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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-1755) BatchWriter blocks all addMutation calls while binning mutations
Date Fri, 26 Feb 2016 23:40:18 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15170117#comment-15170117
] 

ASF GitHub Bot commented on ACCUMULO-1755:
------------------------------------------

Github user keith-turner commented on the pull request:

    https://github.com/apache/accumulo/pull/75#issuecomment-189526782
  
    > I added a catch clause to startProcessing to catch the RejectedExecutionException
that can be thrown. Were you thinking of something else?
    
    What you did is needed, but I was thinking of something else.   If the call to `addMutations()`
in the Runnable throws an unexpected exception, nothing will be done about that exception.
The batch writer should transition to an error state.  Thinking need to do something like
the following.
    
    ```java
    void queueMutations(final MutationSet mutationsToSend) {
          queueThreadPool.submit(new Runnable() {
            public void run() {
              try{
                addMutations(mutationsToSend);
              } catch (Exception e){
                updateUnknownErrors(e);
              }
            }
          });
        }
    
    ```


> 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: 1.8.0
>
>          Time Spent: 0.5h
>  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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