    *
    * @return {@code true} if enabled, {@code otherwise}.
    */
-  public static boolean isEnabled() {
-    if (!initialized) {
-      Config config = Config.get();
-      boolean rumEnabled = config.isRumEnabled();
-      RumInjectorConfig injectorConfig = config.getRumInjectorConfig();
-      if (rumEnabled && injectorConfig != null) {
-        enabled = true;
-        snippet = injectorConfig.getSnippet();
-      } else {
-        enabled = false;
-        snippet = null;
-      }
-      initialized = true;
-    }
-    return enabled;
+  public boolean isEnabled() {
+    return this.enabled;
   }
 
   /**
-   * Get the HTML snippet to inject RUM SDK
+   * Gets the HTML snippet to inject RUM SDK
    *
-   * @return The HTML snippet to inject, {@code null} if RUM injection is disabled to inject.
+   * @return The HTML snippet to inject, {@code null} if RUM injection is disabled.
    */
-  public static byte[] getSnippet(String encoding) {
-    if (!isEnabled()) {
+  @Nullable
+  public byte[] getSnippet(String encoding) {
+    if (!this.enabled) {
       return null;
     }
-    return SNIPPET_CACHE.computeIfAbsent(encoding, SNIPPET_ADDER);
+    return this.snippetCache.computeIfAbsent(encoding, this.snippetAdder);
   }
 
-  public static byte[] getMarker(String encoding) {
-    if (!isEnabled()) {
+  /**
+   * Gets the marker bytes to inject RUM SDK after.
+   *
+   * @param encoding The encoding to get the marker bytes from.
+   * @return The marker bytes, {@code null} if RUM injection is disabled.
+   */
+  @Nullable
+  public byte[] getMarker(String encoding) {
+    if (!this.enabled) {
       return null;
     }
-    return MARKER_CACHE.computeIfAbsent(encoding, MARKER_ADDER);
+    return this.markerCache.computeIfAbsent(encoding, MARKER_ADDER);
   }
 }

From 1c49a79887c0f54301324920f9cec19fd3181672 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Fri, 4 Jul 2025 14:56:38 +0200
Subject: [PATCH 21/36] Use runnable for callback

---
 .../instrumentation/buffer/InjectingPipeOutputStream.java  | 7 +++----
 .../servlet3/RumHttpServletResponseWrapper.java            | 2 +-
 .../servlet3/WrappedServletOutputStream.java               | 6 +-----
 3 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
index ea3322103f7..ec64e51d773 100644
--- a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
+++ b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
@@ -3,7 +3,6 @@
 import java.io.FilterOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
-import java.util.function.Consumer;
 
 /**
  * A circular buffer that holds n+1 bytes and with a lookbehind buffer of n bytes. The first time
@@ -17,7 +16,7 @@ public class InjectingPipeOutputStream extends FilterOutputStream {
   private final byte[] contentToInject;
   private boolean found = false;
   private int matchingPos = 0;
-  private final Consumer<Void> onContentInjected;
+  private final Runnable onContentInjected;
 
   /**
    * @param downstream the delegate output stream
@@ -29,7 +28,7 @@ public InjectingPipeOutputStream(
       final OutputStream downstream,
       final byte[] marker,
       final byte[] contentToInject,
-      final Consumer<Void> onContentInjected) {
+      final Runnable onContentInjected) {
     super(downstream);
     this.marker = marker;
     this.lookbehind = new byte[marker.length + 1];
@@ -52,7 +51,7 @@ public void write(int b) throws IOException {
         found = true;
         out.write(contentToInject);
         if (onContentInjected != null) {
-          onContentInjected.accept(null);
+          onContentInjected.run();
         }
         drain((pos + 1) % lookbehind.length, marker.length);
         return;
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
index 826b38355d1..8d8aa1d6971 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
@@ -70,7 +70,7 @@ public void resetBuffer() {
     super.resetBuffer();
   }
 
-  public void onInjected(Void ignored) {
+  public void onInjected() {
     try {
       setHeader("x-datadog-rum-injected", "1");
     } catch (Throwable ignored2) {
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
index 32323a1cfff..31635a886e0 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
@@ -5,7 +5,6 @@
 import java.io.IOException;
 import java.io.OutputStream;
 import java.lang.invoke.MethodHandle;
-import java.util.function.Consumer;
 import javax.servlet.ServletOutputStream;
 import javax.servlet.WriteListener;
 
@@ -26,10 +25,7 @@ private static final MethodHandle getMh(final String name) {
   }
 
   public WrappedServletOutputStream(
-      ServletOutputStream delegate,
-      byte[] marker,
-      byte[] contentToInject,
-      Consumer<Void> onInjected) {
+      ServletOutputStream delegate, byte[] marker, byte[] contentToInject, Runnable onInjected) {
     this.filtered = new InjectingPipeOutputStream(delegate, marker, contentToInject, onInjected);
     this.delegate = delegate;
   }

From 24c817e49c8be8afb0cb1b00e54029cb55bc8866 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Fri, 4 Jul 2025 17:06:36 +0200
Subject: [PATCH 22/36] improve pipe perfs

---
 .../InjectingPipeOutputStreamBenchmark.java   |  5 +
 .../buffer/InjectingPipeOutputStream.java     | 95 +++++++++++++++----
 2 files changed, 83 insertions(+), 17 deletions(-)

diff --git a/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java b/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java
index 2432469949c..fed7bfe9d77 100644
--- a/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java
+++ b/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java
@@ -21,6 +21,11 @@
 import org.openjdk.jmh.annotations.State;
 import org.openjdk.jmh.annotations.Warmup;
 
+/*
+ * Benchmark                                       Mode  Cnt   Score   Error  Units
+ * InjectingPipeOutputStreamBenchmark.withPipe     avgt    2  16.802          us/op
+ * InjectingPipeOutputStreamBenchmark.withoutPipe  avgt    2  13.001          us/op
+ */
 @State(Scope.Benchmark)
 @Warmup(iterations = 1, time = 30, timeUnit = SECONDS)
 @Measurement(iterations = 2, time = 30, timeUnit = SECONDS)
diff --git a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
index ec64e51d773..18d135d77ad 100644
--- a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
+++ b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
@@ -5,8 +5,8 @@
 import java.io.OutputStream;
 
 /**
- * A circular buffer that holds n+1 bytes and with a lookbehind buffer of n bytes. The first time
- * that the latest n bytes matches the marker, a content is injected before.
+ * A circular buffer with a lookbehind buffer of n bytes. The first time that the latest n bytes
+ * matches the marker, a content is injected before.
  */
 public class InjectingPipeOutputStream extends FilterOutputStream {
   private final byte[] lookbehind;
@@ -43,47 +43,108 @@ public void write(int b) throws IOException {
       out.write(b);
       return;
     }
+
+    if (bufferFilled) {
+      out.write(lookbehind[pos]);
+    }
+
     lookbehind[pos] = (byte) b;
     pos = (pos + 1) % lookbehind.length;
 
+    if (!bufferFilled) {
+      bufferFilled = pos == 0;
+    }
+
     if (marker[matchingPos++] == b) {
       if (matchingPos == marker.length) {
         found = true;
+        out.write(lookbehind[pos]);
+        pos = (pos + 1) % lookbehind.length;
         out.write(contentToInject);
         if (onContentInjected != null) {
           onContentInjected.run();
         }
-        drain((pos + 1) % lookbehind.length, marker.length);
-        return;
+        drain(lookbehind.length - 1);
       }
     } else {
       matchingPos = 0;
     }
+  }
 
-    if (!bufferFilled) {
-      bufferFilled = pos == lookbehind.length - 1;
+  @Override
+  public void write(byte[] b, int off, int len) throws IOException {
+    if (found) {
+      out.write(b, off, len);
+      return;
     }
+    if (len > marker.length * 2) {
+      int idx = arrayContains(b, marker);
+      if (idx >= 0) {
+        // we have a full match. just write everything
+        found = true;
+        drain(lookbehind.length);
+        out.write(b, off, idx);
+        out.write(contentToInject);
+        if (onContentInjected != null) {
+          onContentInjected.run();
+        }
+        out.write(b, off + idx, len - idx);
+      } else {
+        // we don't have a full match. write everything in a bulk except the lookbehind buffer
+        // sequentially
+        for (int i = off; i < off + marker.length; i++) {
+          write(b[i]);
+        }
+        drain(lookbehind.length);
+        out.write(b, off + marker.length, len - marker.length * 2);
+        for (int i = len - marker.length; i < len; i++) {
+          write(b[i]);
+        }
+        drain(lookbehind.length);
+      }
+    } else {
+      // use slow path because the length to write is small and within the lookbehind buffer size
+      super.write(b, off, len);
+    }
+  }
 
-    if (bufferFilled) {
-      super.write(lookbehind[(pos + 1) % lookbehind.length]);
+  private int arrayContains(byte[] array, byte[] search) {
+    for (int i = 0; i < array.length - search.length; i++) {
+      if (array[i] == search[0]) {
+        boolean found = true;
+        int k = i;
+        for (int j = 1; j < search.length; j++) {
+          k++;
+          if (array[k] != search[j]) {
+            found = false;
+            break;
+          }
+        }
+        if (found) {
+          return i;
+        }
+      }
     }
+    return -1;
   }
 
-  private void drain(int from, int size) throws IOException {
-    while (size-- > 0) {
-      super.write(Character.valueOf((char) lookbehind[from]));
-      from = (from + 1) % lookbehind.length;
+  private void drain(int len) throws IOException {
+    if (bufferFilled) {
+      for (int i = 0; i < len; i++) {
+        out.write(lookbehind[(pos + i) % lookbehind.length]);
+      }
+    } else {
+      out.write(this.lookbehind, 0, pos);
     }
+    pos = 0;
+    matchingPos = 0;
+    bufferFilled = false;
   }
 
   @Override
   public void close() throws IOException {
     if (!found) {
-      if (bufferFilled) {
-        drain((pos + 2) % lookbehind.length, marker.length - 1);
-      } else {
-        drain(0, pos);
-      }
+      drain(lookbehind.length);
     }
     super.close();
   }

From 4beb3a862e151d1d87feddf7666e317c1b89f1d0 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Mon, 7 Jul 2025 11:22:51 +0200
Subject: [PATCH 23/36] feat(rum): Add injector and config unit tests

---
 .../datadog/trace/api/ConfigDefaults.java     |   1 +
 .../trace/api/rum/RumInjectorConfig.java      |   4 +-
 .../trace/api/rum/RumInjectorTest.groovy      |  62 +++++
 .../trace/api/rum/RumInjectorConfigTest.java  | 224 ++++++++++++++++++
 4 files changed, 289 insertions(+), 2 deletions(-)
 create mode 100644 internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy
 create mode 100644 internal-api/src/test/java/datadog/trace/api/rum/RumInjectorConfigTest.java

diff --git a/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java b/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
index 3f79a2b9cb3..ac81b2ce326 100644
--- a/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
+++ b/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
@@ -241,6 +241,7 @@ public final class ConfigDefaults {
   static final int DEFAULT_TELEMETRY_DEPENDENCY_RESOLUTION_QUEUE_SIZE = 100000;
 
   static final boolean DEFAULT_RUM_ENABLED = false;
+  public static final String DEFAULT_RUM_SITE = DEFAULT_SITE;
   static final int DEFAULT_RUM_MAJOR_VERSION = 6;
 
   static final boolean DEFAULT_SSI_INJECTION_FORCE = false;
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
index c1d1ca6c8bb..e0a56d310f5 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
@@ -1,5 +1,6 @@
 package datadog.trace.api.rum;
 
