fix(gax): Implement lazy resource name evaluation in ApiTracerContext

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/tracing/ApiTracerContext.java

@@ -37,6 +37,7 @@
 import com.google.common.base.Strings;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.function.Supplier;
 import javax.annotation.Nullable;
 
 /**
@@ -164,9 +165,46 @@ String rpcSystemName() {
   @Nullable
   public abstract String urlDomain();
 
-  /** The destination resource id of the request (e.g. projects/p/locations/l/topics/t). */
   @Nullable
-  public abstract String destinationResourceId();
+  protected abstract Supplier<String> destinationResourceIdSupplier();
+
+  /**
+   * The destination resource id of the request (e.g.
+   * //pubsub.googleapis.com/projects/p/locations/l/topics/t).
+   */
+  @Nullable
+  public String destinationResourceId() {
+    Supplier<String> supplier = destinationResourceIdSupplier();
+    if (supplier == null) {
+      return null;
+    }
+    String resourceId = supplier.get();
+    if (Strings.isNullOrEmpty(resourceId)) {
+      return null;
+    }
+    if (Strings.isNullOrEmpty(urlDomain())) {
+      return resourceId;
+    }
+    return "//" + urlDomain() + "/" + resourceId;
+  }
+
+  <RequestT> ApiTracerContext withResourceNameExtractor(
+      @Nullable RequestT request,
+      @Nullable com.google.api.gax.rpc.ResourceNameExtractor<RequestT> extractor) {
+    if (extractor == null || request == null) {
+      return this;
+    }
+    return toBuilder()
+        .setDestinationResourceIdSupplier(
+            () -> {
+              try {
+                return extractor.extract(request);
+              } catch (Exception e) {
+                return null;
+              }
+            })
+        .build();
+  }
 
   /**
    * @return a map of attributes to be included in attempt-level spans
@@ -284,8 +322,8 @@ ApiTracerContext merge(ApiTracerContext other) {
     if (!Strings.isNullOrEmpty(other.urlDomain())) {
       builder.setUrlDomain(other.urlDomain());
     }
-    if (other.destinationResourceId() != null) {
-      builder.setDestinationResourceId(other.destinationResourceId());
+    if (other.destinationResourceIdSupplier() != null) {
+      builder.setDestinationResourceIdSupplier(other.destinationResourceIdSupplier());
     }
     return builder.build();
   }
@@ -322,7 +360,8 @@ public abstract static class Builder {
 
     public abstract Builder setUrlDomain(@Nullable String urlDomain);
 
-    public abstract Builder setDestinationResourceId(@Nullable String destinationResourceId);
+    public abstract Builder setDestinationResourceIdSupplier(
+        @Nullable Supplier<String> destinationResourceIdSupplier);
 
     public abstract ApiTracerContext build();
   }

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/tracing/TracedUnaryCallable.java

@@ -37,8 +37,6 @@
 import com.google.api.gax.rpc.ResourceNameExtractor;
 import com.google.api.gax.rpc.UnaryCallable;
 import com.google.api.gax.tracing.ApiTracerFactory.OperationType;
-import com.google.common.annotations.VisibleForTesting;
-import com.google.common.base.Strings;
 import com.google.common.util.concurrent.MoreExecutors;
 import javax.annotation.Nullable;
 
@@ -90,8 +88,10 @@ public TracedUnaryCallable(
   public ApiFuture<ResponseT> futureCall(RequestT request, ApiCallContext context) {
     ApiTracer tracer;
     if (apiTracerContext != null) {
-      ApiTracerContext finalContext = extractResourceNameToApiTracerContext(request);
-      tracer = tracerFactory.newTracer(context.getTracer(), finalContext);
+      tracer =
+          tracerFactory.newTracer(
+              context.getTracer(),
+              apiTracerContext.withResourceNameExtractor(request, resourceNameExtractor));
     } else {
       tracer = tracerFactory.newTracer(context.getTracer(), spanName, OperationType.Unary);
     }
@@ -108,15 +108,4 @@ public ApiFuture<ResponseT> futureCall(RequestT request, ApiCallContext context)
       throw e;
     }
   }
-
-  @VisibleForTesting
-  ApiTracerContext extractResourceNameToApiTracerContext(RequestT request) {
-    ApiTracerContext finalContext = apiTracerContext;
-    String resourceName =
-        resourceNameExtractor != null ? resourceNameExtractor.extract(request) : null;
-    if (!Strings.isNullOrEmpty(resourceName)) {
-      finalContext = finalContext.toBuilder().setDestinationResourceId(resourceName).build();
-    }
-    return finalContext;
-  }
 }

