scheduler: use pending amp in hot region scheduler

[lhy1024]

What problem does this PR solve?

In the past, for two stores with large differences, it was easy to have redundant scheduling behavior, because as the difference between the two stores approached, the speed might not come down in time, so we limited the speed by adding pending amps, and the closer the two stores were, the fewer regions were allowed to be scheduled at the same time.

Before

After

What is changed and how it works?

isTolerance checks source store and target store by checking the difference value with pendingAmpFactor * pendingPeer. This will make the hot region scheduling slow even serialized running when each 2 store's pending influence is close.

Check List

Tests

• Unit test

Release note

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• Yisaer
• rleungx

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[codecov]

Codecov Report

Merging #3926 (2cc3ac5) into master (8481fab) will increase coverage by 0.03%.
The diff coverage is 97.56%.

@@            Coverage Diff             @@
##           master    #3926      +/-   ##
==========================================
+ Coverage   74.64%   74.67%   +0.03%     
==========================================
  Files         247      247              
  Lines       25372    25408      +36     
==========================================
+ Hits        18939    18974      +35     
+ Misses       4759     4757       -2     
- Partials     1674     1677       +3     

Flag	Coverage Δ
unittests	74.67% <97.56%> (+0.03%)	⬆️

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

Impacted Files	Coverage Δ
server/schedulers/hot_region.go	84.14% <94.11%> (+0.97%)	⬆️
pkg/mock/mockcluster/mockcluster.go	95.69% <100.00%> (-0.16%)	⬇️
server/core/region_option.go	86.00% <100.00%> (+1.55%)	⬆️
server/schedulers/hot_region_config.go	89.31% <100.00%> (+2.59%)	⬆️
server/schedulers/metrics.go	100.00% <100.00%> (ø)
server/schedulers/utils.go	95.06% <100.00%> (+0.09%)	⬆️
pkg/tempurl/tempurl.go	45.00% <0.00%> (-25.00%)	⬇️
server/schedulers/shuffle_hot_region.go	55.55% <0.00%> (-10.11%)	⬇️
server/schedulers/random_merge.go	60.00% <0.00%> (-3.34%)	⬇️
server/core/storage.go	67.68% <0.00%> (-1.53%)	⬇️
... and 17 more

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[Yisaer]

basically lgtm

[lhy1024]

@rleungx PTAL

[HunDunDM]

/merge

[ti-chi-bot]

@HunDunDM: 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: 0356cce