+import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_SITE;
 import static java.util.Locale.ROOT;
 
 import datadog.json.JsonWriter;
@@ -8,7 +9,6 @@
 import javax.annotation.Nullable;
 
 public class RumInjectorConfig {
-  private static final String DEFAULT_SITE = "datadoghq.com";
   private static final String GOV_CLOUD_SITE = "ddog-gov.com";
   private static final Map<String, String> REGIONS = new HashMap<>();
 
@@ -76,7 +76,7 @@ public RumInjectorConfig(
     }
     this.clientToken = clientToken;
     if (site == null || site.isEmpty()) {
-      this.site = DEFAULT_SITE;
+      this.site = DEFAULT_RUM_SITE;
     } else if (validateSite(site)) {
       this.site = site;
     } else {
diff --git a/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy b/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy
new file mode 100644
index 00000000000..4c2d9f9ad37
--- /dev/null
+++ b/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy
@@ -0,0 +1,62 @@
+package datadog.trace.api.rum
+
+import datadog.trace.api.Config
+import datadog.trace.test.util.DDSpecification
+
+import java.nio.charset.StandardCharsets
+
+import static org.mockito.Mockito.mock
+import static org.mockito.Mockito.when
+
+class RumInjectorTest extends DDSpecification {
+  public static final String UTF8 = StandardCharsets.UTF_8.name()
+
+  void 'disabled injector'(){
+    setup:
+    Config config = mock(Config)
+    RumInjector injector
+
+    when:
+    when(config.isRumEnabled()).thenReturn(false)
+    injector = new RumInjector(config)
+
+    then:
+    !injector.isEnabled()
+    injector.getMarker(UTF8) == null
+    injector.getSnippet(UTF8) == null
+  }
+
+  void 'invalid config injector'() {
+    setup:
+    Config config = mock(Config)
+    RumInjector injector
+
+    when:
+    when(config.isRumEnabled()).thenReturn(true)
+    when(config.rumInjectorConfig).thenReturn(null)
+    injector = new RumInjector(config)
+
+    then:
+    !injector.isEnabled()
+    injector.getMarker(UTF8) == null
+    injector.getSnippet(UTF8) == null
+  }
+
+  void 'enabled injector'() {
+    setup:
+    Config config = mock(Config)
+    def injectorConfig = mock(RumInjectorConfig)
+    RumInjector injector
+
+    when:
+    when(config.isRumEnabled()).thenReturn(true)
+    when(config.rumInjectorConfig).thenReturn(injectorConfig)
+    when(injectorConfig.snippet).thenReturn("<script></script>")
+    injector = new RumInjector(config)
+
+    then:
+    injector.isEnabled()
+    injector.getMarker(UTF8) != null
+    injector.getSnippet(UTF8) != null
+  }
+}
diff --git a/internal-api/src/test/java/datadog/trace/api/rum/RumInjectorConfigTest.java b/internal-api/src/test/java/datadog/trace/api/rum/RumInjectorConfigTest.java
new file mode 100644
index 00000000000..df4a57bacae
--- /dev/null
+++ b/internal-api/src/test/java/datadog/trace/api/rum/RumInjectorConfigTest.java
@@ -0,0 +1,224 @@
+package datadog.trace.api.rum;
+
+import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_SITE;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import datadog.trace.api.rum.RumInjectorConfig.PrivacyLevel;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class RumInjectorConfigTest {
+
+  @ParameterizedTest
+  @CsvSource(
+      value = {
+        // spotless:off
+      // Minimal configuration ID
+      "appId | token | null              | null | null | 6 | null | null  | null  | null  | null | null  | null  | remote-config-id",
+      // Using site
+      "appId | token | datadoghq.com     | null | null | 6 | null | null  | null  | null  | null | null  | null  | remote-config-id",
+      "appId | token | us3.datadoghq.com | null | null | 6 | null | null  | null  | null  | null | null  | null  | remote-config-id",
+      "appId | token | us5.datadoghq.com | null | null | 6 | null | null  | null  | null  | null | null  | null  | remote-config-id",
+      "appId | token | datadoghq.eu      | null | null | 6 | null | null  | null  | null  | null | null  | null  | remote-config-id",
+      "appId | token | ap1.datadoghq.com | null | null | 6 | null | null  | null  | null  | null | null  | null  | remote-config-id",
+      // Using service
+      "appId | token | null              | svc  | null | 6 | null | null  | null  | null  | null | null  | null  | remote-config-id",
+      // Using env
+      "appId | token | null              | null | prod | 6 | null | null  | null  | null  | null | null  | null  | remote-config-id",
+      // Using major version
+      "appId | token | null              | null | null | 5 | null | null  | null  | null  | null | null  | null  | remote-config-id",
+      // Using version
+      "appId | token | null              | null | null | 6 | 1.23 | null  | null  | null  | null | null  | null  | remote-config-id",
+      // Using track user interactions
+      "appId | token | null              | null | null | 6 | 1.23 | true  | null  | null  | null | null  | null  | remote-config-id",
+      "appId | token | null              | null | null | 6 | 1.23 | false | null  | null  | null | null  | null  | remote-config-id",
+      // Using track resources
+      "appId | token | null              | null | null | 6 | 1.23 | null  | true  | null  | null | null  | null  | remote-config-id",
+      "appId | token | null              | null | null | 6 | 1.23 | null  | false | null  | null | null  | null  | remote-config-id",
+      // Using track long task
+      "appId | token | null              | null | null | 6 | 1.23 | null  | null  | true  | null | null  | null  | remote-config-id",
+      "appId | token | null              | null | null | 6 | 1.23 | null  | null  | false | null | null  | null  | remote-config-id",
+      // Using default privacy level
+      "appId | token | null              | null | null | 6 | 1.23 | null  | null  | null  | ALLOW           | null  | null  | remote-config-id",
+      "appId | token | null              | null | null | 6 | 1.23 | null  | null  | null  | MASK            | null  | null  | remote-config-id",
+      "appId | token | null              | null | null | 6 | 1.23 | null  | null  | null  | MASK_USER_INPUT | null  | null  | remote-config-id",
+      // Using session sample rate
+      "appId | token | null              | null | null | 6 | null | null  | null  | null  | null            | 0     | null  | remote-config-id",
+      "appId | token | null              | null | null | 6 | null | null  | null  | null  | null            | 1     | null  | remote-config-id",
+      "appId | token | null              | null | null | 6 | null | null  | null  | null  | null            | 25.5  | null  | remote-config-id",
+      "appId | token | null              | null | null | 6 | null | null  | null  | null  | null            | 100   | null  | remote-config-id",
+      // Using session replay sample rate
+      "appId | token | null              | null | null | 6 | null | null  | null  | null  | null            | null  | 0     | remote-config-id",
+      "appId | token | null              | null | null | 6 | null | null  | null  | null  | null            | null  | 1     | remote-config-id",
+      "appId | token | null              | null | null | 6 | null | null  | null  | null  | null            | null  | 25.5  | remote-config-id",
+      "appId | token | null              | null | null | 6 | null | null  | null  | null  | null            | null  | 100   | remote-config-id",
+      // spotless:on
+      },
+      delimiterString = "|",
+      nullValues = "null")
+  void testSnippet(
+      String applicationId,
+      String clientToken,
+      String site,
+      String service,
+      String env,
+      int majorVersion,
+      String version,
+      Boolean trackUserInteractions,
+      Boolean trackResources,
+      Boolean trackLongTask,
+      PrivacyLevel defaultPrivacyLevel,
+      Float sessionSampleRate,
+      Float sessionReplaySampleRate,
+      String remoteConfigurationId) {
+    RumInjectorConfig injectorConfig =
+        new RumInjectorConfig(
+            applicationId,
+            clientToken,
+            site,
+            service,
+            env,
+            majorVersion,
+            version,
+            trackUserInteractions,
+            trackResources,
+            trackLongTask,
+            defaultPrivacyLevel,
+            sessionSampleRate,
+            sessionReplaySampleRate,
+            remoteConfigurationId);
+
+    String jsonPayload = injectorConfig.jsonPayload();
+    assertTrue(jsonPayload.contains(applicationId));
+    assertTrue(jsonPayload.contains("site"));
+    assertTrue(jsonPayload.contains(clientToken));
+    if (site == null) {
+      assertTrue(jsonPayload.contains(DEFAULT_RUM_SITE));
+    } else {
+      assertTrue(jsonPayload.contains(site));
+    }
+    if (service == null) {
+      assertFalse(jsonPayload.contains("service"));
+    } else {
+      assertTrue(jsonPayload.contains("service"));
+      assertTrue(jsonPayload.contains(service));
+    }
+    if (env == null) {
+      assertFalse(jsonPayload.contains("env"));
+    } else {
+      assertTrue(jsonPayload.contains("env"));
+      assertTrue(jsonPayload.contains(env));
+    }
+    if (version == null) {
+      assertFalse(jsonPayload.contains("version"));
+    } else {
+      assertTrue(jsonPayload.contains("version"));
+      assertTrue(jsonPayload.contains(version));
+    }
+    if (trackUserInteractions == null) {
+      assertFalse(jsonPayload.contains("trackUserInteractions"));
+    } else {
+      assertTrue(jsonPayload.contains("trackUserInteractions"));
+    }
+    if (trackResources == null) {
+      assertFalse(jsonPayload.contains("trackResources"));
+    } else {
+      assertTrue(jsonPayload.contains("trackResources"));
+    }
+    if (trackLongTask == null) {
+      assertFalse(jsonPayload.contains("trackLongTask"));
+    } else {
+      assertTrue(jsonPayload.contains("trackLongTask"));
+    }
+    if (defaultPrivacyLevel == null) {
+      assertFalse(jsonPayload.contains("defaultPrivacyLevel"));
+    } else {
+      assertTrue(jsonPayload.contains("defaultPrivacyLevel"));
+      assertTrue(jsonPayload.contains(defaultPrivacyLevel.toJson()));
+    }
+    if (sessionSampleRate == null) {
+      assertFalse(jsonPayload.contains("sessionSampleRate"));
+    } else {
+      assertTrue(jsonPayload.contains("sessionSampleRate"));
+    }
+    if (sessionReplaySampleRate == null) {
+      assertFalse(jsonPayload.contains("sessionReplaySampleRate"));
+    } else {
+      assertTrue(jsonPayload.contains("sessionReplaySampleRate"));
+    }
+    if (remoteConfigurationId == null) {
+      assertFalse(jsonPayload.contains("remoteConfigurationId"));
+    } else {
+      assertTrue(jsonPayload.contains("remoteConfigurationId"));
+      assertTrue(jsonPayload.contains(remoteConfigurationId));
+    }
+  }
+
+  @ParameterizedTest
+  @CsvSource(
+      value = {
+        // spotless:off
+      // Invalid application ID
+      "null  | token | datadoghq.com | null | null | 6 | null | true | true | true | null | null  | null  | remote-config-id",
+      "''    | token | datadoghq.com | null | null | 6 | null | true | true | true | null | null  | null  | remote-config-id",
+      // Invalid client token
+      "appId | null  | datadoghq.com | null | null | 6 | null | true | true | true | null | null  | null  | remote-config-id",
+      "appId | ''    | datadoghq.com | null | null | 6 | null | true | true | true | null | null  | null  | remote-config-id",
+      // Invalid site
+      "appId | token | other.com     | null | null | 6 | null | true | true | true | null | null  | null  | remote-config-id",
+      // Invalid major version
+      "appId | token | datadoghq.com | null | null | 4 | null | true | true | true | null | null  | null  | remote-config-id",
+      "appId | token | datadoghq.com | null | null | 7 | null | true | true | true | null | null  | null  | remote-config-id",
+      // Invalid session sample rate
+      "appId | token | datadoghq.com | null | null | 6 | null | true | true | true | null | -1    | null  | remote-config-id",
+      "appId | token | datadoghq.com | null | null | 6 | null | true | true | true | null | -0.1  | null  | remote-config-id",
+      "appId | token | datadoghq.com | null | null | 6 | null | true | true | true | null | 101   | null  | remote-config-id",
+      "appId | token | datadoghq.com | null | null | 6 | null | true | true | true | null | 100.1 | null  | remote-config-id",
+      // Invalid session replay sample rate
+      "appId | token | datadoghq.com | null | null | 6 | null | true | true | true | null | null  | -1    | remote-config-id",
+      "appId | token | datadoghq.com | null | null | 6 | null | true | true | true | null | null  | -0.1  | remote-config-id",
+      "appId | token | datadoghq.com | null | null | 6 | null | true | true | true | null | null  | 101   | remote-config-id",
+      "appId | token | datadoghq.com | null | null | 6 | null | true | true | true | null | null  | 100.1 | remote-config-id",
+      // Invalid rates and remote configuration id
+      "appId | token | datadoghq.com | null | null | 6 | null | true | true | true | null | null  | null  | null",
+      // spotless:on
+      },
+      delimiterString = "|",
+      nullValues = "null")
+  void testInvalidConfig(
+      String applicationId,
+      String clientToken,
+      String site,
+      String service,
+      String env,
+      int majorVersion,
+      String version,
+      boolean trackUserInteractions,
+      boolean trackResources,
+      boolean trackLongTask,
+      PrivacyLevel defaultPrivacyLevel,
+      Float sessionSampleRate,
+      Float sessionReplaySampleRate,
+      String remoteConfigurationId) {
+    assertThrows(
+        IllegalArgumentException.class,
+        () ->
+            new RumInjectorConfig(
+                applicationId,
+                clientToken,
+                site,
+                service,
+                env,
+                majorVersion,
+                version,
+                trackUserInteractions,
+                trackResources,
+                trackLongTask,
+                defaultPrivacyLevel,
+                sessionSampleRate,
+                sessionReplaySampleRate,
+                remoteConfigurationId));
+  }
+}

