runner: set capacity to Task channel

[okJiang]

What problem does this PR solve?

Issue Number: Close #9222

What is changed and how does it work?

If the program processPendingTask and handle <-ticker.C in the same time

pd/pkg/ratelimit/runner.go

Line 171 in f86063f

case cr.taskChan <- task:

pd/pkg/ratelimit/runner.go

Line 133 in f86063f

case <-ticker.C:

, the task may be skipped due to taskChan block.

pd/pkg/ratelimit/runner.go

Lines 170 to 175 in f86063f

	select {
	case cr.taskChan <- task:
	cr.pendingTasks = cr.pendingTasks[1:]
	cr.pendingTaskCount[task.name]--
	delete(cr.existTasks, taskID{id: task.id, name: task.name})
	default:

So, we can give a capacity to the task channel to avoid this situation.

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)

• No code

Release note

None.

[okJiang]

/retest

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.12%. Comparing base (0ae92cd) to head (cf13705).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9226      +/-   ##
==========================================
+ Coverage   76.05%   76.12%   +0.06%     
==========================================
  Files         470      470              
  Lines       73028    73028              
==========================================
+ Hits        55543    55589      +46     
+ Misses      14039    14016      -23     
+ Partials     3446     3423      -23     

Flag	Coverage Δ
unittests	76.12% <100.00%> (+0.06%)	⬆️

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[lhy1024]

why change it？

[okJiang]

To pass this ut. Capacity changed the pendingTask index. To ensure the task is not consumed as much as possible, I have increased the region ID a bit more.

[nolouch]

I think the task will be handled well next time, even if you have the capacity, the same problem will still exist.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lhy1024, nolouch

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• OWNERS [lhy1024,nolouch]

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-04-22 10:11:32.155905491 +0000 UTC m=+350435.967695874: ☑️ agreed by lhy1024.
• 2025-04-23 06:16:08.326534174 +0000 UTC m=+422712.138324554: ☑️ agreed by nolouch.

[okJiang]

/retest