core, census, testing, interop-testing, android-interop-testing: move census dependency out of grpc-core (#6577)

Decouples grpc-core with census, while still preserve the default integration of census in grpc-core. Users wishing to enable census needs to add grpc-census to their runtime classpath.

- Created a grpc-census module:
    - Moved CensusStatsModule.java and CensusTracingModule.java into grpc-census from grpc-core. CensusModuleTests.java is also moved. They now belong to io.grpc.census package.
Moved DeprecatedCensusConstants.java into io.grpc.census.internal (is this necessary?) in grpc-census.
    - Created CensusStatsAccessor.java and CensusTracingAccessor.java, which are used to create census ClientInterceptor and ServerStreamTracer.Factory.
    - Everything in grpc-census are package private, except the accessor classes. They only publicly expose ClientInterceptor and ServerStreamTracer.Factory, no Census specific types are exposed.

- Use runtime reflection to load and apply census stats/tracing to channel/server builders, if grpc-census is found in runtime classpath.

- Removed special APIs on AbstractManagedChannelImplBuilder and AbstractServerImplBuilder for overriding census module. They are only used for testing. Now we changed tests to apply Census ClientInterceptor and ServerStreamTracer.Factory just as normal interceptor/stream tracer factory. Test writer is responsible for taking care of the ordering concerns of interceptors and stream tracer factories.

android-interop-testing/app/build.gradle

@@ -73,6 +73,7 @@ dependencies {
 
     // You need to build grpc-java to obtain the grpc libraries below.
     implementation 'io.grpc:grpc-auth:1.27.0-SNAPSHOT' // CURRENT_GRPC_VERSION
+    implementation 'io.grpc:grpc-census:1.27.0-SNAPSHOT' // CURRENT_GRPC_VERSION
     implementation 'io.grpc:grpc-okhttp:1.27.0-SNAPSHOT' // CURRENT_GRPC_VERSION
     implementation 'io.grpc:grpc-protobuf-lite:1.27.0-SNAPSHOT' // CURRENT_GRPC_VERSION
     implementation 'io.grpc:grpc-stub:1.27.0-SNAPSHOT' // CURRENT_GRPC_VERSION

census/BUILD.bazel

@@ -0,0 +1,15 @@
+java_library(
+    name = "census",
+    srcs = glob([
+        "src/main/java/**/*.java",
+    ]),
+    visibility = ["//visibility:public"],
+    deps = [
+            "//api",
+            "//context",
+            "@com_google_code_findbugs_jsr305//jar",
+            "@com_google_guava_guava//jar",
+            "@io_opencensus_opencensus_api//jar",
+            "@io_opencensus_opencensus_contrib_grpc_metrics//jar",
+    ],
+)

census/build.gradle

@@ -0,0 +1,43 @@
+plugins {
+    id "java"
+    id "maven-publish"
+}
+
+description = 'gRPC: Census'
+
+evaluationDependsOn(project(':grpc-api').path)
+
+dependencies {
+    compile project(':grpc-api')
+            
+    compile (libraries.opencensus_api) {
+        // prefer 3.0.2 from libraries instead of 3.0.1
+        exclude group: 'com.google.code.findbugs', module: 'jsr305'
+        // prefer 20.0 from libraries instead of 19.0
+        exclude group: 'com.google.guava', module: 'guava'
+        // we'll always be more up-to-date
+        exclude group: 'io.grpc', module: 'grpc-context'
+    }
+    
+    compile (libraries.opencensus_contrib_grpc_metrics) {
+        // prefer 3.0.2 from libraries instead of 3.0.1
+        exclude group: 'com.google.code.findbugs', module: 'jsr305'
+        // we'll always be more up-to-date
+        exclude group: 'io.grpc', module: 'grpc-context'
+        // prefer 20.0 from libraries instead of 19.0
+        exclude group: 'com.google.guava', module: 'guava'
+    }
+
+    testCompile project(':grpc-api').sourceSets.test.output,
+            project(':grpc-context').sourceSets.test.output,
+            project(':grpc-core').sourceSets.test.output,
+            project(':grpc-testing'),
+            libraries.guava_testlib,
+            libraries.opencensus_impl
+}
+
+javadoc {
+    failOnError false  // no public or protected classes found to document
+    exclude 'io/grpc/census/internal/**'
+    exclude 'io/grpc/census/Internal*'
+}

census/src/main/java/io/grpc/census/CensusStatsModule.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.grpc.internal;
+package io.grpc.census;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Preconditions.checkState;
@@ -35,6 +35,7 @@ import io.grpc.MethodDescriptor;
 import io.grpc.ServerStreamTracer;
 import io.grpc.Status;
 import io.grpc.StreamTracer;
+import io.grpc.census.internal.DeprecatedCensusConstants;
 import io.opencensus.contrib.grpc.metrics.RpcMeasureConstants;
 import io.opencensus.stats.Measure.MeasureDouble;
 import io.opencensus.stats.Measure.MeasureLong;
@@ -67,7 +68,7 @@ import javax.annotation.Nullable;
  * starts earlier than the ServerCall.  Therefore, only one tracer is created per stream/call and
  * it's the tracer that reports the summary to Census.
  */
-public final class CensusStatsModule {
+final class CensusStatsModule {
   private static final Logger logger = Logger.getLogger(CensusStatsModule.class.getName());
   private static final double NANOS_PER_MILLI = TimeUnit.MILLISECONDS.toNanos(1);
 
