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https://issues.apache.org/jira/browse/HBASE-5120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13184251#comment-13184251
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Zhihong Yu commented on HBASE-5120:
-----------------------------------
+1 on patch v5.
> Timeout monitor races with table disable handler
> ------------------------------------------------
>
> Key: HBASE-5120
> URL: https://issues.apache.org/jira/browse/HBASE-5120
> Project: HBase
> Issue Type: Bug
> Affects Versions: 0.92.0
> Reporter: Zhihong Yu
> Assignee: ramkrishna.s.vasudevan
> Priority: Blocker
> Fix For: 0.94.0, 0.92.1
>
> Attachments: HBASE-5120.patch, HBASE-5120_1.patch,
> HBASE-5120_2.patch, HBASE-5120_3.patch, HBASE-5120_4.patch, HBASE-5120_5.patch
>
>
> Here is what J-D described here:
> https://issues.apache.org/jira/browse/HBASE-5119?focusedCommentId=13179176&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13179176
> I think I will retract from my statement that it "used to be extremely racy
> and caused more troubles than it fixed", on my first test I got a stuck
> region in transition instead of being able to recover. The timeout was set to
> 2 minutes to be sure I hit it.
> First the region gets closed
> {quote}
> 2012-01-04 00:16:25,811 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Sent CLOSE to
> sv4r5s38,62023,1325635980913 for region
> test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> {quote}
> 2 minutes later it times out:
> {quote}
> 2012-01-04 00:18:30,026 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Regions in transition timed
> out: test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> state=PENDING_CLOSE, ts=1325636185810, server=null
> 2012-01-04 00:18:30,026 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Region has been
> PENDING_CLOSE for too long, running forced unassign again on
> region=test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> 2012-01-04 00:18:30,027 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of
> region test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> (offlining)
> {quote}
> 100ms later the master finally gets the event:
> {quote}
> 2012-01-04 00:18:30,129 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling
> transition=RS_ZK_REGION_CLOSED, server=sv4r5s38,62023,1325635980913,
> region=1a4b111bcc228043e89f59c4c3f6a791, which is more than 15 seconds late
> 2012-01-04 00:18:30,129 DEBUG
> org.apache.hadoop.hbase.master.handler.ClosedRegionHandler: Handling CLOSED
> event for 1a4b111bcc228043e89f59c4c3f6a791
> 2012-01-04 00:18:30,129 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Table being disabled so
> deleting ZK node and removing from regions in transition, skipping assignment
> of region test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> 2012-01-04 00:18:30,129 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
> master:62003-0x134589d3db03587 Deleting existing unassigned node for
> 1a4b111bcc228043e89f59c4c3f6a791 that is in expected state RS_ZK_REGION_CLOSED
> 2012-01-04 00:18:30,166 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
> master:62003-0x134589d3db03587 Successfully deleted unassigned node for
> region 1a4b111bcc228043e89f59c4c3f6a791 in expected state RS_ZK_REGION_CLOSED
> {quote}
> At this point everything is fine, the region was processed as closed. But
> wait, remember that line where it said it was going to force an unassign?
> {quote}
> 2012-01-04 00:18:30,322 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
> master:62003-0x134589d3db03587 Creating unassigned node for
> 1a4b111bcc228043e89f59c4c3f6a791 in a CLOSING state
> 2012-01-04 00:18:30,328 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Server null returned
> java.lang.NullPointerException: Passed server is null for
> 1a4b111bcc228043e89f59c4c3f6a791
> {quote}
> Now the master is confused, it recreated the RIT znode but the region doesn't
> even exist anymore. It even tries to shut it down but is blocked by NPEs. Now
> this is what's going on.
> The late ZK notification that the znode was deleted (but it got recreated
> after):
> {quote}
> 2012-01-04 00:19:33,285 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: The znode of region
> test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791. has been
> deleted.
> {quote}
> Then it prints this, and much later tries to unassign it again:
> {quote}
> 2012-01-04 00:19:46,607 DEBUG
> org.apache.hadoop.hbase.master.handler.DeleteTableHandler: Waiting on region
> to clear regions in transition;
> test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> state=PENDING_CLOSE, ts=1325636310328, server=null
> ...
> 2012-01-04 00:20:39,623 DEBUG
> org.apache.hadoop.hbase.master.handler.DeleteTableHandler: Waiting on region
> to clear regions in transition;
> test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> state=PENDING_CLOSE, ts=1325636310328, server=null
> 2012-01-04 00:20:39,864 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Regions in transition timed
> out: test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> state=PENDING_CLOSE, ts=1325636310328, server=null
> 2012-01-04 00:20:39,864 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Region has been
> PENDING_CLOSE for too long, running forced unassign again on
> region=test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> 2012-01-04 00:20:39,865 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of
> region test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791.
> (offlining)
> 2012-01-04 00:20:39,865 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Attempted to unassign
> region test1,089cd0c9,1325635015491.1a4b111bcc228043e89f59c4c3f6a791. but it
> is not currently assigned anywhere
> {quote}
> And this is still ongoing.
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