From 23f65fb16ed99c52abaee38efade3741d4dc1fc9 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Mon, 7 Jul 2025 11:47:34 +0200
Subject: [PATCH 24/36] Add rum injection for jakarta servlet

---
 .../src/test/groovy/Jetty11Test.groovy        | 17 ++++
 .../instrumentation/jetty-12/build.gradle     |  2 +
 .../src/test/ee10/groovy/Jetty12Test.groovy   | 19 ++++
 .../RumHttpServletResponseWrapper.java        |  3 +-
 .../src/test/groovy/JettyServlet3Test.groovy  | 66 +-------------
 .../servlet3/RumServlet.groovy                | 43 ++++++++++
 .../JakartaServletInstrumentation.java        | 34 +++++++-
 .../RumHttpServletResponseWrapper.java        | 86 +++++++++++++++++++
 .../servlet5/WrappedServletOutputStream.java  | 53 ++++++++++++
 .../servlet5/RumServlet.groovy                | 43 ++++++++++
 .../groovy/TomcatServletTest.groovy           | 22 ++++-
 .../agent/test/base/HttpServerTest.groovy     | 33 +++++++
 12 files changed, 350 insertions(+), 71 deletions(-)
 create mode 100644 dd-java-agent/instrumentation/servlet/request-3/src/testFixtures/groovy/datadog/trace/instrumentation/servlet3/RumServlet.groovy
 create mode 100644 dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
 create mode 100644 dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/WrappedServletOutputStream.java
 create mode 100644 dd-java-agent/instrumentation/servlet/request-5/src/testFixtures/groovy/datadog/trace/instrumentation/servlet5/RumServlet.groovy

diff --git a/dd-java-agent/instrumentation/jetty-11/src/test/groovy/Jetty11Test.groovy b/dd-java-agent/instrumentation/jetty-11/src/test/groovy/Jetty11Test.groovy
index d7fb8e79b50..f4da48aaaf3 100644
--- a/dd-java-agent/instrumentation/jetty-11/src/test/groovy/Jetty11Test.groovy
+++ b/dd-java-agent/instrumentation/jetty-11/src/test/groovy/Jetty11Test.groovy
@@ -1,7 +1,9 @@
 import datadog.trace.agent.test.base.HttpServer
 import datadog.trace.agent.test.base.HttpServerTest
 import datadog.trace.agent.test.naming.TestingGenericHttpNamingConventions
+import datadog.trace.instrumentation.servlet5.HtmlRumServlet
 import datadog.trace.instrumentation.servlet5.TestServlet5
+import datadog.trace.instrumentation.servlet5.XmlRumServlet
 import org.eclipse.jetty.server.Handler
 import org.eclipse.jetty.server.Server
 
@@ -103,3 +105,18 @@ class Jetty11V1ForkedTest extends Jetty11Test implements TestingGenericHttpNamin
     true
   }
 }
+
+class JettyRumInjectionForkedTest extends Jetty11V0ForkedTest {
+  @Override
+  boolean testRumInjection() {
+    true
+  }
+
+  @Override
+  protected Handler handler() {
+    def handler = JettyServer.servletHandler(TestServlet5)
+    handler.addServlet(HtmlRumServlet, "/gimme-html")
+    handler.addServlet(XmlRumServlet, "/gimme-xml")
+    handler
+  }
+}
diff --git a/dd-java-agent/instrumentation/jetty-12/build.gradle b/dd-java-agent/instrumentation/jetty-12/build.gradle
index 374c30a3753..470dfbe1d3a 100644
--- a/dd-java-agent/instrumentation/jetty-12/build.gradle
+++ b/dd-java-agent/instrumentation/jetty-12/build.gradle
@@ -29,7 +29,9 @@ addTestSuiteForDir('ee9Test', 'test/ee9')
 addTestSuiteExtendingForDir('ee9LatestDepTest', 'latestDepTest', 'test/ee9')
 // ee10
 addTestSuiteForDir('ee10Test', 'test/ee10')
+addTestSuiteExtendingForDir('ee10ForkedTest', 'ee10Test', 'test/ee10')
 addTestSuiteExtendingForDir('ee10LatestDepTest', 'latestDepTest', 'test/ee10')
+addTestSuiteExtendingForDir('ee10LatestDepForkedTest', 'ee10LatestDepTest', 'test/ee10')
 
 [compileMain_java17Java, compileTestJava].each {
   it.configure {
diff --git a/dd-java-agent/instrumentation/jetty-12/src/test/ee10/groovy/Jetty12Test.groovy b/dd-java-agent/instrumentation/jetty-12/src/test/ee10/groovy/Jetty12Test.groovy
index 8134ef2a8cd..32fd829b8e0 100644
--- a/dd-java-agent/instrumentation/jetty-12/src/test/ee10/groovy/Jetty12Test.groovy
+++ b/dd-java-agent/instrumentation/jetty-12/src/test/ee10/groovy/Jetty12Test.groovy
@@ -1,7 +1,11 @@
 import datadog.trace.agent.test.base.HttpServer
 import datadog.trace.agent.test.base.HttpServerTest
 import datadog.trace.agent.test.naming.TestingGenericHttpNamingConventions
+import datadog.trace.instrumentation.servlet5.HtmlRumServlet
 import datadog.trace.instrumentation.servlet5.TestServlet5
+import datadog.trace.instrumentation.servlet5.XmlRumServlet
+import org.eclipse.jetty.ee10.servlet.ServletContextHandler
+import org.eclipse.jetty.server.Handler
 import org.eclipse.jetty.server.Server
 
 class Jetty12Test extends HttpServerTest<Server> implements TestingGenericHttpNamingConventions.ServerV0 {
@@ -61,3 +65,18 @@ class Jetty12PojoWebsocketTest extends Jetty12Test {
     !isLatestDepTest
   }
 }
+
+class Jetty12RumInjectionForkedTest extends Jetty12Test {
+  @Override
+  boolean testRumInjection() {
+    true
+  }
+
+  @Override
+  HttpServer server() {
+    ServletContextHandler handler = JettyServer.servletHandler(TestServlet5)
+    handler.addServlet(HtmlRumServlet, "/gimme-html")
+    handler.addServlet(XmlRumServlet, "/gimme-xml")
+    new JettyServer(handler, useWebsocketPojoEndpoint())
+  }
+}
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
index 8d8aa1d6971..18081e58dcf 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
@@ -3,6 +3,7 @@
 import datadog.trace.api.rum.RumInjector;
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.nio.charset.Charset;
 import javax.servlet.ServletOutputStream;
 import javax.servlet.http.HttpServletResponse;
 import javax.servlet.http.HttpServletResponseWrapper;
@@ -26,7 +27,7 @@ public ServletOutputStream getOutputStream() throws IOException {
     if (outputStream == null) {
       String encoding = getCharacterEncoding();
       if (encoding == null) {
-        encoding = "UTF-8";
+        encoding = Charset.defaultCharset().name();
       }
       outputStream =
           new WrappedServletOutputStream(
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/test/groovy/JettyServlet3Test.groovy b/dd-java-agent/instrumentation/servlet/request-3/src/test/groovy/JettyServlet3Test.groovy
index 2ed349c5402..11bf3eb20e7 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/test/groovy/JettyServlet3Test.groovy
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/test/groovy/JettyServlet3Test.groovy
@@ -3,11 +3,12 @@ import datadog.trace.agent.test.base.HttpServer
 import datadog.trace.agent.test.naming.TestingGenericHttpNamingConventions
 import datadog.trace.api.iast.InstrumentationBridge
 import datadog.trace.api.iast.sink.ApplicationModule
-import datadog.trace.api.rum.RumInjector
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan
 import datadog.trace.bootstrap.instrumentation.api.Tags
 import datadog.trace.instrumentation.servlet3.AsyncDispatcherDecorator
+import datadog.trace.instrumentation.servlet3.HtmlRumServlet
 import datadog.trace.instrumentation.servlet3.TestServlet3
+import datadog.trace.instrumentation.servlet3.XmlRumServlet
 import groovy.servlet.AbstractHttpServlet
 import org.eclipse.jetty.server.Request
 import org.eclipse.jetty.server.Server
@@ -21,7 +22,6 @@ import javax.servlet.AsyncListener
 import javax.servlet.Servlet
 import javax.servlet.ServletException
 import javax.servlet.annotation.WebServlet
-import javax.servlet.http.HttpServlet
 import javax.servlet.http.HttpServletRequest
 import javax.servlet.http.HttpServletResponse
 
