timer: make sure timer which has a max delay will be scheduled first

[lcwangchao]

What problem does this PR solve?

Issue Number: close #57137

This issue is because a trigger action will be sent to the timer worker via the chan:

tidb/pkg/timer/runtime/runtime.go

Lines 285 to 300 in 6004c3e

	select {
	case <-rt.ctx.Done():
	return false
	case worker.ch <- req:
	rt.cache.setTimerProcStatus(timer.ID, procTriggering, eventID)
	default:
	if busyWorkers == nil {
	busyWorkers = make(map[string]struct{})
	}
	busyWorkers[timer.HookClass] = struct{}{}
	retryTimerIDs = append(retryTimerIDs, timer.ID)
	retryTimerKeys = append(retryTimerKeys, fmt.Sprintf("[%s] %s", timer.Namespace, timer.Key))
	}
	return true
	})

If the chan is full, it will fail and retry after a while. However, some tables always have lower priorities even if they are not triggered for a long time.

What changed and how does it work?

reorder timers by nextEventTime before sending them to workers to make sure the timer which has a max delay will be handled first to avoid starvation

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 some times TTL job can not be scheduled when there are a lot of TTL tables.

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[codecov]

Codecov Report

Attention: Patch coverage is 90.90909% with 3 lines in your changes missing coverage. Please review.

Project coverage is 56.7130%. Comparing base (8a62d5a) to head (8fd95e8).
Report is 10 commits behind head on master.

Additional details and impacted files

@@                Coverage Diff                @@
##             master     #57067         +/-   ##
=================================================
- Coverage   73.1889%   56.7130%   -16.4760%     
=================================================
  Files          1655       1783        +128     
  Lines        456297     645164     +188867     
=================================================
+ Hits         333959     365892      +31933     
- Misses       101822     254873     +153051     
- Partials      20516      24399       +3883     

Flag	Coverage Δ
integration	37.1327% <12.1212%> (?)
unit	72.6090% <90.9090%> (+0.1383%)	⬆️

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

Components	Coverage Δ
dumpling	52.9478% <ø> (ø)
parser	∅ <ø> (∅)
br	52.4466% <ø> (+6.7274%)	⬆️

[bb7133]

LGTM

[YangKeao]

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:

• 2024-11-06 03:02:46.569458133 +0000 UTC m=+1010079.408613678: ☑️ agreed by bb7133.
• 2024-11-06 04:15:32.10079388 +0000 UTC m=+1014444.939949418: ☑️ agreed by YangKeao.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #57157.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-7.5: #57158.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #57159.