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https://issues.apache.org/jira/browse/HBASE-2312?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12844335#action_12844335
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Todd Lipcon commented on HBASE-2312:
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Right, I guess the problem with just using a file as a lock is that you also
need to be appending/syncing to the file to know that you still have the lock.
bq. Something else we noticed when looking at the code is that HDFS would
overwrite the existing file if another is created with the same name
Can't we modify the log code to not pass true for overwrite?
bq. Also, in your example, it is possible for the master to fail creating log.4
if the RS comes out of the GC pause
In that case, doesn't that mean the master should give up its recovery, since
the RS is back to life?
> 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: Hadoop HBase
> Issue Type: Bug
> Components: master, regionserver
> Affects Versions: 0.20.3
> Reporter: Karthik Ranganathan
>
> 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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