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https://issues.apache.org/jira/browse/HBASE-24526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17149739#comment-17149739
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Nick Dimiduk commented on HBASE-24526:
--------------------------------------
It also appears we're setting meta location in ZooKeeper before meta has been
confirmed open on the target region server. I think this is a big part of why
the worker pool gets backed up. In this case, it looks like the assigned rs
crashes while opening meta, but since a location is set in ZK, all the other
assign procedures start executing. They flood the worker pool, but none of them
can make progress because meta isn't online. Meanwhile, recovery of meta cannot
proceed because the procedure worker pool is saturated and cannot accept new
work. The cluster hangs in this brown-out state until master is restarted, and
the new master gets to try again.
> Deadlock executing assign meta procedure
> ----------------------------------------
>
> Key: HBASE-24526
> URL: https://issues.apache.org/jira/browse/HBASE-24526
> Project: HBase
> Issue Type: Bug
> Components: proc-v2, Region Assignment
> Affects Versions: 2.3.0
> Reporter: Nick Dimiduk
> Priority: Critical
>
> I have what appears to be a deadlock while assigning meta. During recovery,
> master creates the assign procedure for meta, and immediately marks meta as
> assigned in zookeeper. It then creates the subprocedure to open meta on the
> target region. However, the PEWorker pool is full of procedures that are
> stuck, I think because their calls to update meta are going nowhere. For what
> it's worth, the balancer is running concurrently, and has calculated a plan
> size of 41.
> From the master log,
> {noformat}
> 2020-06-06 00:34:07,314 INFO
> org.apache.hadoop.hbase.master.assignment.TransitRegionStateProcedure:
> Starting pid=17802, ppid=17801,
> state=RUNNABLE:REGION_STATE_TRANSITION_GET_ASSIGN_CANDIDATE, locked=true;
> TransitRegionStateProcedure table=hbase:meta, region=1588230740, ASSIGN;
> state=OPEN, location=null; forceNewPlan=true, retain=false
> 2020-06-06 00:34:07,465 INFO
> org.apache.hadoop.hbase.zookeeper.MetaTableLocator: Setting hbase:meta
> (replicaId=0) location in ZooKeeper as
> hbasedn139.example.com,16020,1591403576247
> 2020-06-06 00:34:07,466 INFO
> org.apache.hadoop.hbase.procedure2.ProcedureExecutor: Initialized
> subprocedures=[{pid=17803, ppid=17802, state=RUNNABLE;
> org.apache.hadoop.hbase.master.assignment.OpenRegionProcedure}]
> {noformat}
> {{pid=17803}} is not mentioned again. hbasedn139 never receives an
> {{openRegion}} RPC.
> Meanwhile, additional procedures are scheduled and picked up by workers, each
> getting "stuck". I see log lines for all 16 PEWorker threads, saying that
> they are stuck.
> {noformat}
> 2020-06-06 00:34:07,961 INFO
> org.apache.hadoop.hbase.master.procedure.MasterProcedureScheduler: Took xlock
> for pid=17804, state=RUNNABLE:REGION_STATE_TRANSITION_CLOSE;
> TransitRegionStateProcedure table=IntegrationTestBigLinkedList,
> region=54f4f6c0e921e6d25e6043cba79c09aa, REOPEN/MOVE
> 2020-06-06 00:34:07,961 INFO
> org.apache.hadoop.hbase.master.assignment.RegionStateStore: pid=17804
> updating hbase:meta row=54f4f6c0e921e6d25e6043cba79c09aa,
> regionState=CLOSING, regionLocation=hbasedn046.example.com,16020,1591402383956
> ...
> 2020-06-06 00:34:22,295 WARN
> org.apache.hadoop.hbase.procedure2.ProcedureExecutor: Worker stuck
> PEWorker-16(pid=17804), run time 14.3340 sec
> ...
> 2020-06-06 00:34:27,295 WARN
> org.apache.hadoop.hbase.procedure2.ProcedureExecutor: Worker stuck
> PEWorker-16(pid=17804), run time 19.3340 sec
> ...
> {noformat}
> The cluster stays in this state, with PEWorker thread stuck for upwards of 15
> minutes. Eventually master starts logging
> {noformat}
> 2020-06-06 00:50:18,033 INFO
> org.apache.hadoop.hbase.client.RpcRetryingCallerImpl: Call exception,
> tries=30, retries=31, started=970072 ms ago, cancelled=false, msg=Call queue
> is full on hbasedn139.example.com,16020,1591403576247, too many items queued
> ?, details=row
> 'IntegrationTestBigLinkedList,,1591398987965.54f4f6c0e921e6d25e6043cba79c09aa.'
> on table 'hbase:meta' at region=hbase:meta,,1.
> 1588230740, hostname=hbasedn139.example.com,16020,1591403576247, seqNum=-1,
> see https://s.apache.org/timeout
> {noformat}
> The master never recovers on its own.
> I'm not sure how common this condition might be. This popped after about 20
> total hours of running ITBLL with ServerKillingMonkey.
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