scheduler: set different priorities for write-leader and write-peer

[lhy1024]

What problem does this PR solve?

write-leader and write-peer need to have different priorities because write leader needs to have balanced metrics that reflect the leader, such as sum of key or qps, but write-peer does not, and write-peer does not necessarily have data on qps.

What is changed and how it works?

set different priorities for write-leader and write-peer

Check List

Tests

• Unit test

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• HunDunDM
• Yisaer

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[codecov]

Codecov Report

Merging #3937 (f52e08e) into master (1b24b4a) will decrease coverage by 0.08%.
The diff coverage is 100.00%.

❗ Current head f52e08e differs from pull request most recent head 7530e42. Consider uploading reports for the commit 7530e42 to get more accurate results

@@            Coverage Diff             @@
##           master    #3937      +/-   ##
==========================================
- Coverage   74.72%   74.63%   -0.09%     
==========================================
  Files         246      246              
  Lines       25068    25068              
==========================================
- Hits        18731    18709      -22     
- Misses       4685     4702      +17     
- Partials     1652     1657       +5     

Flag	Coverage Δ
unittests	74.63% <100.00%> (-0.09%)	⬇️

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

Impacted Files	Coverage Δ
server/schedulers/hot_region.go	85.77% <100.00%> (+0.20%)	⬆️
server/schedulers/hot_region_config.go	82.07% <100.00%> (+1.12%)	⬆️
tools/pd-ctl/pdctl/command/scheduler.go	73.43% <100.00%> (+0.24%)	⬆️
pkg/tempurl/tempurl.go	45.00% <0.00%> (-15.00%)	⬇️
server/tso/local_allocator.go	71.62% <0.00%> (-6.76%)	⬇️
server/region_syncer/client.go	77.46% <0.00%> (-4.23%)	⬇️
pkg/dashboard/adapter/manager.go	79.78% <0.00%> (-3.20%)	⬇️
server/server.go	71.58% <0.00%> (-1.22%)	⬇️
pkg/btree/btree.go	85.30% <0.00%> (-0.97%)	⬇️
server/schedule/operator_controller.go	84.75% <0.00%> (-0.80%)	⬇️
... and 8 more

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[nolouch]

It's may conflict? especially we add qps.

[lhy1024]

It's may conflict? especially we add qps.

In fact, the write leader's priority now has key as first priority and byte as second priority, while the write peer's priority has byte as first priority and key as second priority. They are now different.

This pr doesn't change the default behaviour, it just avoids query in the write peer's scheduling priority. because the follower doesn't have this statistic.

[Yisaer]

Rest LGTM

[HunDunDM]

rest LGTM

[lhy1024]

/merge

[ti-chi-bot]

@lhy1024: 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: 68b184f