impl(o11y): introduce body.size

This PR enhances the OpenTelemetry integration for HTTP JSON transports to explicitly unpack and record the `http.response.body.size` attributes globally inside `google-cloud-java`.

* Safeguarded Extractions: Solidified `extractContentLength` in both `SpanTracer` and `TestApiTracer` to parse `List`-type strings safely and silently skip payload sizes when chunked serialization omits `Content-Length` headers entirely!
* True-Positive Validation Mappings: In `ITOtelTracing`, cleanly simulates exception routing natively while introducing algorithmic boundary estimations `isAtLeast(expectedMagnitude * 0.85)` using actual `Message` object size fingerprints.

Author: diegomarquezp

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

@@ -607,10 +607,11 @@ public ApiTracer getTracer() {
   @Override
   public HttpJsonCallContext withTracer(@Nonnull ApiTracer newTracer) {
     Preconditions.checkNotNull(newTracer);
+    HttpJsonCallOptions newCallOptions = callOptions.toBuilder().setTracer(newTracer).build();
 
     return new HttpJsonCallContext(
         this.channel,
-        this.callOptions,
+        newCallOptions,
         this.timeout,
         this.streamWaitTimeout,
         this.streamIdleTimeout,

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

@@ -35,6 +35,7 @@
 import static com.google.api.gax.util.TimeConversionUtils.toThreetenInstant;
 
 import com.google.api.core.ObsoleteApi;
+import com.google.api.gax.tracing.ApiTracer;
 import com.google.auth.Credentials;
 import com.google.auto.value.AutoValue;
 import com.google.protobuf.TypeRegistry;
@@ -71,6 +72,9 @@ public final org.threeten.bp.Instant getDeadline() {
   @Nullable
   public abstract TypeRegistry getTypeRegistry();
 
+  @Nullable
+  public abstract ApiTracer getTracer();
+
   public abstract Builder toBuilder();
 
   public static Builder newBuilder() {
@@ -106,6 +110,11 @@ public HttpJsonCallOptions merge(HttpJsonCallOptions inputOptions) {
       builder.setTypeRegistry(newTypeRegistry);
     }
 
+    ApiTracer newTracer = inputOptions.getTracer();
+    if (newTracer != null) {
+      builder.setTracer(newTracer);
+    }
+
     return builder.build();
   }
 
@@ -131,6 +140,8 @@ public final Builder setDeadline(org.threeten.bp.Instant value) {
 
     public abstract Builder setTypeRegistry(TypeRegistry value);
 
+    public abstract Builder setTracer(ApiTracer value);
+
     public abstract HttpJsonCallOptions build();
   }
 }

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

@@ -156,6 +156,11 @@ public void setResult(RunnableResult runnableResult) {
       if (runnableResult.getResponseHeaders() != null) {
         pendingNotifications.offer(
             new OnHeadersNotificationTask<>(listener, runnableResult.getResponseHeaders()));
+        if (callOptions.getTracer() != null) {
+          callOptions
+              .getTracer()
+              .responseHeadersReceived(runnableResult.getResponseHeaders().getHeaders());
+        }
       }
     }
 
@@ -428,6 +433,7 @@ private boolean consumeMessageFromStream() throws IOException {
 
     ResponseT message =
         methodDescriptor.getResponseParser().parse(responseReader, callOptions.getTypeRegistry());
+
     pendingNotifications.offer(new OnMessageNotificationTask<>(listener, message));
 
     return allMessagesConsumed;

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

@@ -252,6 +252,16 @@ void testMergeWithTracer() {
         .isSameInstanceAs(defaultTracer);
   }
 
+  @Test
+  void testWithTracer() {
+    ApiTracer tracer = Mockito.mock(ApiTracer.class);
+    HttpJsonCallContext emptyContext = HttpJsonCallContext.createDefault();
+    // Default context has a default tracer.
+    assertNotNull(emptyContext.getTracer());
+    HttpJsonCallContext context = emptyContext.withTracer(tracer);
+    Truth.assertThat(context.getTracer()).isSameInstanceAs(tracer);
+  }
+
   @Test
   void testWithRetrySettings() {
     RetrySettings retrySettings = Mockito.mock(RetrySettings.class);

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

@@ -31,12 +31,22 @@
 
 import static com.google.api.gax.util.TimeConversionTestUtils.testDurationMethod;
 import static com.google.api.gax.util.TimeConversionTestUtils.testInstantMethod;
+import static com.google.common.truth.Truth.assertThat;
 
