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https://issues.apache.org/jira/browse/HBASE-2337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12849877#action_12849877
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Nicolas Spiegelberg commented on HBASE-2337:
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@jd I'll do syntactic cleanups. I should clarify the comment, however it's
logically accurate. I wanted to give users the ability to not store
corruptions and just delete them. To that end, if you explicitly set
'hbase.regionserver.hlog.splitlog.corrupt.dir' in your configuration to '', or
empty string, it should delete instead of move corruptFiles. I need to write
some unit tests to verify functionality. Alternate suggestions on handling
this?
> log recovery: splitLog deletes old logs prematurely
> ---------------------------------------------------
>
> Key: HBASE-2337
> URL: https://issues.apache.org/jira/browse/HBASE-2337
> Project: Hadoop HBase
> Issue Type: Bug
> Reporter: Kannan Muthukkaruppan
> Assignee: Nicolas Spiegelberg
> Priority: Blocker
> Fix For: 0.20.4, 0.21.0
>
> Attachments: HBASE-2337-20.4.patch
>
>
> splitLog()'s purpose is to take a bunch of commit logs of a crashed RS and
> create per-region logs. splitLog() runs in the master. There are two cases
> where splitLog() might end up deleting an old log before actually creating
> (sync/closing) the newly created logs. If the master crashes in between
> deletion of the old log and creation of the new log, then edits could be lost
> irrecoverably.
> More specifically here are the two issues we (Nicolas, Aravind and I) noticed:
> Issue #1: The old logs are read one at a time. An in memory structure,
> logEntries (a map from region name to edits for the region), is populated.
> And the old logs are closed. Then the in-memory map is written out to per
> region files. Fix: We should move the file deletion to later.
> Issue #2: There is another little case. The per-region log file is written
> under the region directory (named oldlogfile.log or the constant
> HREGION_OLDLOGFILE_NAME). Before the master creates the file, it checks to
> see if there is already a file with that name, and if so, it renames it to
> oldlogfile.log.old, and then creates file oldlogfile.log again, and copies
> over the contents of oldlogfile.log.old to oldlogfile.log. It then proceeds
> to delete "oldlogfile.log.old", even though it hasn't closed/sync'ed
> "oldlogfile.log" yet.
> --
> I think we should be able to restructure the code such that all deletion of
> old logs happens *after* the new logs have been created (i.e. written to &
> closed).
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