[jira] [Commented] (HBASE-4395) EnableTableHandler races with itself

["Jean-Daniel Cryans (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-4395?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13104056#comment-13104056 ] 

Jean-Daniel Cryans commented on HBASE-4395:
-------------------------------------------

Looking more into this, deep in the BulkEnabler it waitUntilDone and it has a timeout of 5 minutes. I guess the loop is the way we use to take action when we timeout. I don't think it's a good idea in hindsight.

Since we already have access to both the number of regions in the table and the number of online regions, I think we could do a trick where we count the latter number in a loop and as long we make progress we don't timeout. If we do timeout, the best we can do is logging an angry message in the master log... I don't think looping forever is better, same for calling BulkEnabler multiple times.

> EnableTableHandler races with itself
> ------------------------------------
>
>                 Key: HBASE-4395
>                 URL: https://issues.apache.org/jira/browse/HBASE-4395
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.90.4
>            Reporter: Jean-Daniel Cryans
>            Priority: Blocker
>             Fix For: 0.90.5
>
>
> Very often when we try to enable a big table we get something like:
> {quote}
> 2011-09-02 12:21:56,619 FATAL org.apache.hadoop.hbase.master.HMaster: Unexpected state trying to OFFLINE; huge_ass_region_name state=PENDING_OPEN, ts=1314991316616
> java.lang.IllegalStateException
>         at org.apache.hadoop.hbase.master.AssignmentManager.setOfflineInZooKeeper(AssignmentManager.java:1074)
>         at org.apache.hadoop.hbase.master.AssignmentManager.assign(AssignmentManager.java:1030)
>         at org.apache.hadoop.hbase.master.AssignmentManager.assign(AssignmentManager.java:858)
>         at org.apache.hadoop.hbase.master.AssignmentManager.assign(AssignmentManager.java:838)
>         at org.apache.hadoop.hbase.master.handler.EnableTableHandler$BulkEnabler$1.run(EnableTableHandler.java:154)
>         at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
>         at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
>         at java.lang.Thread.run(Thread.java:662)
> 2011-09-02 12:21:56,620 INFO org.apache.hadoop.hbase.master.HMaster: Aborting
> {quote}
> The issue is that EnableTableHandler calls multiple BulkEnabler and it's possible that by the time it calls it a second time, using a stale list of still-not-enabled regions, that it tries to set one region offline in ZK but just after its state changed. Case in point:
> {quote}
> 2011-09-02 12:21:56,616 DEBUG org.apache.hadoop.hbase.master.AssignmentManager: Assigning region huge_ass_region_name to sv4r23s16,60020,1314880035029
> 2011-09-02 12:21:56,619 FATAL org.apache.hadoop.hbase.master.HMaster: Unexpected state trying to OFFLINE; huge_ass_region_name state=PENDING_OPEN, ts=1314991316616
> {quote}
> Here the first line is the first assign done in the first thread, and the second line is the second thread that got to process the same region around the same time. 3ms difference in time. After that, the master dies, and it's pretty sad when it restarts because it failovers an enabling table and it's ungodly slow.
> I'm pretty sure there's a window where double assignment are possible.
> Talking with Stack, it doesn't really make sense to call multiple enables since the list of regions is static (the table is disabled!). We should just call it and wait. Also there's a lot of cleanup to do in EnableTableHandler since it refers to disabling the table (copy pasta I guess).

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