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https://issues.apache.org/jira/browse/HBASE-2312?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12974029#action_12974029
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HBase Review Board commented on HBASE-2312:
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Message from: "Nicolas" <nspiegelb...@facebook.com>
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This is an automatically generated e-mail. To reply, visit:
http://review.cloudera.org/r/396/
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(Updated 2010-12-21 19:06:32.166768)
Review request for hbase.
Changes
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Version for 0.90. This version utilizes a new HDFS patch to forcibly recover a
file lease (forthcoming). TestZooKeeper will fail without this patch because
it needs to wait until the soft lease expires otherwise.
Summary
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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
Note that this fix requires a healthy dose of HDFS prerequisites: HDFS-617,
HADOOP-6840, HADOOP-6886. I encourage you to review those as well, give
feedback, and hopefully give +1s so we can push the changes through.
This addresses bug HBASE-2312.
http://issues.apache.org/jira/browse/HBASE-2312
Diffs (updated)
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trunk/src/main/java/org/apache/hadoop/hbase/HConstants.java 1051398
trunk/src/main/java/org/apache/hadoop/hbase/master/MasterFileSystem.java
1051398
trunk/src/main/java/org/apache/hadoop/hbase/regionserver/wal/HLog.java
1051398
trunk/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceFileLogWriter.java
1051398
trunk/src/main/java/org/apache/hadoop/hbase/util/FSUtils.java 1051398
trunk/src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestHLogSplit.java
1051398
Diff: http://review.cloudera.org/r/396/diff
Testing
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mvn test;
bin/start-hbase.sh
bin/hbase shell < scan '.META.', get, put, etc
Thanks,
Nicolas
> 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: 0.90.1
>
>
> 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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