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https://issues.apache.org/jira/browse/HDFS-12647?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16253951#comment-16253951
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Nanda kumar commented on HDFS-12647:
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Patch v000 brings support for async processing of all the DatanodeCommands
except {{DatanodeProtocol.DNA_REGISTER}} which is still synchronous operation.
The patch doesn't change the behavior of FBR, IBR or CacheReports.
> DN commands processing should be async
> --------------------------------------
>
> Key: HDFS-12647
> URL: https://issues.apache.org/jira/browse/HDFS-12647
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode
> Affects Versions: 2.8.0
> Reporter: Daryn Sharp
> Assignee: Nanda kumar
> Attachments: HDFS-12647.000.patch
>
>
> Due to dataset lock contention, service actors may encounter significant
> latency while processing DN commands. Even the queuing of async deletions
> require multiple lock acquisitions. A slow disk will cause a backlog of
> xceivers instantiating block sender/receivers which starves the actor and
> leads to the NN falsely declaring the node dead.
> Async processing of all commands will free the actor to perform its primary
> purpose of heartbeating and block reporting. Note that FBRs will be
> dependent on queued block invalidations not being included in the report.
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