@@ -98,7 +99,7 @@ public final class CensusStatsModule {
   /**
    * Creates a {@link CensusStatsModule} with the given OpenCensus implementation.
    */
-  public CensusStatsModule(
+  CensusStatsModule(
       final Tagger tagger,
       final TagContextBinarySerializer tagCtxSerializer,
       StatsRecorder statsRecorder, Supplier<Stopwatch> stopwatchSupplier,

census/src/main/java/io/grpc/census/CensusTracingModule.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.grpc.internal;
+package io.grpc.census;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 

census/src/main/java/io/grpc/census/InternalCensusStatsAccessor.java

@@ -0,0 +1,117 @@
+/*
+ * Copyright 2019 The gRPC 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.grpc.census;
+
+import com.google.common.base.Stopwatch;
+import com.google.common.base.Supplier;
+import io.grpc.ClientInterceptor;
+import io.grpc.Internal;
+import io.grpc.ServerStreamTracer;
+import io.opencensus.stats.StatsRecorder;
+import io.opencensus.tags.Tagger;
+import io.opencensus.tags.propagation.TagContextBinarySerializer;
+
+/**
+ * Accessor for getting {@link ClientInterceptor} or {@link ServerStreamTracer.Factory} with
+ * default Census stats implementation.
+ */
+@Internal
+public final class InternalCensusStatsAccessor {
+
+  private static final Supplier<Stopwatch> STOPWATCH_SUPPLIER = new Supplier<Stopwatch>() {
+    @Override
+    public Stopwatch get() {
+      return Stopwatch.createUnstarted();
+    }
+  };
+
+  // Prevent instantiation.
+  private InternalCensusStatsAccessor() {
+  }
+
+  /**
+   * Returns a {@link ClientInterceptor} with default stats implementation.
+   */
+  public static ClientInterceptor getClientInterceptor(
+      boolean recordStartedRpcs,
+      boolean recordFinishedRpcs,
+      boolean recordRealTimeMetrics) {
+    CensusStatsModule censusStats =
+        new CensusStatsModule(
+            STOPWATCH_SUPPLIER,
+            true, /* propagateTags */
+            recordStartedRpcs,
+            recordFinishedRpcs,
+            recordRealTimeMetrics);
+    return censusStats.getClientInterceptor();
+  }
+
+  /**
+   * Returns a {@link ClientInterceptor} with custom stats implementation.
+   */
+  public static ClientInterceptor getClientInterceptor(
+      Tagger tagger,
+      TagContextBinarySerializer tagCtxSerializer,
+      StatsRecorder statsRecorder,
+      Supplier<Stopwatch> stopwatchSupplier,
+      boolean propagateTags,
+      boolean recordStartedRpcs,
+      boolean recordFinishedRpcs,
+      boolean recordRealTimeMetrics) {
+    CensusStatsModule censusStats =
+        new CensusStatsModule(
+            tagger, tagCtxSerializer, statsRecorder, stopwatchSupplier,
+            propagateTags, recordStartedRpcs, recordFinishedRpcs, recordRealTimeMetrics);
+    return censusStats.getClientInterceptor();
+  }
+
+  /**
+   * Returns a {@link ServerStreamTracer.Factory} with default stats implementation.
+   */
+  public static ServerStreamTracer.Factory getServerStreamTracerFactory(
+      boolean recordStartedRpcs,
+      boolean recordFinishedRpcs,
+      boolean recordRealTimeMetrics) {
+    CensusStatsModule censusStats =
+        new CensusStatsModule(
+            STOPWATCH_SUPPLIER,
+            true, /* propagateTags */
+            recordStartedRpcs,
+            recordFinishedRpcs,
+            recordRealTimeMetrics);
+    return censusStats.getServerTracerFactory();
+  }
+
+  /**
+   * Returns a {@link ServerStreamTracer.Factory} with custom stats implementation.
+   */
+  public static ServerStreamTracer.Factory getServerStreamTracerFactory(
+      Tagger tagger,
+      TagContextBinarySerializer tagCtxSerializer,
+      StatsRecorder statsRecorder,
+      Supplier<Stopwatch> stopwatchSupplier,
+      boolean propagateTags,
+      boolean recordStartedRpcs,
+      boolean recordFinishedRpcs,
+      boolean recordRealTimeMetrics) {
+    CensusStatsModule censusStats =
+        new CensusStatsModule(
+            tagger, tagCtxSerializer, statsRecorder, stopwatchSupplier,
+            propagateTags, recordStartedRpcs, recordFinishedRpcs, recordRealTimeMetrics);
+    return censusStats.getServerTracerFactory();
+  }
+}

census/src/main/java/io/grpc/census/InternalCensusTracingAccessor.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2019 The gRPC 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.grpc.census;
+
+import io.grpc.ClientInterceptor;
+import io.grpc.Internal;
+import io.grpc.ServerStreamTracer;
+import io.opencensus.trace.Tracing;
+
+/**
+ * Accessor for getting {@link ClientInterceptor} or {@link ServerStreamTracer.Factory} with
+ * default Census tracing implementation.
+ */
+@Internal
+public final class InternalCensusTracingAccessor {
+
+  // Prevent instantiation.
+  private InternalCensusTracingAccessor() {
+  }
+
+  /**
+   * Returns a {@link ClientInterceptor} with default tracing implementation.
+   */
+  public static ClientInterceptor getClientInterceptor() {
+    CensusTracingModule censusTracing =
+        new CensusTracingModule(
+            Tracing.getTracer(),
+            Tracing.getPropagationComponent().getBinaryFormat());
+    return censusTracing.getClientInterceptor();
+  }
+
+  /**
+   * Returns a {@link ServerStreamTracer.Factory} with default stats implementation.
+   */
+  public static ServerStreamTracer.Factory getServerStreamTracerFactory() {
+    CensusTracingModule censusTracing =
+        new CensusTracingModule(
+            Tracing.getTracer(),
+            Tracing.getPropagationComponent().getBinaryFormat());
+    return censusTracing.getServerTracerFactory();
+  }
+}

census/src/main/java/io/grpc/census/internal/DeprecatedCensusConstants.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.grpc.internal;
+package io.grpc.census.internal;
 
 import com.google.common.annotations.VisibleForTesting;
 import io.opencensus.contrib.grpc.metrics.RpcMeasureConstants;

census/src/test/java/io/grpc/census/CensusModulesTest.java

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-package io.grpc.internal;
+package io.grpc.census;
 
