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From "Adam Fuchs (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-1052) Minor compactions not finishing before master kills tabletserver can very large number of files per tablet
Date Fri, 08 Feb 2013 19:59:12 GMT


Adam Fuchs commented on ACCUMULO-1052:

Commits shouldn't be held just because a tablet is minor compacting, right? The tablet server
has to run out of space in the write buffer across all tablets, or the tablets would have
to be in a state of migration or going offline. Do you know what's causing the commit hold?
Are minor compactions on tablets on this tablet server less efficient (this should be evident
in the performance debug logs for that tablet server)? Could this be that the merging minor
compactions are kicking in and reducing the compaction efficiency?

If the number of files is growing unbounded then that seems to indicated the merging minor
compactions are not kicking in. Is that a separate issue, or perhaps something related? How
many files are referenced by the tablet in question?
> Minor compactions not finishing before master kills tabletserver can very large number
of files per tablet
> ----------------------------------------------------------------------------------------------------------
>                 Key: ACCUMULO-1052
>                 URL:
>             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

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