sdk-platform-java/gax-java/gax/src/test/java/com/google/api/gax/tracing/ApiTracerContextTest.java

@@ -310,7 +310,7 @@ void testGetAttemptAttributes_destinationResourceId() {
     ApiTracerContext context =
         ApiTracerContext.newBuilder()
             .setLibraryMetadata(LibraryMetadata.empty())
-            .setDestinationResourceId("projects/123/instances/abc")
+            .setDestinationResourceIdSupplier(() -> "projects/123/instances/abc")
             .build();
     Map<String, Object> attributes = context.getAttemptAttributes();
 
@@ -383,13 +383,13 @@ void testMerge_destinationResourceId() {
     ApiTracerContext context1 =
         ApiTracerContext.newBuilder()
             .setLibraryMetadata(LibraryMetadata.empty())
-            .setDestinationResourceId("name1")
+            .setDestinationResourceIdSupplier(() -> "name1")
             .build();
 
     ApiTracerContext context2 =
         ApiTracerContext.newBuilder()
             .setLibraryMetadata(LibraryMetadata.empty())
-            .setDestinationResourceId("name2")
+            .setDestinationResourceIdSupplier(() -> "name2")
             .build();
 
     ApiTracerContext merged = context1.merge(context2);
@@ -434,4 +434,121 @@ void testMerge_httpFields() {
     assertThat(merged.httpMethod()).isEqualTo("GET");
     assertThat(merged.httpPathTemplate()).isEqualTo("v1/projects/{project}");
   }
+
+  @Test
+  void testDestinationResourceId_withUrlDomain() {
+    ApiTracerContext context =
+        ApiTracerContext.newBuilder()
+            .setLibraryMetadata(LibraryMetadata.empty())
+            .setUrlDomain("compute.googleapis.com")
+            .setDestinationResourceIdSupplier(() -> "projects/my-project/locations/us-central1")
+            .build();
+
+    assertThat(context.destinationResourceId())
+        .isEqualTo("//compute.googleapis.com/projects/my-project/locations/us-central1");
+  }
+
+  @Test
+  void testDestinationResourceId_withoutUrlDomain() {
+    ApiTracerContext context =
+        ApiTracerContext.newBuilder()
+            .setLibraryMetadata(LibraryMetadata.empty())
+            .setDestinationResourceIdSupplier(() -> "projects/my-project/locations/us-central1")
+            .build();
+
+    assertThat(context.destinationResourceId())
+        .isEqualTo("projects/my-project/locations/us-central1");
+  }
+
+  @Test
+  void testWithResourceNameExtractor_nullExtractor() {
+    ApiTracerContext context = ApiTracerContext.empty();
+    ApiTracerContext result = context.withResourceNameExtractor("request", null);
+    assertThat(result).isSameInstanceAs(context);
+  }
+
+  @Test
+  void testWithResourceNameExtractor_extractorReturnsNull() {
+    ApiTracerContext context = ApiTracerContext.empty();
+    ApiTracerContext result = context.withResourceNameExtractor("request", req -> null);
+    assertThat(result.destinationResourceId()).isNull();
+  }
+
+  @Test
+  void testWithResourceNameExtraction_lazyExtractor() {
+    ApiTracerContext context = ApiTracerContext.empty();
+    boolean[] extracted = {false};
+    ApiTracerContext result =
+        context.withResourceNameExtractor(
+            "request",
+            req -> {
+              extracted[0] = true;
+              return "extracted-id";
+            });
+
+    assertThat(extracted[0]).isFalse(); // Should be lazily evaluated
+    assertThat(result.destinationResourceId()).isEqualTo("extracted-id");
+    assertThat(extracted[0]).isTrue();
+  }
+
+  @Test
+  void testWithResourceNameExtractor_extractorThrowsException() {
+    ApiTracerContext context = ApiTracerContext.empty();
+    ApiTracerContext result =
+        context.withResourceNameExtractor(
+            "request",
+            req -> {
+              throw new RuntimeException("Intentional mock extraction failure");
+            });
+
+    assertThat(result.destinationResourceId()).isNull();
+  }
+
+  @Test
+  void testDestinationResourceId_emptyIdWithUrlDomain() {
+    ApiTracerContext context =
+        ApiTracerContext.newBuilder()
+            .setLibraryMetadata(LibraryMetadata.empty())
+            .setUrlDomain("compute.googleapis.com")
+            .setDestinationResourceIdSupplier(() -> "")
+            .build();
+
+    assertThat(context.destinationResourceId()).isNull();
+  }
+
+  @Test
+  void testMerge_preservesLaziness() {
+    ApiTracerContext context1 = ApiTracerContext.empty();
+    boolean[] extracted = {false};
+    ApiTracerContext context2 =
+        ApiTracerContext.empty()
+            .withResourceNameExtractor(
+                "request",
+                req -> {
+                  extracted[0] = true;
+                  return "lazy-id";
+                });
+
+    ApiTracerContext merged = context1.merge(context2);
+    assertThat(extracted[0]).isFalse(); // Should not be evaluated during merge
+    assertThat(merged.destinationResourceId()).isEqualTo("lazy-id");
+    assertThat(extracted[0]).isTrue(); // Evaluated upon calling getter
+  }
+
+  @Test
+  void testDestinationResourceId_evaluatedEveryTime() {
+    ApiTracerContext context = ApiTracerContext.empty();
+    int[] counter = {0};
+    ApiTracerContext result =
+        context.withResourceNameExtractor(
+            "request",
+            req -> {
+              counter[0]++;
+              return "extracted-id-" + counter[0];
+            });
+
+    assertThat(result.destinationResourceId()).isEqualTo("extracted-id-1");
+    assertThat(result.destinationResourceId()).isEqualTo("extracted-id-2");
+    assertThat(counter[0]).isEqualTo(2);
+  }
 }

