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https://issues.apache.org/jira/browse/HBASE-6060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13292470#comment-13292470
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stack commented on HBASE-6060:
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bq. We need to consider regions in OPEN state also(along with OPENING) for
assignment.
Yes. Makes sense.
bq. you mean to say skip assignment of the regions in OFFLINE or PENDING_OPEN
while processing server shutdown, because they will be assigned as part of
retry?
Yes.
bq. Lets suppose Region server went down after spawning OpenRegionHandler and
before transitioning to OPENING then its SSH responsibility to assign regions
in OFFLINE/PENDING_OPEN.
This is a good one. I'd argue this is a hole in our transition states. Region
is OFFLINE but the regionserver is supposed to have control. I'd suggest that
a regionserver not return from open region until its moved the znode from
PENDING_OPEN to OPENING (need to look more into what would be involved making
this happen -- and what to do on bulk assign though it seems we drop a bunch of
the handling already when bulk assigning). Shouldn't region belong to master
or regionserver without a gray area in-between while PENDING_OPEN is going on?
bq. during opening region if destination server details not updated in META
then the region wont present in hris...
This is also a good one. I found it earlier this afternoon making your tests
work w/ the alternate patch (There is another 'hole' that I found in the case
where there are no regions on the server that died; in this case we'll skip out
early and not find associated OPENING or OPEN regions -- my patch is much
larger than four lines now (smile)).
What do you think of this alternate solution Rajeshbabu? Assuming I close the
above holes, do you think it easier to reason about? We don't have to keep up
state distributed across AM and SSH (I think it more clear whats going on), we
don't have to use a special RegionPlan to signal the single region assign
method to give up on its assign (I'd think we'd want regions assigned by the
single-assign call rather than the bulk assign since the single assign does
more checking), and we are not built atop the current state of regionplans,
which seems a little bit of an indirect foundation given we are trying to keep
up RegionState in regionsInTransition.
Thanks for the thorough review.
> 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_alternative_suggestion.txt,
> 6060_suggestion2_based_off_v3.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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