@@ -236,50 +236,9 @@ class JettyServlet3TestSync extends JettyServlet3Test {
 }
 
 class JettyServlet3SyncRumInjectionForkedTest extends JettyServlet3TestSync {
-
-  static class RumServlet extends HttpServlet {
-    private final String mimeType
-
-    RumServlet(String mime) {
-      this.mimeType = mime
-    }
-
-    @Override
-    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
-      resp.setContentType(mimeType)
-      try (def writer = resp.getWriter()) {
-        writer.println("\n" +
-        "<!doctype html>\n" +
-        "<html>\n" +
-        "  <head>\n" +
-        "    <title>This is the title of the webpage!</title>\n" +
-        "  </head>\n" +
-        "  <body>\n" +
-        "    <p>This is an example paragraph. Anything in the <strong>body</strong> tag will appear on the page, just like this <strong>p</strong> tag and its contents.</p>\n" +
-        "  </body>\n" +
-        "</html>")
-      }
-    }
-  }
-
-  static class HtmlRumServlet extends RumServlet {
-    HtmlRumServlet() {
-      super("text/html")
-    }
-  }
-
-  static class XmlRumServlet extends RumServlet {
-    XmlRumServlet() {
-      super("text/xml")
-    }
-  }
-
   @Override
-  protected void configurePreAgent() {
-    super.configurePreAgent()
-    injectSysConfig("rum.enabled", "true")
-    injectSysConfig("rum.application.id", "test")
-    injectSysConfig("rum.client.token", "secret")
+  boolean testRumInjection() {
+    true
   }
 
   @Override
@@ -288,25 +247,8 @@ class JettyServlet3SyncRumInjectionForkedTest extends JettyServlet3TestSync {
     addServlet(servletContextHandler, "/gimme-html", HtmlRumServlet)
     addServlet(servletContextHandler, "/gimme-xml", XmlRumServlet)
   }
-
-  def "test rum injection in head for mime #mime"() {
-    setup:
-    def request = new okhttp3.Request.Builder().url(server.address().resolve("gimme-$mime").toURL())
-      .get().build()
-    when:
-    def response = client.newCall(request).execute()
-    then:
-    assert response.code() == 200
-    assert response.body().string().contains(new String(RumInjector.getSnippet("UTF-8"), "UTF-8")) == expected
-    assert response.header("x-datadog-rum-injected") == (expected ? "1" : null)
-    where:
-    mime   | expected
-    "html" | true
-    "xml"  | false
-  }
 }
 
-
 class JettyServlet3SyncV1ForkedTest extends JettyServlet3TestSync implements TestingGenericHttpNamingConventions.ServerV1 {
 
 }
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/testFixtures/groovy/datadog/trace/instrumentation/servlet3/RumServlet.groovy b/dd-java-agent/instrumentation/servlet/request-3/src/testFixtures/groovy/datadog/trace/instrumentation/servlet3/RumServlet.groovy
new file mode 100644
index 00000000000..127950fc385
--- /dev/null
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/testFixtures/groovy/datadog/trace/instrumentation/servlet3/RumServlet.groovy
@@ -0,0 +1,43 @@
+package datadog.trace.instrumentation.servlet3
+
+import javax.servlet.ServletException
+import javax.servlet.http.HttpServlet
+import javax.servlet.http.HttpServletRequest
+import javax.servlet.http.HttpServletResponse
+
+class RumServlet extends HttpServlet {
+  private final String mimeType
+
+  RumServlet(String mime) {
+    this.mimeType = mime
+  }
+
+  @Override
+  protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+    resp.setContentType(mimeType)
+    try (def writer = resp.getWriter()) {
+      writer.println("\n" +
+      "<!doctype html>\n" +
+      "<html>\n" +
+      "  <head>\n" +
+      "    <title>This is the title of the webpage!</title>\n" +
+      "  </head>\n" +
+      "  <body>\n" +
+      "    <p>This is an example paragraph. Anything in the <strong>body</strong> tag will appear on the page, just like this <strong>p</strong> tag and its contents.</p>\n" +
+      "  </body>\n" +
+      "</html>")
+    }
+  }
+}
+
+class HtmlRumServlet extends RumServlet {
+  HtmlRumServlet() {
+    super("text/html")
+  }
+}
+
+class XmlRumServlet extends RumServlet {
+  XmlRumServlet() {
+    super("text/xml")
+  }
+}
diff --git a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/JakartaServletInstrumentation.java b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/JakartaServletInstrumentation.java
index d60711b404c..6ef4940a41e 100644
--- a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/JakartaServletInstrumentation.java
+++ b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/JakartaServletInstrumentation.java
@@ -1,7 +1,9 @@
 package datadog.trace.instrumentation.servlet5;
 
 import static datadog.trace.agent.tooling.bytebuddy.matcher.HierarchyMatchers.hasSuperType;
+import static datadog.trace.agent.tooling.bytebuddy.matcher.HierarchyMatchers.implementsInterface;
 import static datadog.trace.agent.tooling.bytebuddy.matcher.NameMatchers.named;
+import static datadog.trace.bootstrap.instrumentation.decorator.HttpServerDecorator.DD_RUM_INJECTED;
 import static datadog.trace.bootstrap.instrumentation.decorator.HttpServerDecorator.DD_SPAN_ATTRIBUTE;
 import static net.bytebuddy.matcher.ElementMatchers.isMethod;
 import static net.bytebuddy.matcher.ElementMatchers.isPublic;
@@ -14,10 +16,13 @@
 import datadog.trace.api.ClassloaderConfigurationOverrides;
 import datadog.trace.api.Config;
 import datadog.trace.api.DDTags;
+import datadog.trace.api.rum.RumInjector;
 import datadog.trace.bootstrap.CallDepthThreadLocalMap;
 import datadog.trace.bootstrap.instrumentation.api.AgentSpan;
 import jakarta.servlet.ServletRequest;
+import jakarta.servlet.ServletResponse;
 import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
 import net.bytebuddy.asm.Advice;
 import net.bytebuddy.description.type.TypeDescription;
 import net.bytebuddy.matcher.ElementMatcher;
@@ -34,9 +39,17 @@ public String hierarchyMarkerType() {
     return "jakarta.servlet.http.HttpServlet";
   }
 
+  @Override
+  public String[] helperClassNames() {
+    return new String[] {
+      packageName + ".RumHttpServletResponseWrapper", packageName + ".WrappedServletOutputStream",
+    };
+  }
+
   @Override
   public ElementMatcher<TypeDescription> hierarchyMatcher() {
-    return hasSuperType(named(hierarchyMarkerType()));
+    return hasSuperType(named(hierarchyMarkerType()))
+        .or(implementsInterface(named("jakarta.servlet.FilterChain")));
   }
 
   @Override
@@ -48,15 +61,28 @@ public void methodAdvice(MethodTransformer transformer) {
             .and(takesArguments(2))
             .and(takesArgument(0, named("jakarta.servlet.ServletRequest")))
             .and(takesArgument(1, named("jakarta.servlet.ServletResponse"))),
-        getClass().getName() + "$ExtractPrincipalAdvice");
+        getClass().getName() + "$JakartaServletAdvice");
   }
 
