From e38d4ad1057d6283d48ce9cef3db9371eb11eeee Mon Sep 17 00:00:00 2001
From: jon-wei <jon.wei@imply.io>
Date: Wed, 21 Feb 2018 17:44:42 -0800
Subject: [PATCH 1/2] Automatically adjust com.metamx.metrics monitor class
 references

---
 .../druid/server/metrics/MonitorsConfig.java  | 40 ++++++++++++++++++-
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/server/src/main/java/io/druid/server/metrics/MonitorsConfig.java b/server/src/main/java/io/druid/server/metrics/MonitorsConfig.java
index 17b03b646d25..d320bc59cb09 100644
--- a/server/src/main/java/io/druid/server/metrics/MonitorsConfig.java
+++ b/server/src/main/java/io/druid/server/metrics/MonitorsConfig.java
@@ -37,15 +37,33 @@ public class MonitorsConfig
 {
   public static final String METRIC_DIMENSION_PREFIX = "druid.metrics.emitter.dimension.";
 
+  /**
+   * Prior to 0.12.0, Druid used Monitor classes from the `com.metamx.metrics` package.
+   * In 0.12.0, these Monitor classes were moved into Druid under `io.druid.java.util.metrics`.
+   * See https://github.com/druid-io/druid/pull/5289 for details.
+   *
+   * We automatically adjust old `com.metamx.metrics` package references to `io.druid.java.util.metrics`
+   * for backwards compatibility purposes, easing the upgrade process for users.
+   */
+  public static final String OLD_METAMX_PACKAGE_NAME = "com.metamx.metrics";
+  public static final String NEW_DRUID_PACKAGE_NAME = "io.druid.java.util.metrics";
+
   @JsonProperty("monitors")
   @NotNull
-  private List<Class<? extends Monitor>> monitors = Lists.newArrayList();
+  private List<Class<? extends Monitor>> monitors;
 
   public List<Class<? extends Monitor>> getMonitors()
   {
     return monitors;
   }
 
+  public MonitorsConfig(
+      @JsonProperty("monitors") List<String> monitorNames
+  )
+  {
+    monitors = getMonitorsFromNames(monitorNames);
+  }
+
   @Override
   public String toString()
   {
@@ -54,7 +72,6 @@ public String toString()
            '}';
   }
 
-
   public static Map<String, String[]> mapOfDatasourceAndTaskID(
       final String datasource,
       final String taskId
@@ -86,4 +103,23 @@ public static Map<String, String[]> extractDimensions(Properties props, List<Str
     }
     return dimensionsMap;
   }
+
+  private static List<Class<? extends Monitor>> getMonitorsFromNames(List<String> monitorNames)
+  {
+    List<Class<? extends Monitor>> monitors = Lists.newArrayList();
+    if (monitorNames == null) {
+      return monitors;
+    }
+    try {
+      for (String monitorName : monitorNames) {
+        String effectiveMonitorName = monitorName.replace(OLD_METAMX_PACKAGE_NAME, NEW_DRUID_PACKAGE_NAME);
+        Class<? extends Monitor> monitorClass = (Class<? extends Monitor>) Class.forName(effectiveMonitorName);
+        monitors.add(monitorClass);
+      }
+      return monitors;
+    }
+    catch (ClassNotFoundException cnfe) {
+      throw new RuntimeException(cnfe);
+    }
+  }
 }

From bf99174720eea385a290139a6d206c5b3a0a33a6 Mon Sep 17 00:00:00 2001
From: jon-wei <jon.wei@imply.io>
Date: Wed, 21 Feb 2018 18:41:13 -0800
Subject: [PATCH 2/2] Log warning for old class names

---
 .../java/io/druid/server/metrics/MonitorsConfig.java  | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/server/src/main/java/io/druid/server/metrics/MonitorsConfig.java b/server/src/main/java/io/druid/server/metrics/MonitorsConfig.java
index d320bc59cb09..05ccdc8a03fe 100644
--- a/server/src/main/java/io/druid/server/metrics/MonitorsConfig.java
+++ b/server/src/main/java/io/druid/server/metrics/MonitorsConfig.java
@@ -22,6 +22,7 @@
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.Lists;
+import io.druid.java.util.common.logger.Logger;
 import io.druid.java.util.metrics.Monitor;
 import io.druid.query.DruidMetrics;
 
@@ -35,6 +36,8 @@
  */
 public class MonitorsConfig
 {
+  private static final Logger log = new Logger(MonitorsConfig.class);
+
   public static final String METRIC_DIMENSION_PREFIX = "druid.metrics.emitter.dimension.";
 
   /**
@@ -113,6 +116,14 @@ private static List<Class<? extends Monitor>> getMonitorsFromNames(List<String>
     try {
       for (String monitorName : monitorNames) {
         String effectiveMonitorName = monitorName.replace(OLD_METAMX_PACKAGE_NAME, NEW_DRUID_PACKAGE_NAME);
+        if (!effectiveMonitorName.equals(monitorName)) {
+          log.warn(
+              "Deprecated Monitor class name [%s] found, please use package %s instead of %s",
+              monitorName,
+              NEW_DRUID_PACKAGE_NAME,
+              OLD_METAMX_PACKAGE_NAME
+          );
+        }
         Class<? extends Monitor> monitorClass = (Class<? extends Monitor>) Class.forName(effectiveMonitorName);
         monitors.add(monitorClass);
       }