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Posted to issues@hbase.apache.org by "Nicolas Spiegelberg (Resolved) (JIRA)" <ji...@apache.org> on 2011/11/02 21:37:32 UTC
[jira] [Resolved] (HBASE-2312) Possible data loss when RS goes into
GC pause while rolling HLog
[ https://issues.apache.org/jira/browse/HBASE-2312?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Nicolas Spiegelberg resolved HBASE-2312.
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Resolution: Fixed
> Possible data loss when RS goes into GC pause while rolling HLog
> ----------------------------------------------------------------
>
> Key: HBASE-2312
> URL: https://issues.apache.org/jira/browse/HBASE-2312
> Project: HBase
> Issue Type: Bug
> Components: master, regionserver
> Affects Versions: 0.90.0
> Reporter: Karthik Ranganathan
> Assignee: Nicolas Spiegelberg
> Priority: Critical
> Fix For: 0.92.0
>
> Attachments: D99.1.patch, D99.2.patch, D99.3.patch
>
>
> There is a very corner case when bad things could happen(ie data loss):
> 1) RS #1 is going to roll its HLog - not yet created the new one, old one will get no more writes
> 2) RS #1 enters GC Pause of Death
> 3) Master lists HLog files of RS#1 that is has to split as RS#1 is dead, starts splitting
> 4) RS #1 wakes up, created the new HLog (previous one was rolled) and appends an edit - which is lost
> The following seems like a possible solution:
> 1) Master detects RS#1 is dead
> 2) The master renames the /hbase/.logs/<regionserver name> directory to something else (say /hbase/.logs/<regionserver name>-dead)
> 3) Add mkdir support (as opposed to mkdirs) to HDFS - so that a file create fails if the directory doesn't exist. Dhruba tells me this is very doable.
> 4) RS#1 comes back up and is not able create the new hlog. It restarts itself.
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