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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-16162) Unnecessary push active segments to pipeline
Date Fri, 01 Jul 2016 07:41:11 GMT
Anoop Sam John created HBASE-16162:
--------------------------------------

             Summary: Unnecessary push active segments to pipeline
                 Key: HBASE-16162
                 URL: https://issues.apache.org/jira/browse/HBASE-16162
             Project: HBase
          Issue Type: Sub-task
            Reporter: Anoop Sam John
            Assignee: Anoop Sam John


We have flow like this
{code}
protected void checkActiveSize() {
    if (shouldFlushInMemory()) {
         InMemoryFlushRunnable runnable = new InMemoryFlushRunnable();
      }
      getPool().execute(runnable);
    }
  }
private boolean shouldFlushInMemory() {
    if(getActive().getSize() > inmemoryFlushSize) {
      // size above flush threshold
      return (allowCompaction.get() && !inMemoryFlushInProgress.get());
    }
    return false;
  }

void flushInMemory() throws IOException {
    // Phase I: Update the pipeline
    getRegionServices().blockUpdates();
    try {
      MutableSegment active = getActive();
      pushActiveToPipeline(active);
    } finally {
      getRegionServices().unblockUpdates();
    }
    // Phase II: Compact the pipeline
    try {
      if (allowCompaction.get() && inMemoryFlushInProgress.compareAndSet(false, true))
{
        // setting the inMemoryFlushInProgress flag again for the case this method is invoked
        // directly (only in tests) in the common path setting from true to true is idempotent
        // Speculative compaction execution, may be interrupted if flush is forced while
        // compaction is in progress
        compactor.startCompaction();
      }
{code}
So every write of cell will produce the check checkActiveSize().   When we are at border of
in mem flush,  many threads doing writes to this memstore can get this check to pass.  Yes
the AtomicBoolean is still false only. It is turned ON after some time once the new thread
is started run and it push the active to pipeline etc.
So all these threads can push the same active to pipeline.  We unnecessarily passing through
same segment many times. 



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