From 01ddd769e19e3507211ff0b6d36b69d21b501c19 Mon Sep 17 00:00:00 2001
From: jwatson <jwatson@newrelic.com>
Date: Tue, 1 Oct 2019 16:10:41 -0700
Subject: [PATCH 1/8] A rough idea of how named tracers might look in the API.

---
 .../opentelemetry/DefaultTracerFactory.java   | 24 +++++++
 .../java/io/opentelemetry/OpenTelemetry.java  | 62 ++++++++++---------
 ...TracerProvider.java => TracerFactory.java} | 18 ++++--
 .../io/opentelemetry/OpenTelemetryTest.java   | 24 ++++---
 ...SdkProvider.java => TracerSdkFactory.java} | 22 ++++++-
 .../io.opentelemetry.trace.spi.TracerFactory  |  1 +
 .../io.opentelemetry.trace.spi.TracerProvider |  1 -
 .../sdk/trace/TracerSdkProviderTest.java      |  2 +-
 8 files changed, 110 insertions(+), 44 deletions(-)
 create mode 100644 api/src/main/java/io/opentelemetry/DefaultTracerFactory.java
 rename api/src/main/java/io/opentelemetry/trace/spi/{TracerProvider.java => TracerFactory.java} (63%)
 rename sdk/src/main/java/io/opentelemetry/sdk/trace/{TracerSdkProvider.java => TracerSdkFactory.java} (53%)
 create mode 100644 sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactory
 delete mode 100644 sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerProvider

diff --git a/api/src/main/java/io/opentelemetry/DefaultTracerFactory.java b/api/src/main/java/io/opentelemetry/DefaultTracerFactory.java
new file mode 100644
index 00000000000..4bd8bd75da8
--- /dev/null
+++ b/api/src/main/java/io/opentelemetry/DefaultTracerFactory.java
@@ -0,0 +1,24 @@
+package io.opentelemetry;
+
+import io.opentelemetry.trace.DefaultTracer;
+import io.opentelemetry.trace.Tracer;
+import io.opentelemetry.trace.spi.TracerFactory;
+
+public class DefaultTracerFactory implements TracerFactory {
+
+  private static final TracerFactory instance = new DefaultTracerFactory();
+
+  public static TracerFactory getInstance() {
+    return instance;
+  }
+
+  @Override
+  public Tracer create() {
+    return DefaultTracer.getInstance();
+  }
+
+  @Override
+  public Tracer get(String instrumentationName, String instrumentationVersion) {
+    return create();
+  }
+}
diff --git a/api/src/main/java/io/opentelemetry/OpenTelemetry.java b/api/src/main/java/io/opentelemetry/OpenTelemetry.java
index 74049c8e8d3..cf9cb1befca 100644
--- a/api/src/main/java/io/opentelemetry/OpenTelemetry.java
+++ b/api/src/main/java/io/opentelemetry/OpenTelemetry.java
@@ -24,7 +24,7 @@
 import io.opentelemetry.metrics.spi.MeterProvider;
 import io.opentelemetry.trace.DefaultTracer;
 import io.opentelemetry.trace.Tracer;
-import io.opentelemetry.trace.spi.TracerProvider;
+import io.opentelemetry.trace.spi.TracerFactory;
 import java.util.ServiceLoader;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
@@ -35,7 +35,7 @@
  *
  * <p>The telemetry objects are lazy-loaded singletons resolved via {@link ServiceLoader} mechanism.
  *
- * @see TracerProvider
+ * @see TracerFactory
  * @see MeterProvider
  * @see DistributedContextManagerProvider
  */
@@ -44,7 +44,7 @@ public final class OpenTelemetry {
 
   @Nullable private static volatile OpenTelemetry instance;
 
-  private final Tracer tracer;
+  private final TracerFactory tracerFactory;
   private final Meter meter;
   private final DistributedContextManager contextManager;
 
@@ -56,7 +56,11 @@ public final class OpenTelemetry {
    * @since 0.1.0
    */
   public static Tracer getTracer() {
-    return getInstance().tracer;
+    return getTracer("defaultName", "defaultVersion");
+  }
+
+  public static Tracer getTracer(String instrumentationName, String instrumentationVersion) {
+    return getInstance().tracerFactory.get(instrumentationName, instrumentationVersion);
   }
 
   /**
@@ -83,6 +87,31 @@ public static DistributedContextManager getDistributedContextManager() {
     return getInstance().contextManager;
   }
 
+  /** Lazy loads an instance. */
+  private static OpenTelemetry getInstance() {
+    if (instance == null) {
+      synchronized (OpenTelemetry.class) {
+        if (instance == null) {
+          instance = new OpenTelemetry();
+        }
+      }
+    }
+    return instance;
+  }
+
+  private OpenTelemetry() {
+    TracerFactory tracerFactory = loadSpi(TracerFactory.class);
+    this.tracerFactory = tracerFactory != null ? tracerFactory : DefaultTracerFactory.getInstance();
+    MeterProvider meterProvider = loadSpi(MeterProvider.class);
+    meter = meterProvider != null ? meterProvider.create() : DefaultMeter.getInstance();
+    DistributedContextManagerProvider contextManagerProvider =
+        loadSpi(DistributedContextManagerProvider.class);
+    contextManager =
+        contextManagerProvider != null
+            ? contextManagerProvider.create()
+            : DefaultDistributedContextManager.getInstance();
+  }
+
   /**
    * Load provider class via {@link ServiceLoader}. A specific provider class can be requested via
    * setting a system property with FQCN.
@@ -108,31 +137,6 @@ private static <T> T loadSpi(Class<T> providerClass) {
     return null;
   }
 