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth.assertWithMessage;
@@ -56,7 +56,10 @@ import io.grpc.ServerCall;
 import io.grpc.ServerCallHandler;
 import io.grpc.ServerServiceDefinition;
 import io.grpc.ServerStreamTracer;
+import io.grpc.ServerStreamTracer.ServerCallInfo;
 import io.grpc.Status;
+import io.grpc.census.internal.DeprecatedCensusConstants;
+import io.grpc.internal.FakeClock;
 import io.grpc.internal.testing.StatsTestUtils;
 import io.grpc.internal.testing.StatsTestUtils.FakeStatsRecorder;
 import io.grpc.internal.testing.StatsTestUtils.FakeTagContextBinarySerializer;
@@ -95,6 +98,7 @@ import java.util.List;
 import java.util.Random;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
+import javax.annotation.Nullable;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Rule;
@@ -1044,7 +1048,7 @@ public class CensusModulesTest {
     assertSame(spyServerSpan, ContextUtils.getValue(filteredContext));
 
     serverStreamTracer.serverCallStarted(
-        new ServerCallInfoImpl<>(method, Attributes.EMPTY, null));
+        new CallInfo<>(method, Attributes.EMPTY, null));
 
     verify(spyServerSpan, never()).end(any(EndSpanOptions.class));
 
@@ -1087,7 +1091,7 @@ public class CensusModulesTest {
     serverStreamTracer.filterContext(Context.ROOT);
 
     serverStreamTracer.serverCallStarted(
-        new ServerCallInfoImpl<>(sampledMethod, Attributes.EMPTY, null));
+        new CallInfo<>(sampledMethod, Attributes.EMPTY, null));
 
     serverStreamTracer.streamClosed(Status.CANCELLED);
 
@@ -1250,8 +1254,39 @@ public class CensusModulesTest {
         new Function<AggregationData, Long>() {
           @Override
           public Long apply(AggregationData arg) {
-            return ((io.opencensus.stats.AggregationData.MeanData) arg).getCount();
+            return ((AggregationData.MeanData) arg).getCount();
           }
         });
   }
+
+  private static class CallInfo<ReqT, RespT> extends ServerCallInfo<ReqT, RespT> {
+    private final MethodDescriptor<ReqT, RespT> methodDescriptor;
+    private final Attributes attributes;
+    private final String authority;
+
+    CallInfo(
+        MethodDescriptor<ReqT, RespT> methodDescriptor,
+        Attributes attributes,
+        @Nullable String authority) {
+      this.methodDescriptor = methodDescriptor;
+      this.attributes = attributes;
+      this.authority = authority;
+    }
+
+    @Override
+    public MethodDescriptor<ReqT, RespT> getMethodDescriptor() {
+      return methodDescriptor;
+    }
+
+    @Override
+    public Attributes getAttributes() {
+      return attributes;
+    }
+
+    @Nullable
+    @Override
+    public String getAuthority() {
+      return authority;
+    }
+  }
 }

core/BUILD.bazel

@@ -38,8 +38,6 @@ java_library(
         "@com_google_errorprone_error_prone_annotations//jar",
         "@com_google_guava_guava//jar",
         "@com_google_j2objc_j2objc_annotations//jar",
-        "@io_opencensus_opencensus_api//jar",
-        "@io_opencensus_opencensus_contrib_grpc_metrics//jar",
         "@io_perfmark_perfmark_api//jar",
         "@org_codehaus_mojo_animal_sniffer_annotations//jar",
     ],

core/build.gradle

@@ -20,25 +20,14 @@ dependencies {
     compile (libraries.perfmark) {
         exclude group: 'com.google.errorprone', module: 'error_prone_annotations'
     }
-    compile (libraries.opencensus_api) {
-        // prefer our own versions instead of opencensus-api's dependency
-        exclude group: 'com.google.code.findbugs', module: 'jsr305'
-        exclude group: 'com.google.guava', module: 'guava'
-        exclude group: 'io.grpc', module: 'grpc-context'
-    }
-    compile (libraries.opencensus_contrib_grpc_metrics) {
-        // prefer our own versions instead of opencensus-contrib's dependency
-        exclude group: 'com.google.code.findbugs', module: 'jsr305'
-        exclude group: 'io.grpc', module: 'grpc-context'
-        exclude group: 'com.google.guava', module: 'guava'
-    }
 
     testCompile project(':grpc-context').sourceSets.test.output,
             project(':grpc-api').sourceSets.test.output,
             project(':grpc-testing'),
             project(':grpc-grpclb'),
-            libraries.guava_testlib,
+            libraries.guava_testlib
-            libraries.opencensus_impl
+    
+    testRuntimeOnly project(':grpc-census')
 
     jmh project(':grpc-testing')
 

core/src/main/java/io/grpc/internal/AbstractManagedChannelImplBuilder.java

@@ -33,7 +33,8 @@ import io.grpc.ManagedChannelBuilder;
 import io.grpc.NameResolver;
 import io.grpc.NameResolverRegistry;
 import io.grpc.ProxyDetector;
-import io.opencensus.trace.Tracing;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.net.SocketAddress;
 import java.net.URI;
 import java.net.URISyntaxException;
@@ -45,6 +46,8 @@ import java.util.List;
 import java.util.Map;
 import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 import javax.annotation.Nullable;
 
