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From "ASF GitHub Bot (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-1755) BatchWriter blocks all addMutation calls while binning mutations
Date Sat, 27 Feb 2016 00:39:18 GMT


ASF GitHub Bot commented on ACCUMULO-1755:

Github user keith-turner commented on a diff in the pull request:
    --- Diff: core/src/main/java/org/apache/accumulo/core/client/impl/
    @@ -638,6 +648,21 @@ public MutationWriter(int numSendThreads) {
           queued = new HashSet<String>();
           sendThreadPool = new SimpleThreadPool(numSendThreads, this.getClass().getName());
           locators = new HashMap<String,TabletLocator>();
    +      binTimer.schedule(new TimerTask() {
    +        @Override
    +        public void run() {
    +          MutationSet m = queue.poll();
    +          while (null != m) {
    +            try {
    +              addMutations(m);
    +            } catch (Exception e) {
    +              updateUnknownErrors("Error processing mutation set", e);
    +            }
    +            m = queue.poll();
    +          }
    +        }
    +      }, 0, 500);
    --- End diff --
    > Well, in the previous revision I was adding a MutationSet to an ExecutorService that
had an unbounded queue and 1 thread. That's not immediate
    Yeah, its certainly not immediate.   However, it probably much less than 1ms between adding
to thread pool and thread calling run() on Runnable (when thread is idle).   Relative to ~250ms,
its like kinda immediate.
    > Can MutationSets be binned concurrently?
    I have no idea.  Could not say yes w/o much more review of the code than I want to do
late on a Fri afternoon :).  I suspect something would blow up.

> BatchWriter blocks all addMutation calls while binning mutations
> ----------------------------------------------------------------
>                 Key: ACCUMULO-1755
>                 URL:
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: client
>            Reporter: Adam Fuchs
>            Assignee: Dave Marion
>             Fix For: 1.8.0
>          Time Spent: 40m
>  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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