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https://issues.apache.org/jira/browse/HBASE-5081?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13175172#comment-13175172
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Zhihong Yu commented on HBASE-5081:
-----------------------------------
Currently SplitLogManager.Task doesn't have flag indicating whether the
deletion was caused by successful splitting.
I think we should introduce such flag through boolean or enum so that
stopTrackingTasks() can make better decision.
Looking at the code from 0.89-fb, I can see some subtle differences between
0.89-fb and TRUNK.
e.g. task.batch.notify() in 0.89-fb is guarded by a condition:
{code}
if (!task.isOrphan()) {
synchronized (task.batch) {
if (status == SUCCESS) {
task.batch.done++;
} else {
task.batch.error++;
}
if ((task.batch.done + task.batch.error) == task.batch.installed) {
task.batch.notify();
}
}
}
{code}
I think we should unify the two codebases so that our observations have common
ground.
> Distributed log splitting deleteNode races againsth splitLog retry
> -------------------------------------------------------------------
>
> Key: HBASE-5081
> URL: https://issues.apache.org/jira/browse/HBASE-5081
> Project: HBase
> Issue Type: Bug
> Components: wal
> Affects Versions: 0.92.0, 0.94.0
> Reporter: Jimmy Xiang
> Assignee: Jimmy Xiang
> Fix For: 0.92.0
>
> Attachments: distributed-log-splitting-screenshot.png,
> hbase-5081-patch-v6.txt, hbase-5081-patch-v7.txt,
> hbase-5081_patch_for_92_v4.txt, hbase-5081_patch_v5.txt, patch_for_92.txt,
> patch_for_92_v2.txt, patch_for_92_v3.txt
>
>
> Recently, during 0.92 rc testing, we found distributed log splitting hangs
> there forever. Please see attached screen shot.
> I looked into it and here is what happened I think:
> 1. One rs died, the servershutdownhandler found it out and started the
> distributed log splitting;
> 2. All three tasks failed, so the three tasks were deleted, asynchronously;
> 3. Servershutdownhandler retried the log splitting;
> 4. During the retrial, it created these three tasks again, and put them in a
> hashmap (tasks);
> 5. The asynchronously deletion in step 2 finally happened for one task, in
> the callback, it removed one
> task in the hashmap;
> 6. One of the newly submitted tasks' zookeeper watcher found out that task is
> unassigned, and it is not
> in the hashmap, so it created a new orphan task.
> 7. All three tasks failed, but that task created in step 6 is an orphan so
> the batch.err counter was one short,
> so the log splitting hangs there and keeps waiting for the last task to
> finish which is never going to happen.
> So I think the problem is step 2. The fix is to make deletion sync, instead
> of async, so that the retry will have
> a clean start.
> Async deleteNode will mess up with split log retrial. In extreme situation,
> if async deleteNode doesn't happen
> soon enough, some node created during the retrial could be deleted.
> deleteNode should be sync.
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