-  /** Lazy loads an instance. */
-  private static OpenTelemetry getInstance() {
-    if (instance == null) {
-      synchronized (OpenTelemetry.class) {
-        if (instance == null) {
-          instance = new OpenTelemetry();
-        }
-      }
-    }
-    return instance;
-  }
-
-  private OpenTelemetry() {
-    TracerProvider tracerProvider = loadSpi(TracerProvider.class);
-    tracer = tracerProvider != null ? tracerProvider.create() : DefaultTracer.getInstance();
-    MeterProvider meterProvider = loadSpi(MeterProvider.class);
-    meter = meterProvider != null ? meterProvider.create() : DefaultMeter.getInstance();
-    DistributedContextManagerProvider contextManagerProvider =
-        loadSpi(DistributedContextManagerProvider.class);
-    contextManager =
-        contextManagerProvider != null
-            ? contextManagerProvider.create()
-            : DefaultDistributedContextManager.getInstance();
-  }
-
   // for testing
   static void reset() {
     instance = null;
diff --git a/api/src/main/java/io/opentelemetry/trace/spi/TracerProvider.java b/api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java
similarity index 63%
rename from api/src/main/java/io/opentelemetry/trace/spi/TracerProvider.java
rename to api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java
index 08949bb1a52..10fdbc93ff9 100644
--- a/api/src/main/java/io/opentelemetry/trace/spi/TracerProvider.java
+++ b/api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java
@@ -20,17 +20,17 @@
 import javax.annotation.concurrent.ThreadSafe;
 
 /**
- * TracerProvider is a service provider for {@link Tracer}. Fully qualified class name of the
+ * TracerFactory is a service provider for {@link Tracer}s. Fully qualified class name of the
  * implementation should be registered in {@code
- * META-INF/services/io.opentelemetry.trace.spi.TracerProvider}. <br>
+ * META-INF/services/io.opentelemetry.trace.spi.TracerFactory}. <br>
  * <br>
  * A specific implementation can be selected by a system property {@code
- * io.opentelemetry.trace.spi.TracerProvider} with value of fully qualified class name.
+ * io.opentelemetry.trace.spi.TracerFactory} with value of fully qualified class name.
  *
  * @see io.opentelemetry.OpenTelemetry
  */
 @ThreadSafe
-public interface TracerProvider {
+public interface TracerFactory {
 
   /**
    * Creates a new tracer instance.
@@ -39,4 +39,14 @@ public interface TracerProvider {
    * @since 0.1.0
    */
   Tracer create();
+
+  /**
+   * Gets or creates a named and versioned tracer instance.
+   *
+   * @param instrumentationName The name of the instrumentation library.
+   * @param instrumentationVersion The version of the instrumentation library.
+   * @return a tracer instance.
+   * @since 0.1.0
+   */
+  Tracer get(String instrumentationName, String instrumentationVersion);
 }
diff --git a/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java b/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
index d05f24e4631..f15d4f382fc 100644
--- a/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
+++ b/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
@@ -42,7 +42,7 @@
 import io.opentelemetry.trace.Span;
 import io.opentelemetry.trace.SpanContext;
 import io.opentelemetry.trace.Tracer;
-import io.opentelemetry.trace.spi.TracerProvider;
+import io.opentelemetry.trace.spi.TracerFactory;
 import java.io.File;
 import java.io.FileWriter;
 import java.io.IOException;
@@ -70,7 +70,7 @@ public static void beforeClass() {
   @After
   public void after() {
     OpenTelemetry.reset();
-    System.clearProperty(TracerProvider.class.getName());
+    System.clearProperty(TracerFactory.class.getName());
     System.clearProperty(MeterProvider.class.getName());
     System.clearProperty(DistributedContextManagerProvider.class.getName());
   }
@@ -89,7 +89,7 @@ public void testDefault() {
 
   @Test
   public void testTracerLoadArbitrary() throws IOException {
-    File serviceFile = createService(TracerProvider.class, FirstTracer.class, SecondTracer.class);
+    File serviceFile = createService(TracerFactory.class, FirstTracer.class, SecondTracer.class);
     try {
       assertTrue(
           (OpenTelemetry.getTracer() instanceof FirstTracer)
@@ -102,8 +102,8 @@ public void testTracerLoadArbitrary() throws IOException {
 
   @Test
   public void testTracerSystemProperty() throws IOException {
-    File serviceFile = createService(TracerProvider.class, FirstTracer.class, SecondTracer.class);
-    System.setProperty(TracerProvider.class.getName(), SecondTracer.class.getName());
+    File serviceFile = createService(TracerFactory.class, FirstTracer.class, SecondTracer.class);
+    System.setProperty(TracerFactory.class.getName(), SecondTracer.class.getName());
     try {
       assertThat(OpenTelemetry.getTracer()).isInstanceOf(SecondTracer.class);
       assertThat(OpenTelemetry.getTracer()).isEqualTo(OpenTelemetry.getTracer());
@@ -114,7 +114,7 @@ public void testTracerSystemProperty() throws IOException {
 
   @Test
   public void testTracerNotFound() {
-    System.setProperty(TracerProvider.class.getName(), "io.does.not.exists");
+    System.setProperty(TracerFactory.class.getName(), "io.does.not.exists");
     thrown.expect(IllegalStateException.class);
     OpenTelemetry.getTracer();
   }
@@ -217,14 +217,24 @@ public static class SecondTracer extends FirstTracer {
     public Tracer create() {
       return new SecondTracer();
     }
+
+    @Override
+    public Tracer get(String instrumentationName, String instrumentationVersion) {
+      return create();
+    }
   }
 
-  public static class FirstTracer implements Tracer, TracerProvider {
+  public static class FirstTracer implements Tracer, TracerFactory {
     @Override
     public Tracer create() {
       return new FirstTracer();
     }
 
+    @Override
+    public Tracer get(String instrumentationName, String instrumentationVersion) {
+      return create();
+    }
+
     @Nullable
     @Override
     public Span getCurrentSpan() {
diff --git a/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkProvider.java b/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java
similarity index 53%
rename from sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkProvider.java
rename to sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java
index faf3271819d..4e01849a5c7 100644
--- a/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkProvider.java
+++ b/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java
@@ -17,17 +17,35 @@
 package io.opentelemetry.sdk.trace;
 
 import io.opentelemetry.trace.Tracer;
+import io.opentelemetry.trace.spi.TracerFactory;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
 
 /**
- * {@code Tracer} provider implementation for {@link io.opentelemetry.trace.spi.TracerProvider}.
+ * {@code Tracer} provider implementation for {@link TracerFactory}.
  *
  * <p>This class is not intended to be used in application code and it is used only by {@link
  * io.opentelemetry.OpenTelemetry}.
  */
-public class TracerSdkProvider implements io.opentelemetry.trace.spi.TracerProvider {
+public class TracerSdkFactory implements TracerFactory {
+  private final Map<String, Tracer> tracersByKey =
+      Collections.synchronizedMap(new HashMap<String, Tracer>());
 