 /**
@@ -56,6 +59,9 @@ public abstract class AbstractManagedChannelImplBuilder
         <T extends AbstractManagedChannelImplBuilder<T>> extends ManagedChannelBuilder<T> {
   private static final String DIRECT_ADDRESS_SCHEME = "directaddress";
 
+  private static final Logger log =
+      Logger.getLogger(AbstractManagedChannelImplBuilder.class.getName());
+
   public static ManagedChannelBuilder<?> forAddress(String name, int port) {
     throw new UnsupportedOperationException("Subclass failed to hide static factory");
   }
@@ -184,9 +190,6 @@ public abstract class AbstractManagedChannelImplBuilder
   private boolean recordRealTimeMetrics = false;
   private boolean tracingEnabled = true;
 
-  @Nullable
-  private CensusStatsModule censusStatsOverride;
-
   protected AbstractManagedChannelImplBuilder(String target) {
     this.target = Preconditions.checkNotNull(target, "target");
     this.directServerAddress = null;
@@ -376,15 +379,6 @@ public abstract class AbstractManagedChannelImplBuilder
     return thisT();
   }
 
-  /**
-   * Override the default stats implementation.
-   */
-  @VisibleForTesting
-  protected final T overrideCensusStatsModule(CensusStatsModule censusStats) {
-    this.censusStatsOverride = censusStats;
-    return thisT();
-  }
-
   @Override
   public T proxyDetector(@Nullable ProxyDetector proxyDetector) {
     this.proxyDetector = proxyDetector;
@@ -565,22 +559,49 @@ public abstract class AbstractManagedChannelImplBuilder
     temporarilyDisableRetry = false;
     if (statsEnabled) {
       temporarilyDisableRetry = true;
-      CensusStatsModule censusStats = this.censusStatsOverride;
+      ClientInterceptor statsInterceptor = null;
-      if (censusStats == null) {
+      try {
-        censusStats = new CensusStatsModule(
+        Class<?> censusStatsAccessor =
-            GrpcUtil.STOPWATCH_SUPPLIER, true, recordStartedRpcs, recordFinishedRpcs,
+            Class.forName("io.grpc.census.InternalCensusStatsAccessor");
+        Method getClientInterceptorMethod =
+            censusStatsAccessor.getDeclaredMethod(
+                "getClientInterceptor",
+                boolean.class,
+                boolean.class,
+                boolean.class);
+        statsInterceptor =
+            (ClientInterceptor) getClientInterceptorMethod
+                .invoke(
+                    null,
+                    recordStartedRpcs,
+                    recordFinishedRpcs,
                     recordRealTimeMetrics);
+      } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException
+          | InvocationTargetException e) {
+        log.log(Level.FINE, "Unable to apply census stats", e);
       }
+      if (statsInterceptor != null) {
         // First interceptor runs last (see ClientInterceptors.intercept()), so that no
         // other interceptor can override the tracer factory we set in CallOptions.
-      effectiveInterceptors.add(0, censusStats.getClientInterceptor());
+        effectiveInterceptors.add(0, statsInterceptor);
+      }
     }
     if (tracingEnabled) {
       temporarilyDisableRetry = true;
-      CensusTracingModule censusTracing =
+      ClientInterceptor tracingInterceptor = null;
-          new CensusTracingModule(Tracing.getTracer(),
+      try {
-              Tracing.getPropagationComponent().getBinaryFormat());
+        Class<?> censusTracingAccessor =
-      effectiveInterceptors.add(0, censusTracing.getClientInterceptor());
+            Class.forName("io.grpc.census.InternalCensusTracingAccessor");
+        Method getClientInterceptroMethod =
+            censusTracingAccessor.getDeclaredMethod("getClientInterceptor");
+        tracingInterceptor = (ClientInterceptor) getClientInterceptroMethod.invoke(null);
+      } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException
+          | InvocationTargetException e) {
+        log.log(Level.FINE, "Unable to apply census tracing", e);
+      }
+      if (tracingInterceptor != null) {
+        effectiveInterceptors.add(0, tracingInterceptor);
+      }
     }
     return effectiveInterceptors;
   }

core/src/main/java/io/grpc/internal/AbstractServerImplBuilder.java

@@ -37,12 +37,15 @@ import io.grpc.ServerMethodDefinition;
 import io.grpc.ServerServiceDefinition;
 import io.grpc.ServerStreamTracer;
 import io.grpc.ServerTransportFilter;
-import io.opencensus.trace.Tracing;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 import javax.annotation.Nullable;
 
 /**
@@ -53,6 +56,8 @@ import javax.annotation.Nullable;
 public abstract class AbstractServerImplBuilder<T extends AbstractServerImplBuilder<T>>
         extends ServerBuilder<T> {
 
+  private static final Logger log = Logger.getLogger(AbstractServerImplBuilder.class.getName());
+
   public static ServerBuilder<?> forPort(int port) {
     throw new UnsupportedOperationException("Subclass failed to hide static factory");
   }
@@ -80,7 +85,6 @@ public abstract class AbstractServerImplBuilder<T extends AbstractServerImplBuil
   CompressorRegistry compressorRegistry = DEFAULT_COMPRESSOR_REGISTRY;
   long handshakeTimeoutMillis = DEFAULT_HANDSHAKE_TIMEOUT_MILLIS;
   Deadline.Ticker ticker = Deadline.getSystemTicker();
-  @Nullable private CensusStatsModule censusStatsOverride;
   private boolean statsEnabled = true;
   private boolean recordStartedRpcs = true;
   private boolean recordFinishedRpcs = true;
@@ -165,15 +169,6 @@ public abstract class AbstractServerImplBuilder<T extends AbstractServerImplBuil
     return thisT();
   }
 
