chore: PoC for App Centric metrics

[blakeli0]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @blakeli0, 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 proof-of-concept for application-centric metrics within GAX-Java, leveraging OpenTelemetry. The primary goal is to provide more detailed and standardized observability into client request durations and outcomes. This involves introducing a new metrics recorder and updating existing tracing components to use consistent attribute naming conventions, ensuring that critical operational data is captured and made available for monitoring and analysis.

Highlights

• New App-Centric Metrics Recorder: Introduced AppCentricMetricsRecorder to enable OpenTelemetry-based application-centric metrics for GAX-Java, specifically recording gcp.client.request.duration.
• Standardized Metric Attribute Keys: Standardized metric attribute keys for RPC method and status to rpc.method and grpc.status respectively, aligning with OpenTelemetry conventions.
• Comprehensive Integration Tests: Added extensive integration tests in ITAppCentricMetrics to validate the new metrics recording functionality across various gRPC and HTTP/JSON scenarios, including successful operations, cancellations, failures, and retries, and verifying custom attributes.

Changelog

• gax-java/gax/src/main/java/com/google/api/gax/tracing/AppCentricMetricsRecorder.java
  • Added a new class AppCentricMetricsRecorder that implements MetricsRecorder to record gcp.client.request.duration histogram metrics using OpenTelemetry.
  • Implemented a method to convert a map of string attributes to OpenTelemetry Attributes.
• gax-java/gax/src/main/java/com/google/api/gax/tracing/MetricsTracer.java
  • Updated the METHOD_ATTRIBUTE constant from "method" to "rpc.method".
  • Updated the STATUS_ATTRIBUTE constant from "status" to "grpc.status".
• java-showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITAppCentricMetrics.java
  • Added a new integration test suite ITAppCentricMetrics to verify the correct recording of app-centric metrics.
  • Included tests for successful gRPC and HTTP/JSON operations, cancelled operations, failed operations, and operations with retries.
  • Verified the presence and correctness of default and custom attributes in the recorded metrics.
  • Ensured proper method name recording when using GrpcOpenTelemetry.

Activity

• No human activity (comments, reviews, etc.) has been recorded on this pull request yet.

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[gemini-code-assist]

Code Review

This pull request introduces an AppCentricMetricsRecorder as a proof-of-concept for app-centric metrics. It also updates some metric attribute names to align with OpenTelemetry conventions and adds a new integration test suite.

My review has identified a couple of issues:

• There's a unit mismatch in AppCentricMetricsRecorder where latency in milliseconds is recorded for a metric with units of seconds.
• The new integration test ITAppCentricMetrics seems to contain incorrect logic, as it appears to be testing for metrics produced by a different recorder (OpenTelemetryMetricsRecorder) and makes wrong assumptions about how AppCentricMetricsRecorder works.

Please see the detailed comments for suggestions on how to address these points.

[gemini-code-assist]

The test logic in this class appears to be based on OpenTelemetryMetricsRecorder rather than AppCentricMetricsRecorder, leading to incorrect assertions. AppCentricMetricsRecorder only records a single metric gcp.client.request.duration once per operation.

Specifically:

1. verifyPointDataSum checks for metrics that are not produced (ShowcaseTest/operation_latency, ShowcaseTest/attempt_latency). It should be verifying gcp.client.request.duration.
2. verifyStatusAttribute incorrectly assumes that a metric point is recorded for each attempt. It should verify only the single final status of the whole operation. For example, in testGrpc_multipleFailedAttempts_successfulOperation, only a single point with status OK will be recorded.
3. Several constants like ATTEMPT_LATENCY, OPERATION_LATENCY, GAX_METRICS, and NUM_GAX_OTEL_METRICS are unused or related to the old logic and should be removed.

The test class needs to be revised to correctly test the behavior of AppCentricMetricsRecorder. This involves updating the verification methods to check for the gcp.client.request.duration metric and its properties (e.g., single data point per operation, correct final status).

[gemini-code-assist]

There is a unit mismatch here. The Javadoc for operationLatency on line 74 specifies the unit as milliseconds (ms), but the requestDurationRecorder histogram is configured with seconds (s) as its unit on line 66. The value is being recorded without conversion.

This will lead to incorrect metric values (e.g., a latency of 100ms will be recorded as 100s).

Please convert the latency to seconds before recording.

Suggested change

	requestDurationRecorder.record(operationLatency, toOtelAttributes(attributes));
	requestDurationRecorder.record(operationLatency / 1000.0, toOtelAttributes(attributes));