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fix(gax): Manage span scope in SpanTracer #12680

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fix(gax): Manage span scope in SpanTracer #12680

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5 changes: 5 additions & 0 deletions sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/tracing/SpanTracer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,8 @@
import io.opentelemetry.api.trace.SpanBuilder;
import io.opentelemetry.api.trace.SpanKind;
import io.opentelemetry.api.trace.Tracer;
import io.opentelemetry.context.Scope;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.CancellationException;
Expand All @@ -53,6 +55,7 @@ public class SpanTracer implements ApiTracer {
private final String attemptSpanName;
private final ApiTracerContext apiTracerContext;
private Span attemptSpan;
private io.opentelemetry.context.Scope scope;

@Override
public void injectTraceContext(java.util.Map<String, String> carrier) {
Expand Down Expand Up @@ -144,6 +147,7 @@ public void attemptStarted(Object request, int attemptNumber) {
spanBuilder.setAllAttributes(ObservabilityUtils.toOtelAttributes(currentAttemptAttributes));

this.attemptSpan = spanBuilder.startSpan();
this.scope = attemptSpan.makeCurrent();
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@gemini-code-assist gemini-code-assist bot Apr 4, 2026

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high

Managing an OpenTelemetry Scope as a class field is risky in asynchronous environments. Scope is thread-local and must be closed on the same thread it was opened. In gax-java, ApiTracer methods like attemptStarted and endAttempt are frequently called on different threads (e.g., the request thread and the gRPC callback thread). Closing the scope on a different thread will lead to incorrect context restoration and potential state corruption in OpenTelemetry.

}

@Override
Expand Down Expand Up @@ -249,6 +253,7 @@ private void endAttempt() {
return;
}

scope.close();
attemptSpan.end();
attemptSpan = null;
Comment on lines +256 to 258
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@gemini-code-assist gemini-code-assist bot Apr 4, 2026

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high

To ensure exception safety and adhere to the LIFO rule for resource management, scope.close() should be wrapped in a try-finally block. This guarantees that attemptSpan.end() is called even if an unexpected exception occurs during scope closure. Additionally, a null check for scope is recommended to prevent potential NPEs if makeCurrent() failed or wasn't called, and the field should be cleared after closing.

    try {
      if (scope != null) {
        scope.close();
      }
    } finally {
      scope = null;
      attemptSpan.end();
      attemptSpan = null;
    }
References
  1. When managing a collection of closeable resources (e.g., scopes), ensure they are closed in the reverse order of their creation (LIFO). The implementation must be exception-safe to prevent resource leaks, meaning all opened resources should be closed even if exceptions occur during their creation or closing.

}
Expand Down
34 changes: 31 additions & 3 deletions sdk-platform-java/gax-java/gax/src/test/java/com/google/api/gax/tracing/SpanTracerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -33,9 +33,7 @@
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.ArgumentMatchers.anyString;
import static org.mockito.ArgumentMatchers.eq;
import static org.mockito.Mockito.never;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
import static org.mockito.Mockito.*;

import com.google.api.gax.rpc.ApiException;
import com.google.api.gax.rpc.ErrorDetails;
Expand All @@ -48,6 +46,7 @@
import io.opentelemetry.api.trace.SpanBuilder;
import io.opentelemetry.api.trace.SpanKind;
import io.opentelemetry.api.trace.Tracer;
import io.opentelemetry.context.Scope;
import java.net.ConnectException;
import java.net.SocketTimeoutException;
import org.junit.jupiter.api.BeforeEach;
Expand All @@ -62,6 +61,7 @@ class SpanTracerTest {
@Mock private Tracer tracer;
@Mock private SpanBuilder spanBuilder;
@Mock private Span span;
@Mock private Scope scope;
private SpanTracer spanTracer;
private static final String ATTEMPT_SPAN_NAME = "Service/Method/attempt";

Expand All @@ -71,6 +71,7 @@ void setUp() {
when(spanBuilder.setSpanKind(any(SpanKind.class))).thenReturn(spanBuilder);
when(spanBuilder.setAllAttributes(any(Attributes.class))).thenReturn(spanBuilder);
when(spanBuilder.startSpan()).thenReturn(span);
lenient().when(span.makeCurrent()).thenReturn(scope);
spanTracer = new SpanTracer(tracer, ApiTracerContext.empty(), ATTEMPT_SPAN_NAME);
}

Expand Down Expand Up @@ -625,4 +626,31 @@ void testInjectTraceContext_addsHeaders() {
assertThat(carrier.get("traceparent")).contains("00000000000000000000000000000001");
assertThat(carrier.get("traceparent")).contains("0000000000000002");
}

@Test
void testAttemptStarted_makesSpanCurrent() {
spanTracer.attemptStarted(new Object(), 1);
verify(span).makeCurrent();
}

@Test
void testAttemptEnded_closesScope_succeeded() {
spanTracer.attemptStarted(new Object(), 1);
spanTracer.attemptSucceeded();
verify(scope).close();
}

@Test
void testAttemptEnded_closesScope_failed() {
spanTracer.attemptStarted(new Object(), 1);
spanTracer.attemptFailedRetriesExhausted(new RuntimeException());
verify(scope).close();
}

@Test
void testAttemptEnded_closesScope_cancelled() {
spanTracer.attemptStarted(new Object(), 1);
spanTracer.attemptCancelled();
verify(scope).close();
}
}
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