chore: normalize query param keys to lowercase in KeyRecipe and fix lock contention in KeyRangeCache

[rahul2393]

Fixes: b/482811543

KeyRecipe.queryParamsToTargetRange — case-insensitive parameter lookup

The server sends routing recipe identifiers (e.g. "id") that may differ in case from the query parameter names bound by the user (e.g. "Id" or "ID"). Without normalization, the routing key lookup silently missed, causing all requests to fall back to the default endpoint instead of being routed to the optimal server.

Fix: both the recipe identifier and the user's parameter keys are now normalized with toLowerCase(Locale.ROOT) before the HashMap lookup, so case differences no longer cause routing misses.

KeyRangeCache.CachedGroup.fillRoutingHint — avoid holding lock during channel creation

Previously, CachedGroup.fillRoutingHint was a synchronized method, which meant the group lock was held for the entire duration including the call to endpointCache.get(address). That call can block on a network dial when creating a new gRPC channel for the first time, serializing all concurrent routing decisions on the same group.

Fix: the lock is now released before calling endpointCache.get(). The tablet selection (cheap, in-memory) still runs
under the lock. If the endpoint is already cached, it is returned directly without ever releasing the lock (fast path).
If a new channel needs to be dialed, the address is captured, the lock is released, the channel is created, and the lock is re-acquired to update the tablet's cached endpoint atomically — only if the address hasn't changed in the meantime

[gemini-code-assist]

Summary of Changes

Hello, 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 enhances the KeyRecipe class by introducing case-insensitive matching for query parameter keys. It achieves this by normalizing all incoming query parameter keys to lowercase before processing, which improves the robustness and user-friendliness of key resolution by accommodating variations in key casing. The change includes necessary utility imports and is thoroughly covered by new unit tests.

Highlights

• Case-Insensitive Query Parameter Keys: Implemented logic within the KeyRecipe class to normalize query parameter keys to lowercase, enabling case-insensitive matching when resolving target ranges.
• Duplicate Key Handling: Ensured that if multiple query parameters with keys that normalize to the same lowercase value are provided, the value associated with the last occurrence of that key is used.
• Comprehensive Testing: Added new unit tests to validate the case-insensitive behavior for query parameters and to confirm the correct handling of duplicate keys with varying casing.

Changelog

• google-cloud-spanner/src/main/java/com/google/cloud/spanner/spi/v1/KeyRecipe.java
  • Implemented case-insensitive lookup for query parameter keys in queryParamsToTargetRange.
  • Added necessary utility imports for HashMap, Locale, and Map.
• google-cloud-spanner/src/test/java/com/google/cloud/spanner/spi/v1/KeyRecipeTest.java
  • Added assertFalse import.
  • Introduced queryParamsCaseInsensitiveFallback test to verify case-insensitive matching.
  • Introduced queryParamsCaseInsensitiveDuplicateUsesLastValue test to verify handling of duplicate keys.
  • Added expectedTagOnlyKey helper method for test setup.

Activity

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[gemini-code-assist]

Code Review

This pull request correctly implements case-insensitive handling for query parameter keys in KeyRecipe by normalizing them to lowercase. The accompanying tests effectively validate this new logic, including edge cases with duplicate keys. I have one minor suggestion to remove a newly added but unused helper method in the test file to improve code clarity.

[rahul2393]

Reference: googleapis/google-cloud-go#13877 (comment)

[rahul2393]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces two valuable changes. First, it addresses a lock contention issue in KeyRangeCache by refactoring fillRoutingHint to avoid holding a lock during potentially blocking network operations. The implementation correctly uses a pattern similar to double-checked locking to ensure thread safety and handle race conditions. Second, it fixes a bug in KeyRecipe by normalizing query parameter keys to lowercase, enabling case-insensitive lookups. This change is accompanied by thorough unit tests covering various scenarios, including edge cases. Both changes are well-implemented and improve the robustness and performance of the code.