census: expose client interceptors

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

@@ -0,0 +1,176 @@
+/*
+ * Copyright 2025 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.ExperimentalApi;
+import io.grpc.ManagedChannelBuilder;
+import io.grpc.ServerBuilder;
+import io.grpc.ServerStreamTracer;
+import io.opencensus.trace.Tracing;
+
+/**
+ *  The entrypoint for OpenCensus instrumentation functionality in gRPC.
+ *
+ *  <p>GrpcCensus uses {@link io.opencensus.api.OpenCensus} APIs for instrumentation.
+ *
+ */
+@ExperimentalApi("https://github.com/grpc/grpc-java/issues/12178")
+public final class GrpcCensus {
+
+  private final boolean statsEnabled;
+  private final boolean tracingEnabled;
+
+  private GrpcCensus(Builder builder) {
+    this.statsEnabled = builder.statsEnabled;
+    this.tracingEnabled = builder.tracingEnabled;
+  }
+
+  /**
+   * Creates a new builder for {@link GrpcCensus}.
+   */
+  public static Builder newBuilder() {
+    return new Builder();
+  }
+
+  private static final Supplier<Stopwatch> STOPWATCH_SUPPLIER = new Supplier<Stopwatch>() {
+    @Override
+    public Stopwatch get() {
+      return Stopwatch.createUnstarted();
+    }
+  };
+
+  /**
+   * Configures a {@link ServerBuilder} to enable census stats and tracing.
+   *
+   * @param serverBuilder The server builder to configure.
+   * @return The configured server builder.
+   */
+  public <T extends ServerBuilder<T>> T configureServerBuilder(T serverBuilder) {
+    if (statsEnabled) {
+      serverBuilder.addStreamTracerFactory(newServerStatsStreamTracerFactory());
+    }
+    if (tracingEnabled) {
+      serverBuilder.addStreamTracerFactory(newServerTracingStreamTracerFactory());
+    }
+    return serverBuilder;
+  }
+
+  /**
+   * Configures a {@link ManagedChannelBuilder} to enable census stats and tracing.
+   *
+   * @param channelBuilder The channel builder to configure.
+   * @return The configured channel builder.
+   */
+  public <T extends ManagedChannelBuilder<T>> T configureChannelBuilder(T channelBuilder) {
+    if (statsEnabled) {
+      channelBuilder.intercept(newClientStatsInterceptor());
+    }
+    if (tracingEnabled) {
+      channelBuilder.intercept(newClientTracingInterceptor());
+    }
+    return channelBuilder;
+  }
+
+  /**
+   * Returns a {@link ClientInterceptor} with default stats implementation.
+   */
+  private static ClientInterceptor newClientStatsInterceptor() {
+    CensusStatsModule censusStats =
+        new CensusStatsModule(
+            STOPWATCH_SUPPLIER,
+            true,
+            true,
+            true,
+            false,
+            true);
+    return censusStats.getClientInterceptor();
+  }
+
+  /**
+   * Returns a {@link ClientInterceptor} with default tracing implementation.
+   */
+  private static ClientInterceptor newClientTracingInterceptor() {
+    CensusTracingModule censusTracing =
+        new CensusTracingModule(
+            Tracing.getTracer(),
+            Tracing.getPropagationComponent().getBinaryFormat());
+    return censusTracing.getClientInterceptor();
+  }
+
+  /**
+   * Returns a {@link ServerStreamTracer.Factory} with default stats implementation.
+   */
+  private static ServerStreamTracer.Factory newServerStatsStreamTracerFactory() {
+    CensusStatsModule censusStats =
+        new CensusStatsModule(
+            STOPWATCH_SUPPLIER,
+            true,
+            true,
+            true,
+            false,
+            true);
+    return censusStats.getServerTracerFactory();
+  }
+
+  /**
+   * Returns a {@link ServerStreamTracer.Factory} with default tracing implementation.
+   */
+  private static ServerStreamTracer.Factory newServerTracingStreamTracerFactory() {
+    CensusTracingModule censusTracing =
+        new CensusTracingModule(
+            Tracing.getTracer(),
+            Tracing.getPropagationComponent().getBinaryFormat());
+    return censusTracing.getServerTracerFactory();
+  }
+
+  /**
+   * Builder for {@link GrpcCensus}.
+   */
+  public static final class Builder {
+    private boolean statsEnabled = true;
+    private boolean tracingEnabled = true;
+
+    private Builder() {
+    }
+
+    /**
+     * Disables stats collection.
+     */
+    public Builder disableStats() {
+      this.statsEnabled = false;
+      return this;
+    }
+
+    /**
+     * Disables tracing.
+     */
+    public Builder disableTracing() {
+      this.tracingEnabled = false;
+      return this;
+    }
+
+    /**
+     * Builds a new {@link GrpcCensus}.
+     */
+    public GrpcCensus build() {
+      return new GrpcCensus(this);
+    }
+  }
+}

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

@@ -99,7 +99,7 @@ public static ServerBuilder<?> forPort(int port) {
   ServerCallExecutorSupplier executorSupplier;
 
   /**
-   * An interface to provide to provide transport specific information for the server. This method
+   * An interface to provide transport specific information for the server. This method
    * is meant for Transport implementors and should not be used by normal users.
    */
   public interface ClientTransportServersBuilder {