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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13146) Race Condition in ScheduledChore and ChoreService
Date Tue, 03 Mar 2015 22:57:07 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13146?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14345938#comment-14345938
] 

Hudson commented on HBASE-13146:
--------------------------------

SUCCESS: Integrated in HBase-1.1 #244 (See [https://builds.apache.org/job/HBase-1.1/244/])
HBASE-13146 Race Condition in ScheduledChore and ChoreService (stack: rev 0c4c60a99ecdd211b59bf127e62d3572cfe781e0)
* hbase-common/src/main/java/org/apache/hadoop/hbase/ChoreService.java


> 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
>
>         Attachments: HBASE-13146.patch
>
>
> 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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