   @Override
   public Tracer create() {
     return new TracerSdk();
   }
+
+  @Override
+  public Tracer get(String instrumentationName, String instrumentationVersion) {
+    String key = instrumentationName + "/" + instrumentationVersion;
+    Tracer tracer = tracersByKey.get(key);
+    if (tracer == null) {
+      // todo: pass in the name & version here to the implementation to be used for purposes.
+      tracer = new TracerSdk();
+      tracersByKey.put(key, tracer);
+    }
+    return tracer;
+  }
 }
diff --git a/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactory b/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactory
new file mode 100644
index 00000000000..45a5d30d51f
--- /dev/null
+++ b/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactory
@@ -0,0 +1 @@
+io.opentelemetry.sdk.trace.TracerSdkFactory
diff --git a/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerProvider b/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerProvider
deleted file mode 100644
index c7d60538e5e..00000000000
--- a/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerProvider
+++ /dev/null
@@ -1 +0,0 @@
-io.opentelemetry.sdk.trace.TracerSdkProvider
diff --git a/sdk/src/test/java/io/opentelemetry/sdk/trace/TracerSdkProviderTest.java b/sdk/src/test/java/io/opentelemetry/sdk/trace/TracerSdkProviderTest.java
index c0431b979d8..f480cbbcbe7 100644
--- a/sdk/src/test/java/io/opentelemetry/sdk/trace/TracerSdkProviderTest.java
+++ b/sdk/src/test/java/io/opentelemetry/sdk/trace/TracerSdkProviderTest.java
@@ -27,6 +27,6 @@ public class TracerSdkProviderTest {
 
   @Test
   public void testDefault() {
-    assertThat(new TracerSdkProvider().create()).isInstanceOf(TracerSdk.class);
+    assertThat(new TracerSdkFactory().create()).isInstanceOf(TracerSdk.class);
   }
 }

From ae0a625a1b61698ce9de0cf31fe515ca78f9ec4c Mon Sep 17 00:00:00 2001
From: jwatson <jwatson@newrelic.com>
Date: Wed, 2 Oct 2019 10:19:02 -0700
Subject: [PATCH 2/8] update to require at least a name for the tracer

---
 .../opentelemetry/DefaultTracerFactory.java   | 20 ++++++++++--
 .../trace/spi/TracerFactory.java              |  3 +-
 .../io/opentelemetry/OpenTelemetryTest.java   | 32 +++++++++----------
 .../sdk/trace/TracerSdkFactory.java           |  4 +--
 .../sdk/trace/TracerSdkProviderTest.java      |  2 +-
 5 files changed, 39 insertions(+), 22 deletions(-)

diff --git a/api/src/main/java/io/opentelemetry/DefaultTracerFactory.java b/api/src/main/java/io/opentelemetry/DefaultTracerFactory.java
index 4bd8bd75da8..226e5d772ca 100644
--- a/api/src/main/java/io/opentelemetry/DefaultTracerFactory.java
+++ b/api/src/main/java/io/opentelemetry/DefaultTracerFactory.java
@@ -1,3 +1,19 @@
+/*
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package io.opentelemetry;
 
 import io.opentelemetry.trace.DefaultTracer;
@@ -13,12 +29,12 @@ public static TracerFactory getInstance() {
   }
 
   @Override
-  public Tracer create() {
+  public Tracer get(String instrumentationName) {
     return DefaultTracer.getInstance();
   }
 
   @Override
   public Tracer get(String instrumentationName, String instrumentationVersion) {
-    return create();
+    return get(instrumentationName);
   }
 }
diff --git a/api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java b/api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java
index 10fdbc93ff9..91ecc9310ac 100644
--- a/api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java
+++ b/api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java
@@ -35,10 +35,11 @@ public interface TracerFactory {
   /**
    * Creates a new tracer instance.
    *
+   * @param instrumentationName The name of the instrumentation library.
    * @return a tracer instance.
    * @since 0.1.0
    */
-  Tracer create();
+  Tracer get(String instrumentationName);
 
   /**
    * Gets or creates a named and versioned tracer instance.
diff --git a/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java b/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
index f15d4f382fc..c0dc0cae0df 100644
--- a/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
+++ b/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
@@ -89,12 +89,12 @@ public void testDefault() {
 
   @Test
   public void testTracerLoadArbitrary() throws IOException {
-    File serviceFile = createService(TracerFactory.class, FirstTracer.class, SecondTracer.class);
+    File serviceFile =
+        createService(TracerFactory.class, FirstTracerFactory.class, SecondTracerFactory.class);
     try {
       assertTrue(
-          (OpenTelemetry.getTracer() instanceof FirstTracer)
-              || (OpenTelemetry.getTracer() instanceof SecondTracer));
-      assertThat(OpenTelemetry.getTracer()).isEqualTo(OpenTelemetry.getTracer());
+          (OpenTelemetry.getTracer() instanceof FirstTracerFactory)
+              || (OpenTelemetry.getTracer() instanceof SecondTracerFactory));
     } finally {
       serviceFile.delete();
     }
@@ -102,11 +102,11 @@ public void testTracerLoadArbitrary() throws IOException {
 
   @Test
   public void testTracerSystemProperty() throws IOException {
-    File serviceFile = createService(TracerFactory.class, FirstTracer.class, SecondTracer.class);
-    System.setProperty(TracerFactory.class.getName(), SecondTracer.class.getName());
+    File serviceFile =
+        createService(TracerFactory.class, FirstTracerFactory.class, SecondTracerFactory.class);
+    System.setProperty(TracerFactory.class.getName(), SecondTracerFactory.class.getName());
     try {
-      assertThat(OpenTelemetry.getTracer()).isInstanceOf(SecondTracer.class);
-      assertThat(OpenTelemetry.getTracer()).isEqualTo(OpenTelemetry.getTracer());
+      assertThat(OpenTelemetry.getTracer()).isInstanceOf(SecondTracerFactory.class);
     } finally {
       serviceFile.delete();
     }
@@ -212,27 +212,27 @@ private static File createService(Class<?> service, Class<?>... impls) throws IO
     return file;
   }
 
