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From "Dave Marion (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-1755) BatchWriter blocks all addMutation calls while binning mutations
Date Thu, 03 Mar 2016 19:12:18 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15178398#comment-15178398
] 

Dave Marion commented on ACCUMULO-1755:
---------------------------------------

bq.  The previous implementation blocked all client threads from calling BatchWriter.addMutation(),
meaning the clients could not do any work. In the new implementation the clients will be able
to continue to do work, adding mutations, and even binning them in their own thread if necessary,
before blocking.

My statement from above is incorrect. We didn't remove the synchronization from TabletServerBatchWriter.addMutation.
We only made it such that the binning is done either in a background thread or the current
thread.

> BatchWriter blocks all addMutation calls while binning mutations
> ----------------------------------------------------------------
>
>                 Key: ACCUMULO-1755
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-1755
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: client
>            Reporter: Adam Fuchs
>            Assignee: Dave Marion
>             Fix For: 1.6.6, 1.7.2, 1.8.0
>
>         Attachments: ACCUMULO-1755.patch
>
>          Time Spent: 2h
>  Remaining Estimate: 0h
>
> Through code inspection, we found that the BatchWriter bins mutations inside of a synchronized
block that covers calls to addMutation. Binning potentially involves lookups of tablet metadata
and processes a fair amount of information. We will get better parallelism if we can either
unlock the lock while binning, dedicate another thread to do the binning, or use one of the
send threads to do the binning.
> This has not been verified empirically yet, so there is not yet any profiling info to
indicate the level of improvement that we should expect. Profiling and repeatable demonstration
of this performance bottleneck should be the first step on this ticket.



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