-  /**
-   * Override the default stats implementation.
-   */
-  @VisibleForTesting
-  protected final T overrideCensusStatsModule(@Nullable CensusStatsModule censusStats) {
-    this.censusStatsOverride = censusStats;
-    return thisT();
-  }
-
   @VisibleForTesting
   public final T setTransportTracerFactory(TransportTracer.Factory transportTracerFactory) {
     this.transportTracerFactory = transportTracerFactory;
@@ -241,19 +236,47 @@ public abstract class AbstractServerImplBuilder<T extends AbstractServerImplBuil
   final List<? extends ServerStreamTracer.Factory> getTracerFactories() {
     ArrayList<ServerStreamTracer.Factory> tracerFactories = new ArrayList<>();
     if (statsEnabled) {
-      CensusStatsModule censusStats = censusStatsOverride;
+      ServerStreamTracer.Factory censusStatsTracerFactory = null;
-      if (censusStats == null) {
+      try {
-        censusStats = new CensusStatsModule(
+        Class<?> censusStatsAccessor =
-            GrpcUtil.STOPWATCH_SUPPLIER, true, recordStartedRpcs, recordFinishedRpcs,
+            Class.forName("io.grpc.census.InternalCensusStatsAccessor");
+        Method getServerStreamTracerFactoryMethod =
+            censusStatsAccessor.getDeclaredMethod(
+                "getServerStreamTracerFactory",
+                boolean.class,
+                boolean.class,
+                boolean.class);
+        censusStatsTracerFactory =
+            (ServerStreamTracer.Factory) getServerStreamTracerFactoryMethod
+                .invoke(
+                    null,
+                    recordStartedRpcs,
+                    recordFinishedRpcs,
                     recordRealTimeMetrics);
+      } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException
+          | InvocationTargetException e) {
+        log.log(Level.FINE, "Unable to apply census stats", e);
+      }
+      if (censusStatsTracerFactory != null) {
+        tracerFactories.add(censusStatsTracerFactory);
       }
-      tracerFactories.add(censusStats.getServerTracerFactory());
     }
     if (tracingEnabled) {
-      CensusTracingModule censusTracing =
+      ServerStreamTracer.Factory tracingStreamTracerFactory = null;
-          new CensusTracingModule(Tracing.getTracer(),
+      try {
-              Tracing.getPropagationComponent().getBinaryFormat());
+        Class<?> censusTracingAccessor =
-      tracerFactories.add(censusTracing.getServerTracerFactory());
+            Class.forName("io.grpc.census.InternalCensusTracingAccessor");
+        Method getServerStreamTracerFactoryMethod =
+            censusTracingAccessor.getDeclaredMethod("getServerStreamTracerFactory");
+        tracingStreamTracerFactory =
+            (ServerStreamTracer.Factory) getServerStreamTracerFactoryMethod.invoke(null);
+      } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException
+          | InvocationTargetException e) {
+        log.log(Level.FINE, "Unable to apply census tracing", e);
+      }
+      if (tracingStreamTracerFactory != null) {
+        tracerFactories.add(tracingStreamTracerFactory);
+      }
     }
     tracerFactories.addAll(streamTracerFactories);
     tracerFactories.trimToSize();

core/src/test/java/io/grpc/internal/AbstractManagedChannelImplBuilderTest.java

@@ -36,9 +36,6 @@ import io.grpc.CompressorRegistry;
 import io.grpc.DecompressorRegistry;
 import io.grpc.MethodDescriptor;
 import io.grpc.NameResolver;
-import io.grpc.internal.testing.StatsTestUtils.FakeStatsRecorder;
-import io.grpc.internal.testing.StatsTestUtils.FakeTagContextBinarySerializer;
-import io.grpc.internal.testing.StatsTestUtils.FakeTagger;
 import java.net.InetSocketAddress;
 import java.net.SocketAddress;
 import java.net.URI;
@@ -284,10 +281,10 @@ public class AbstractManagedChannelImplBuilderTest {
     builder.intercept(DUMMY_USER_INTERCEPTOR);
     List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
     assertEquals(3, effectiveInterceptors.size());
-    assertThat(effectiveInterceptors.get(0))
+    assertThat(effectiveInterceptors.get(0).getClass().getName())
-        .isInstanceOf(CensusTracingModule.TracingClientInterceptor.class);
+        .isEqualTo("io.grpc.census.CensusTracingModule$TracingClientInterceptor");
-    assertThat(effectiveInterceptors.get(1))
+    assertThat(effectiveInterceptors.get(1).getClass().getName())
-        .isInstanceOf(CensusStatsModule.StatsClientInterceptor.class);
+        .isEqualTo("io.grpc.census.CensusStatsModule$StatsClientInterceptor");
     assertThat(effectiveInterceptors.get(2)).isSameInstanceAs(DUMMY_USER_INTERCEPTOR);
   }
 
@@ -297,8 +294,8 @@ public class AbstractManagedChannelImplBuilderTest {
     builder.setStatsEnabled(false);
     List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
     assertEquals(2, effectiveInterceptors.size());
-    assertThat(effectiveInterceptors.get(0))
+    assertThat(effectiveInterceptors.get(0).getClass().getName())
-        .isInstanceOf(CensusTracingModule.TracingClientInterceptor.class);
+        .isEqualTo("io.grpc.census.CensusTracingModule$TracingClientInterceptor");
     assertThat(effectiveInterceptors.get(1)).isSameInstanceAs(DUMMY_USER_INTERCEPTOR);
   }
 
