ttl: reschedule task to other instances when shrinking worker

[lcwangchao]

What problem does this PR solve?

Issue Number: close #57990

What changed and how does it work?

This PR makes some changes:

1. Flush expired rows not deleted in delWorker before it stops.
2. When stopping a scanWorker, wait for all rows to be deleted before writing its state to task meta.
3. Mark the status of a task back to waiting when its worker stops to ensure it can be obtained by other instances again.
4. When task heartbeating, merge the current statistics and the old one that recovered from the task meta.
5. Add more logs.

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

[tiprow]

Hi @lcwangchao. Thanks for your PR.

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[YangKeao]

LGTM

[lcwangchao]

/retest

[tiprow]

@lcwangchao: Cannot trigger testing until a trusted user reviews the PR and leaves an /ok-to-test message.

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/retest

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[bb7133]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bb7133, YangKeao

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-12-05 08:39:01.311913915 +0000 UTC m=+1316928.931568431: ☑️ agreed by YangKeao.
• 2024-12-05 18:14:47.709558408 +0000 UTC m=+1351475.329212921: ☑️ agreed by bb7133.

[tiprow]

@lcwangchao: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
fast_test_tiprow	2808f3b	link	true	/test fast_test_tiprow

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #58719.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #58772.

[lcwangchao]

/cherry-pick release-8.5

[ti-chi-bot]

@lcwangchao: new pull request could not be created: failed to create pull request against pingcap/tidb#release-8.5 from head ti-chi-bot:cherry-pick-57703-to-release-8.5: status code 422 not one of [201], body: {"message":"Validation Failed","errors":[{"resource":"PullRequest","code":"custom","message":"A pull request already exists for ti-chi-bot:cherry-pick-57703-to-release-8.5."}],"documentation_url":"https://docs.github.com/rest/pulls/pulls#create-a-pull-request","status":"422"}

In response to this:

/cherry-pick release-8.5

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[lcwangchao]

/cherry-pick release-8.5

[ti-chi-bot]

@lcwangchao: new pull request created to branch release-8.5: #58778.

In response to this:

/cherry-pick release-8.5

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