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https://issues.apache.org/jira/browse/HBASE-2312?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13141943#comment-13141943
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Phabricator commented on HBASE-2312:
------------------------------------
stack has commented on the revision "HBASE-2312 [jira] Possible data loss when
RS goes into GC pause while rolling HLog".
+1 on commit. Minor comments that should not get in way of this patch.
Attach the patch Nicolas to JIRA and then submit the patch and let the
patch-build run its course. Good stuff.
INLINE COMMENTS
src/main/java/org/apache/hadoop/hbase/master/MasterFileSystem.java:208
trivial nit -- not important: FYI, I prefer the operator at EOF rather than at
start; when a hanging operator, its useful as signifier of more to come (Did
you format this with your apache formatter?)
src/main/java/org/apache/hadoop/hbase/master/MasterFileSystem.java:201 Next
time, this messing w/ suffix belongs out in a method.
src/main/java/org/apache/hadoop/hbase/master/MasterFileSystem.java:253 Should
we throw only if "hbase.hlog.split.skip.errors" is NOT set?
src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceFileLogWriter.java:84
These gymnastics belong out in a dedicated method rather than inline here in
init method. Next time.
REVISION DETAIL
https://reviews.facebook.net/D99
> 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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