-  public static class SecondTracer extends FirstTracer {
+  public static class SecondTracerFactory extends FirstTracerFactory {
     @Override
-    public Tracer create() {
-      return new SecondTracer();
+    public Tracer get(String instrumentationName) {
+      return new SecondTracerFactory();
     }
 
     @Override
     public Tracer get(String instrumentationName, String instrumentationVersion) {
-      return create();
+      return get(instrumentationName);
     }
   }
 
-  public static class FirstTracer implements Tracer, TracerFactory {
+  public static class FirstTracerFactory implements Tracer, TracerFactory {
     @Override
-    public Tracer create() {
-      return new FirstTracer();
+    public Tracer get(String instrumentationName) {
+      return new FirstTracerFactory();
     }
 
     @Override
     public Tracer get(String instrumentationName, String instrumentationVersion) {
-      return create();
+      return get(instrumentationName);
     }
 
     @Nullable
diff --git a/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java b/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java
index 4e01849a5c7..310341de09a 100644
--- a/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java
+++ b/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java
@@ -33,8 +33,8 @@ public class TracerSdkFactory implements TracerFactory {
       Collections.synchronizedMap(new HashMap<String, Tracer>());
 
   @Override
-  public Tracer create() {
-    return new TracerSdk();
+  public Tracer get(String instrumentationName) {
+    return get(instrumentationName, null);
   }
 
   @Override
diff --git a/sdk/src/test/java/io/opentelemetry/sdk/trace/TracerSdkProviderTest.java b/sdk/src/test/java/io/opentelemetry/sdk/trace/TracerSdkProviderTest.java
index f480cbbcbe7..b92088bc411 100644
--- a/sdk/src/test/java/io/opentelemetry/sdk/trace/TracerSdkProviderTest.java
+++ b/sdk/src/test/java/io/opentelemetry/sdk/trace/TracerSdkProviderTest.java
@@ -27,6 +27,6 @@ public class TracerSdkProviderTest {
 
   @Test
   public void testDefault() {
-    assertThat(new TracerSdkFactory().create()).isInstanceOf(TracerSdk.class);
+    assertThat(new TracerSdkFactory().get("testInstrumentation")).isInstanceOf(TracerSdk.class);
   }
 }

From 5eb46564e1b914b9724c1e99e19bd6ab4ff9b3a7 Mon Sep 17 00:00:00 2001
From: jwatson <jwatson@newrelic.com>
Date: Fri, 11 Oct 2019 07:48:17 -0700
Subject: [PATCH 3/8] Introduce another layer of factory for the provider

---
 .../java/io/opentelemetry/OpenTelemetry.java  | 21 ++++++++--
 .../{ => trace}/DefaultTracerFactory.java     |  6 +--
 .../trace/DefaultTracerFactoryProvider.java   | 32 ++++++++++++++
 .../trace/{spi => }/TracerFactory.java        | 12 ++----
 .../trace/spi/TracerFactoryProvider.java      | 42 +++++++++++++++++++
 .../io/opentelemetry/OpenTelemetryTest.java   | 27 ++++++++----
 .../sdk/trace/TracerSdkFactory.java           |  2 +-
 .../sdk/trace/TracerSdkFactoryProvider.java   | 28 +++++++++++++
 .../io.opentelemetry.trace.spi.TracerFactory  |  1 -
 ...ntelemetry.trace.spi.TracerFactoryProvider |  1 +
 10 files changed, 146 insertions(+), 26 deletions(-)
 rename api/src/main/java/io/opentelemetry/{ => trace}/DefaultTracerFactory.java (86%)
 create mode 100644 api/src/main/java/io/opentelemetry/trace/DefaultTracerFactoryProvider.java
 rename api/src/main/java/io/opentelemetry/trace/{spi => }/TracerFactory.java (74%)
 create mode 100644 api/src/main/java/io/opentelemetry/trace/spi/TracerFactoryProvider.java
 create mode 100644 sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactoryProvider.java
 delete mode 100644 sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactory
 create mode 100644 sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactoryProvider

diff --git a/api/src/main/java/io/opentelemetry/OpenTelemetry.java b/api/src/main/java/io/opentelemetry/OpenTelemetry.java
index cf9cb1befca..b07e2061897 100644
--- a/api/src/main/java/io/opentelemetry/OpenTelemetry.java
+++ b/api/src/main/java/io/opentelemetry/OpenTelemetry.java
@@ -23,8 +23,10 @@
 import io.opentelemetry.metrics.Meter;
 import io.opentelemetry.metrics.spi.MeterProvider;
 import io.opentelemetry.trace.DefaultTracer;
+import io.opentelemetry.trace.DefaultTracerFactoryProvider;
 import io.opentelemetry.trace.Tracer;
-import io.opentelemetry.trace.spi.TracerFactory;
+import io.opentelemetry.trace.TracerFactory;
+import io.opentelemetry.trace.spi.TracerFactoryProvider;
 import java.util.ServiceLoader;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
@@ -56,9 +58,16 @@ public final class OpenTelemetry {
    * @since 0.1.0
    */
   public static Tracer getTracer() {
-    return getTracer("defaultName", "defaultVersion");
+    return getTracer("defaultInstrumentationName", "defaultInstrumentationVersion");
   }
 
