chore(spanner): attach Request ID headers to Spanner RPCs

[olavloite]

Automatically attach unique x-goog-spanner-request-id headers to Spanner queries and reads, tracking attempt numbers across unary and streaming RPC retries.

[gemini-code-assist]

Code Review

This pull request implements automatic generation and propagation of Spanner request IDs across unary and streaming RPCs, including proper handling of retries and aborted transactions. The review feedback suggests optimizing the retry logic in ResultSet by using std::mem::take to avoid an unnecessary clone of GaxRequestOptions when updating the request ID header.

[codecov]

Codecov Report

❌ Patch coverage is 99.11972% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.08%. Comparing base (93d9a0f) to head (ad968fd).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/spanner/src/client.rs	97.64%	2 Missing ⚠️
src/spanner/src/request_id.rs	99.53%	2 Missing ⚠️
src/spanner/src/result_set.rs	94.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6248      +/-   ##
==========================================
+ Coverage   96.07%   96.08%   +0.01%     
==========================================
  Files         273      273              
  Lines       68742    69267     +525     
==========================================
+ Hits        66042    66557     +515     
- Misses       2700     2710      +10     

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[olavloite]

/gemini review

[gemini-code-assist]

Code Review

This pull request implements request ID propagation and tracking for Spanner RPCs (both unary and streaming), ensuring that retries are correctly tracked by incrementing the attempt suffix in the x-goog-spanner-request-id header. It introduces a SpannerRequestIdInterceptor to handle the headers, updates ResultSet to manually increment the attempt suffix on streaming retries, and adds comprehensive tests. The review feedback points out that applying #[allow(dead_code)] to the entire impl RequestIdCreator block silences compiler warnings for active production code, and suggests moving test-only methods to a separate block or marking them individually.

[olavloite]

/gemini review

[gemini-code-assist]

Code Review

This pull request implements Spanner request ID generation and propagation across unary, streaming, and retried RPCs. It introduces a SpannerRequestIdInterceptor to append attempt numbers to the x-goog-spanner-request-id header, and updates ResultSet to manually increment the attempt suffix during streaming retries. A review comment identifies a potential integer overflow panic and incorrect channel ID mapping when using channel_hint + 1 directly, suggesting a safer modulo-based channel ID calculation instead.

[olavloite]

/gemini review

[gemini-code-assist]

Code Review

This pull request implements robust propagation and retry handling for the x-goog-spanner-request-id header across unary and streaming Spanner RPCs. It introduces request ID generation, integrates it with various client operations, and updates the attempt interceptor and result set retry logic to correctly track and increment attempt numbers. Feedback is provided to optimize the stream retry logic in result_set.rs by avoiding unnecessary cloning of the HeaderMap unless a modification is actually required.