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https://issues.apache.org/jira/browse/HBASE-5081?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13174926#comment-13174926
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[email protected] commented on HBASE-5081:
------------------------------------------------------
bq. On 2011-12-22 15:08:38, Michael Stack wrote:
bq. > This patch seems to be raising too many questions. Should we try going
other route of ensuring the async delete removes the 'right' task?
Due to the race issue, we have to put more than the "filename" in the node and
the hashmap, so as to removes the right task.
That's much bigger change and will raise more questions.
bq. On 2011-12-22 15:08:38, Michael Stack wrote:
bq. > src/main/java/org/apache/hadoop/hbase/master/SplitLogManager.java, line
349
bq. > <https://reviews.apache.org/r/3292/diff/8/?file=65682#file65682line349>
bq. >
bq. > Why check for success up here rather than down inside the
synchronize on task.batch? Why not do this safeToDeleteNodeAsync in there in
the else clause where we up the count of errors? Is it not safe to do the
delete of zk node NOW under the synchronize block?
It is safe to do the delete under the synchronize block. The reason is that I
don't want to hold the lock on task.batch while delete the node synchronously.
bq. On 2011-12-22 15:08:38, Michael Stack wrote:
bq. > src/main/java/org/apache/hadoop/hbase/master/SplitLogManager.java, line
378
bq. > <https://reviews.apache.org/r/3292/diff/8/?file=65682#file65682line378>
bq. >
bq. > Are we duplicating the code from deleteNode here? Should we have
sync/async versions?
deleteNode is the async version. deleteNodeNow is the sync version. The async
version can have unlimited retries. The sync version can retry up to certain
configured number (3 by default).
So the sync version doesn't guarantee it will be deleted. The code wise, it's
hard to reuse.
- Jimmy
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On 2011-12-22 00:31:23, Jimmy Xiang wrote:
bq.
bq. -----------------------------------------------------------
bq. This is an automatically generated e-mail. To reply, visit:
bq. https://reviews.apache.org/r/3292/
bq. -----------------------------------------------------------
bq.
bq. (Updated 2011-12-22 00:31:23)
bq.
bq.
bq. Review request for hbase, Ted Yu, Michael Stack, and Lars Hofhansl.
bq.
bq.
bq. Summary
bq. -------
bq.
bq. In this patch, after a task is done, we don't delete the node if the task
is failed. So that when it's retried later on, there won't be race problem.
bq.
bq. It used to delete the node always.
bq.
bq.
bq. This addresses bug HBASE-5081.
bq. https://issues.apache.org/jira/browse/HBASE-5081
bq.
bq.
bq. Diffs
bq. -----
bq.
bq. src/main/java/org/apache/hadoop/hbase/master/SplitLogManager.java
667a8b1
bq. src/test/java/org/apache/hadoop/hbase/master/TestSplitLogManager.java
32ad7e8
bq.
bq. Diff: https://reviews.apache.org/r/3292/diff
bq.
bq.
bq. Testing
bq. -------
bq.
bq. mvn -Dtest=TestDistributedLogSplitting clean test
bq.
bq.
bq. Thanks,
bq.
bq. Jimmy
bq.
bq.
> 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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