fix(spanner): disable metrics tracer when built-in metrics are disabled

[rahul2393]

Summary

• Track built-in metrics enablement on each Spanner instance
• Sync MetricsTracerFactory.enabled with the instance's computed metrics state during configureMetrics_()
• Prevent MetricsTracer and metric interceptor creation when built-in metrics are disabled via client option, env var, or insecure credentials

Why

When disableBuiltInMetrics was true, metrics export setup was skipped, but MetricsTracerFactory.enabled could still remain true from its default value or prior state. If projectId_ was set, requests could still create MetricsTracer instances even though built-in metrics were disabled.

This change computes metrics enablement during client setup and uses the instance-level state to guard tracer/
interceptor creation.

[gemini-code-assist]

Code Review

This pull request updates the Spanner client to explicitly set the MetricsTracerFactory.enabled flag based on the instance's configuration and changes the default value of this static property to false. A significant issue was identified where setting a static property based on instance-specific logic creates a global side effect, potentially causing configuration conflicts in applications that utilize multiple Spanner clients with different settings.

[rahul2393]

/gemini review

[rahul2393]

/gemini summary

[gemini-code-assist]

Code Review

This pull request introduces an instance-level _metricsEnabled property to the Spanner class, replacing the global MetricsTracerFactory.enabled check to allow for more granular control over metrics collection. Feedback indicates a logic error in configureMetrics_ where _metricsEnabled fails to incorporate the _isInSecureCredentials check. This omission leads to inconsistent behavior when guarding tracer creation in the request and requestStream methods.

[gemini-code-assist]

Summary of Changes

This pull request refactors the metrics configuration logic in the Spanner client to move away from global state management. By introducing an instance-specific flag, it ensures that metrics settings are correctly isolated across different client instances, preventing side effects where one client's configuration could inadvertently affect others. The changes also improve the reliability of the metrics disabling mechanism by ensuring all relevant conditions are consistently evaluated.

Highlights

• Instance-based Metrics Control: Introduced a private _metricsEnabled property to the Spanner class to manage metrics state per-instance, replacing the problematic global MetricsTracerFactory.enabled flag.
• Metrics Configuration Logic: Updated configureMetrics_ to centralize the logic for disabling metrics, ensuring it correctly accounts for client options, environment variables, and insecure credentials.
• Tracer Creation Guard: Added checks for _metricsEnabled in request and requestStream methods to prevent unnecessary MetricsTracer creation when built-in metrics are disabled.

Activity

• The pull request was created by rahul2393.
• Gemini Code Assist identified a high-priority issue regarding global state side effects in the initial implementation.
• The author requested a review and summary.
• Gemini Code Assist provided further feedback on the implementation of the metrics guard logic.

[rahul2393]

/gemini review

[rahul2393]

/gemini summary

[gemini-code-assist]

Code Review

This pull request transitions the metrics enablement state from a global static property (MetricsTracerFactory.enabled) to an instance-specific property (_metricsEnabled) within the Spanner class. This change allows for independent metrics configuration across different Spanner client instances, preventing global state side effects. The request and requestStream methods, as well as the interceptor logic, have been updated to reference this instance property. I have no feedback to provide.

[gemini-code-assist]

Summary of Changes

This pull request refactors the metrics configuration logic in the Spanner client to eliminate reliance on global state. By moving the metrics-enabled status to an instance-specific property, the changes prevent configuration leakage between multiple Spanner clients and ensure that metrics are consistently disabled when required by client options, environment variables, or insecure credentials.

Highlights

• Instance-based Metrics Control: Replaced the global MetricsTracerFactory.enabled flag with a private _metricsEnabled property in the Spanner class to ensure metrics configuration is isolated per client instance.
• Centralized Configuration Logic: Updated configureMetrics_ to consolidate the logic for disabling metrics, ensuring it correctly evaluates client options, environment variables, and insecure credentials.
• Tracer Creation Guard: Added strict checks for _metricsEnabled in request and requestStream methods to prevent the creation of MetricsTracer instances when built-in metrics are disabled.

Activity

• The pull request was created by rahul2393.
• Gemini Code Assist identified a high-priority issue regarding global state side effects.
• Gemini Code Assist provided feedback on the implementation of the metrics guard logic to ensure insecure credentials are properly handled.
• User surbhigarg92 requested clarification on the inclusion of the insecure credentials check in the metrics guard.
• The author updated the implementation to address the feedback and ensure consistent metrics disabling.