server: make region statistic loss some precision

[nolouch]

Signed-off-by: nolouch [email protected]

What problem does this PR solve?

In the current situation, a change in traffic will trigger the update of save cache in the region heartbeat, which will cause the heartbeat to become more stressful. In fact, this part of the statistical data can work normally as long as it is within a certain accuracy.

What is changed and how it works?

Check List

• Unit test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has configuration change
• Has HTTP API interfaces change (Don't forget to add the declarative for API)
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• PR to update pingcap/tidb-ansible:
• Need to cherry-pick to the release branch

Release note

add `flow-round-by-digit` to reduce the statistics update overhead

[codecov]

Codecov Report

Merging #3728 (e6f7eec) into master (da4cdd4) will increase coverage by 0.20%.
The diff coverage is 89.47%.

@@            Coverage Diff             @@
##           master    #3728      +/-   ##
==========================================
+ Coverage   74.81%   75.01%   +0.20%     
==========================================
  Files         244      244              
  Lines       24423    24437      +14     
==========================================
+ Hits        18271    18332      +61     
+ Misses       4521     4487      -34     
+ Partials     1631     1618      -13     

Flag	Coverage Δ
unittests	75.01% <89.47%> (+0.20%)	⬆️

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

Impacted Files	Coverage Δ
server/config/config.go	75.15% <66.66%> (-0.11%)	⬇️
server/cluster/cluster.go	82.76% <100.00%> (-0.28%)	⬇️
server/core/region.go	89.94% <100.00%> (+0.41%)	⬆️
server/core/region_option.go	84.09% <100.00%> (+0.36%)	⬆️
server/grpc_service.go	47.77% <100.00%> (+<0.01%)	⬆️
server/schedule/operator/step.go	67.44% <0.00%> (-1.00%)	⬇️
server/core/storage.go	67.68% <0.00%> (-0.77%)	⬇️
... and 12 more

---

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[nolouch]

PTAL @rleungx @HunDunDM

[rleungx]

Why the error is PD:filepath:ErrFilePathAbs?

[nolouch]

updated. PTAL

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• HunDunDM
• Yisaer

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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: e1293db

[ti-chi-bot]

@nolouch: Your PR was out of date, I have automatically updated it for you.

At the same time I will also trigger all tests for you:

/run-all-tests

If the CI test fails, you just re-trigger the test that failed and the bot will merge the PR for you after the CI passes.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the ti-community-infra/tichi repository.