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https://issues.apache.org/jira/browse/HDFS-14186?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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He Xiaoqiao updated HDFS-14186:
-------------------------------
    Affects Version/s: 2.7.1

> 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
>    Affects Versions: 2.7.1
>            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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