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https://issues.apache.org/jira/browse/HBASE-13330?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Devaraj Das updated HBASE-13330:
--------------------------------
Attachment: 13330-branch-1.txt
The meta had the location of the region 0d6cf37c18c54c6f4744750c6a7be837 as
dnj1-bcpc-r3n8.example.com,60020,1425598187703 (which was dead). However, there
existed an RIT node in the RS_ZK_REGION_FAILED_OPEN state with
dnj1-bcpc-r3n2.example.com,60020,1425603618259 as the servername (which was
alive), and hence the SSH for dnj1-bcpc-r3n8.example.com,60020,1425598187703
wouldn't recover this region (as designed).
The region stays offline for ever after that, and activity happens on the
region when dnj1-bcpc-r3n2.example.com,60020,1425603618259 expires. At that
time, the SSH for dnj1-bcpc-r3n2.example.com,60020,1425603618259 finds the
region in an unexpected state "CLOSED". And, the regions stays unassigned for
ever.
The patch attached makes it so that, at startup, for nodes with the state
RS_ZK_REGION_FAILED_OPEN, the servername from the RIT node is set as the last
assigned server (overwrites the servername obtained from the meta for the
region in question). By doing this, the attempted assignment should go through
since the region won't be considered as belonging to the dead server anymore
(step (6) in the description of the ticket).
> Region left unassigned due to AM & SSH each thinking the assignment would be
> done by the other
> ----------------------------------------------------------------------------------------------
>
> Key: HBASE-13330
> URL: https://issues.apache.org/jira/browse/HBASE-13330
> Project: HBase
> Issue Type: Bug
> Components: master, Region Assignment
> Reporter: Devaraj Das
> Fix For: 1.1.0
>
> Attachments: 13330-branch-1.txt
>
>
> Here is what I found during analysis of an issue. Raising this jira and a fix
> will follow.
> The TL;DR of this is that the AssignmentManager thinks the
> ServerShutdownHandler would assign the region and the ServerShutdownHandler
> thinks that the AssignmentManager would assign the region. The region
> (0d6cf37c18c54c6f4744750c6a7be837) ultimately never gets assigned. Below is
> an analysis from the logs that captures the flow of events.
> 1. The AssignmentManager had initially assigned this region to
> dnj1-bcpc-r3n8.example.com,60020,1425598187703
> 2. When the master restarted it did a scan of the meta to learn about the
> regions in the cluster. It found this region being assigned to
> dnj1-bcpc-r3n8.example.com,60020,1425598187703 from the meta record.
> 3. However, this server (dnj1-bcpc-r3n8.example.com,60020,1425598187703) was
> not alive anymore. So, the AssignmentManager queued up a
> ServerShutdownHandling task for this (that asynchronously executes):
> {noformat}
> 2015-03-06 14:09:31,355 DEBUG org.apache.hadoop.hbase.master.ServerManager:
> Added=dnj1-bcpc-r3n8.example.com,60020,1425598187703 to dead servers,
> submitted shutdown handler to be executed meta=false
> {noformat}
> 4. The AssignmentManager proceeded to read the RIT nodes from ZK. It found
> this region as well:
> {noformat}
> 2015-03-06 14:09:31,527 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Processing
> 0d6cf37c18c54c6f4744750c6a7be837
> in state: RS_ZK_REGION_FAILED_OPEN
> {noformat}
> 5. The region was moved to CLOSED state:
> {noformat}
> 2015-03-06 14:09:31,527 WARN org.apache.hadoop.hbase.master.RegionStates:
> 0d6cf37c18c54c6f4744750c6a7be837 moved to CLOSED on
> dnj1-bcpc-r3n2.example.com,60020,1425603618259, expected
> dnj1-bcpc-r3n8.example.com,60020,1425598187703
> {noformat}
> Note the reference to dnj1-bcpc-r3n2.example.com,60020,1425603618259. This
> means that the region was assigned to
> dnj1-bcpc-r3n2.example.com,60020,1425603618259 but that regionserver couldn't
> open the region for some reason, and it changed the state to
> RS_ZK_REGION_FAILED_OPEN in RIT znode on ZK.
> 6. After that the AssignmentManager tried to assign it again. However, the
> assignment didn't happen because the ServerShutdownHandling task queued
> earlier didn't yet execute:
> {noformat}
> 2015-03-06 14:09:31,527 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Skip assigning
> phMonthlyVersion,\x89\x80\x00\x00,1423149098980.0d6cf37c18c54c6f4744750c6a7be837.,
> it's host dnj1-bcpc-r3n8.example.com,60020,1425598187703 is dead but not
> processed yet
> {noformat}
> 7. Eventually the ServerShutdownHandling task executed.
> {noformat}
> 2015-03-06 14:09:35,188 INFO
> org.apache.hadoop.hbase.master.handler.ServerShutdownHandler: Splitting logs
> for dnj1-bcpc-r3n8.example.com,60020,1425598187703 before assignment.
> 2015-03-06 14:09:35,209 INFO
> org.apache.hadoop.hbase.master.handler.ServerShutdownHandler: Reassigning 19
> region(s) that dnj1-bcpc-r3n8.example.com,60020,1425598187703 was
> carrying (and 0 regions(s) that were opening on this server)
> 2015-03-06 14:09:35,211 INFO
> org.apache.hadoop.hbase.master.handler.ServerShutdownHandler: Finished
> processing of shutdown of dnj1-bcpc-r3n8.example.com,60020,1425598187703
> {noformat}
> 8. However, the ServerShutdownHandling task skipped the region in question.
> This was because this region was in RIT, and the ServerShutdownHandling task
> thinks that the AssignmentManager would assign it as part of handling the RIT
> nodes:
> {noformat}
> 2015-03-06 14:09:35,210 INFO
> org.apache.hadoop.hbase.master.handler.ServerShutdownHandler: Skip assigning
> region in transition on other server{0d6cf37c18c54c6f4744750c6a7be837
> state=CLOSED, ts=1425668971527,
> server=dnj1-bcpc-r3n2.example.com,60020,1425603618259}
> {noformat}
> 9. At some point in the future, when the server
> dnj1-bcpc-r3n2.example.com,60020,1425603618259 dies, the
> ServerShutdownHandling for it gets queued up (from the log
> hbase-hbase-master-dnj1-bcpc-r3n1.log):
> {noformat}
> 2015-03-09 11:35:10,607 INFO
> org.apache.hadoop.hbase.zookeeper.RegionServerTracker: RegionServer ephemeral
> node deleted,
> processing expiration [dnj1-bcpc-r3n2.example.com,60020,1425603618259]
> {noformat}
> 10. In RegionStates.java:serverOffline, there is a check that happens on the
> state of the region's state. Since the region is in CLOSED state, the log is
> displayed:
> {noformat}
> 2015-03-09 11:35:15,711 WARN org.apache.hadoop.hbase.master.RegionStates:
> THIS SHOULD NOT HAPPEN: unexpected {0d6cf37c18c54c6f4744750c6a7be837
> state=CLOSED, ts=1425668971527,
> server=dnj1-bcpc-r3n2.example.com,60020,1425603618259}
> {noformat}
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