scheduler: reduce GetStore in hot-region-scheduler (#3870)

[ti-chi-bot]

This is an automated cherry-pick of #3870

Signed-off-by: HunDunDM [email protected]

What problem does this PR solve?

• fix hot scheduler causes pd panic when scale out #3868

What is changed and how it works?

Reduce GetStore in hot-region-scheduler. In addition to preventing panic caused by data inconsistency, it can also reduce the use of BasicCluster locks.

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 PD may panic during scaling out TiKV.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• lhy1024
• nolouch

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[disksing]

@HunDunDM Need to resolve conflict

[codecov]

Codecov Report

Merging #3910 (0960dbc) into release-5.0 (1b3f93e) will increase coverage by 0.14%.
The diff coverage is 100.00%.

@@               Coverage Diff               @@
##           release-5.0    #3910      +/-   ##
===============================================
+ Coverage        74.62%   74.77%   +0.14%     
===============================================
  Files              245      245              
  Lines            24241    24248       +7     
===============================================
+ Hits             18091    18132      +41     
+ Misses            4528     4502      -26     
+ Partials          1622     1614       -8     

Flag	Coverage Δ
unittests	74.77% <100.00%> (+0.14%)	⬆️

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

Impacted Files	Coverage Δ
server/schedulers/utils.go	93.10% <ø> (ø)
server/schedulers/hot_region.go	80.79% <100.00%> (+0.96%)	⬆️
server/schedulers/shuffle_hot_region.go	65.30% <100.00%> (+1.09%)	⬆️
server/election/leadership.go	83.52% <0.00%> (-3.53%)	⬇️
server/cluster/coordinator.go	75.17% <0.00%> (-0.72%)	⬇️
server/cluster/cluster.go	83.31% <0.00%> (+0.36%)	⬆️
server/handler.go	42.46% <0.00%> (+0.49%)	⬆️
client/base_client.go	82.98% <0.00%> (+0.51%)	⬆️
server/grpc_service.go	47.17% <0.00%> (+0.56%)	⬆️
pkg/btree/btree.go	86.26% <0.00%> (+0.96%)	⬆️
... and 4 more

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[nolouch]

/merge

[ti-chi-bot]

@nolouch: 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.

Commit hash: 0960dbc