store/tikv/client: remove the lock for idle connection recycle

[tiancaiamao]

Signed-off-by: tiancaiamao tiancaiamao@gmail.com

What problem does this PR solve?

Cherry pick tikv/client-go#278 to TiDB 5.1 branch

Problem Summary:

What is changed and how it works?

Fix the recycle idle connection lock blocks send request operation.

What's Changed:

How it Works:

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

Check the result error will not make TiDB unavailable, instead, a rpc error is returned, and TiDB will fill region cache and retry.

• [] No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Fix a batch client bug that recycle idle connection may block sending requests in some rare cases.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• crazycs520
• disksing

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[zhouqiang-cl]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 58e87d9

[zhouqiang-cl]

/merge

[tiancaiamao]

Close #32500