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Hudson commented on HBASE-2312: ------------------------------- Integrated in HBase-0.92 #102 (See [https://builds.apache.org/job/HBase-0.92/102/]) HBASE-2312 [jira] Possible data loss when RS goes into GC pause while rolling HLog Summary: 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. Test Plan: EMPTY Reviewers: JIRA, stack, khemani Reviewed By: khemani CC: tedyu, nspiegelberg, stack, Kannan, khemani, jgray Differential Revision: 99 nspiegelberg : Files : * /hbase/branches/0.92/src/main/java/org/apache/hadoop/hbase/master/MasterFileSystem.java * /hbase/branches/0.92/src/main/java/org/apache/hadoop/hbase/master/handler/ServerShutdownHandler.java * /hbase/branches/0.92/src/main/java/org/apache/hadoop/hbase/regionserver/wal/HLog.java * /hbase/branches/0.92/src/main/java/org/apache/hadoop/hbase/regionserver/wal/HLogSplitter.java * /hbase/branches/0.92/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceFileLogWriter.java * /hbase/branches/0.92/src/main/java/org/apache/hadoop/hbase/replication/regionserver/ReplicationSource.java * /hbase/branches/0.92/src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestHLogSplit.java > 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. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa For more information on JIRA, see: http://www.atlassian.com/software/jira