-  public static class ExtractPrincipalAdvice {
+  public static class JakartaServletAdvice {
     @Advice.OnMethodEnter(suppress = Throwable.class)
-    public static AgentSpan before(@Advice.Argument(0) final ServletRequest request) {
+    public static AgentSpan before(
+        @Advice.Argument(0) final ServletRequest request,
+        @Advice.Argument(value = 1, readOnly = false) ServletResponse response) {
       if (!(request instanceof HttpServletRequest)) {
         return null;
       }
+
+      if (response instanceof HttpServletResponse) {
+        final HttpServletRequest httpServletRequest = (HttpServletRequest) request;
+
+        if (RumInjector.get().isEnabled()
+            && httpServletRequest.getAttribute(DD_RUM_INJECTED) == null) {
+          httpServletRequest.setAttribute(DD_RUM_INJECTED, Boolean.TRUE);
+          response = new RumHttpServletResponseWrapper((HttpServletResponse) response);
+        }
+      }
+
       Object span = request.getAttribute(DD_SPAN_ATTRIBUTE);
       if (span instanceof AgentSpan
           && CallDepthThreadLocalMap.incrementCallDepth(HttpServletRequest.class) == 0) {
diff --git a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
new file mode 100644
index 00000000000..45caf9750ed
--- /dev/null
+++ b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
@@ -0,0 +1,86 @@
+package datadog.trace.instrumentation.servlet5;
+
+import datadog.trace.api.rum.RumInjector;
+import jakarta.servlet.ServletOutputStream;
+import jakarta.servlet.http.HttpServletResponse;
+import jakarta.servlet.http.HttpServletResponseWrapper;
+import java.io.IOException;
+import java.io.PrintWriter;
+
+public class RumHttpServletResponseWrapper extends HttpServletResponseWrapper {
+  private final RumInjector rumInjector;
+  private ServletOutputStream outputStream;
+  private PrintWriter printWriter;
+  private boolean shouldInject;
+
+  public RumHttpServletResponseWrapper(HttpServletResponse response) {
+    super(response);
+    this.rumInjector = RumInjector.get();
+  }
+
+  @Override
+  public ServletOutputStream getOutputStream() throws IOException {
+    if (!shouldInject) {
+      return super.getOutputStream();
+    }
+    if (outputStream == null) {
+      String encoding = getCharacterEncoding();
+      if (encoding == null) {
+        encoding = "UTF-8";
+      }
+      outputStream =
+          new WrappedServletOutputStream(
+              super.getOutputStream(),
+              rumInjector.getMarker(encoding),
+              rumInjector.getSnippet(encoding),
+              this::onInjected);
+    }
+    return outputStream;
+  }
+
+  @Override
+  public PrintWriter getWriter() throws IOException {
+    if (!shouldInject) {
+      return super.getWriter();
+    }
+    if (printWriter == null) {
+      printWriter = new PrintWriter(getOutputStream());
+    }
+    return printWriter;
+  }
+
+  @Override
+  public void setContentLength(int len) {
+    // don't set it since we don't know if we will inject
+  }
+
+  @Override
+  public void reset() {
+    this.outputStream = null;
+    this.printWriter = null;
+    this.shouldInject = false;
+    super.reset();
+  }
+
+  @Override
+  public void resetBuffer() {
+    this.outputStream = null;
+    this.printWriter = null;
+    this.shouldInject = false;
+    super.resetBuffer();
+  }
+
+  public void onInjected() {
+    try {
+      setHeader("x-datadog-rum-injected", "1");
+    } catch (Throwable ignored2) {
+    }
+  }
+
+  @Override
+  public void setContentType(String type) {
+    if (type != null && type.contains("html")) {
+      shouldInject = true;
+    }
+  }
+}
diff --git a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/WrappedServletOutputStream.java b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/WrappedServletOutputStream.java
new file mode 100644
index 00000000000..2c43af795f8
--- /dev/null
+++ b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/WrappedServletOutputStream.java
@@ -0,0 +1,53 @@
+package datadog.trace.instrumentation.servlet5;
+
+import datadog.trace.bootstrap.instrumentation.buffer.InjectingPipeOutputStream;
+import jakarta.servlet.ServletOutputStream;
+import jakarta.servlet.WriteListener;
+import java.io.IOException;
+import java.io.OutputStream;
+
+public class WrappedServletOutputStream extends ServletOutputStream {
+  private final OutputStream filtered;
+  private final ServletOutputStream delegate;
+
+  public WrappedServletOutputStream(
+      ServletOutputStream delegate, byte[] marker, byte[] contentToInject, Runnable onInjected) {
+    this.filtered = new InjectingPipeOutputStream(delegate, marker, contentToInject, onInjected);
+    this.delegate = delegate;
+  }
+
+  @Override
+  public void write(int b) throws IOException {
+    filtered.write(b);
+  }
+
+  @Override
+  public void write(byte[] b) throws IOException {
+    filtered.write(b);
+  }
+
+  @Override
+  public void write(byte[] b, int off, int len) throws IOException {
+    filtered.write(b, off, len);
+  }
+
+  @Override
+  public void flush() throws IOException {
+    filtered.flush();
+  }
+
+  @Override
+  public void close() throws IOException {
+    filtered.close();
+  }
+
+  @Override
+  public boolean isReady() {
+    return delegate.isReady();
+  }
+
+  @Override
+  public void setWriteListener(WriteListener writeListener) {
+    delegate.setWriteListener(writeListener);
+  }
+}
diff --git a/dd-java-agent/instrumentation/servlet/request-5/src/testFixtures/groovy/datadog/trace/instrumentation/servlet5/RumServlet.groovy b/dd-java-agent/instrumentation/servlet/request-5/src/testFixtures/groovy/datadog/trace/instrumentation/servlet5/RumServlet.groovy
new file mode 100644
index 00000000000..1fa57d02da8
--- /dev/null
+++ b/dd-java-agent/instrumentation/servlet/request-5/src/testFixtures/groovy/datadog/trace/instrumentation/servlet5/RumServlet.groovy
@@ -0,0 +1,43 @@
+package datadog.trace.instrumentation.servlet5
+
+import jakarta.servlet.ServletException
+import jakarta.servlet.http.HttpServlet
+import jakarta.servlet.http.HttpServletRequest
+import jakarta.servlet.http.HttpServletResponse
+
+class RumServlet extends HttpServlet {
+  private final String mimeType
+
+  RumServlet(String mime) {
+    this.mimeType = mime
+  }
+
+  @Override
+  protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
+    resp.setContentType(mimeType)
+    try (def writer = resp.getWriter()) {
+      writer.println("\n" +
+      "<!doctype html>\n" +
+      "<html>\n" +
+      "  <head>\n" +
+      "    <title>This is the title of the webpage!</title>\n" +
+      "  </head>\n" +
+      "  <body>\n" +
+      "    <p>This is an example paragraph. Anything in the <strong>body</strong> tag will appear on the page, just like this <strong>p</strong> tag and its contents.</p>\n" +
+      "  </body>\n" +
+      "</html>")
+    }
+  }
+}
+
+class HtmlRumServlet extends RumServlet {
+  HtmlRumServlet() {
+    super("text/html")
+  }
+}
+
+class XmlRumServlet extends RumServlet {
+  XmlRumServlet() {
+    super("text/xml")
+  }
+}
diff --git a/dd-java-agent/instrumentation/tomcat-5.5/src/latestDepTest/groovy/TomcatServletTest.groovy b/dd-java-agent/instrumentation/tomcat-5.5/src/latestDepTest/groovy/TomcatServletTest.groovy
index 541b1b56380..999d9d62c8a 100644
--- a/dd-java-agent/instrumentation/tomcat-5.5/src/latestDepTest/groovy/TomcatServletTest.groovy
+++ b/dd-java-agent/instrumentation/tomcat-5.5/src/latestDepTest/groovy/TomcatServletTest.groovy
@@ -1,9 +1,8 @@
-import datadog.trace.api.ProcessTags
-
-import static datadog.trace.agent.test.base.HttpServerTest.ServerEndpoint.WEBSOCKET
-
 import datadog.trace.agent.test.base.HttpServer
+import datadog.trace.api.ProcessTags
+import datadog.trace.instrumentation.servlet5.HtmlRumServlet
 import datadog.trace.instrumentation.servlet5.TestServlet5
+import datadog.trace.instrumentation.servlet5.XmlRumServlet
 import jakarta.servlet.Filter
 import jakarta.servlet.Servlet
 import jakarta.servlet.ServletException
@@ -23,6 +22,7 @@ import static datadog.trace.agent.test.base.HttpServerTest.ServerEndpoint.CUSTOM
 import static datadog.trace.agent.test.base.HttpServerTest.ServerEndpoint.EXCEPTION
 import static datadog.trace.agent.test.base.HttpServerTest.ServerEndpoint.SUCCESS
 import static datadog.trace.agent.test.base.HttpServerTest.ServerEndpoint.TIMEOUT_ERROR
+import static datadog.trace.agent.test.base.HttpServerTest.ServerEndpoint.WEBSOCKET
 import static datadog.trace.api.config.GeneralConfig.EXPERIMENTAL_PROPAGATE_PROCESS_TAGS_ENABLED
 import static org.junit.Assume.assumeTrue
 
@@ -293,6 +293,20 @@ class TomcatServletEnvEntriesTagTest extends TomcatServletTest {
   }
 }
 
+class TomcatRumInjectionForkedTest extends TomcatServletTest {
+  @Override
+  boolean testRumInjection() {
+    true
+  }
+
+  @Override
+  protected void setupServlets(Context context) {
+    super.setupServlets(context)
+    addServlet(context, "/gimme-html", HtmlRumServlet)
+    addServlet(context, "/gimme-xml", XmlRumServlet)
+  }
+}
+
 
 
 
diff --git a/dd-java-agent/testing/src/main/groovy/datadog/trace/agent/test/base/HttpServerTest.groovy b/dd-java-agent/testing/src/main/groovy/datadog/trace/agent/test/base/HttpServerTest.groovy
index 0bb81fd1102..a06de2014f2 100644
--- a/dd-java-agent/testing/src/main/groovy/datadog/trace/agent/test/base/HttpServerTest.groovy
+++ b/dd-java-agent/testing/src/main/groovy/datadog/trace/agent/test/base/HttpServerTest.groovy
@@ -27,6 +27,7 @@ import datadog.trace.api.gateway.RequestContextSlot
 import datadog.trace.api.http.StoredBodySupplier
 import datadog.trace.api.iast.IastContext
 import datadog.trace.api.normalize.SimpleHttpPathNormalizer
+import datadog.trace.api.rum.RumInjector
 import datadog.trace.api.telemetry.Endpoint
 import datadog.trace.api.telemetry.EndpointCollector
 import datadog.trace.bootstrap.blocking.BlockingActionHelper
@@ -167,6 +168,12 @@ abstract class HttpServerTest<SERVER> extends WithHttpServer<SERVER> {
     injectSysConfig(TRACE_WEBSOCKET_MESSAGES_ENABLED, "true")
     // allow endpoint discover for the tests
     injectSysConfig(API_SECURITY_ENDPOINT_COLLECTION_ENABLED, "true")
+    if (testRumInjection()) {
+      injectSysConfig("rum.enabled", "true")
+      injectSysConfig("rum.application.id", "test")
+      injectSysConfig("rum.client.token", "secret")
+      injectSysConfig("rum.remote.configuration.id", "12345")
+    }
   }
 
   // used in blocking tests to check if the handler was skipped
@@ -423,6 +430,10 @@ abstract class HttpServerTest<SERVER> extends WithHttpServer<SERVER> {
     false
   }
 
+  boolean testRumInjection() {
+    false
+  }
+
   /**
    * To be set if the integration name (_dd.integration) differs from the component.
    * This happen when the controller integration modify the parent component name (i.e. jaxrs)
@@ -2191,6 +2202,28 @@ abstract class HttpServerTest<SERVER> extends WithHttpServer<SERVER> {
     assertEndpointDiscovery(discovered)
   }
 
+
+  /**
+   * This test should be done in a forked test class
+   * @return
+   */
+  def "test rum injection in head for mime #mime"() {
+    setup:
+    assumeTrue(testRumInjection())
+    def request = new Request.Builder().url(server.address().resolve("gimme-$mime").toURL())
+    .get().build()
+    when:
+    def response = client.newCall(request).execute()
+    then:
+    assert response.code() == 200
+    assert response.body().string().contains(new String(RumInjector.get().getSnippet("UTF-8"), "UTF-8")) == expected
+    assert response.header("x-datadog-rum-injected") == (expected ? "1" : null)
+    where:
+    mime   | expected
+    "html" | true
+    "xml"  | false
+  }
+
   // to be overridden for more specific asserts
   void assertEndpointDiscovery(final List<?> endpoints) { }
 

From dc3beab934ed59bc4aa51baf98f3a08e9870c0ca Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Mon, 7 Jul 2025 12:03:12 +0200
Subject: [PATCH 25/36] codenarc

---
 .../jetty-12/src/test/ee10/groovy/Jetty12Test.groovy             | 1 -
 1 file changed, 1 deletion(-)

diff --git a/dd-java-agent/instrumentation/jetty-12/src/test/ee10/groovy/Jetty12Test.groovy b/dd-java-agent/instrumentation/jetty-12/src/test/ee10/groovy/Jetty12Test.groovy
index 32fd829b8e0..9914b8e7a1f 100644
--- a/dd-java-agent/instrumentation/jetty-12/src/test/ee10/groovy/Jetty12Test.groovy
+++ b/dd-java-agent/instrumentation/jetty-12/src/test/ee10/groovy/Jetty12Test.groovy
@@ -5,7 +5,6 @@ import datadog.trace.instrumentation.servlet5.HtmlRumServlet
 import datadog.trace.instrumentation.servlet5.TestServlet5
 import datadog.trace.instrumentation.servlet5.XmlRumServlet
 import org.eclipse.jetty.ee10.servlet.ServletContextHandler
-import org.eclipse.jetty.server.Handler
 import org.eclipse.jetty.server.Server
 
 class Jetty12Test extends HttpServerTest<Server> implements TestingGenericHttpNamingConventions.ServerV0 {

From 58c8ef38b570407bba28cd43a3fe0a10b785ffab Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Mon, 7 Jul 2025 13:27:17 +0200
Subject: [PATCH 26/36] fix(rum): Fix smoke test merge

---
 .../smoketest/rum/tomcat10/Tomcat10RumSmokeTest.groovy        | 4 ++--
 .../smoketest/rum/tomcat11/Tomcat11RumSmokeTest.groovy        | 4 ++--
 .../datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy  | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/dd-smoke-tests/rum/tomcat-10/src/test/groovy/datadog/smoketest/rum/tomcat10/Tomcat10RumSmokeTest.groovy b/dd-smoke-tests/rum/tomcat-10/src/test/groovy/datadog/smoketest/rum/tomcat10/Tomcat10RumSmokeTest.groovy
index 54a07fe3f3e..67b0b17df44 100644
--- a/dd-smoke-tests/rum/tomcat-10/src/test/groovy/datadog/smoketest/rum/tomcat10/Tomcat10RumSmokeTest.groovy
+++ b/dd-smoke-tests/rum/tomcat-10/src/test/groovy/datadog/smoketest/rum/tomcat10/Tomcat10RumSmokeTest.groovy
@@ -1,7 +1,7 @@
 package datadog.smoketest.rum.tomcat10
 
