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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 Mon, 29 Feb 2016 15:35:18 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15172004#comment-15172004
] 

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

Github user keith-turner commented on a diff in the pull request:

    https://github.com/apache/accumulo/pull/75#discussion_r54425522
  
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/impl/TabletServerBatchWriter.java
---
    @@ -699,7 +711,33 @@ else if (Tables.getTableState(context.getInstance(), table) == TableState.OFFLIN
     
         }
     
    -    void addMutations(MutationSet mutationsToSend) {
    +    void queueMutations(final MutationSet mutationsToSend) throws InterruptedException
{
    +      if (null == mutationsToSend)
    +        return;
    +      boolean transferred = queue.tryTransfer(new Runnable() {
    +        final MutationSet m = mutationsToSend;
    +
    +        @Override
    +        public void run() {
    +          if (null != m) {
    +            try {
    +              addMutations(m);
    +            } catch (Exception e) {
    +              updateUnknownErrors("Error processing mutation set", e);
    +            }
    +          }
    +        }
    +      });
    +      if (!transferred) {
    +        try {
    +          addMutations(mutationsToSend);
    --- End diff --
    
    I like this.  Its an interesting approach of having multiple threads bin if it happens
to be busy.  All batchwriter code was written w/ assumption that one thread would bin, so
this change needs careful review of all code called by binning code.


> 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: 50m
>  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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