Refactor: Introduce thread-safe GlobalSchemaCache for gRPC handlers

[jac0626]

• Global Singleton: Replaced instance-level caches with a thread-safe GlobalSchemaCache
• Key Isolation: Added {endpoint}/{db}/{collection} keying for multi-cluster/multi-db support.
• LRU Eviction: Implemented LRU logic with a 4096 capacity.
• Efficiency: Reduced redundant describe_collection calls across client instances.
• Verified: 96 tests passed (including 13 new cache tests).
  see [Bug]: Implement Global Thread-Safe Schema Cache with Eviction Policy #3186

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[gemini-code-assist]

Summary of Changes

Hello @jac0626, 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 introduces a fundamental refactoring of the schema caching mechanism within the pymilvus gRPC handlers. By transitioning from localized, instance-bound caches to a global, thread-safe, and LRU-managed schema cache, the change aims to enhance the client's efficiency and scalability. This centralized approach prevents repetitive schema fetches, particularly beneficial in multi-threaded or multi-client environments, while also providing clear isolation for different Milvus instances and databases.

Highlights

• Global Singleton Cache: Replaced instance-level schema caches in gRPC handlers with a single, thread-safe GlobalSchemaCache.
• Multi-Tenant Keying: Implemented a robust keying strategy ({endpoint}/{db}/{collection}) to ensure proper isolation and support for multiple Milvus clusters and databases.
• LRU Eviction: Integrated an LRU (Least Recently Used) eviction policy with a capacity of 4096 entries to manage cache size efficiently.
• Efficiency Improvement: Significantly reduced redundant describe_collection calls across client instances, leading to improved performance.
• Comprehensive Testing: Added 13 new dedicated tests for the caching mechanism, contributing to a total of 96 passing tests.

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[gemini-code-assist]

Code Review

This pull request effectively refactors the schema caching mechanism by introducing a thread-safe, global LRU cache. This is a significant improvement that will reduce redundant describe_collection calls and enhance efficiency. The implementation of the GlobalSchemaCache singleton is solid, and the accompanying tests are comprehensive. I've provided a few suggestions to further refine the implementation for better performance and readability, such as using a more appropriate lock and simplifying some of the cache interaction patterns.

[codecov]

Codecov Report

❌ Patch coverage is 85.13514% with 11 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (master@5d377b2). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
pymilvus/client/async_grpc_handler.py	15.38%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #3188   +/-   ##
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  Coverage          ?   46.95%           
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  Files             ?       69           
  Lines             ?    14860           
  Branches          ?        0           
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  Hits              ?     6977           
  Misses            ?     7883           
  Partials          ?        0           

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[XuanYang-cn]

I think a popular library cachetools can help alot.

[jac0626]

I think a popular library cachetools can help alot.

cachetools

done

[XuanYang-cn]

The second is redundent, see numpy for reference.

I think the first might be unnecessary too, because packages often maintain supported python ranges, and pip should be able to resolve it to the correct highest-version for python3.8.

[jac0626]

done