@@ -308,8 +305,8 @@ public class AbstractManagedChannelImplBuilderTest {
     builder.setTracingEnabled(false);
     List<ClientInterceptor> effectiveInterceptors = builder.getEffectiveInterceptors();
     assertEquals(2, effectiveInterceptors.size());
-    assertThat(effectiveInterceptors.get(0))
+    assertThat(effectiveInterceptors.get(0).getClass().getName())
-        .isInstanceOf(CensusStatsModule.StatsClientInterceptor.class);
+        .isEqualTo("io.grpc.census.CensusStatsModule$StatsClientInterceptor");
     assertThat(effectiveInterceptors.get(1)).isSameInstanceAs(DUMMY_USER_INTERCEPTOR);
   }
 
@@ -500,24 +497,10 @@ public class AbstractManagedChannelImplBuilderTest {
   static class Builder extends AbstractManagedChannelImplBuilder<Builder> {
     Builder(String target) {
       super(target);
-      overrideCensusStatsModule(
-          new CensusStatsModule(
-              new FakeTagger(),
-              new FakeTagContextBinarySerializer(),
-              new FakeStatsRecorder(),
-              GrpcUtil.STOPWATCH_SUPPLIER,
-              true, true, true, true));
     }
 
     Builder(SocketAddress directServerAddress, String authority) {
       super(directServerAddress, authority);
-      overrideCensusStatsModule(
-          new CensusStatsModule(
-              new FakeTagger(),
-              new FakeTagContextBinarySerializer(),
-              new FakeStatsRecorder(),
-              GrpcUtil.STOPWATCH_SUPPLIER,
-              true, true, true, true));
     }
 
     @Override

core/src/test/java/io/grpc/internal/AbstractServerImplBuilderTest.java

@@ -21,9 +21,6 @@ import static org.junit.Assert.assertEquals;
 
 import io.grpc.Metadata;
 import io.grpc.ServerStreamTracer;
-import io.grpc.internal.testing.StatsTestUtils.FakeStatsRecorder;
-import io.grpc.internal.testing.StatsTestUtils.FakeTagContextBinarySerializer;
-import io.grpc.internal.testing.StatsTestUtils.FakeTagger;
 import java.io.File;
 import java.util.List;
 import org.junit.Test;
@@ -51,8 +48,10 @@ public class AbstractServerImplBuilderTest {
     List<? extends ServerStreamTracer.Factory> factories = builder.getTracerFactories();
 
     assertEquals(3, factories.size());
-    assertThat(factories.get(0)).isInstanceOf(CensusStatsModule.ServerTracerFactory.class);
+    assertThat(factories.get(0).getClass().getName())
-    assertThat(factories.get(1)).isInstanceOf(CensusTracingModule.ServerTracerFactory.class);
+        .isEqualTo("io.grpc.census.CensusStatsModule$ServerTracerFactory");
+    assertThat(factories.get(1).getClass().getName())
+        .isEqualTo("io.grpc.census.CensusTracingModule$ServerTracerFactory");
     assertThat(factories.get(2)).isSameInstanceAs(DUMMY_USER_TRACER);
   }
 
@@ -64,7 +63,8 @@ public class AbstractServerImplBuilderTest {
     List<? extends ServerStreamTracer.Factory> factories = builder.getTracerFactories();
 
     assertEquals(2, factories.size());
-    assertThat(factories.get(0)).isInstanceOf(CensusTracingModule.ServerTracerFactory.class);
+    assertThat(factories.get(0).getClass().getName())
+        .isEqualTo("io.grpc.census.CensusTracingModule$ServerTracerFactory");
     assertThat(factories.get(1)).isSameInstanceAs(DUMMY_USER_TRACER);
   }
 
@@ -76,7 +76,8 @@ public class AbstractServerImplBuilderTest {
     List<? extends ServerStreamTracer.Factory> factories = builder.getTracerFactories();
 
     assertEquals(2, factories.size());
-    assertThat(factories.get(0)).isInstanceOf(CensusStatsModule.ServerTracerFactory.class);
+    assertThat(factories.get(0).getClass().getName())
+        .isEqualTo("io.grpc.census.CensusStatsModule$ServerTracerFactory");
     assertThat(factories.get(1)).isSameInstanceAs(DUMMY_USER_TRACER);
   }
 
@@ -90,15 +91,6 @@ public class AbstractServerImplBuilderTest {
   }
 
   static class Builder extends AbstractServerImplBuilder<Builder> {
-    Builder() {
-      overrideCensusStatsModule(
-          new CensusStatsModule(
-              new FakeTagger(),
-              new FakeTagContextBinarySerializer(),
-              new FakeStatsRecorder(),
-              GrpcUtil.STOPWATCH_SUPPLIER,
-              true, true, true, true));
-    }
 
     @Override
     protected List<io.grpc.internal.InternalServer> buildTransportServers(

interop-testing/build.gradle

@@ -18,6 +18,7 @@ evaluationDependsOn(project(':grpc-context').path)
 dependencies {
     compile project(':grpc-alts'),
             project(':grpc-auth'),
+            project(':grpc-census'),
             project(':grpc-core'),
             project(':grpc-netty'),
             project(':grpc-okhttp'),

interop-testing/src/main/java/io/grpc/testing/integration/AbstractInteropTest.java

