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https://issues.apache.org/jira/browse/HDDS-3459?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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runzhiwang updated HDDS-3459:
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Attachment: (was: screenshot-7.png)
> Datanode use a single thread to process the command of scm
> ----------------------------------------------------------
>
> Key: HDDS-3459
> URL: https://issues.apache.org/jira/browse/HDDS-3459
> Project: Hadoop Distributed Data Store
> Issue Type: Bug
> Reporter: runzhiwang
> Assignee: runzhiwang
> Priority: Major
>
> *What's the problem ?*
> Datanode use a single [command-processor-thread
> |https://github.com/apache/hadoop-ozone/blob/master/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/statemachine/DatanodeStateMachine.java#L482]
> to process the command of scm. Sometimes the thread maybe blocked a very
> long time, then all the command from scm can not be processed, it maybe cause
> some problem.
> For example, a group has leader, follower1, follower2, Steps to reproduce the
> problem are as following:
> 1. Some datanodes crash, and follower2 begin streaming container data to
> other datanode, then the command-processor-thread was blocked at
> [cont.writeLock()|https://github.com/apache/hadoop-ozone/blob/master/hadoop-hdds/container-service/src/main/java/org/apache/hadoop/ozone/container/common/statemachine/commandhandler/DeleteBlocksCommandHandler.java#L130],
> because streaming container data need to hold the RwLock of container.
> 2. follower2 report close pipeline
> 3. scm send close pipeline command
> 4. leader and follower1 remove group, but follower2 can not remove group
> because the command-processor-thread was blocked.
> 5. follower2 then begin infinite LeaderElection about 13 hours, leader and
> follower1 response group not found.
> You can see find it in following screenshot.
> 1. follower2 begin streaming container data
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