timer: make sure timer which has a max delay will be scheduled first (#57067)

[ti-chi-bot]

This is an automated cherry-pick of #57067

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.

[lcwangchao]

/retest

[YangKeao]

LGTM

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

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

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-11-06 08:43:45.557934068 +0000 UTC m=+1030538.397089606: ☑️ agreed by lcwangchao.
• 2024-11-06 08:44:32.480970476 +0000 UTC m=+1030585.320126021: ☑️ agreed by YangKeao.

[lcwangchao]

/retest

[codecov]

Codecov Report

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

Please upload report for BASE (release-8.1@849dcc0). Learn more about missing BASE report.

Additional details and impacted files

@@               Coverage Diff                @@
##             release-8.1     #57159   +/-   ##
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  Coverage               ?   71.2074%           
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  Hits                   ?     301402           
  Misses                 ?     101370           
  Partials               ?      20501           

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Components	Coverage Δ
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br	41.3055% <0.0000%> (?)