[jira] [Resolved] (HDFS-852) Balancer shutdown synchronisation could do with a review

["Tsz Wo Nicholas Sze (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-852?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tsz Wo Nicholas Sze resolved HDFS-852.
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    Resolution: Not A Problem

I think this issue got stale.  Resolving as Not a Problem.  Please feel free to reopen if you disagree.

> Balancer shutdown synchronisation could do with a review
> --------------------------------------------------------
>
>                 Key: HDFS-852
>                 URL: https://issues.apache.org/jira/browse/HDFS-852
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: balancer & mover
>    Affects Versions: 0.22.0
>            Reporter: Steve Loughran
>            Priority: Minor
>
> Looking at the source of the Balancer, there's a lot {{catch(InterruptedException)}} clauses, which runs the risk of swallowing exceptions, making it harder to shut down a balancer.
> for example, the {{AccessKeyUpdater swallows the InterruptedExceptions which get used to tell it to shut down, and while it does poll the shared field {{shouldRun}}, that field isn't volatile: the shutdown may }}not work. 
> Elsewhere, the {{dispatchBlocks()}} method swallows interruptions without even looking for any shutdown flag. 
> This is all minor as it is shutdown logic, but it is the stuff that it hard to test and leads to problems in the field, the problems that leave the ops team resorting to {{kill -9}}, and we don't want that.



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