sdk-platform-java/gax-java/gax/src/test/java/com/google/api/gax/tracing/TracedUnaryCallableTest.java

@@ -208,30 +208,4 @@ void testResourceNameExtractorUsed() {
     assertThat(contextCaptor.getValue().destinationResourceId())
         .isEqualTo("extracted-resource-name");
   }
-
-  @Test
-  void testExtractResourceNameToApiTracerContext_nullExtractor() {
-    tracedUnaryCallable =
-        new TracedUnaryCallable<>(innerCallable, tracerFactory, TRACER_CONTEXT, null);
-    ApiTracerContext context = tracedUnaryCallable.extractResourceNameToApiTracerContext("request");
-    assertThat(context).isEqualTo(TRACER_CONTEXT);
-  }
-
-  @Test
-  void testExtractResourceNameToApiTracerContext_extractorReturnsNull() {
-    tracedUnaryCallable =
-        new TracedUnaryCallable<>(innerCallable, tracerFactory, TRACER_CONTEXT, request -> null);
-    ApiTracerContext context = tracedUnaryCallable.extractResourceNameToApiTracerContext("request");
-    assertThat(context).isEqualTo(TRACER_CONTEXT);
-  }
-
-  @Test
-  void testExtractResourceNameToApiTracerContext_extractorReturnsResourceId() {
-    tracedUnaryCallable =
-        new TracedUnaryCallable<>(
-            innerCallable, tracerFactory, TRACER_CONTEXT, request -> "extracted-id");
-    ApiTracerContext context = tracedUnaryCallable.extractResourceNameToApiTracerContext("request");
-    assertThat(context).isNotSameInstanceAs(TRACER_CONTEXT);
-    assertThat(context.destinationResourceId()).isEqualTo("extracted-id");
-  }
 }