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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 Wed, 24 Feb 2016 19:44:18 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15163587#comment-15163587
] 

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

Adam, I have this issue now where i have N clients sharing a batch writer. As you noted in
the description, all the threads wait on binning mutations. I could use a batch writer per
thread, and that may be the solution in the end. I think I can remove the synchronized modifier
from addMutation, but I think in the end I may just be pushing the problem to an area of the
code that the client has no control over. I'm interested in solving this issue though, any
time you can spare would be appreciated.

> 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
>
> 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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