+import com.google.api.gax.tracing.ApiTracer;
 import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
 
 public class HttpJsonCallOptionsTest {
   private final HttpJsonCallOptions.Builder OPTIONS_BUILDER = HttpJsonCallOptions.newBuilder();
 
+  @Test
+  void testTracer() {
+    ApiTracer tracer = Mockito.mock(ApiTracer.class);
+    HttpJsonCallOptions options = OPTIONS_BUILDER.setTracer(tracer).build();
+    assertThat(options.getTracer()).isSameInstanceAs(tracer);
+  }
+
   @Test
   public void testDeadline() {
     final long millis = 3;

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

@@ -29,15 +29,35 @@
  */
 package com.google.api.gax.httpjson;
 
+import static com.google.common.truth.Truth.assertThat;
+
 import com.google.api.client.http.HttpTransport;
+import com.google.api.gax.httpjson.testing.MockHttpService;
+import com.google.api.gax.httpjson.testing.TestApiTracer;
+import com.google.api.gax.rpc.EndpointContext;
+import com.google.api.gax.rpc.ResponseObserver;
+import com.google.api.gax.rpc.StreamController;
+import com.google.auth.Credentials;
 import com.google.common.truth.Truth;
+import com.google.protobuf.Field;
 import com.google.protobuf.TypeRegistry;
 import java.io.ByteArrayInputStream;
 import java.io.InputStream;
 import java.io.Reader;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledThreadPoolExecutor;
 import java.util.concurrent.TimeUnit;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.mockito.Mock;
@@ -135,4 +155,170 @@ void responseReceived_cancellationTaskExists_isCancelledProperly() throws Interr
     // Scheduler is not waiting for any task and should terminate quickly
     Truth.assertThat(deadlineSchedulerExecutor.isTerminated()).isTrue();
   }
+
+  private static final ApiMethodDescriptor<Field, Field> FAKE_METHOD_DESCRIPTOR =
+      ApiMethodDescriptor.<Field, Field>newBuilder()
+          .setFullMethodName("google.cloud.v1.Fake/FakeMethod")
+          .setHttpMethod("POST")
+          .setRequestFormatter(
+              ProtoMessageRequestFormatter.<Field>newBuilder()
+                  .setPath(
+                      "/fake/v1/name/{name}",
+                      request -> {
+                        Map<String, String> fields = new HashMap<>();
+                        ProtoRestSerializer<Field> serializer = ProtoRestSerializer.create();
+                        serializer.putPathParam(fields, "name", request.getName());
+                        return fields;
+                      })
+                  .setQueryParamsExtractor(request -> new HashMap<>())
+                  .setRequestBodyExtractor(
+                      request ->
+                          ProtoRestSerializer.create()
+                              .toBody("*", request.toBuilder().clearName().build(), false))
+                  .build())
+          .setResponseParser(
+              ProtoMessageResponseParser.<Field>newBuilder()
+                  .setDefaultInstance(Field.getDefaultInstance())
+                  .build())
+          .build();
+
+  private static final MockHttpService MOCK_SERVICE =
+      new MockHttpService(Collections.singletonList(FAKE_METHOD_DESCRIPTOR), "google.com:443");
+
+  private static ExecutorService executorService;
+  private ManagedHttpJsonChannel channel;
+  private TestApiTracer tracer;
+
+  @BeforeAll
+  static void initialize() {
+    executorService = Executors.newFixedThreadPool(2);
+  }
+
+  @AfterAll
+  static void destroy() {
+    executorService.shutdownNow();
+  }
+
+  @BeforeEach
+  void setUp() {
+    channel =
+        ManagedHttpJsonChannel.newBuilder()
+            .setEndpoint("google.com:443")
+            .setExecutor(executorService)
+            .setHttpTransport(MOCK_SERVICE)
+            .build();
+    tracer = new TestApiTracer();
+  }
+
+  @AfterEach
+  void tearDown() {
+    MOCK_SERVICE.reset();
+  }
+
+  @Test
+  void testBodySizeRecording() throws Exception {
+    HttpJsonDirectCallable<Field, Field> callable =
+        new HttpJsonDirectCallable<>(FAKE_METHOD_DESCRIPTOR);
+
+    EndpointContext endpointContext = Mockito.mock(EndpointContext.class);
+    Mockito.lenient()
+        .doNothing()
+        .when(endpointContext)
+        .validateUniverseDomain(
+            Mockito.any(Credentials.class), Mockito.any(HttpJsonStatusCode.class));
+
+    HttpJsonCallContext callContext =
+        HttpJsonCallContext.createDefault()