+  /**
+   * Returns a named {@link Tracer} with the provided instrumentation name and version.
+   *
+   * @return registered tracer or default via {@link DefaultTracer#getInstance()}.
+   * @throws IllegalStateException if a specified tracer (via system properties) could not be found.
+   * @since 0.1.0
+   */
   public static Tracer getTracer(String instrumentationName, String instrumentationVersion) {
     return getInstance().tracerFactory.get(instrumentationName, instrumentationVersion);
   }
@@ -100,8 +109,12 @@ private static OpenTelemetry getInstance() {
   }
 
   private OpenTelemetry() {
-    TracerFactory tracerFactory = loadSpi(TracerFactory.class);
-    this.tracerFactory = tracerFactory != null ? tracerFactory : DefaultTracerFactory.getInstance();
+    TracerFactoryProvider tracerFactoryProvider = loadSpi(TracerFactoryProvider.class);
+    this.tracerFactory =
+        tracerFactoryProvider != null
+            ? tracerFactoryProvider.create()
+            : DefaultTracerFactoryProvider.getInstance().create();
+
     MeterProvider meterProvider = loadSpi(MeterProvider.class);
     meter = meterProvider != null ? meterProvider.create() : DefaultMeter.getInstance();
     DistributedContextManagerProvider contextManagerProvider =
diff --git a/api/src/main/java/io/opentelemetry/DefaultTracerFactory.java b/api/src/main/java/io/opentelemetry/trace/DefaultTracerFactory.java
similarity index 86%
rename from api/src/main/java/io/opentelemetry/DefaultTracerFactory.java
rename to api/src/main/java/io/opentelemetry/trace/DefaultTracerFactory.java
index 226e5d772ca..7ed2775f081 100644
--- a/api/src/main/java/io/opentelemetry/DefaultTracerFactory.java
+++ b/api/src/main/java/io/opentelemetry/trace/DefaultTracerFactory.java
@@ -14,11 +14,7 @@
  * limitations under the License.
  */
 
-package io.opentelemetry;
-
-import io.opentelemetry.trace.DefaultTracer;
-import io.opentelemetry.trace.Tracer;
-import io.opentelemetry.trace.spi.TracerFactory;
+package io.opentelemetry.trace;
 
 public class DefaultTracerFactory implements TracerFactory {
 
diff --git a/api/src/main/java/io/opentelemetry/trace/DefaultTracerFactoryProvider.java b/api/src/main/java/io/opentelemetry/trace/DefaultTracerFactoryProvider.java
new file mode 100644
index 00000000000..0b31d4bd7b0
--- /dev/null
+++ b/api/src/main/java/io/opentelemetry/trace/DefaultTracerFactoryProvider.java
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opentelemetry.trace;
+
+import io.opentelemetry.trace.spi.TracerFactoryProvider;
+
+public class DefaultTracerFactoryProvider implements TracerFactoryProvider {
+  private static final TracerFactoryProvider instance = new DefaultTracerFactoryProvider();
+
+  public static TracerFactoryProvider getInstance() {
+    return instance;
+  }
+
+  @Override
+  public TracerFactory create() {
+    return DefaultTracerFactory.getInstance();
+  }
+}
diff --git a/api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java b/api/src/main/java/io/opentelemetry/trace/TracerFactory.java
similarity index 74%
rename from api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java
rename to api/src/main/java/io/opentelemetry/trace/TracerFactory.java
index 91ecc9310ac..cdae6544cc0 100644
--- a/api/src/main/java/io/opentelemetry/trace/spi/TracerFactory.java
+++ b/api/src/main/java/io/opentelemetry/trace/TracerFactory.java
@@ -14,20 +14,16 @@
  * limitations under the License.
  */
 
-package io.opentelemetry.trace.spi;
+package io.opentelemetry.trace;
 
-import io.opentelemetry.trace.Tracer;
 import javax.annotation.concurrent.ThreadSafe;
 
 /**
- * TracerFactory is a service provider for {@link Tracer}s. Fully qualified class name of the
- * implementation should be registered in {@code
- * META-INF/services/io.opentelemetry.trace.spi.TracerFactory}. <br>
- * <br>
- * A specific implementation can be selected by a system property {@code
- * io.opentelemetry.trace.spi.TracerFactory} with value of fully qualified class name.
+ * A factory for creating named {@link Tracer}s.
  *
  * @see io.opentelemetry.OpenTelemetry
+ * @see io.opentelemetry.trace.Tracer
+ * @since 0.1.0
  */
 @ThreadSafe
 public interface TracerFactory {
diff --git a/api/src/main/java/io/opentelemetry/trace/spi/TracerFactoryProvider.java b/api/src/main/java/io/opentelemetry/trace/spi/TracerFactoryProvider.java
new file mode 100644
index 00000000000..7cd11047906
--- /dev/null
+++ b/api/src/main/java/io/opentelemetry/trace/spi/TracerFactoryProvider.java
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opentelemetry.trace.spi;
+
+import io.opentelemetry.trace.TracerFactory;
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * TracerFactoryProvider is a service provider for a {@link TracerFactory}s. Fully qualified class
+ * name of the implementation should be registered in {@code
+ * META-INF/services/io.opentelemetry.trace.spi.TracerFactoryProvider}. <br>
+ * <br>
+ * A specific implementation can be selected by a system property {@code
+ * io.opentelemetry.trace.spi.TracerFactoryProvider} with value of fully qualified class name.
+ *
+ * @see io.opentelemetry.OpenTelemetry
+ */
+@ThreadSafe
+public interface TracerFactoryProvider {
+
+  /**
+   * Creates a new TracerFactory.
+   *
+   * @return a new TracerFactory.
+   * @since 0.1.0
+   */
+  TracerFactory create();
+}
diff --git a/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java b/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
index c0dc0cae0df..174fbf90139 100644
--- a/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
+++ b/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
@@ -42,7 +42,8 @@
 import io.opentelemetry.trace.Span;
 import io.opentelemetry.trace.SpanContext;
 import io.opentelemetry.trace.Tracer;
-import io.opentelemetry.trace.spi.TracerFactory;
+import io.opentelemetry.trace.TracerFactory;
+import io.opentelemetry.trace.spi.TracerFactoryProvider;
 import java.io.File;
 import java.io.FileWriter;
 import java.io.IOException;
@@ -70,7 +71,7 @@ public static void beforeClass() {
   @After
   public void after() {
     OpenTelemetry.reset();
-    System.clearProperty(TracerFactory.class.getName());
+    System.clearProperty(TracerFactoryProvider.class.getName());
     System.clearProperty(MeterProvider.class.getName());
     System.clearProperty(DistributedContextManagerProvider.class.getName());
   }
@@ -90,7 +91,8 @@ public void testDefault() {
   @Test
   public void testTracerLoadArbitrary() throws IOException {
     File serviceFile =
-        createService(TracerFactory.class, FirstTracerFactory.class, SecondTracerFactory.class);
+        createService(
+            TracerFactoryProvider.class, FirstTracerFactory.class, SecondTracerFactory.class);
     try {
       assertTrue(
           (OpenTelemetry.getTracer() instanceof FirstTracerFactory)
@@ -103,8 +105,9 @@ public void testTracerLoadArbitrary() throws IOException {
   @Test
   public void testTracerSystemProperty() throws IOException {
     File serviceFile =
-        createService(TracerFactory.class, FirstTracerFactory.class, SecondTracerFactory.class);
-    System.setProperty(TracerFactory.class.getName(), SecondTracerFactory.class.getName());
+        createService(
+            TracerFactoryProvider.class, FirstTracerFactory.class, SecondTracerFactory.class);
+    System.setProperty(TracerFactoryProvider.class.getName(), SecondTracerFactory.class.getName());
     try {
       assertThat(OpenTelemetry.getTracer()).isInstanceOf(SecondTracerFactory.class);
     } finally {
@@ -114,7 +117,7 @@ public void testTracerSystemProperty() throws IOException {
 
