feat: Register trace propagation interceptors by default

Author: westarle

sdk-platform-java/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/InstantiatingGrpcChannelProvider.java

@@ -790,6 +790,7 @@ public ManagedChannelBuilder<?> createDecoratedChannelBuilder() throws IOExcepti
             .intercept(new GrpcChannelUUIDInterceptor())
             .intercept(new GrpcLoggingInterceptor())
             .intercept(headerInterceptor)
+            .intercept(new GrpcTracePropagationInterceptor())
             .intercept(metadataHandlerInterceptor)
             .userAgent(headerInterceptor.getUserAgentHeader())
             .executor(executor);

sdk-platform-java/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/InstantiatingHttpJsonChannelProvider.java

@@ -217,6 +217,7 @@ private HttpJsonTransportChannel createChannel() throws IOException, GeneralSecu
 
     channel = new ManagedHttpJsonInterceptorChannel(channel, new HttpJsonLoggingInterceptor());
     channel = new ManagedHttpJsonInterceptorChannel(channel, headerInterceptor);
+    channel = new ManagedHttpJsonInterceptorChannel(channel, new HttpJsonTracePropagationInterceptor());
     if (interceptorProvider != null && interceptorProvider.getInterceptors() != null) {
       for (HttpJsonClientInterceptor interceptor : interceptorProvider.getInterceptors()) {
         channel = new ManagedHttpJsonInterceptorChannel(channel, interceptor);

sdk-platform-java/gax-java/gax-httpjson/src/test/java/com/google/api/gax/httpjson/InstantiatingHttpJsonChannelProviderTest.java

@@ -131,14 +131,7 @@ void managedChannelUsesDefaultChannelExecutor() throws IOException {
     HttpJsonTransportChannel httpJsonTransportChannel =
         instantiatingHttpJsonChannelProvider.getTransportChannel();
 
-    // By default, the channel will be wrapped with ManagedHttpJsonInterceptorChannel
-    ManagedHttpJsonInterceptorChannel interceptorChannel =
-        (ManagedHttpJsonInterceptorChannel) httpJsonTransportChannel.getManagedChannel();
-    // call getChannel() twice because interceptors are chained in layers by recursive construction
-    // inside com.google.api.gax.httpjson.InstantiatingHttpJsonChannelProvider.createChannel
-    ManagedHttpJsonInterceptorChannel managedHttpJsonChannel =
-        (ManagedHttpJsonInterceptorChannel) interceptorChannel.getChannel();
-    ManagedHttpJsonChannel channel = managedHttpJsonChannel.getChannel();
+    ManagedHttpJsonChannel channel = unwrapChannel(httpJsonTransportChannel.getManagedChannel());
     assertThat(channel.getExecutor()).isNotNull();
 
     // Clean up the resources (executor, deadlineScheduler, httpTransport)
@@ -164,14 +157,7 @@ void managedChannelUsesCustomExecutor() throws IOException {
     HttpJsonTransportChannel httpJsonTransportChannel =
         instantiatingHttpJsonChannelProvider.getTransportChannel();
 
-    // By default, the channel will be wrapped with ManagedHttpJsonInterceptorChannel
-    ManagedHttpJsonInterceptorChannel interceptorChannel =
-        (ManagedHttpJsonInterceptorChannel) httpJsonTransportChannel.getManagedChannel();
-    // call getChannel() twice because interceptors are chained in layers by recursive construction
-    // inside com.google.api.gax.httpjson.InstantiatingHttpJsonChannelProvider.createChannel
-    ManagedHttpJsonInterceptorChannel managedHttpJsonChannel =
-        (ManagedHttpJsonInterceptorChannel) interceptorChannel.getChannel();
-    ManagedHttpJsonChannel channel = managedHttpJsonChannel.getChannel();
+    ManagedHttpJsonChannel channel = unwrapChannel(httpJsonTransportChannel.getManagedChannel());
 
     assertThat(channel.getExecutor()).isNotNull();
     assertThat(channel.getExecutor()).isEqualTo(executor);
@@ -180,6 +166,13 @@ void managedChannelUsesCustomExecutor() throws IOException {
     instantiatingHttpJsonChannelProvider.getTransportChannel().shutdownNow();
   }
 
+  private ManagedHttpJsonChannel unwrapChannel(HttpJsonChannel channel) {
+    while (channel instanceof ManagedHttpJsonInterceptorChannel) {
+      channel = ((ManagedHttpJsonInterceptorChannel) channel).getChannel();
+    }
+    return (ManagedHttpJsonChannel) channel;
+  }
+
   @Override
   protected Object getMtlsObjectFromTransportChannel(
       MtlsProvider provider, CertificateBasedAccess certificateBasedAccess)