statistics: support global singleflight for sync load (#52796)

[ti-chi-bot]

This is an automated cherry-pick of #52796

What problem does this PR solve?

Issue Number: close #52797

Problem Summary:

What changed and how does it work?

before

All items the query needs will be put into the global task channel( the default capacity is 1000). And workers will merge the same task with the singleflight. So performance depends on the number of tasks that can be concurrently executed.
Under poor performance conditions, he will not be able to handle a sufficient number of tasks, resulting in slow processing. But there are still many same tasks in the channel. So they still need to check whether to sync load. And They will fill up this channel. Query can not insert the sync load task into it and load necessary stats.

after

So we need to refactor this code. We need first to let the query pass through singleflight to merge identical tasks. Then insert the task into the channel to make the worker syncload it.

So why is it that during the startup of Wetech, the queries are very unstable and there are severe timeouts with sync load? The problem lies right here.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[hawkingrei]

/retest

[codecov]

Codecov Report

Attention: Patch coverage is 84.09091% with 7 lines in your changes are missing coverage. Please review.

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Additional details and impacted files

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Flag	Coverage Δ
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Components	Coverage Δ
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parser	∅ <0.0000%> (?)
br	53.4659% <0.0000%> (?)

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hawkingrei, hi-rustin

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-05-17 08:06:02.404649563 +0000 UTC m=+1813316.161785130: ☑️ agreed by hawkingrei.
• 2024-05-17 08:08:14.346270283 +0000 UTC m=+1813448.103405856: ☑️ agreed by hi-rustin.