feat: Add Metrics feature flag #4044

diegomarquezp · 2026-01-07T23:27:46Z

This PR introduces a feature flag to control the collection of metrics in GAX. Metrics are now disabled by default and can be enabled via an environment variable or system property.

Changes:

Feature Flag Implementation:
- Added MetricsUtils.java to handle the feature flag logic. It checks for the GOOGLE_CLOUD_ENABLE_METRICS environment variable or system property.
- Updated MetricsTracerFactory.java to respect the feature flag. If metrics are disabled, newTracer now returns a BaseApiTracer (no-op) instead of a MetricsTracer.
Discovery and Warning:
- Updated MetricsTracer.java to log an INFO message once per JVM instance if it is instantiated while metrics are disabled. This helps users who have explicitly configured a MetricsTracerFactory discover that they also need to enable the global feature flag.
Testing:
- Unit Tests: Added MetricsUtilsTest.java to verify the feature flag logic. Updated MetricsTracerFactoryTest.java to ensure it correctly returns a no-op tracer when metrics are disabled.
- Integration Tests: Updated ITOtelMetrics.java in the showcase module to include a new test case testMetricsFeatureFlag(), which verifies the end-to-end behavior of the flag.
Maintenance:
- Updated copyright years in modified files.
- Improved test setup in MetricsTracerFactoryTest.java using @ExtendWith(MockitoExtension.class).

How to enable metrics:

To enable metrics collection, set the following environment variable or system property to true:
GOOGLE_CLOUD_ENABLE_METRICS=true

gemini-code-assist · 2026-01-07T23:28:06Z

Summary of Changes

Hello @diegomarquezp, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request implements a new feature flag to control the activation of metrics tracing within the GAX library. This enhancement allows developers to easily enable or disable metrics collection at runtime using system properties or environment variables, providing more flexibility and control over application performance monitoring. The changes include a dedicated utility class for flag management, modifications to the metrics tracer factory, and thorough testing to ensure robust and predictable behavior.

Highlights

Metrics Feature Flag: Introduced a new feature flag, GOOGLE_CLOUD_ENABLE_METRICS, which allows users to enable or disable metrics collection via system properties or environment variables. This provides granular control over when metrics are active.
New Utility Class: A new utility class, MetricsUtils, has been added to encapsulate the logic for checking the status of the metrics feature flag, making the decision-making process centralized and reusable.
Conditional Metrics Tracing: The MetricsTracerFactory now conditionally creates a MetricsTracer instance. If the GOOGLE_CLOUD_ENABLE_METRICS flag is not enabled, it will return a BaseApiTracer instead, effectively disabling metrics tracing.
Comprehensive Testing: New unit tests for MetricsUtils and additional test cases for MetricsTracerFactory have been added to ensure the feature flag logic works as expected. Integration tests were also updated to validate the flag's behavior in a broader context.
Copyright Year Update: The copyright year in several files has been updated to 2026.

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Code Review

This pull request introduces a feature flag, GOOGLE_CLOUD_ENABLE_METRICS, to control metrics collection. The implementation in MetricsUtils correctly checks for a system property or environment variable. The changes are well-tested, including unit tests for the new utility class and integration tests for the feature flag behavior. My review includes suggestions to improve test code style by using explicit imports and to enhance the robustness of a test case by avoiding the use of a null MetricsRecorder.

java-showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITOtelMetrics.java

…/v1beta1/it/ITOtelMetrics.java Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

…leapis/sdk-platform-java into observability/feature-flags

sonarqubecloud · 2026-01-07T23:58:02Z

Quality Gate passed for 'gapic-generator-java-root'

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

sonarqubecloud · 2026-01-08T00:01:51Z

Quality Gate failed for 'java_showcase_integration_tests'

Failed conditions
65.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

westarle · 2026-01-08T15:36:37Z

gax-java/gax/src/main/java/com/google/api/gax/tracing/MetricsTracerFactory.java


  @Override
  public ApiTracer newTracer(ApiTracer parent, SpanName spanName, OperationType operationType) {
+    if (!MetricsUtils.isMetricsEnabled()) {


I don't want to change how existing metrics works, the flag is intended to protect new metric instrumentation from people taking dependencies on it while it stabilizes.

westarle

I like the API and the implementation, but we shouldn't apply it to existing metrics. I also think the first one we might be interested in is for tracing, if we are going to work on tracing first.

/cc @blakeli0

westarle · 2026-01-08T15:39:49Z

gax-java/gax/src/main/java/com/google/api/gax/tracing/MetricsUtils.java

+   * system property.
+   */
+  public static boolean isMetricsEnabled() {
+    String enableMetrics = System.getProperty(GOOGLE_CLOUD_ENABLE_METRICS);


I would like this to have the words "JAVA" and "EXPERIMENTAL" or "UNSTABLE" in it. The Go one is GOOGLE_SDK_GO_EXPERIMENTAL_FOO

The "JAVA" part of this comment is intended to apply to the env variable rather than the Java property...

westarle · 2026-01-08T15:41:24Z

gax-java/gax/src/main/java/com/google/api/gax/tracing/MetricsUtils.java

+  public static boolean isMetricsEnabled() {
+    String enableMetrics = System.getProperty(GOOGLE_CLOUD_ENABLE_METRICS);
+    if (enableMetrics == null) {
+      enableMetrics = System.getenv(GOOGLE_CLOUD_ENABLE_METRICS);


Do we need to cache the result, or can we put a note on the method that it should be cached by clients (I'd like to avoid a read to env or properties on every RPC).

diegomarquezp · 2026-01-08T21:07:17Z

I will close this for now and keep the feedback for the next iteration.

diegomarquezp added 3 commits January 7, 2026 17:27

feat: add feature flag for Metrics

dc4729f

chore: add tests

23bf45f

chore: update copyright year

e0356b4

product-auto-label bot added the size: m Pull request size is medium. label Jan 7, 2026

diegomarquezp changed the title ~~feat: Add Metrics feature flag'~~ feat: Add Metrics feature flag Jan 7, 2026

gemini-code-assist bot reviewed Jan 7, 2026

View reviewed changes

java-showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITOtelMetrics.java Outdated Show resolved Hide resolved

java-showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITOtelMetrics.java Outdated Show resolved Hide resolved

diegomarquezp and others added 4 commits January 7, 2026 18:40

chore: warn of disabled metrics

878328f

Update java-showcase/gapic-showcase/src/test/java/com/google/showcase…

912bfbb

…/v1beta1/it/ITOtelMetrics.java Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

test: add recorder to feature flag IT

f6ced37

Merge branch 'observability/feature-flags' of https://github.com/goog…

6c6ab75

…leapis/sdk-platform-java into observability/feature-flags

westarle reviewed Jan 8, 2026

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westarle requested changes Jan 8, 2026

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diegomarquezp closed this Jan 8, 2026

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Changes:

How to enable metrics:

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Quality Gate passed for 'gapic-generator-java-root'

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Quality Gate failed for 'java_showcase_integration_tests'

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