--consolidator-query-waiter-cap to set the max number of waiter for consolidated query

[jwangace]

Description

This PR proposed to use config ConsolidatorQueryWaiterCap to set the max number of clients Wait() for all consolidated queries, more same queries will fall back to use getConn() where is protected by connection pools.

With configureable ConsolidatorQueryWaiterCap (default to 0 means unlimit, user can adjust this value accordingly), when properly set would help to prevent when the Result of first query been returned, same Result would be sent concurrently to large number of clients, cause memory abruptly went high.

Related Issue(s)

Issue: #17243
Documentation: vitessio/website#1900

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

[vitess-bot]

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[harshit-gangal]

This would also require addition to summary notes for v22 over https://github.com/vitessio/vitess/blob/main/changelog/22.0/22.0.0/summary.md

You can see v21 summary notes to see the template to add new configuration to release notes

[harshit-gangal]

Website docs would also need an update https://vitess.io/docs/22.0/user-guides/configuration-advanced/query-consolidation/

[jwangace]

This would also require addition to summary notes for v22 over https://github.com/vitessio/vitess/blob/main/changelog/22.0/22.0.0/summary.md

You can see v21 summary notes to see the template to add new configuration to release notes

Updated.

[jwangace]

Website docs would also need an update https://vitess.io/docs/22.0/user-guides/configuration-advanced/query-consolidation/

Hi @harshit-gangal This is not in this repo, is it?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 67.65%. Comparing base (1df1dc8) to head (f774619).
Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17244      +/-   ##
==========================================
+ Coverage   67.63%   67.65%   +0.01%     
==========================================
  Files        1586     1586              
  Lines      255566   255576      +10     
==========================================
+ Hits       172850   172907      +57     
+ Misses      82716    82669      -47     

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[harshit-gangal]

I think this check is not thread safe, so multiple threads can pass this check and can exceed the waiter cap.
I believe this should be acceptable.

[jwangace]

Hi @harshit-gangal Thank you so much for your approval! Could I kindly ask for your help to get a second review & approval from someone else? It would be valuable for us if Vitess could accept it, as it helps address the Pod OOM issues we’re facing.

[frouioui]

Hi @jwangace, can you merge main on your PR? There has been some changes to our GitHub Actions, and the PR is not mergeable without these recent changes.