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From "Josh Elser (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-1052) Minor compactions not finishing before master kills tabletserver can very large number of files per tablet
Date Mon, 18 Feb 2013 20:23:13 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1052?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13580813#comment-13580813
] 

Josh Elser commented on ACCUMULO-1052:
--------------------------------------

bq. We could probably use a better mechanism for throttling. Meanwhile, an alternative solution
might be to add more major compaction threads and reduce the number of minor compaction threads.

I created ACCUMULO-1055 as a potential simple fix to address this. Dynamically adjusting thread
pool sizes could also be an option, but that does change how minc/majc threads are currently
configured.
                
> Minor compactions not finishing before master kills tabletserver can very large number
of files per tablet
> ----------------------------------------------------------------------------------------------------------
>
>                 Key: ACCUMULO-1052
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-1052
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: master, tserver
>    Affects Versions: 1.4.2
>         Environment: Large, write-heavy cluster
>            Reporter: Josh Elser
>            Assignee: Eric Newton
>
> On a cluster that is being saturated with heavy ingest, a tserver is observed attempting
to perform a minor compaction for a tablet with multiple WALs. Because of this, commits to
this tablet end up being held.
> After churning on the minc for some time, the master's hold-time limit for tservers is
exceeded, however the minc didn't finish. The tserver is forcibly killed, the tablet is migrated,
recovery occurs on the new tserver and the problem repeats.
> Some of the minor compactions must finish, as the number of files for that tablet continue
to grow, but major compactions must not have time to finish since the number of files grow
unbounded.

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