feat(o11y): introduce http.request.method and span name for HTTP requests

[diegomarquezp]

• feat(o11y): add http.request.method to span tracing
• test: update tests

[gemini-code-assist]

Summary of Changes

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This pull request significantly enhances the observability of HTTP requests within the system by introducing detailed HTTP-specific attributes to tracing spans. It refactors the mechanism for generating span context, allowing for the inclusion of HTTP method and path template, which provides more granular and actionable insights into the performance and behavior of HTTP interactions.

Highlights

• Enhanced HTTP Tracing: Introduced http.request.method and http.request.path_template attributes to HTTP request tracing spans for improved observability.
• Dynamic HTTP Span Naming: Updated the naming convention for HTTP spans to dynamically include the HTTP method and path template, providing more descriptive span names.
• Refactored Span Context: Migrated from SpanName to ApiTracerContext for generating span context, allowing for richer metadata and more flexible attribute management.

Changelog

• gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonCallableFactory.java
  • Imported LibraryMetadata and ApiTracerContext.
  • Removed SpanName import.
  • Replaced getSpanName with getApiTracerContext which now builds a comprehensive ApiTracerContext including HTTP method, path template, and transport type.
• gax-java/gax-httpjson/src/test/java/com/google/api/gax/httpjson/HttpJsonCallableFactoryTest.java
  • Updated imports to include Mockito and ApiTracerContext.
  • Refactored testGetSpanName to testGetApiTracerContext to test the new ApiTracerContext fields.
  • Added a new test testGetApiTracerContext_populatesHttpFields to specifically verify HTTP method and path template population.
• gax-java/gax/src/main/java/com/google/api/gax/tracing/ApiTracerContext.java
  • Added abstract methods httpMethod() and httpPathTemplate() to ApiTracerContext.
  • Modified getAttemptAttributes() to include http.request.method attribute if the transport is HTTP.
  • Updated the merge method in the Builder to handle the new httpMethod and httpPathTemplate fields.
  • Added setHttpMethod and setHttpPathTemplate to the Builder.
• gax-java/gax/src/main/java/com/google/api/gax/tracing/ObservabilityAttributes.java
  • Added a new constant HTTP_METHOD_ATTRIBUTE for the http.request.method span attribute.
• gax-java/gax/src/main/java/com/google/api/gax/tracing/SpanTracerFactory.java
  • Modified the newTracer method to construct HTTP span names using the httpMethod and httpPathTemplate from ApiTracerContext instead of a generic client/method name.
• gax-java/gax/src/test/java/com/google/api/gax/tracing/ApiTracerContextTest.java
  • Added testGetAttemptAttributes_httpMethod to verify the inclusion of the HTTP method attribute.
  • Added testGetAttemptAttributes_httpMethod_notHttpTransport to ensure the HTTP method attribute is only added for HTTP transport.
  • Added testMerge_httpFields to verify correct merging of HTTP-related fields in ApiTracerContext.
• java-showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITOtelTracing.java
  • Updated the expected span name in testTracing_successfulEcho_httpjson to reflect the new HTTP method and path template format.
  • Added an assertion to verify the http.request.method attribute is present and correct in the HTTPJSON attempt span.

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[gemini-code-assist]

Code Review

This pull request introduces observability improvements for HTTP requests by adding the http.request.method attribute to traces and defining a more informative span name format (<HTTP_METHOD> <HTTP_PATH_TEMPLATE>). The changes are well-structured and include corresponding updates to unit and integration tests. However, I've identified a bug in SpanTracerFactory where an incorrect context is used to generate the new span name, which could lead to errors. My review includes a specific comment with a suggested fix for this issue.

[gemini-code-assist]

There's a bug here where the span name for HTTP requests is constructed using the apiTracerContext parameter directly, instead of the merged context variable. The context variable correctly holds the merged properties from both the factory-level and call-level contexts. Using apiTracerContext bypasses any factory-level context, which could lead to incorrect span names or a NullPointerException if httpMethod or httpPathTemplate are not present in the call-level context but are in the factory-level one.

Please use the context variable to ensure the merged context is used.

      attemptSpanName =
          String.format("%s %s", context.httpMethod(), context.httpPathTemplate());

[diegomarquezp]

Done