ttl: fix the infinite waiting for delRateLimiter when tidb_ttl_delete_rate_limit changes

[lcwangchao]

What problem does this PR solve?

Issue Number: close #58484

Problem Summary:

Copied from PR, the below comments describe how this bug happens.

//  1. The `tidb_ttl_delete_rate_limit` set to some non-zero value such as 128.
//  2. Some delWorker delete rows concurrency and try to wait for the inner `rate.Limiter`.
//  3. Before internal `l.limiter.Wait` is called, the `tidb_ttl_delete_rate_limit` is set to 0.
//     It resets the internal `rate.Limiter` (in the bug codes, its rate is set to 0).
//  4. The delWorkers in step 2 continue to call l.limiter.Wait.
//     In the bug codes, some of them are blocked forever because the rate is set to 0.

What changed and how does it work?

Set the inner limiter rate to rate.Inf when tidb_ttl_delete_rate_limit is set to 0

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.

ttl: fix the infinite waiting for delRateLimiter when `tidb_ttl_delete_rate_limit` changes

[tiprow]

Hi @lcwangchao. Thanks for your PR.

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[YangKeao]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.4952%. Comparing base (52de47d) to head (17dec34).
Report is 7 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #58485        +/-   ##
================================================
- Coverage   73.5398%   73.4952%   -0.0447%     
================================================
  Files          1681       1681                
  Lines        464075     467116      +3041     
================================================
+ Hits         341280     343308      +2028     
- Misses       101975     103032      +1057     
+ Partials      20820      20776        -44     

Flag	Coverage Δ
integration	43.2904% <6.6666%> (?)
unit	72.4116% <100.0000%> (+0.1050%)	⬆️

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Components	Coverage Δ
dumpling	52.6910% <ø> (ø)
parser	∅ <ø> (∅)
br	45.2614% <ø> (-0.5309%)	⬇️

[lcwangchao]

/retest

[tiprow]

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

In response to this:

/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:

• 2024-12-23 11:05:45.180907284 +0000 UTC m=+1473335.269709812: ☑️ agreed by YangKeao.
• 2024-12-24 02:50:26.519970275 +0000 UTC m=+1530016.608772806: ☑️ agreed by bb7133.