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From "He Xiaoqiao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-13183) Standby NameNode process getBlocks request to reduce Active load
Date Fri, 23 Feb 2018 13:20:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-13183?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16374325#comment-16374325
] 

He Xiaoqiao commented on HDFS-13183:
------------------------------------

The WIP patch V1 demonstrates approach for Standby NameNode changes. It's not ready to run
Jenkins yet. The key idea is to remove operation check when Standby NameNode receive #getBlocks
request.

> Standby NameNode process getBlocks request to reduce Active load
> ----------------------------------------------------------------
>
>                 Key: HDFS-13183
>                 URL: https://issues.apache.org/jira/browse/HDFS-13183
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: balancer &amp; mover, namenode
>    Affects Versions: 2.7.5, 3.1.0, 2.9.1, 2.8.4, 3.0.2
>            Reporter: He Xiaoqiao
>            Assignee: He Xiaoqiao
>            Priority: Major
>         Attachments: HDFS-13183-trunk.001.patch
>
>
> The performance of Active NameNode could be impact when {{Balancer}} requests #getBlocks,
since query blocks of overly full DNs performance is extremely inefficient currently. The
main reason is {{NameNodeRpcServer#getBlocks}} hold read lock for long time. In extreme case,
all handlers of Active NameNode RPC server are occupied by one reader {{NameNodeRpcServer#getBlocks}}
and other write operation calls, thus Active NameNode enter a state of false death for number
of seconds even for minutes.
> The similar performance concerns of Balancer have reported by HDFS-9412, HDFS-7967, etc.
> If Standby NameNode can shoulder #getBlocks heavy burden, it could speed up the progress
of balancing and reduce performance impact to Active NameNode.



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