   @Test
   public void testTracerNotFound() {
-    System.setProperty(TracerFactory.class.getName(), "io.does.not.exists");
+    System.setProperty(TracerFactoryProvider.class.getName(), "io.does.not.exists");
     thrown.expect(IllegalStateException.class);
     OpenTelemetry.getTracer();
   }
@@ -222,9 +225,14 @@ public Tracer get(String instrumentationName) {
     public Tracer get(String instrumentationName, String instrumentationVersion) {
       return get(instrumentationName);
     }
+
+    @Override
+    public TracerFactory create() {
+      return new SecondTracerFactory();
+    }
   }
 
-  public static class FirstTracerFactory implements Tracer, TracerFactory {
+  public static class FirstTracerFactory implements Tracer, TracerFactory, TracerFactoryProvider {
     @Override
     public Tracer get(String instrumentationName) {
       return new FirstTracerFactory();
@@ -264,6 +272,11 @@ public BinaryFormat<SpanContext> getBinaryFormat() {
     public HttpTextFormat<SpanContext> getHttpTextFormat() {
       return null;
     }
+
+    @Override
+    public TracerFactory create() {
+      return new FirstTracerFactory();
+    }
   }
 
   public static class SecondMeter extends FirstMeter {
diff --git a/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java b/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java
index 310341de09a..0081d93fb3b 100644
--- a/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java
+++ b/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactory.java
@@ -17,7 +17,7 @@
 package io.opentelemetry.sdk.trace;
 
 import io.opentelemetry.trace.Tracer;
-import io.opentelemetry.trace.spi.TracerFactory;
+import io.opentelemetry.trace.TracerFactory;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
diff --git a/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactoryProvider.java b/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactoryProvider.java
new file mode 100644
index 00000000000..cf1a7ba2155
--- /dev/null
+++ b/sdk/src/main/java/io/opentelemetry/sdk/trace/TracerSdkFactoryProvider.java
@@ -0,0 +1,28 @@
+/*
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opentelemetry.sdk.trace;
+
+import io.opentelemetry.trace.TracerFactory;
+import io.opentelemetry.trace.spi.TracerFactoryProvider;
+
+/** SDK implementation of the TracerProviderFactory for SPI. */
+public class TracerSdkFactoryProvider implements TracerFactoryProvider {
+  @Override
+  public TracerFactory create() {
+    return new TracerSdkFactory();
+  }
+}
diff --git a/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactory b/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactory
deleted file mode 100644
index 45a5d30d51f..00000000000
--- a/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactory
+++ /dev/null
@@ -1 +0,0 @@
-io.opentelemetry.sdk.trace.TracerSdkFactory
diff --git a/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactoryProvider b/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactoryProvider
new file mode 100644
index 00000000000..6be0bc33c27
--- /dev/null
+++ b/sdk/src/main/resources/META-INF/services/io.opentelemetry.trace.spi.TracerFactoryProvider
@@ -0,0 +1 @@
+io.opentelemetry.sdk.trace.TracerSdkFactoryProvider

From b959240d7a086714747e5262e8d7c899fe710228 Mon Sep 17 00:00:00 2001
From: jwatson <jwatson@newrelic.com>
Date: Mon, 14 Oct 2019 13:55:20 -0700
Subject: [PATCH 4/8] remove convenience tracer methods from the OpenTelemetry
 class.

---
 .../java/io/opentelemetry/OpenTelemetry.java  | 24 ++++++-------------
 .../io/opentelemetry/OpenTelemetryTest.java   | 14 ++++++-----
 .../opentracingshim/TraceShim.java            |  4 +++-
 .../opentelemetry/sdk/OpenTelemetrySdk.java   |  9 +++----
 .../sdk/OpenTelemetrySdkTest.java             |  3 ++-
 5 files changed, 25 insertions(+), 29 deletions(-)

diff --git a/api/src/main/java/io/opentelemetry/OpenTelemetry.java b/api/src/main/java/io/opentelemetry/OpenTelemetry.java
index b07e2061897..cbce580e7c4 100644
--- a/api/src/main/java/io/opentelemetry/OpenTelemetry.java
+++ b/api/src/main/java/io/opentelemetry/OpenTelemetry.java
@@ -22,7 +22,7 @@
 import io.opentelemetry.metrics.DefaultMeter;
 import io.opentelemetry.metrics.Meter;
 import io.opentelemetry.metrics.spi.MeterProvider;
-import io.opentelemetry.trace.DefaultTracer;
+import io.opentelemetry.trace.DefaultTracerFactory;
 import io.opentelemetry.trace.DefaultTracerFactoryProvider;
 import io.opentelemetry.trace.Tracer;
 import io.opentelemetry.trace.TracerFactory;
@@ -51,25 +51,15 @@ public final class OpenTelemetry {
   private final DistributedContextManager contextManager;
 
