region_scatterer: fix the bug that could generate schedule with too many peers (#5920)

[ti-chi-bot]

This is an automated cherry-pick of #5920

What problem does this PR solve?

Issue Number: Close #5909

What is changed and how does it work?

Introduced in #4570 , used stores were not excluded resulting in possible selection of too many targeterPeers.

Check List

Tests

• Unit test

Code changes

Side effects

Related changes

• Need to cherry-pick to the release branch

Release note

Fix the bug that the region scatterer may generate the schedule with too many peers.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lhy1024
• rleungx

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[codecov]

Codecov Report

Base: 75.54% // Head: 75.61% // Increases project coverage by +0.07% 🎉

Coverage data is based on head (40b8cee) compared to base (d1c0d84).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-6.5    #5923      +/-   ##
===============================================
+ Coverage        75.54%   75.61%   +0.07%     
===============================================
  Files              330      330              
  Lines            32951    32952       +1     
===============================================
+ Hits             24894    24918      +24     
+ Misses            5907     5887      -20     
+ Partials          2150     2147       -3     

Flag	Coverage Δ
unittests	75.61% <100.00%> (+0.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/schedule/operator/step.go	73.09% <100.00%> (ø)
server/schedule/region_scatterer.go	79.13% <100.00%> (+1.26%)	⬆️
server/tso/tso.go	66.85% <0.00%> (-7.87%)	⬇️
server/id/id.go	83.05% <0.00%> (-6.78%)	⬇️
server/tso/local_allocator.go	64.86% <0.00%> (-6.76%)	⬇️
server/schedulers/random_merge.go	62.50% <0.00%> (-3.13%)	⬇️
server/schedule/checker/rule_checker.go	81.31% <0.00%> (-0.74%)	⬇️
server/schedule/operator/builder.go	85.62% <0.00%> (-0.33%)	⬇️
server/server.go	74.53% <0.00%> (ø)
server/grpc_service.go	49.79% <0.00%> (ø)
... and 15 more

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[joccau]

LGTM

[ti-chi-bot]

@joccau: Thanks for your review. The bot only counts approvals from reviewers and higher roles in list, but you're still welcome to leave your comments.

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LGTM

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[ti-chi-bot]

@3pointer: Thanks for your review. The bot only counts approvals from reviewers and higher roles in list, but you're still welcome to leave your comments.

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[rleungx]

/merge

[ti-chi-bot]

@rleungx: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

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

Details

Commit hash: 40b8cee