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https://issues.apache.org/jira/browse/HDFS-14576?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16865687#comment-16865687
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Wei-Chiu Chuang commented on HDFS-14576:
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Make sense to me.
At Cloudera, we recommend large clusters to use iptable to filter DN block
reports. Effectively, it's as if DataNodes are started in batches after NN
restarts. However, this is rarely seen in more recent versions of CDH5.x due to
the various improvements in block reports. I suppose this can still be an issue
at 10k node scale.
[~sodonnell] FYI.
> Avoid block report retry and slow down namenode startup
> -------------------------------------------------------
>
> Key: HDFS-14576
> URL: https://issues.apache.org/jira/browse/HDFS-14576
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Reporter: He Xiaoqiao
> Assignee: He Xiaoqiao
> Priority: Major
>
> During namenode startup, the load will be very high since it has to process
> every datanodes blockreport one by one. If there are hundreds datanodes block
> reports pending process, the issue will be more serious even
> #processFirstBlockReport is processed a lot more efficiently than ordinary
> block reports. Then some of datanode will retry blockreport and lengthens
> restart times. I think we should filter the block report request (via
> datanode blockreport retries) which has be processed and return directly then
> shorten down restart time. I want to state this proposal may be obvious only
> for large cluster.
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