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From "Jean-Daniel Cryans (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HBASE-1439) race between master and regionserver after missed heartbeat
Date Tue, 09 Jun 2009 22:48:07 GMT

     [ https://issues.apache.org/jira/browse/HBASE-1439?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Jean-Daniel Cryans updated HBASE-1439:

    Assignee: Jean-Daniel Cryans

The region servers should watch their own znodes to make sure that they don't continue to
live even if the master sees them as dead. Masters should also watch their own nodes.

> race between master and regionserver after missed heartbeat
> -----------------------------------------------------------
>                 Key: HBASE-1439
>                 URL: https://issues.apache.org/jira/browse/HBASE-1439
>             Project: Hadoop HBase
>          Issue Type: Bug
>    Affects Versions: 0.19.1
>         Environment: CentOS 5.2 x86_64, HBase 0.19.1, Hadoop 0.19.1
>            Reporter: Andrew Purtell
>            Assignee: Jean-Daniel Cryans
>             Fix For: 0.20.0
> Seen on one of our 0.19.1 clusters:
> {code}
> java.io.FileNotFoundException: File does not exist: hdfs://jdc2-atr-dc-2.atr.trendmicro.com:50000
> /data/hbase/log_10.3.134.207_1242286427894_60020/hlog.dat.1242528291898
>  at org.apache.hadoop.hdfs.DistributedFileSystem.getFileStatus(DistributedFileSystem.java:415)
>  at org.apache.hadoop.fs.FileSystem.getLength(FileSystem.java:679)
>  at org.apache.hadoop.hbase.io.SequenceFile$Reader.<init>(SequenceFile.java:1431)
>  at org.apache.hadoop.hbase.io.SequenceFile$Reader.<init>(SequenceFile.java:1426)
>  at org.apache.hadoop.hbase.regionserver.HLog.splitLog(HLog.java:753)
>  at org.apache.hadoop.hbase.regionserver.HLog.splitLog(HLog.java:716)
>  at org.apache.hadoop.hbase.master.ProcessServerShutdown.process(ProcessServerShutdown.java:249)
>  at org.apache.hadoop.hbase.master.HMaster.processToDoQueue(HMaster.java:442)
>  at org.apache.hadoop.hbase.master.HMaster.run(HMaster.java:377)
> 2009-05-17 04:05:55,481 INFO org.apache.hadoop.hbase.master.RegionServerOperation: process
> shutdown of server logSplit: false, rootRescanned: false, numberOfMetaRegions:
> onlineMetaRegions.size(): 1
> {code}
> I do not have the region server log yet, but here is my conjecture:
> Here, the write ahead log for is missing in DFS: java.io.FileNotFoundException:
when the master tries to split it after declaring the region server crashed. There have been
recent trouble reports on this cluster that indicate severe memory stress, e.g. kernel panics
due to OOM. Based on that I think it is likely that the region server here missed a heartbeat
so the master declared it crashed and began to split the log. But, the log was then deleted
out from underneath the master's split thread. I think the region server was actually still
running but partially swapped out or the node was otherwise overloaded so it missed its heartbeat.
Then, when the region server came back after being swapped in, it realized it missed its heartbeat
and shut down, deleting the log as is normally done. 
> Even if the above is not the actual cause in this case, I think the scenario is plausible.
What do you think?

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