+import datadog.environment.JavaVirtualMachine
 import datadog.smoketest.rum.AbstractRumServerSmokeTest
-import datadog.trace.api.Platform
 
 class Tomcat10RumSmokeTest extends AbstractRumServerSmokeTest {
   @Override
@@ -12,7 +12,7 @@ class Tomcat10RumSmokeTest extends AbstractRumServerSmokeTest {
     command.add(javaPath())
     command.addAll(defaultJavaProperties)
     command.addAll(defaultRumProperties)
-    if (Platform.isJavaVersionAtLeast(17)) {
+    if (JavaVirtualMachine.isJavaVersionAtLeast(17)) {
       command.addAll((String[]) ['--add-opens', 'java.base/java.lang=ALL-UNNAMED'])
     }
     command.addAll(['-jar', jarPath, Integer.toString(httpPort)])
diff --git a/dd-smoke-tests/rum/tomcat-11/src/test/groovy/datadog/smoketest/rum/tomcat11/Tomcat11RumSmokeTest.groovy b/dd-smoke-tests/rum/tomcat-11/src/test/groovy/datadog/smoketest/rum/tomcat11/Tomcat11RumSmokeTest.groovy
index 993b69dbe66..5ab1bff993c 100644
--- a/dd-smoke-tests/rum/tomcat-11/src/test/groovy/datadog/smoketest/rum/tomcat11/Tomcat11RumSmokeTest.groovy
+++ b/dd-smoke-tests/rum/tomcat-11/src/test/groovy/datadog/smoketest/rum/tomcat11/Tomcat11RumSmokeTest.groovy
@@ -1,7 +1,7 @@
 package datadog.smoketest.rum.tomcat11
 
+import datadog.environment.JavaVirtualMachine
 import datadog.smoketest.rum.AbstractRumServerSmokeTest
-import datadog.trace.api.Platform
 
 class Tomcat11RumSmokeTest extends AbstractRumServerSmokeTest {
   @Override
@@ -12,7 +12,7 @@ class Tomcat11RumSmokeTest extends AbstractRumServerSmokeTest {
     command.add(javaPath())
     command.addAll(defaultJavaProperties)
     command.addAll(defaultRumProperties)
-    if (Platform.isJavaVersionAtLeast(17)) {
+    if (JavaVirtualMachine.isJavaVersionAtLeast(17)) {
       command.addAll((String[]) ['--add-opens', 'java.base/java.lang=ALL-UNNAMED'])
     }
     command.addAll(['-jar', jarPath, Integer.toString(httpPort)])
diff --git a/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
index 8555fb773b9..fa26bf2a041 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
+++ b/dd-smoke-tests/rum/tomcat-9/src/test/groovy/datadog/smoketest/rum/tomcat9/Tomcat9RumSmokeTest.groovy
@@ -1,7 +1,7 @@
 package datadog.smoketest.rum.tomcat9
 
+import datadog.environment.JavaVirtualMachine
 import datadog.smoketest.rum.AbstractRumServerSmokeTest
-import datadog.trace.api.Platform
 
 class Tomcat9RumSmokeTest extends AbstractRumServerSmokeTest {
 
@@ -14,7 +14,7 @@ class Tomcat9RumSmokeTest extends AbstractRumServerSmokeTest {
     command.add(javaPath())
     command.addAll(defaultJavaProperties)
     command.addAll(defaultRumProperties)
-    if (Platform.isJavaVersionAtLeast(17)) {
+    if (JavaVirtualMachine.isJavaVersionAtLeast(17)) {
       command.addAll((String[]) ['--add-opens', 'java.base/java.lang=ALL-UNNAMED'])
     }
     command.addAll(['-jar', jarPath, Integer.toString(httpPort)])

From 71a0923cc08ac8308bf8b611df31df7f8f69f738 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Mon, 7 Jul 2025 13:56:05 +0200
Subject: [PATCH 27/36] exclude spring virtual filter chain

---
 .../agent/tooling/bytebuddy/matcher/ignored_class_name.trie      | 1 +
 1 file changed, 1 insertion(+)

diff --git a/dd-java-agent/agent-tooling/src/main/resources/datadog/trace/agent/tooling/bytebuddy/matcher/ignored_class_name.trie b/dd-java-agent/agent-tooling/src/main/resources/datadog/trace/agent/tooling/bytebuddy/matcher/ignored_class_name.trie
index 18a88747eec..e479329c814 100644
--- a/dd-java-agent/agent-tooling/src/main/resources/datadog/trace/agent/tooling/bytebuddy/matcher/ignored_class_name.trie
+++ b/dd-java-agent/agent-tooling/src/main/resources/datadog/trace/agent/tooling/bytebuddy/matcher/ignored_class_name.trie
@@ -350,6 +350,7 @@
 0 org.springframework.web.context.support.AbstractRefreshableWebApplicationContext
 0 org.springframework.web.context.support.GenericWebApplicationContext
 0 org.springframework.web.context.support.XmlWebApplicationContext
+1 org.springframework.web.filter.CompositeFilter$VirtualFilterChain
 0 org.springframework.web.reactive.*
 0 org.springframework.web.servlet.*
 0 org.springframework.web.socket.*

From af937dc4dbbd3d9f66fe076e7dd634b0f75a5f94 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Mon, 7 Jul 2025 14:33:45 +0200
Subject: [PATCH 28/36] fix(rum): Fix SDK snippet

---
 .../src/main/java/datadog/trace/api/rum/RumInjectorConfig.java   | 1 +
 1 file changed, 1 insertion(+)

diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
index e0a56d310f5..9f37cb75553 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
@@ -186,6 +186,7 @@ public String jsonPayload() {
       if (this.remoteConfigurationId != null) {
         writer.name("remoteConfigurationId").value(this.remoteConfigurationId);
       }
+      writer.endObject();
       return writer.toString();
     } catch (Exception e) {
       throw new IllegalStateException("Fail to generate config payload", e);

From 79db3cef3c8ce39f2403ae4663bae385dc2e8086 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Mon, 7 Jul 2025 14:58:19 +0200
Subject: [PATCH 29/36] final fixes

---
 .../servlet3/RumHttpServletResponseWrapper.java          | 6 ++----
 .../servlet5/RumHttpServletResponseWrapper.java          | 9 ++++-----
 .../smoketest/rum/AbstractRumServerSmokeTest.groovy      | 3 ++-
 .../rum/tomcat-9/src/main/java/com/example/Main.java     | 2 +-
 4 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
index 18081e58dcf..7dc9b1fd07d 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
@@ -12,7 +12,7 @@ public class RumHttpServletResponseWrapper extends HttpServletResponseWrapper {
   private final RumInjector rumInjector;
   private ServletOutputStream outputStream;
   private PrintWriter printWriter;
-  private boolean shouldInject;
+  private boolean shouldInject = false;
 
   public RumHttpServletResponseWrapper(HttpServletResponse response) {
     super(response);
@@ -80,8 +80,6 @@ public void onInjected() {
 
   @Override
   public void setContentType(String type) {
-    if (type != null && type.contains("html")) {
-      shouldInject = true;
-    }
+    shouldInject = type != null && type.contains("text/html");
   }
 }
diff --git a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
index 45caf9750ed..5a5a6493d20 100644
--- a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
+++ b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
@@ -6,12 +6,13 @@
 import jakarta.servlet.http.HttpServletResponseWrapper;
 import java.io.IOException;
 import java.io.PrintWriter;
+import java.nio.charset.Charset;
 
 public class RumHttpServletResponseWrapper extends HttpServletResponseWrapper {
   private final RumInjector rumInjector;
   private ServletOutputStream outputStream;
   private PrintWriter printWriter;
-  private boolean shouldInject;
+  private boolean shouldInject = false;
 
   public RumHttpServletResponseWrapper(HttpServletResponse response) {
     super(response);
@@ -26,7 +27,7 @@ public ServletOutputStream getOutputStream() throws IOException {
     if (outputStream == null) {
       String encoding = getCharacterEncoding();
       if (encoding == null) {
-        encoding = "UTF-8";
+        encoding = Charset.defaultCharset().name();
       }
       outputStream =
           new WrappedServletOutputStream(
@@ -79,8 +80,6 @@ public void onInjected() {
 
   @Override
   public void setContentType(String type) {
-    if (type != null && type.contains("html")) {
-      shouldInject = true;
-    }
+    shouldInject = type != null && type.contains("text/html");
   }
 }
diff --git a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
index 1431c541ed4..d9ece96fde9 100644
--- a/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
+++ b/dd-smoke-tests/rum/src/main/groovy/datadog/smoketest/rum/AbstractRumServerSmokeTest.groovy
@@ -10,7 +10,8 @@ class AbstractRumServerSmokeTest extends AbstractServerSmokeTest {
   protected String[] defaultRumProperties = [
     "-Ddd.rum.enabled=true",
     "-Ddd.rum.application.id=appid",
-    "-Ddd.rum.client.token=token"
+    "-Ddd.rum.client.token=token",
+    "-Ddd.rum.remote.configuration.id=12345",
   ]
 
   void 'test RUM SDK injection on html'() {
diff --git a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
index 96a5f07cd87..d9992f37c92 100644
--- a/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
+++ b/dd-smoke-tests/rum/tomcat-9/src/main/java/com/example/Main.java
@@ -26,7 +26,7 @@ public static void main(String[] args) throws LifecycleException {
     context.addServletContainerInitializer(
         (c, ctx) -> {
           ctx.addServlet("htmlServlet", new HtmlServlet()).addMapping("/html");
-          ctx.addServlet("xmlServlet", new HtmlServlet()).addMapping("/xml");
+          ctx.addServlet("xmlServlet", new XmlServlet()).addMapping("/xml");
         },
         null);
 

From 6672db96735ff42e296b6a3ce6019d929a96321b Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Mon, 7 Jul 2025 16:09:08 +0200
Subject: [PATCH 30/36] fix more tests

---
 .../rum/tomcat-10/src/main/java/com/example/Main.java           | 2 +-
 .../rum/tomcat-11/src/main/java/com/example/Main.java           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/Main.java b/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/Main.java
index 96a5f07cd87..d9992f37c92 100644
--- a/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/Main.java
+++ b/dd-smoke-tests/rum/tomcat-10/src/main/java/com/example/Main.java
@@ -26,7 +26,7 @@ public static void main(String[] args) throws LifecycleException {
     context.addServletContainerInitializer(
         (c, ctx) -> {
           ctx.addServlet("htmlServlet", new HtmlServlet()).addMapping("/html");
-          ctx.addServlet("xmlServlet", new HtmlServlet()).addMapping("/xml");
+          ctx.addServlet("xmlServlet", new XmlServlet()).addMapping("/xml");
         },
         null);
 
diff --git a/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/Main.java b/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/Main.java
index 96a5f07cd87..d9992f37c92 100644
--- a/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/Main.java
+++ b/dd-smoke-tests/rum/tomcat-11/src/main/java/com/example/Main.java
@@ -26,7 +26,7 @@ public static void main(String[] args) throws LifecycleException {
     context.addServletContainerInitializer(
         (c, ctx) -> {
           ctx.addServlet("htmlServlet", new HtmlServlet()).addMapping("/html");
-          ctx.addServlet("xmlServlet", new HtmlServlet()).addMapping("/xml");
+          ctx.addServlet("xmlServlet", new XmlServlet()).addMapping("/xml");
         },
         null);
 

From fc23ee8c4e400406d3fdad3c7311e362a62c4661 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Mon, 7 Jul 2025 16:26:41 +0200
Subject: [PATCH 31/36] fix(rum): Fix privacy level encoding