+            .withChannel(channel)
+            .withEndpointContext(endpointContext)
+            .withTracer(tracer);
+
+    Field request = Field.newBuilder().setName("bob").setNumber(42).build();
+    Field response = Field.newBuilder().setName("alice").setNumber(43).build();
+
+    MOCK_SERVICE.addResponse(response);
+
+    callable.futureCall(request, callContext).get();
+
+    // Verify response size
+    // MockHttpService uses ProtoRestSerializer which pretty-prints.
+    String expectedResponseBody = ProtoRestSerializer.create().toBody("*", response, false);
+    long expectedResponseSize = expectedResponseBody.getBytes("UTF-8").length;
+    assertThat(tracer.getResponseReceivedSize()).isEqualTo(expectedResponseSize);
+  }
+
+  @Test
+  void testBodySizeRecordingServerStreaming() throws Exception {
+    ApiMethodDescriptor<Field, Field> methodServerStreaming =
+        FAKE_METHOD_DESCRIPTOR.toBuilder()
+            .setType(ApiMethodDescriptor.MethodType.SERVER_STREAMING)
+            .build();
+
+    MockHttpService streamingMockService =
+        new MockHttpService(Collections.singletonList(methodServerStreaming), "google.com:443");
+    ManagedHttpJsonChannel streamingChannel =
+        ManagedHttpJsonChannel.newBuilder()
+            .setEndpoint("google.com:443")
+            .setExecutor(executorService)
+            .setHttpTransport(streamingMockService)
+            .build();
+
+    HttpJsonDirectServerStreamingCallable<Field, Field> callable =
+        new HttpJsonDirectServerStreamingCallable<>(methodServerStreaming);
+
+    EndpointContext endpointContext = Mockito.mock(EndpointContext.class);
+    Mockito.lenient()
+        .doNothing()
+        .when(endpointContext)
+        .validateUniverseDomain(
+            Mockito.any(Credentials.class), Mockito.any(HttpJsonStatusCode.class));
+
+    HttpJsonCallContext callContext =
+        HttpJsonCallContext.createDefault()
+            .withChannel(streamingChannel)
+            .withEndpointContext(endpointContext)
+            .withTracer(tracer);
+
+    Field request = Field.newBuilder().setName("bob").setNumber(42).build();
+    Field response1 = Field.newBuilder().setName("alice1").setNumber(43).build();
+    Field response2 = Field.newBuilder().setName("alice2").setNumber(44).build();
+
+    streamingMockService.addResponse(new Field[] {response1, response2});
+
+    final List<Field> receivedResponses = new java.util.ArrayList<>();
+    final CountDownLatch latch = new CountDownLatch(1);
+
+    callable.call(
+        request,
+        new ResponseObserver<Field>() {
+          @Override
+          public void onStart(StreamController controller) {
+            // no behavior needed
+          }
+
+          @Override
+          public void onResponse(Field response) {
+            receivedResponses.add(response);
+          }
+
+          @Override
+          public void onError(Throwable t) {
+            latch.countDown();
+          }
+
+          @Override
+          public void onComplete() {
+            latch.countDown();
+          }
+        },
+        callContext);
+
+    latch.await(10, TimeUnit.SECONDS);
+
+    assertThat(receivedResponses).hasSize(2);
+
+    // Verify response size (0 because streaming chunked responses don't include Content-Length)
+    assertThat(tracer.getResponseReceivedSize()).isEqualTo(0);
+    streamingChannel.shutdownNow();
+  }
 }

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

@@ -43,6 +43,7 @@
 import com.google.common.collect.ImmutableListMultimap;
 import com.google.common.collect.LinkedListMultimap;
 import com.google.common.collect.Multimap;
+import java.nio.charset.StandardCharsets;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Queue;
@@ -261,7 +262,11 @@ public MockLowLevelHttpResponse getHttpResponse(String httpMethod, String fullTa
           httpContent = methodDescriptor.getResponseParser().serialize(response);
         }
 
-        httpResponse.setContent(httpContent.getBytes());
+        byte[] contentBytes = httpContent.getBytes(StandardCharsets.UTF_8);
+        httpResponse.setContent(contentBytes);
+        if (methodDescriptor.getType() != MethodType.SERVER_STREAMING) {
+          httpResponse.addHeader("Content-Length", String.valueOf(contentBytes.length));
+        }
         httpResponse.setStatusCode(200);
         return httpResponse;
       }