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https://issues.apache.org/jira/browse/HBASE-16270?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15402649#comment-15402649
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Enis Soztutar commented on HBASE-16270:
---------------------------------------
I would like to understand this better since it seems that there is a race
condition happening although we are protecting the flush replay handling with
the synchronization via {{HRegion.writeState}}. In
{{HRegion.replayWALFlushCommitMarker()}} we look at whether we are already
flushing through {{writestate.flushing}} which means that there must be a
memstore snapshot already. So, then the flush commit marker received, we will
try to clear the existing snapshot. Do you have logs from the same regionserver
which is getting the UnexpectedStateException for the same region. If you grep
the region's encoded name, that might help us a lot, because we usually have
extensive logging for flush or replay operations.
> When using region replicas, get thousands of occurrences of
> UnexpectedStateException: Current snapshot id is -1
> ---------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-16270
> URL: https://issues.apache.org/jira/browse/HBASE-16270
> Project: HBase
> Issue Type: Bug
> Components: Replication
> Affects Versions: 1.1.2
> Reporter: Robert Yokota
> Attachments: HBASE-16270-branch-1.2.patch, HBASE-16270-master.patch
>
>
> We have an HBase (1.1.2) production cluster with 58 region servers and a
> staging cluster with 6 region servers.
> For both clusters, we enabled region replicas with the following settings:
> hbase.regionserver.storefile.refresh.period = 0
> hbase.region.replica.replication.enabled = true
> hbase.region.replica.replication.memstore.enabled = true
> hbase.master.hfilecleaner.ttl = 3600000
> hbase.master.loadbalancer.class =
> org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer
> hbase.meta.replica.count = 3
> hbase.regionserver.meta.storefile.refresh.period = 30000
> hbase.region.replica.wait.for.primary.flush = true
> hbase.region.replica.storefile.refresh.memstore.multiplier = 4
> We then altered our HBase tables to have REGION_REPLICATION => 2
> Both clusters got into a state where a few region servers were spewing the
> following error below in the HBase logs. In one instance the error occurred
> over 70K times. At this time, these region servers would see 10x write
> traffic (the hadoop.HBase.RegionServer.Server.writeRequestCount metric) and
> in some instances would crash.
> At the same time, we would see secondary regions move and then go into the
> "reads are disabled" state for extended periods.
> It appears there is a race condition where the DefaultMemStore::clearSnapshot
> method might be called more than once in succession. The first call would set
> snapshotId to -1, but the second call would throw an exception. It seems the
> second call should just return if the snapshotId is already -1, rather than
> throwing an exception.
> Thu Jul 21 08:38:50 UTC 2016,
> RpcRetryingCaller{globalStartTime=1469090201543, pause=100, retries=35},
> org.apache.hadoop.hbase.regionserver.UnexpectedStateException:
> org.apache.hadoop.hbase.regionserver.UnexpectedStateException: Current
> snapshot id is -1,passed 1469085004304
> at
> org.apache.hadoop.hbase.regionserver.DefaultMemStore.clearSnapshot(DefaultMemStore.java:187)
> at
> org.apache.hadoop.hbase.regionserver.HStore.updateStorefiles(HStore.java:1054)
> at
> org.apache.hadoop.hbase.regionserver.HStore.access$500(HStore.java:128)
> at
> org.apache.hadoop.hbase.regionserver.HStore$StoreFlusherImpl.replayFlush(HStore.java:2270)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.replayFlushInStores(HRegion.java:4487)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.replayWALFlushCommitMarker(HRegion.java:4388)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.replayWALFlushMarker(HRegion.java:4191)
> at
> org.apache.hadoop.hbase.regionserver.RSRpcServices.doReplayBatchOp(RSRpcServices.java:776)
> at
> org.apache.hadoop.hbase.regionserver.RSRpcServices.replay(RSRpcServices.java:1655)
> at
> org.apache.hadoop.hbase.protobuf.generated.AdminProtos$AdminService$2.callBlockingMethod(AdminProtos.java:22255)
> at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2114)
> at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:101)
> at
> org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:130)
> at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:107)
> at java.lang.Thread.run(Thread.java:745)
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