dead chanel in UpdateNewAndDoneWatch

Bug Report

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1. Minimal reproduce step (Required)

It started here

Lines 75 to 80 in e601725

    
           err = do.runawayManager.UpdateNewAndDoneWatch() 
        
           if err == nil { 
        
           	logutil.BgLogger().Info("preparations for the runaway manager are finished and start runaway manager loop") 
        
           	do.wg.Run(do.runawayManager.RunawayRecordFlushLoop, "runawayRecordFlushLoop") 
        
           	do.wg.Run(do.runawayManager.RunawayWatchSyncLoop, "runawayWatchSyncLoop") 
        
           	do.runawayManager.MarkSyncerInitialized()

will insert record into channels here

tidb/pkg/resourcegroup/runaway/manager.go

Lines 424 to 426 in 6a12f31

    
           } else if ttl <= 0 { 
        
           	rm.staleQuarantineRecord <- record 
        
           	return

The receive loop however is started later than the first call of UpdateNewAndDoneWatch(RunawayRecordFlushLoop)

tidb/pkg/resourcegroup/runaway/manager.go

Line 211 in 6a12f31

case r := <-staleQuarantineRecordCh:

If the channel exceeds the maximum(1024), it blocks.

introduced by #52283

2. What did you expect to see? (Required)

non blocking.

3. What did you see instead (Required)

runawayStartLoop blocks forever

4. What is your TiDB version? (Required)

v8.1.0 and later

fix(runaway): resolve the dead channel in UpdateNewAndDoneWatch (#61795)

fix(runaway): resolve the dead channel in UpdateNewAndDoneWatch (#61795…

Upgrade branch meets this issue:
source: <=8.1.0
target: v8.1.1-v8.5.2
blocking stage: post upgrade
workaround: manually delete the rows in the table on the working tidb instance.

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dead chanel in UpdateNewAndDoneWatch #61782

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3. What did you see instead (Required)

4. What is your TiDB version? (Required)

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	err = do.runawayManager.UpdateNewAndDoneWatch()
	if err == nil {
	logutil.BgLogger().Info("preparations for the runaway manager are finished and start runaway manager loop")
	do.wg.Run(do.runawayManager.RunawayRecordFlushLoop, "runawayRecordFlushLoop")
	do.wg.Run(do.runawayManager.RunawayWatchSyncLoop, "runawayWatchSyncLoop")
	do.runawayManager.MarkSyncerInitialized()

	} else if ttl <= 0 {
	rm.staleQuarantineRecord <- record
	return

dead chanel in UpdateNewAndDoneWatch #61782

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Bug Report

1. Minimal reproduce step (Required)

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

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seiya-annie commented on Aug 26, 2025

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