@@ -61,9 +61,9 @@ import io.grpc.ServerStreamTracer;
 import io.grpc.Status;
 import io.grpc.StatusRuntimeException;
 import io.grpc.auth.MoreCallCredentials;
+import io.grpc.census.InternalCensusStatsAccessor;
+import io.grpc.census.internal.DeprecatedCensusConstants;
 import io.grpc.internal.AbstractServerImplBuilder;
-import io.grpc.internal.CensusStatsModule;
-import io.grpc.internal.DeprecatedCensusConstants;
 import io.grpc.internal.GrpcUtil;
 import io.grpc.internal.testing.StatsTestUtils;
 import io.grpc.internal.testing.StatsTestUtils.FakeStatsRecorder;
@@ -240,15 +240,15 @@ public abstract class AbstractInteropTest {
         .addStreamTracerFactory(serverStreamTracerFactory);
     if (builder instanceof AbstractServerImplBuilder) {
       customCensusModulePresent = true;
-      AbstractServerImplBuilder<?> sb = (AbstractServerImplBuilder<?>) builder;
+      ServerStreamTracer.Factory censusTracerFactory =
-      io.grpc.internal.TestingAccessor.setStatsImplementation(
+          InternalCensusStatsAccessor
-          sb,
+              .getServerStreamTracerFactory(
-          new CensusStatsModule(
+                  tagger, tagContextBinarySerializer, serverStatsRecorder,
-              tagger,
-              tagContextBinarySerializer,
-              serverStatsRecorder,
                   GrpcUtil.STOPWATCH_SUPPLIER,
-              true, true, true, false /* real-time metrics */));
+                  true, true, true, false /* real-time metrics */);
+      AbstractServerImplBuilder<?> sb = (AbstractServerImplBuilder<?>) builder;
+      io.grpc.internal.TestingAccessor.setStatsEnabled(sb, false);
+      sb.addStreamTracerFactory(censusTracerFactory);
     }
     if (metricsExpected()) {
       assertThat(builder).isInstanceOf(AbstractServerImplBuilder.class);
@@ -353,9 +353,12 @@ public abstract class AbstractInteropTest {
     return null;
   }
 
-  protected final CensusStatsModule createClientCensusStatsModule() {
+  protected final ClientInterceptor createCensusStatsClientInterceptor() {
-    return new CensusStatsModule(
+    return
-        tagger, tagContextBinarySerializer, clientStatsRecorder, GrpcUtil.STOPWATCH_SUPPLIER,
+        InternalCensusStatsAccessor
+            .getClientInterceptor(
+                tagger, tagContextBinarySerializer, clientStatsRecorder,
+                GrpcUtil.STOPWATCH_SUPPLIER,
                 true, true, true, false /* real-time metrics */);
   }
 

interop-testing/src/main/java/io/grpc/testing/integration/TestServiceClient.java

@@ -450,9 +450,9 @@ public class TestServiceClient {
         }
         builder = okBuilder;
       }
-      io.grpc.internal.TestingAccessor.setStatsImplementation(
+      // Disable the default census stats interceptor, use testing interceptor instead.
-          builder, createClientCensusStatsModule());
+      io.grpc.internal.TestingAccessor.setStatsEnabled(builder, false);
-      return builder.build();
+      return builder.intercept(createCensusStatsClientInterceptor()).build();
     }
 
     @Override

interop-testing/src/test/java/io/grpc/testing/integration/AutoWindowSizingOnTest.java

@@ -46,8 +46,8 @@ public class AutoWindowSizingOnTest extends AbstractInteropTest {
     NettyChannelBuilder builder = NettyChannelBuilder.forAddress(getListenAddress())
         .negotiationType(NegotiationType.PLAINTEXT)
         .maxInboundMessageSize(AbstractInteropTest.MAX_MESSAGE_SIZE);
-    io.grpc.internal.TestingAccessor.setStatsImplementation(
+    // Disable the default census stats interceptor, use testing interceptor instead.
-        builder, createClientCensusStatsModule());
+    io.grpc.internal.TestingAccessor.setStatsEnabled(builder, false);
-    return builder.build();
+    return builder.intercept(createCensusStatsClientInterceptor()).build();
   }
 }

interop-testing/src/test/java/io/grpc/testing/integration/Http2NettyLocalChannelTest.java

@@ -57,9 +57,9 @@ public class Http2NettyLocalChannelTest extends AbstractInteropTest {
         .eventLoopGroup(eventLoopGroup)
         .flowControlWindow(65 * 1024)
         .maxInboundMessageSize(AbstractInteropTest.MAX_MESSAGE_SIZE);
-    io.grpc.internal.TestingAccessor.setStatsImplementation(
+    // Disable the default census stats interceptor, use testing interceptor instead.
-        builder, createClientCensusStatsModule());
+    io.grpc.internal.TestingAccessor.setStatsEnabled(builder, false);
-    return builder.build();
+    return builder.intercept(createCensusStatsClientInterceptor()).build();
   }
 
   @Override

interop-testing/src/test/java/io/grpc/testing/integration/Http2NettyTest.java

@@ -71,9 +71,9 @@ public class Http2NettyTest extends AbstractInteropTest {
               .trustManager(TestUtils.loadX509Cert("ca.pem"))
               .ciphers(TestUtils.preferredTestCiphers(), SupportedCipherSuiteFilter.INSTANCE)
               .build());
-      io.grpc.internal.TestingAccessor.setStatsImplementation(
+      // Disable the default census stats interceptor, use testing interceptor instead.
-          builder, createClientCensusStatsModule());
+      io.grpc.internal.TestingAccessor.setStatsEnabled(builder, false);
-      return builder.build();
+      return builder.intercept(createCensusStatsClientInterceptor()).build();
     } catch (Exception ex) {
       throw new RuntimeException(ex);
     }

interop-testing/src/test/java/io/grpc/testing/integration/Http2OkHttpTest.java

@@ -100,15 +100,15 @@ public class Http2OkHttpTest extends AbstractInteropTest {
             .build())
         .overrideAuthority(GrpcUtil.authorityFromHostAndPort(
             TestUtils.TEST_SERVER_HOST, port));
-    io.grpc.internal.TestingAccessor.setStatsImplementation(
-        builder, createClientCensusStatsModule());
     try {
       builder.sslSocketFactory(TestUtils.newSslSocketFactoryForCa(Platform.get().getProvider(),
           TestUtils.loadCert("ca.pem")));
     } catch (Exception e) {
       throw new RuntimeException(e);
     }
-    return builder;
+    // Disable the default census stats interceptor, use testing interceptor instead.
+    io.grpc.internal.TestingAccessor.setStatsEnabled(builder, false);
+    return builder.intercept(createCensusStatsClientInterceptor());
   }
 
