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https://issues.apache.org/jira/browse/HBASE-2413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12854286#action_12854286
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stack commented on HBASE-2413:
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So, looking at log sent via back channel, a few things:
1. When the restarted server shows up and we treat it as though it a new
server, the load balancer rules the cluster unbalanced and starts to shed
regions. This is before the znode expires. Looking in log, we'll have
succesfully done a bit of distribution before the we start the processing of
the failed server instance. This is bad because this is churn.
2. Suspicious in the master is the serverAddressToServerInfo Map. Its keyed by
server+port. When znode expires, server is removed from this list using
server+port for key. Will remove the server that had reported in as new ten
seconds or so earlier. Looking still for damage this causes.
> Master does not respect generation stamps, may result in meta getting
> permanently offlined
> ------------------------------------------------------------------------------------------
>
> Key: HBASE-2413
> URL: https://issues.apache.org/jira/browse/HBASE-2413
> Project: Hadoop HBase
> Issue Type: Bug
> Components: master
> Affects Versions: 0.20.3
> Reporter: Karthik Ranganathan
>
> This happens if the RS is restarted before the zk node expires. The sequence
> is as follows:
> 1. RS1 dies - lets say its server string was HOST1:PORT1:TS1
> 2. In a few seconds RS1 is restarted, it comes up as HOST1:PORT1:TS2 (TS2 is
> more recent than TS1)
> 3. Master gets a start up message from RS1 with the server name as
> HOST1:PORT1:TS2
> 4. Master adds this as a new RS, tries to red
> ---- The master does not use the generation stamps to detect that RS1 has
> already restarted.
> ---- Also, if RS1 contained meta, master would try to go to HOST1:PORT1:TS1.
> It would end up talking to HOST1:PORT1:TS2, which spews a bunch of not
> serving region exceptions.
> 5. zk node expires for HOST1:PORT1:TS1
> 6. Master tries to process shutdown for HOST1:PORT1:TS1 - this probably
> interferes with HOST1:PORT1:TS2 and ends up somehow removing the reassign
> meta in the master's queue.
> ---- Meta never comes online and master continues logging the following
> exception indefinitely:
> 2010-04-06 11:02:23,988 DEBUG org.apache.hadoop.hbase.master.HMaster:
> Processing todo: ProcessRegionClose of test1,7094000000,1270220428234, false,
> reassign: true
> 2010-04-06 11:02:23,988 DEBUG
> org.apache.hadoop.hbase.master.ProcessRegionClose$1: Exception in
> RetryableMetaOperation:
> java.lang.NullPointerException
> at
> org.apache.hadoop.hbase.master.RetryableMetaOperation.doWithRetries(RetryableMetaOperation.java:64)
> at
> org.apache.hadoop.hbase.master.ProcessRegionClose.process(ProcessRegionClose.java:63)
> at
> org.apache.hadoop.hbase.master.HMaster.processToDoQueue(HMaster.java:494)
> at org.apache.hadoop.hbase.master.HMaster.run(HMaster.java:429)
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