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From "Arpit Agarwal (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11514) ChooseRandom can potentially be optimized
Date Wed, 15 Mar 2017 03:06:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15925461#comment-15925461

Arpit Agarwal commented on HDFS-11514:

The change looks good. Just one comment - the {{synchronized(childrenStorageInfo)}} blocks
are unnecessary because the caller of add/remove must hold {{NetworkTopology#netLock}}. I
missed that earlier.

> ChooseRandom can potentially be optimized
> -----------------------------------------
>                 Key: HDFS-11514
>                 URL: https://issues.apache.org/jira/browse/HDFS-11514
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>            Reporter: Chen Liang
>            Assignee: Chen Liang
>         Attachments: HDFS-11514.001.patch, HDFS-11514.002.patch
> Based on the offline discussion, one potential improvement to the {{chooseRandomWithStorageType}}
added in HDFS-11482 is that, currently given a node, the method iterates all its children
to sum up the number of candidate datanodes. Since datanode status change is much less frequent
than block placement request. It is more efficient to get rid of this iteration check, by
probably maintaining another disk type counter map. This JIRA tracks (but not limited) this

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