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https://issues.apache.org/jira/browse/HBASE-6060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13291565#comment-13291565
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ramkrishna.s.vasudevan commented on HBASE-6060:
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bq. This patch will not fix a concurrent balance that goes to move a region and
a concurrent user-orchestrated move?
Currently does not handle this. But if we are sure that the region assignments
goes smoothly after this patch we can surely have a mechanism to initmate the
user that some plan is already in progress and wait for that to complete before
we initiate the user triggered move or assign.
@Enis
bq.very nervous about all the state combinations distributed between zk / meta
/ rs-memory and master-memory.
Can you tell me any problems that you foresee. Happy to address that too here.
Infact we have not introduced any new states. Just using the maps and
zookeeper states available. The REgionplan state we introduced here is
something internal to know the difference which we will address in our next
patch as per Stack's suggestion.
Your comments and feedback are always welcome.
> Regions's in OPENING state from failed regionservers takes a long time to
> recover
> ---------------------------------------------------------------------------------
>
> Key: HBASE-6060
> URL: https://issues.apache.org/jira/browse/HBASE-6060
> Project: HBase
> Issue Type: Bug
> Components: master, regionserver
> Reporter: Enis Soztutar
> Assignee: rajeshbabu
> Fix For: 0.96.0, 0.94.1, 0.92.3
>
> Attachments: 6060-94-v3.patch, 6060-94-v4.patch, 6060-94-v4_1.patch,
> 6060-94-v4_1.patch, 6060-trunk.patch, 6060-trunk.patch, 6060-trunk_2.patch,
> 6060-trunk_3.patch, 6060_suggestion_based_off_v3.patch, HBASE-6060-92.patch,
> HBASE-6060-94.patch
>
>
> we have seen a pattern in tests, that the regions are stuck in OPENING state
> for a very long time when the region server who is opening the region fails.
> My understanding of the process:
>
> - master calls rs to open the region. If rs is offline, a new plan is
> generated (a new rs is chosen). RegionState is set to PENDING_OPEN (only in
> master memory, zk still shows OFFLINE). See HRegionServer.openRegion(),
> HMaster.assign()
> - RegionServer, starts opening a region, changes the state in znode. But
> that znode is not ephemeral. (see ZkAssign)
> - Rs transitions zk node from OFFLINE to OPENING. See
> OpenRegionHandler.process()
> - rs then opens the region, and changes znode from OPENING to OPENED
> - when rs is killed between OPENING and OPENED states, then zk shows OPENING
> state, and the master just waits for rs to change the region state, but since
> rs is down, that wont happen.
> - There is a AssignmentManager.TimeoutMonitor, which does exactly guard
> against these kind of conditions. It periodically checks (every 10 sec by
> default) the regions in transition to see whether they timedout
> (hbase.master.assignment.timeoutmonitor.timeout). Default timeout is 30 min,
> which explains what you and I are seeing.
> - ServerShutdownHandler in Master does not reassign regions in OPENING
> state, although it handles other states.
> Lowering that threshold from the configuration is one option, but still I
> think we can do better.
> Will investigate more.
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