   /**
-   * Returns a singleton {@link Tracer}.
+   * Returns a singleton {@link TracerFactory}.
    *
-   * @return registered tracer or default via {@link DefaultTracer#getInstance()}.
-   * @throws IllegalStateException if a specified tracer (via system properties) could not be found.
-   * @since 0.1.0
-   */
-  public static Tracer getTracer() {
-    return getTracer("defaultInstrumentationName", "defaultInstrumentationVersion");
-  }
-
-  /**
-   * Returns a named {@link Tracer} with the provided instrumentation name and version.
-   *
-   * @return registered tracer or default via {@link DefaultTracer#getInstance()}.
-   * @throws IllegalStateException if a specified tracer (via system properties) could not be found.
+   * @return registered TracerFactory of default via {@link DefaultTracerFactory#getInstance()}.
+   * @throws IllegalStateException if a specified TracerFactory (via system properties) could not be
+   *     found.
    * @since 0.1.0
    */
-  public static Tracer getTracer(String instrumentationName, String instrumentationVersion) {
-    return getInstance().tracerFactory.get(instrumentationName, instrumentationVersion);
+  public static TracerFactory getTracerFactory() {
+    return getInstance().tracerFactory;
   }
 
   /**
diff --git a/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java b/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
index 174fbf90139..7c64e7c3700 100644
--- a/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
+++ b/api/src/test/java/io/opentelemetry/OpenTelemetryTest.java
@@ -78,8 +78,10 @@ public void after() {
 
   @Test
   public void testDefault() {
-    assertThat(OpenTelemetry.getTracer()).isInstanceOf(DefaultTracer.getInstance().getClass());
-    assertThat(OpenTelemetry.getTracer()).isEqualTo(OpenTelemetry.getTracer());
+    assertThat(OpenTelemetry.getTracerFactory().get("testTracer"))
+        .isInstanceOf(DefaultTracer.getInstance().getClass());
+    assertThat(OpenTelemetry.getTracerFactory().get("testTracer"))
+        .isEqualTo(OpenTelemetry.getTracerFactory().get("testTracer"));
     assertThat(OpenTelemetry.getMeter()).isInstanceOf(DefaultMeter.getInstance().getClass());
     assertThat(OpenTelemetry.getMeter()).isEqualTo(OpenTelemetry.getMeter());
     assertThat(OpenTelemetry.getDistributedContextManager())
@@ -95,8 +97,8 @@ public void testTracerLoadArbitrary() throws IOException {
             TracerFactoryProvider.class, FirstTracerFactory.class, SecondTracerFactory.class);
     try {
       assertTrue(
-          (OpenTelemetry.getTracer() instanceof FirstTracerFactory)
-              || (OpenTelemetry.getTracer() instanceof SecondTracerFactory));
+          (OpenTelemetry.getTracerFactory() instanceof FirstTracerFactory)
+              || (OpenTelemetry.getTracerFactory() instanceof SecondTracerFactory));
     } finally {
       serviceFile.delete();
     }
@@ -109,7 +111,7 @@ public void testTracerSystemProperty() throws IOException {
             TracerFactoryProvider.class, FirstTracerFactory.class, SecondTracerFactory.class);
     System.setProperty(TracerFactoryProvider.class.getName(), SecondTracerFactory.class.getName());
     try {
-      assertThat(OpenTelemetry.getTracer()).isInstanceOf(SecondTracerFactory.class);
+      assertThat(OpenTelemetry.getTracerFactory()).isInstanceOf(SecondTracerFactory.class);
     } finally {
       serviceFile.delete();
     }
@@ -119,7 +121,7 @@ public void testTracerSystemProperty() throws IOException {
   public void testTracerNotFound() {
     System.setProperty(TracerFactoryProvider.class.getName(), "io.does.not.exists");
     thrown.expect(IllegalStateException.class);
-    OpenTelemetry.getTracer();
+    OpenTelemetry.getTracerFactory().get("testTracer");
   }
 
   @Test
diff --git a/opentracing_shim/src/main/java/io/opentelemetry/opentracingshim/TraceShim.java b/opentracing_shim/src/main/java/io/opentelemetry/opentracingshim/TraceShim.java
index 50086716ed2..68ac7baca6f 100644
--- a/opentracing_shim/src/main/java/io/opentelemetry/opentracingshim/TraceShim.java
+++ b/opentracing_shim/src/main/java/io/opentelemetry/opentracingshim/TraceShim.java
@@ -32,7 +32,9 @@ private TraceShim() {}
    */
   public static io.opentracing.Tracer createTracerShim() {
     return new TracerShim(
-        new TelemetryInfo(OpenTelemetry.getTracer(), OpenTelemetry.getDistributedContextManager()));
+        new TelemetryInfo(
+            OpenTelemetry.getTracerFactory().get("openTracingShim"),
+            OpenTelemetry.getDistributedContextManager()));
   }
 
   /**
diff --git a/sdk/src/main/java/io/opentelemetry/sdk/OpenTelemetrySdk.java b/sdk/src/main/java/io/opentelemetry/sdk/OpenTelemetrySdk.java
index a85b75e6fec..7d3d6c66194 100644
--- a/sdk/src/main/java/io/opentelemetry/sdk/OpenTelemetrySdk.java
+++ b/sdk/src/main/java/io/opentelemetry/sdk/OpenTelemetrySdk.java
@@ -20,6 +20,7 @@
 import io.opentelemetry.sdk.distributedcontext.DistributedContextManagerSdk;
 import io.opentelemetry.sdk.metrics.MeterSdk;
 import io.opentelemetry.sdk.trace.TracerSdk;
+import io.opentelemetry.sdk.trace.TracerSdkFactory;
 import javax.annotation.concurrent.ThreadSafe;
 
 /**
@@ -34,13 +35,13 @@
 @ThreadSafe
 public final class OpenTelemetrySdk {
   /**
-   * Returns a {@link TracerSdk}.
+   * Returns a {@link TracerSdkFactory}.
    *
-   * @return tracer returned by {@link OpenTelemetry#getTracer()}.
+   * @return TracerFactory returned by {@link OpenTelemetry#getTracerFactory()}.
    * @since 0.1.0
    */
-  public static TracerSdk getTracer() {
-    return (TracerSdk) OpenTelemetry.getTracer();
+  public static TracerSdkFactory getTracerFactory() {
+    return (TracerSdkFactory) OpenTelemetry.getTracerFactory();
   }
 
