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Posted to issues@hbase.apache.org by "Karthik Ranganathan (JIRA)" <ji...@apache.org> on 2010/04/07 02:44:33 UTC
[jira] Commented: (HBASE-2413) Master does not respect generation
stamps, may result in meta getting permanently offlined
[ https://issues.apache.org/jira/browse/HBASE-2413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12854282#action_12854282 ]
Karthik Ranganathan commented on HBASE-2413:
--------------------------------------------
Fix is to have master recognize the RS1 restart before the zk node expires and handle it right away. There should only be one entry for each HOST:PORT - the one with the latest TS.
> 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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