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From "zhangduo (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-13146) Race Condition in ScheduledChore and ChoreService
Date Tue, 03 Mar 2015 14:41:05 GMT
zhangduo created HBASE-13146:
--------------------------------

             Summary: Race Condition in ScheduledChore and ChoreService
                 Key: HBASE-13146
                 URL: https://issues.apache.org/jira/browse/HBASE-13146
             Project: HBase
          Issue Type: Bug
          Components: regionserver
    Affects Versions: 2.0.0, 1.1.0
            Reporter: zhangduo
            Assignee: zhangduo
             Fix For: 2.0.0, 1.1.0


Here is my findings when addressing HBASE-13145.

{code:title=ChoreService.java}
  public synchronized boolean scheduleChore(ScheduledChore chore) {
      ...
      ScheduledFuture<?> future =
          scheduler.scheduleAtFixedRate(chore, chore.getInitialDelay(), chore.getPeriod(),
            chore.getTimeUnit());
      chore.setChoreServicer(this);
      ...
  }
{code}
So we schedule the chore first, and then set chore servicer. And for CompactionChecker, the
initialDelay is 0, so it is possible that the chore is run before we set chore servicer for
it. And see this
{code:title=ScheduledChore.java}
  public void run() {
    ...
    else if (stopper.isStopped() || !isScheduled()) {
      cancel(false);
      cleanup();
      if (LOG.isInfoEnabled()) LOG.info("Chore: " + getName() + " was stopped");
    }
    ...
  }
    ...
  public synchronized boolean isScheduled() {
    return choreServicer != null && choreServicer.isChoreScheduled(this);
  }
{code}
So it is possible that isScheduled() returns false and we start to cancel the chore. You can
insert a sleep between scheduled chore and set chore servicer, then you can always get the
log ' Chore: CompactionChecker was stopped'. But it does not always actually cancel the chore
because the cancel method's implementation.
{code:title=ScheduledChore.java}
  public synchronized void cancel(boolean mayInterruptIfRunning) {
    if (isScheduled()) choreServicer.cancelChore(this, mayInterruptIfRunning);

    choreServicer = null;
  }
{code}
So if you insert a sleep before cancel(remember to set a larger sleep time here), then you
can make the test always fail.



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