feat: Switch Eef metrics to using built in open telemetry

[kinsaurralde]

Switching to built in open telemetry since the eef metrics are internal metrics

[gemini-code-assist]

Summary of Changes

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This pull request refactors the internal EEF metrics collection within the Spanner client library to leverage the existing built-in OpenTelemetry infrastructure. This change streamlines metric reporting by consolidating internal metrics under a unified observability framework, improving consistency and reducing the need for custom metric handling.

Highlights

• OpenTelemetry Integration: Switched the internal EEF (Enhanced Error Handling) metrics to use the built-in OpenTelemetry system, aligning with the project's observability strategy.
• New Metric Definitions: Introduced new constants for gRPC-GCP specific metrics, including eef.fallback_count and eef.call_status, along with their associated OpenTelemetry attribute keys and view configurations.
• Metric View Configuration: Implemented a new defineGrpcGcpView method to properly configure OpenTelemetry views for the new gRPC-GCP metrics, ensuring correct aggregation and attribute filtering.
• Built-in OpenTelemetry Access: Added a public method getBuiltInOpenTelemetry to SpannerOptions to provide access to the internal OpenTelemetry instance for consistent metric reporting.
• Fallback Metrics Update: Modified GapicSpannerRpc to utilize the newly exposed built-in OpenTelemetry instance for GcpFallbackOpenTelemetry metrics, ensuring these internal metrics are reported through the standard OpenTelemetry pipeline.

Changelog

• google-cloud-spanner/src/main/java/com/google/cloud/spanner/BuiltInMetricsConstant.java
  • Added a new constant for the gRPC-GCP meter name.
  • Introduced constants for EEF fallback count and call status metric names.
  • Defined new AttributeKey constants for channel names and status codes.
  • Created sets for gRPC-GCP EEF fallback count and call status attributes.
  • Defined a map for gRPC-GCP metric additional attributes and a collection of gRPC-GCP metrics to enable.
  • Invoked the new defineGrpcGcpView method within getAllViews.
  • Added the defineGrpcGcpView method to configure OpenTelemetry views for gRPC-GCP metrics.
• google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerCloudMonitoringExporterUtils.java
  • Imported the new GRPC_GCP_METER_NAME constant.
  • Updated the metric data filtering logic to include the GRPC_GCP_METER_NAME.
• google-cloud-spanner/src/main/java/com/google/cloud/spanner/SpannerOptions.java
  • Added a new public method getBuiltInOpenTelemetry to retrieve the internal OpenTelemetry instance.
• google-cloud-spanner/src/main/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpc.java
  • Imported the OpenTelemetry class.
  • Added a new @VisibleForTesting method getFallbackOpenTelemetry to conditionally return the built-in OpenTelemetry instance.
  • Modified the interceptCall method to use getFallbackOpenTelemetry(options) when initializing GcpFallbackOpenTelemetry.
• google-cloud-spanner/src/test/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpcTest.java
  • Overrode the getFallbackOpenTelemetry method in TestableGapicSpannerRpc to return options.getOpenTelemetry().
  • Overrode the getFallbackOpenTelemetry method in TestableGapicSpannerRpcWithLowerMinFailedCalls to return options.getOpenTelemetry().

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[gemini-code-assist]

Code Review

This pull request correctly switches the EEF metrics to use the built-in OpenTelemetry instance, which is appropriate for internal metrics. The changes involve exposing the built-in OpenTelemetry instance through SpannerOptions and utilizing it in GapicSpannerRpc for the fallback channel's telemetry. Additionally, new constants and views for the EEF metrics are introduced. The implementation appears solid. I have one suggestion to enhance code maintainability by refactoring a lengthy conditional statement.

[gemini-code-assist]

The chain of || conditions is getting long and can be hard to read. To improve readability and maintainability, consider using a Set of allowed meter names for this check.

You could define a public static Set<String> in BuiltInMetricsConstant.java:

// In BuiltInMetricsConstant.java
public static final String SPANNER_METER_NAME = "spanner-java"; // Make public
public static final String GRPC_METER_NAME = "grpc-java"; // Make public

public static final java.util.Set<String> ALLOWED_BUILT_IN_METRICS_METERS =
    com.google.common.collect.ImmutableSet.of(
        GAX_METER_NAME, SPANNER_METER_NAME, GRPC_METER_NAME, GRPC_GCP_METER_NAME);

Then, you can simplify this check to:

if (!BuiltInMetricsConstant.ALLOWED_BUILT_IN_METRICS_METERS.contains(
    metricData.getInstrumentationScopeInfo().getName())) {
  // ...
}