[jira] [Commented] (HDFS-7461) Reduce impact of laggards on Mover

["Arpit Agarwal (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-7461?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14250945#comment-14250945 ] 

Arpit Agarwal commented on HDFS-7461:
-------------------------------------

Hi Benoy, do you have a prototype/rough patch?

> Reduce impact of laggards on Mover
> ----------------------------------
>
>                 Key: HDFS-7461
>                 URL: https://issues.apache.org/jira/browse/HDFS-7461
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: balancer & mover
>    Affects Versions: 2.6.0
>            Reporter: Benoy Antony
>            Assignee: Benoy Antony
>         Attachments: continuousmovement.pdf
>
>
> The current Mover logic is as follows :
> {code}
>  for (Path target : targetPaths) {
>         hasRemaining |= processPath(target.toUri().getPath());
>       }
> // wait for pending move to finish and retry the failed migration
> hasRemaining |= Dispatcher.waitForMoveCompletion(storages.targets.values());
> {code}
> The _processPath_ will schedule moves, but it is bounded by the number of concurrent moves (default is 5 per node} .  Once block moves are scheduled,  it will wait for ALL  scheduled moves to finish in _waitForMoveCompletion_.
> One slow move could keep the Mover  idle for a long time. 
> It will be a  performance improvement to schedule the next moves as soon as any (source , target) slot is available instead of waiting for all the scheduled moves to finish. 



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