---
 .../datadog/trace/api/rum/RumInjectorConfig.java  | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
index 9f37cb75553..4bfb228a54b 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
@@ -1,7 +1,6 @@
 package datadog.trace.api.rum;
 
 import static datadog.trace.api.ConfigDefaults.DEFAULT_RUM_SITE;
-import static java.util.Locale.ROOT;
 
 import datadog.json.JsonWriter;
 import java.util.HashMap;
@@ -194,12 +193,18 @@ public String jsonPayload() {
   }
 
   public enum PrivacyLevel {
-    ALLOW,
-    MASK,
-    MASK_USER_INPUT;
+    ALLOW("allow"),
+    MASK("mask"),
+    MASK_USER_INPUT("mask-user-input");
+
+    private final String json;
+
+    PrivacyLevel(String json) {
+      this.json = json;
+    }
 
     public String toJson() {
-      return toString().toLowerCase(ROOT);
+      return this.json;
     }
   }
 }

From b1ea903a72161316c45f1d3e748b0361afc5aae8 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Tue, 8 Jul 2025 09:44:49 +0200
Subject: [PATCH 32/36] Apply suggestions

---
 .../servlet3/RumHttpServletResponseWrapper.java   |  3 ++-
 .../servlet3/WrappedServletOutputStream.java      | 15 ++++++++++-----
 .../servlet5/RumHttpServletResponseWrapper.java   |  3 ++-
 .../java/datadog/trace/api/rum/RumInjector.java   | 12 ++++++------
 .../datadog/trace/api/rum/RumInjectorTest.groovy  |  4 +---
 5 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
index 7dc9b1fd07d..d87009351ba 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
@@ -74,7 +74,8 @@ public void resetBuffer() {
   public void onInjected() {
     try {
       setHeader("x-datadog-rum-injected", "1");
-    } catch (Throwable ignored2) {
+    } catch (Throwable ignored) {
+      // suppress exception if arisen setting this header by us.
     }
   }
 
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
index 31635a886e0..d22d7899836 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/WrappedServletOutputStream.java
@@ -15,7 +15,7 @@ public class WrappedServletOutputStream extends ServletOutputStream {
   private static final MethodHandle IS_READY_MH = getMh("isReady");
   private static final MethodHandle SET_WRITELISTENER_MH = getMh("setWriteListener");
 
-  private static final MethodHandle getMh(final String name) {
+  private static MethodHandle getMh(final String name) {
     try {
       return new MethodHandles(ServletOutputStream.class.getClassLoader())
           .method(ServletOutputStream.class, name);
@@ -24,6 +24,11 @@ private static final MethodHandle getMh(final String name) {
     }
   }
 
+  @SuppressWarnings("unchecked")
+  private static <E extends Throwable> void sneakyThrow(Throwable e) throws E {
+    throw (E) e;
+  }
+
   public WrappedServletOutputStream(
       ServletOutputStream delegate, byte[] marker, byte[] contentToInject, Runnable onInjected) {
     this.filtered = new InjectingPipeOutputStream(delegate, marker, contentToInject, onInjected);
@@ -62,8 +67,9 @@ public boolean isReady() {
     try {
       return (boolean) IS_READY_MH.invoke(delegate);
     } catch (Throwable e) {
-      // how to sneaky throw?
-      throw new RuntimeException(e);
+      sneakyThrow(e);
+      // will never return a value but added for the compiler
+      return false;
     }
   }
 
@@ -74,8 +80,7 @@ public void setWriteListener(WriteListener writeListener) {
     try {
       SET_WRITELISTENER_MH.invoke(delegate, writeListener);
     } catch (Throwable e) {
-      // how to sneaky throw?
-      throw new RuntimeException(e);
+      sneakyThrow(e);
     }
   }
 }
diff --git a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
index 5a5a6493d20..ece77c9173e 100644
--- a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
+++ b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
@@ -74,7 +74,8 @@ public void resetBuffer() {
   public void onInjected() {
     try {
       setHeader("x-datadog-rum-injected", "1");
-    } catch (Throwable ignored2) {
+    } catch (Throwable ignored) {
+      // suppress exception if arisen setting this header by us.
     }
   }
 
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
index 36b84d62ac1..356d1309ec4 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjector.java
@@ -9,7 +9,7 @@
 public final class RumInjector {
   private static final RumInjector INSTANCE = new RumInjector(Config.get());
   private static final String MARKER = "</head>";
-  private static final Function<String, byte[]> MARKER_ADDER =
+  private static final Function<String, byte[]> MARKER_BYTES =
       charset -> {
         try {
           return MARKER.getBytes(charset);
@@ -23,7 +23,7 @@ public final class RumInjector {
 
   private final DDCache<String, byte[]> snippetCache;
   private final DDCache<String, byte[]> markerCache;
-  private final Function<String, byte[]> snippetAdder;
+  private final Function<String, byte[]> snippetBytes;
 
   RumInjector(Config config) {
     boolean rumEnabled = config.isRumEnabled();
@@ -34,7 +34,7 @@ public final class RumInjector {
       this.snippet = injectorConfig.getSnippet();
       this.snippetCache = DDCaches.newFixedSizeCache(16);
       this.markerCache = DDCaches.newFixedSizeCache(16);
-      this.snippetAdder =
+      this.snippetBytes =
           charset -> {
             try {
               return snippet.getBytes(charset);
@@ -47,7 +47,7 @@ public final class RumInjector {
       this.snippet = null;
       this.snippetCache = null;
       this.markerCache = null;
-      this.snippetAdder = null;
+      this.snippetBytes = null;
     }
   }
 
@@ -74,7 +74,7 @@ public byte[] getSnippet(String encoding) {
     if (!this.enabled) {
       return null;
     }
-    return this.snippetCache.computeIfAbsent(encoding, this.snippetAdder);
+    return this.snippetCache.computeIfAbsent(encoding, this.snippetBytes);
   }
 
   /**
@@ -88,6 +88,6 @@ public byte[] getMarker(String encoding) {
     if (!this.enabled) {
       return null;
     }
-    return this.markerCache.computeIfAbsent(encoding, MARKER_ADDER);
+    return this.markerCache.computeIfAbsent(encoding, MARKER_BYTES);
   }
 }
diff --git a/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy b/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy
index 4c2d9f9ad37..4985ca5b7a2 100644
--- a/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy
+++ b/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy
@@ -3,13 +3,11 @@ package datadog.trace.api.rum
 import datadog.trace.api.Config
 import datadog.trace.test.util.DDSpecification
 
-import java.nio.charset.StandardCharsets
-
 import static org.mockito.Mockito.mock
 import static org.mockito.Mockito.when
 
 class RumInjectorTest extends DDSpecification {
-  public static final String UTF8 = StandardCharsets.UTF_8.name()
+  public static final String UTF8 = "UTF-8"
 
   void 'disabled injector'(){
     setup:

From 6fb58b4e0547140b5f88a1dd43ff1ba6882a9488 Mon Sep 17 00:00:00 2001
From: Bruce Bujon <bruce.bujon@datadoghq.com>
Date: Tue, 8 Jul 2025 10:43:37 +0200
Subject: [PATCH 33/36] feat(rum): Improve config related to PR review feedback

---
 .../src/main/java/datadog/trace/api/ConfigDefaults.java   | 2 +-
 .../java/datadog/trace/api/rum/RumInjectorConfig.java     | 8 ++++++--
 .../groovy/datadog/trace/api/rum/RumInjectorTest.groovy   | 2 +-
 .../java/datadog/trace/api/rum/RumInjectorConfigTest.java | 2 +-
 4 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java b/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
index ac81b2ce326..c03af8bbd82 100644
--- a/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
+++ b/dd-trace-api/src/main/java/datadog/trace/api/ConfigDefaults.java
@@ -242,7 +242,7 @@ public final class ConfigDefaults {
 
   static final boolean DEFAULT_RUM_ENABLED = false;
   public static final String DEFAULT_RUM_SITE = DEFAULT_SITE;
-  static final int DEFAULT_RUM_MAJOR_VERSION = 6;
+  public static final int DEFAULT_RUM_MAJOR_VERSION = 6;
 
   static final boolean DEFAULT_SSI_INJECTION_FORCE = false;
   static final String DEFAULT_INSTRUMENTATION_SOURCE = "manual";
diff --git a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
index 4bfb228a54b..882b4add458 100644
--- a/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
+++ b/internal-api/src/main/java/datadog/trace/api/rum/RumInjectorConfig.java
@@ -17,6 +17,7 @@ public class RumInjectorConfig {
     REGIONS.put("us5.datadoghq.com", "us5");
     REGIONS.put("datadoghq.eu", "eu1");
     REGIONS.put("ap1.datadoghq.com", "ap1");
+    REGIONS.put("ap2.datadoghq.com", "ap2");
   }
 
   /** RUM application ID */
@@ -30,7 +31,7 @@ public class RumInjectorConfig {
   /** The environment of the service (e.g., `prod`, `staging` or `dev). */
   @Nullable public final String env;
   /** SDK major version. */
-  public int majorVersion;
+  public final int majorVersion;
   /** The version of the service (e.g., `0.1.0`, `a8dj92`, `2024-30`). */
   @Nullable public final String version;
   /** Enables or disables the automatic collection of users actions (e.g., clicks). */
@@ -50,6 +51,8 @@ public class RumInjectorConfig {
   @Nullable public final Float sessionReplaySampleRate;
   /** The remote configuration identifier. */
   @Nullable public final String remoteConfigurationId;
+  /** The JSON representation of injector config to use in the injected SDK snippet. */
+  public final String jsonPayload;
 
   public RumInjectorConfig(
       String applicationId,
@@ -108,6 +111,7 @@ public RumInjectorConfig(
       throw new IllegalArgumentException(
           "Either remote configuration id or both session and session replay sample rates must be set");
     }
+    this.jsonPayload = jsonPayload();
   }
 
   private static boolean validateSite(String site) {
@@ -130,7 +134,7 @@ public String getSnippet() {
         + "','DD_RUM')\n"
         + "window.DD_RUM.onReady(function() {\n"
         + "  window.DD_RUM.init("
-        + jsonPayload()
+        + this.jsonPayload
         + ");\n"
         + "});\n"
         + "</script>\n";
diff --git a/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy b/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy
index 4985ca5b7a2..12541f452fc 100644
--- a/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy
+++ b/internal-api/src/test/groovy/datadog/trace/api/rum/RumInjectorTest.groovy
@@ -7,7 +7,7 @@ import static org.mockito.Mockito.mock
 import static org.mockito.Mockito.when
 
 class RumInjectorTest extends DDSpecification {
-  public static final String UTF8 = "UTF-8"
+  static final String UTF8 = "UTF-8"
 
   void 'disabled injector'(){
     setup:
diff --git a/internal-api/src/test/java/datadog/trace/api/rum/RumInjectorConfigTest.java b/internal-api/src/test/java/datadog/trace/api/rum/RumInjectorConfigTest.java
index df4a57bacae..ba561e2e40c 100644
--- a/internal-api/src/test/java/datadog/trace/api/rum/RumInjectorConfigTest.java
+++ b/internal-api/src/test/java/datadog/trace/api/rum/RumInjectorConfigTest.java
@@ -58,7 +58,7 @@ class RumInjectorConfigTest {
       },
       delimiterString = "|",
       nullValues = "null")
-  void testSnippet(
+  void testValidConfig(
       String applicationId,
       String clientToken,
       String site,

From 1e6faf998b4911da285acbe1fa748131d82bfe77 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Tue, 8 Jul 2025 11:15:07 +0200
Subject: [PATCH 34/36] Improve and fix circular buffer

