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https://issues.apache.org/jira/browse/HDFS-14186?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16750247#comment-16750247
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Daryn Sharp commented on HDFS-14186:
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Kihwal asked me to take a look. Safe mode logic has historically been very
brittle so I worry about the unexpected consequences of changing the logic. I
think change is very simple.
BR processing is serialized via queuing for the
{{BlockManager.BlockReportProcessingThread}}. The main issue is probably the
{{enqueue}} method will block when the queue is full. If the queue offer
fails, it should throw a {{RetriableException}}. This will prevent stalling
the RPC handlers which leads to a vicious cycle of timeout/retries.
> blockreport storm slow down namenode restart seriously in large cluster
> -----------------------------------------------------------------------
>
> Key: HDFS-14186
> URL: https://issues.apache.org/jira/browse/HDFS-14186
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Reporter: He Xiaoqiao
> Assignee: He Xiaoqiao
> Priority: Major
> Attachments: HDFS-14186.001.patch
>
>
> In the current implementation, the datanode sends blockreport immediately
> after register to namenode successfully when restart, and the blockreport
> storm will make namenode high load to process them. One result is some
> received RPC have to skip because queue time is timeout. If some datanodes'
> heartbeat RPC are continually skipped for long times (default is
> heartbeatExpireInterval=630s) it will be set DEAD, then datanode has to
> re-register and send blockreport again, aggravate blockreport storm and trap
> in a vicious circle, and slow down (more than one hour and even more)
> namenode startup seriously in a large (several thousands of datanodes) and
> busy cluster especially. Although there are many work to optimize namenode
> startup, the issue still exists.
> I propose to postpone dead datanode check when namenode have finished startup.
> Any comments and suggestions are welcome.
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