   /**
diff --git a/sdk/src/test/java/io/opentelemetry/sdk/OpenTelemetrySdkTest.java b/sdk/src/test/java/io/opentelemetry/sdk/OpenTelemetrySdkTest.java
index d4391c0b5a8..87c543edfb8 100644
--- a/sdk/src/test/java/io/opentelemetry/sdk/OpenTelemetrySdkTest.java
+++ b/sdk/src/test/java/io/opentelemetry/sdk/OpenTelemetrySdkTest.java
@@ -28,7 +28,8 @@ public class OpenTelemetrySdkTest {
 
   @Test
   public void testDefault() {
-    assertThat(OpenTelemetrySdk.getTracer()).isSameInstanceAs(OpenTelemetry.getTracer());
+    assertThat(OpenTelemetrySdk.getTracerFactory())
+        .isSameInstanceAs(OpenTelemetry.getTracerFactory());
     assertThat(OpenTelemetrySdk.getDistributedContextManager())
         .isSameInstanceAs(OpenTelemetry.getDistributedContextManager());
     assertThat(OpenTelemetrySdk.getMeter()).isSameInstanceAs(OpenTelemetry.getMeter());

From 3fdb6344dd6a9b1e93bcd8927ead46a31da65e79 Mon Sep 17 00:00:00 2001
From: John Watson <jkwatson@gmail.com>
Date: Tue, 15 Oct 2019 09:48:17 -0700
Subject: [PATCH 5/8] Update
 api/src/main/java/io/opentelemetry/trace/spi/TracerFactoryProvider.java

Co-Authored-By: Armin Ruech <armin.ruech@gmail.com>
---
 .../java/io/opentelemetry/trace/spi/TracerFactoryProvider.java  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/api/src/main/java/io/opentelemetry/trace/spi/TracerFactoryProvider.java b/api/src/main/java/io/opentelemetry/trace/spi/TracerFactoryProvider.java
index 7cd11047906..8f052284862 100644
--- a/api/src/main/java/io/opentelemetry/trace/spi/TracerFactoryProvider.java
+++ b/api/src/main/java/io/opentelemetry/trace/spi/TracerFactoryProvider.java
@@ -20,7 +20,7 @@
 import javax.annotation.concurrent.ThreadSafe;
 
 /**
- * TracerFactoryProvider is a service provider for a {@link TracerFactory}s. Fully qualified class
+ * TracerFactoryProvider is a service provider for a {@link TracerFactory}. Fully qualified class
  * name of the implementation should be registered in {@code
  * META-INF/services/io.opentelemetry.trace.spi.TracerFactoryProvider}. <br>
  * <br>

From 65d9869bf1f0e7ea7b8782c74b97f4e0f93e2278 Mon Sep 17 00:00:00 2001
From: John Watson <jkwatson@gmail.com>
Date: Tue, 15 Oct 2019 09:48:35 -0700
Subject: [PATCH 6/8] Update
 api/src/main/java/io/opentelemetry/trace/TracerFactory.java

Co-Authored-By: Armin Ruech <armin.ruech@gmail.com>
---
 api/src/main/java/io/opentelemetry/trace/TracerFactory.java | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/api/src/main/java/io/opentelemetry/trace/TracerFactory.java b/api/src/main/java/io/opentelemetry/trace/TracerFactory.java
index cdae6544cc0..505f95770cb 100644
--- a/api/src/main/java/io/opentelemetry/trace/TracerFactory.java
+++ b/api/src/main/java/io/opentelemetry/trace/TracerFactory.java
@@ -29,7 +29,7 @@
 public interface TracerFactory {
 
   /**
-   * Creates a new tracer instance.
+   * Gets or creates a named tracer instance.
    *
    * @param instrumentationName The name of the instrumentation library.
    * @return a tracer instance.

From d8f4283999fd4bc80427ef9f25a4c0a7f08677df Mon Sep 17 00:00:00 2001
From: jwatson <jwatson@newrelic.com>
Date: Tue, 15 Oct 2019 11:03:39 -0700
Subject: [PATCH 7/8] Add clarifying javadoc, per PR review

---
 api/src/main/java/io/opentelemetry/trace/TracerFactory.java | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/api/src/main/java/io/opentelemetry/trace/TracerFactory.java b/api/src/main/java/io/opentelemetry/trace/TracerFactory.java
index 505f95770cb..f1ef1b671ca 100644
--- a/api/src/main/java/io/opentelemetry/trace/TracerFactory.java
+++ b/api/src/main/java/io/opentelemetry/trace/TracerFactory.java
@@ -31,7 +31,8 @@ public interface TracerFactory {
   /**
    * Gets or creates a named tracer instance.
    *
-   * @param instrumentationName The name of the instrumentation library.
+   * @param instrumentationName The name of the instrumentation library, not the name of the
+   *     instrument*ed* library.
    * @return a tracer instance.
    * @since 0.1.0
    */
@@ -40,7 +41,8 @@ public interface TracerFactory {
   /**
    * Gets or creates a named and versioned tracer instance.
    *
-   * @param instrumentationName The name of the instrumentation library.
+   * @param instrumentationName The name of the instrumentation library, not the name of the
+   *     instrument*ed* library.
    * @param instrumentationVersion The version of the instrumentation library.
    * @return a tracer instance.
    * @since 0.1.0

From 11f30edd6b7bcda3533bd98ac911d08093a5fdaf Mon Sep 17 00:00:00 2001
From: jwatson <jwatson@newrelic.com>
Date: Mon, 21 Oct 2019 08:49:44 -0700
Subject: [PATCH 8/8] reverse who calls whom

---
 .../java/io/opentelemetry/trace/DefaultTracerFactory.java     | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/api/src/main/java/io/opentelemetry/trace/DefaultTracerFactory.java b/api/src/main/java/io/opentelemetry/trace/DefaultTracerFactory.java
index 7ed2775f081..72a31145c12 100644
--- a/api/src/main/java/io/opentelemetry/trace/DefaultTracerFactory.java
+++ b/api/src/main/java/io/opentelemetry/trace/DefaultTracerFactory.java
@@ -26,11 +26,11 @@ public static TracerFactory getInstance() {
 
   @Override
   public Tracer get(String instrumentationName) {
-    return DefaultTracer.getInstance();
+    return get(instrumentationName, null);
   }
 
   @Override
   public Tracer get(String instrumentationName, String instrumentationVersion) {
-    return get(instrumentationName);
+    return DefaultTracer.getInstance();
   }
 }