---
 .../InjectingPipeOutputStreamBenchmark.java   |  4 +--
 .../buffer/InjectingPipeOutputStream.java     | 28 +++++++++----------
 2 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java b/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java
index fed7bfe9d77..8b90b4678a7 100644
--- a/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java
+++ b/dd-java-agent/agent-bootstrap/src/jmh/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamBenchmark.java
@@ -23,8 +23,8 @@
 
 /*
  * Benchmark                                       Mode  Cnt   Score   Error  Units
- * InjectingPipeOutputStreamBenchmark.withPipe     avgt    2  16.802          us/op
- * InjectingPipeOutputStreamBenchmark.withoutPipe  avgt    2  13.001          us/op
+ * InjectingPipeOutputStreamBenchmark.withPipe     avgt    2  15.515          us/op
+ * InjectingPipeOutputStreamBenchmark.withoutPipe  avgt    2  12.861          us/op
  */
 @State(Scope.Benchmark)
 @Warmup(iterations = 1, time = 30, timeUnit = SECONDS)
diff --git a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
index 18d135d77ad..47780d5cbb1 100644
--- a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
+++ b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
@@ -31,7 +31,7 @@ public InjectingPipeOutputStream(
       final Runnable onContentInjected) {
     super(downstream);
     this.marker = marker;
-    this.lookbehind = new byte[marker.length + 1];
+    this.lookbehind = new byte[marker.length];
     this.pos = 0;
     this.contentToInject = contentToInject;
     this.onContentInjected = onContentInjected;
@@ -58,13 +58,11 @@ public void write(int b) throws IOException {
     if (marker[matchingPos++] == b) {
       if (matchingPos == marker.length) {
         found = true;
-        out.write(lookbehind[pos]);
-        pos = (pos + 1) % lookbehind.length;
         out.write(contentToInject);
         if (onContentInjected != null) {
           onContentInjected.run();
         }
-        drain(lookbehind.length - 1);
+        drain();
       }
     } else {
       matchingPos = 0;
@@ -77,12 +75,15 @@ public void write(byte[] b, int off, int len) throws IOException {
       out.write(b, off, len);
       return;
     }
-    if (len > marker.length * 2) {
+    if (len > marker.length * 2 - 2) {
+      // if the content is large enough, we can bulk write everything but the N trail and tail.
+      // This because the buffer can already contain some byte from a previous single write.
+      // Also we need to fill the buffer with the tail since we don't know about the next write.
       int idx = arrayContains(b, marker);
       if (idx >= 0) {
         // we have a full match. just write everything
         found = true;
-        drain(lookbehind.length);
+        drain();
         out.write(b, off, idx);
         out.write(contentToInject);
         if (onContentInjected != null) {
@@ -92,15 +93,14 @@ public void write(byte[] b, int off, int len) throws IOException {
       } else {
         // we don't have a full match. write everything in a bulk except the lookbehind buffer
         // sequentially
-        for (int i = off; i < off + marker.length; i++) {
+        for (int i = off; i < off + marker.length - 1; i++) {
           write(b[i]);
         }
-        drain(lookbehind.length);
-        out.write(b, off + marker.length, len - marker.length * 2);
-        for (int i = len - marker.length; i < len; i++) {
+        drain();
+        out.write(b, off + marker.length - 1, len - marker.length * 2 + 2);
+        for (int i = len - marker.length + 1; i < len; i++) {
           write(b[i]);
         }
-        drain(lookbehind.length);
       }
     } else {
       // use slow path because the length to write is small and within the lookbehind buffer size
@@ -128,9 +128,9 @@ private int arrayContains(byte[] array, byte[] search) {
     return -1;
   }
 
-  private void drain(int len) throws IOException {
+  private void drain() throws IOException {
     if (bufferFilled) {
-      for (int i = 0; i < len; i++) {
+      for (int i = 0; i < lookbehind.length; i++) {
         out.write(lookbehind[(pos + i) % lookbehind.length]);
       }
     } else {
@@ -144,7 +144,7 @@ private void drain(int len) throws IOException {
   @Override
   public void close() throws IOException {
     if (!found) {
-      drain(lookbehind.length);
+      drain();
     }
     super.close();
   }

From a4d960d9e778a0ff949056dd934134059e57cc37 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Tue, 8 Jul 2025 16:00:01 +0200
Subject: [PATCH 35/36] review

---
 .../buffer/InjectingPipeOutputStream.java     |  6 ++-
 .../InjectingPipeOutputStreamTest.groovy      | 48 ++++++++++++++++++-
 .../RumHttpServletResponseWrapper.java        |  1 +
 .../RumHttpServletResponseWrapper.java        |  1 +
 4 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
index 47780d5cbb1..74d5b1361d8 100644
--- a/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
+++ b/dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStream.java
@@ -17,6 +17,7 @@ public class InjectingPipeOutputStream extends FilterOutputStream {
   private boolean found = false;
   private int matchingPos = 0;
   private final Runnable onContentInjected;
+  private final int bulkWriteThreshold;
 
   /**
    * @param downstream the delegate output stream
@@ -35,6 +36,7 @@ public InjectingPipeOutputStream(
     this.pos = 0;
     this.contentToInject = contentToInject;
     this.onContentInjected = onContentInjected;
+    this.bulkWriteThreshold = marker.length * 2 - 2;
   }
 
   @Override
@@ -75,7 +77,7 @@ public void write(byte[] b, int off, int len) throws IOException {
       out.write(b, off, len);
       return;
     }
-    if (len > marker.length * 2 - 2) {
+    if (len > bulkWriteThreshold) {
       // if the content is large enough, we can bulk write everything but the N trail and tail.
       // This because the buffer can already contain some byte from a previous single write.
       // Also we need to fill the buffer with the tail since we don't know about the next write.
@@ -97,7 +99,7 @@ public void write(byte[] b, int off, int len) throws IOException {
           write(b[i]);
         }
         drain();
-        out.write(b, off + marker.length - 1, len - marker.length * 2 + 2);
+        out.write(b, off + marker.length - 1, len - bulkWriteThreshold);
         for (int i = len - marker.length + 1; i < len; i++) {
           write(b[i]);
         }
diff --git a/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy b/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy
index d01b38d3a1e..48d552e0a8f 100644
--- a/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy
+++ b/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy
@@ -1,8 +1,27 @@
 package datadog.trace.bootstrap.instrumentation.buffer
 
+import datadog.trace.test.util.DDSpecification
 import spock.lang.Specification
 
-class InjectingPipeOutputStreamTest extends Specification {
+class InjectingPipeOutputStreamTest extends DDSpecification {
+
+  static class ExceptionControlledOutputStream extends FilterOutputStream {
+
+    boolean failWrite = false
+
+    ExceptionControlledOutputStream(OutputStream out) {
+      super(out)
+    }
+
+    @Override
+    void write(int b) throws IOException {
+      if (failWrite) {
+        throw new IOException("Failed")
+      }
+      super.write(b)
+    }
+  }
+
   def 'should filter a buffer and inject if found #found'() {
     setup:
     def downstream = new ByteArrayOutputStream()
@@ -20,4 +39,31 @@ class InjectingPipeOutputStreamTest extends Specification {
     "<html><body/></html>"                    | "</head>"         | "<something/>"          | false | "<html><body/></html>"
     "<foo/>"                                  | "<longerThanFoo>" | "<nothing>"             | false | "<foo/>"
   }
+
+  def 'should maintain the state in case of IOException for epilogue #epilogue'() {
+    setup:
+    def baos = new ByteArrayOutputStream()
+    def downstream = new ExceptionControlledOutputStream(baos)
+    def piped = new OutputStreamWriter(new InjectingPipeOutputStream(downstream, "</head>".getBytes("UTF-8"), "<injected/>".getBytes("UTF-8"), null),
+    "UTF-8")
+    when:
+    piped.write(prologue)
+    piped.flush()
+    downstream.failWrite = true
+    piped.write(epilogue)
+    piped.flush()
+    then:
+    thrown IOException
+    when:
+    downstream.failWrite = false
+    piped.write(epilogue)
+    piped.close()
+    then:
+    def expected = prologue + epilogue
+    assert expected == new String(baos.toByteArray(), "UTF-8")
+    where:
+    prologue                | epilogue
+    "<html><head><script/>" | "</head></html>"
+    "<html><head><script/>" | "</html>"
+  }
 }
diff --git a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
index d87009351ba..6703a47480b 100644
--- a/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
+++ b/dd-java-agent/instrumentation/servlet/request-3/src/main/java/datadog/trace/instrumentation/servlet3/RumHttpServletResponseWrapper.java
@@ -82,5 +82,6 @@ public void onInjected() {
   @Override
   public void setContentType(String type) {
     shouldInject = type != null && type.contains("text/html");
+    super.setContentType(type);
   }
 }
diff --git a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
index ece77c9173e..b9abf618833 100644
--- a/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
+++ b/dd-java-agent/instrumentation/servlet/request-5/src/main/java/datadog/trace/instrumentation/servlet5/RumHttpServletResponseWrapper.java
@@ -82,5 +82,6 @@ public void onInjected() {
   @Override
   public void setContentType(String type) {
     shouldInject = type != null && type.contains("text/html");
+    super.setContentType(type);
   }
 }

From d4e5f6fcb7f6b37ae63ad88073b23e310cab9470 Mon Sep 17 00:00:00 2001
From: Andrea Marziali <andrea.marziali@datadoghq.com>
Date: Tue, 8 Jul 2025 17:04:13 +0200
Subject: [PATCH 36/36] bad commit

---
 .../InjectingPipeOutputStreamTest.groovy      | 28 -------------------
 1 file changed, 28 deletions(-)

diff --git a/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy b/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy
index 48d552e0a8f..3ffa60acc61 100644
--- a/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy
+++ b/dd-java-agent/agent-bootstrap/src/test/groovy/datadog/trace/bootstrap/instrumentation/buffer/InjectingPipeOutputStreamTest.groovy
@@ -1,7 +1,6 @@
 package datadog.trace.bootstrap.instrumentation.buffer
 
 import datadog.trace.test.util.DDSpecification
-import spock.lang.Specification
 
 class InjectingPipeOutputStreamTest extends DDSpecification {
 
@@ -39,31 +38,4 @@ class InjectingPipeOutputStreamTest extends DDSpecification {
     "<html><body/></html>"                    | "</head>"         | "<something/>"          | false | "<html><body/></html>"
     "<foo/>"                                  | "<longerThanFoo>" | "<nothing>"             | false | "<foo/>"
   }
-
-  def 'should maintain the state in case of IOException for epilogue #epilogue'() {
-    setup:
-    def baos = new ByteArrayOutputStream()
-    def downstream = new ExceptionControlledOutputStream(baos)
-    def piped = new OutputStreamWriter(new InjectingPipeOutputStream(downstream, "</head>".getBytes("UTF-8"), "<injected/>".getBytes("UTF-8"), null),
-    "UTF-8")
-    when:
-    piped.write(prologue)
-    piped.flush()
-    downstream.failWrite = true
-    piped.write(epilogue)
-    piped.flush()
-    then:
-    thrown IOException
-    when:
-    downstream.failWrite = false
-    piped.write(epilogue)
-    piped.close()
-    then:
-    def expected = prologue + epilogue
-    assert expected == new String(baos.toByteArray(), "UTF-8")
-    where:
-    prologue                | epilogue
-    "<html><head><script/>" | "</head></html>"
-    "<html><head><script/>" | "</html>"
-  }
 }