   @Test

interop-testing/src/test/java/io/grpc/testing/integration/InProcessTest.java

@@ -38,9 +38,9 @@ public class InProcessTest extends AbstractInteropTest {
   @Override
   protected ManagedChannel createChannel() {
     InProcessChannelBuilder builder = InProcessChannelBuilder.forName(SERVER_NAME);
-    io.grpc.internal.TestingAccessor.setStatsImplementation(
+    // Disable the default census stats interceptor, use testing interceptor instead.
-        builder, createClientCensusStatsModule());
+    io.grpc.internal.TestingAccessor.setStatsEnabled(builder, false);
-    return builder.build();
+    return builder.intercept(createCensusStatsClientInterceptor()).build();
   }
 
   @Override

interop-testing/src/test/java/io/grpc/testing/integration/TransportCompressionTest.java

@@ -165,9 +165,9 @@ public class TransportCompressionTest extends AbstractInteropTest {
           }
         })
         .usePlaintext();
-    io.grpc.internal.TestingAccessor.setStatsImplementation(
+    // Disable the default census stats interceptor, use testing interceptor instead.
-        builder, createClientCensusStatsModule());
+    io.grpc.internal.TestingAccessor.setStatsEnabled(builder, false);
-    return builder.build();
+    return builder.intercept(createCensusStatsClientInterceptor()).build();
   }
 
   /**

repositories.bzl

@@ -70,6 +70,7 @@ IO_GRPC_GRPC_JAVA_OVERRIDE_TARGETS = {
     "io.grpc:grpc-alts": "@io_grpc_grpc_java//alts",
     "io.grpc:grpc-api": "@io_grpc_grpc_java//api",
     "io.grpc:grpc-auth": "@io_grpc_grpc_java//auth",
+    "io.grpc:grpc-census": "@io_grpc_grpc_java//census",
     "io.grpc:grpc-context": "@io_grpc_grpc_java//context",
     "io.grpc:grpc-core": "@io_grpc_grpc_java//core:core_maven",
     "io.grpc:grpc-grpclb": "@io_grpc_grpc_java//grpclb",

settings.gradle

@@ -29,6 +29,7 @@ include ":grpc-api"
 include ":grpc-core"
 include ":grpc-context"
 include ":grpc-stub"
+include ":grpc-census"
 include ":grpc-auth"
 include ":grpc-okhttp"
 include ":grpc-protobuf"
@@ -51,6 +52,7 @@ project(':grpc-api').projectDir = "$rootDir/api" as File
 project(':grpc-core').projectDir = "$rootDir/core" as File
 project(':grpc-context').projectDir = "$rootDir/context" as File
 project(':grpc-stub').projectDir = "$rootDir/stub" as File
+project(':grpc-census').projectDir = "$rootDir/census" as File
 project(':grpc-auth').projectDir = "$rootDir/auth" as File
 project(':grpc-okhttp').projectDir = "$rootDir/okhttp" as File
 project(':grpc-protobuf').projectDir = "$rootDir/protobuf" as File

testing/BUILD.bazel

@@ -31,5 +31,6 @@ java_library(
     deps = [
         "//api",
         "//core:internal",
+        "@io_opencensus_opencensus_api//jar",
     ],
 )

testing/build.gradle

@@ -14,6 +14,15 @@ dependencies {
             project(':grpc-stub'),
             libraries.junit
 
+    compile (libraries.opencensus_api) {
+        // prefer 3.0.2 from libraries instead of 3.0.1
+        exclude group: 'com.google.code.findbugs', module: 'jsr305'
+        // prefer 20.0 from libraries instead of 19.0
+        exclude group: 'com.google.guava', module: 'guava'
+        // we'll always be more up-to-date
+        exclude group: 'io.grpc', module: 'grpc-context'
+    }
+
     testCompile (libraries.mockito) {
         // prefer our own versions instead of mockito's dependency
         exclude group: 'org.hamcrest', module: 'hamcrest-core'

testing/src/main/java/io/grpc/internal/TestingAccessor.java

@@ -21,19 +21,20 @@ package io.grpc.internal;
  */
 public final class TestingAccessor {
   /**
-   * Sets a custom stats implementation for tests.
+   * Disable or enable client side census stats features.
    */
-  public static void setStatsImplementation(
+  public static void setStatsEnabled(
-      AbstractManagedChannelImplBuilder<?> builder, CensusStatsModule censusStats) {
+      AbstractManagedChannelImplBuilder<?> builder, boolean statsEnabled) {
-    builder.overrideCensusStatsModule(censusStats);
+    builder.setStatsEnabled(statsEnabled);
   }
 
   /**
-   * Sets a custom stats implementation for tests.
+   * Disable or enable server side census stats features.
    */
-  public static void setStatsImplementation(
+  public static void setStatsEnabled(
-      AbstractServerImplBuilder<?> builder, CensusStatsModule censusStats) {
+      AbstractServerImplBuilder<?> builder,
-    builder.overrideCensusStatsModule(censusStats);
+      boolean statsEnabled) {
+    builder.setStatsEnabled(statsEnabled);
   }
 
   private TestingAccessor() {