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https://issues.apache.org/jira/browse/HBASE-2413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12854360#action_12854360
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Jonathan Gray commented on HBASE-2413:
--------------------------------------

Definitely need a good checkup/cleanup on where we use server+port vs 
server+port+startcode.  So I guess we already have the map to check if we exist 
when receiving a startup.  Good stuff guys.

@stack, assign to u?

> 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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