schedule: fix panic during hot schedule

[Yisaer]

Signed-off-by: Song Gao disxiaofei@163.com

What problem does this PR solve?

hot-region scheduler may cause PD panic in the following order:

1. load storesLoads before hot region scheduling

	storesLoads := cluster.GetStoresLoads()

2. receive new PutStore request

// put Store in grpc_service.go
if err := rc.PutStore(store); err != nil {
	return nil, status.Errorf(codes.Unknown, err.Error())
}

3. select candidates from raft.cluster

candidates = bs.cluster.GetStores()

This will cause make pickDstStores panic in following code because stLoadDetail didn't have the storeID which candidates hold as it was newly put before.

detail := bs.stLoadDetail[store.GetID()]

What is changed and how it works?

Make the candidates should be searched from stLoadDetail during hot region schedule

Check List

Tests

• Unit test

Release note

• No release note

[codecov]

Codecov Report

Merging #3483 (ccbf4c4) into master (92ddb62) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3483      +/-   ##
==========================================
+ Coverage   74.57%   74.59%   +0.01%     
==========================================
  Files         244      244              
  Lines       23981    23982       +1     
==========================================
+ Hits        17885    17889       +4     
+ Misses       4481     4480       -1     
+ Partials     1615     1613       -2     

Flag	Coverage Δ
unittests	74.59% <100.00%> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
server/schedulers/hot_region.go	80.91% <100.00%> (+0.03%)	⬆️
pkg/errs/errs.go	75.00% <0.00%> (-25.00%)	⬇️
server/region_syncer/server.go	83.33% <0.00%> (-6.07%)	⬇️
server/tso/global_allocator.go	72.26% <0.00%> (-5.11%)	⬇️
server/encryptionkm/key_manager.go	71.78% <0.00%> (-1.66%)	⬇️
server/tso/tso.go	69.93% <0.00%> (-1.23%)	⬇️
client/base_client.go	83.24% <0.00%> (-0.55%)	⬇️
client/client.go	71.69% <0.00%> (-0.29%)	⬇️
server/grpc_service.go	49.13% <0.00%> (ø)
server/config/persist_options.go	92.12% <0.00%> (+0.78%)	⬆️
... and 8 more

---

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[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• HunDunDM
• lhy1024

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[Yisaer]

/merge

[ti-chi-bot]

@Yisaer: 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: ccbf4c4

[ti-srebot]

cherry pick to release-4.0 in PR #3485

[ti-srebot]

cherry pick to release-5.0 in PR #3486