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https://issues.apache.org/jira/browse/HDFS-2709?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13181031#comment-13181031
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Todd Lipcon commented on HDFS-2709:
-----------------------------------
I'm skeptical of the fix -- the question is _why_ we see the wrong log version
here. We investigated and it looks like there's a race when a log file is
created -- it preallocates the file with all 0xFFFFFFFF, and then it goes back
and writes the version number. Adding a sleep() after the preallocate() call in
EditLogFileOutputStream triggers this reliably. So, I think we should file
another JIRA to fix that race.
Separately, I agree that we should probably change this to be an exception
instead of assert. But I think LogHeaderCorruptException is probably a better
choice.
> HA: Appropriately handle error conditions in EditLogTailer
> ----------------------------------------------------------
>
> Key: HDFS-2709
> URL: https://issues.apache.org/jira/browse/HDFS-2709
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ha, name-node
> Affects Versions: HA branch (HDFS-1623)
> Reporter: Todd Lipcon
> Assignee: Aaron T. Myers
> Priority: Critical
> Attachments: HDFS-2709-HDFS-1623.patch, HDFS-2709-HDFS-1623.patch,
> HDFS-2709-HDFS-1623.patch, HDFS-2709-HDFS-1623.patch,
> HDFS-2709-HDFS-1623.patch, HDFS-2709-HDFS-1623.patch,
> HDFS-2709-HDFS-1623.patch
>
>
> Currently if the edit log tailer experiences an error replaying edits in the
> middle of a file, it will go back to retrying from the beginning of the file
> on the next tailing iteration. This is incorrect since many of the edits will
> have already been replayed, and not all edits are idempotent.
> Instead, we either need to (a) support reading from the middle of a finalized
> file (ie skip those edits already applied), or (b) abort the standby if it
> hits an error while tailing. If "a" isn't simple, let's do "b" for now and
> come back to 'a' later since this is a rare circumstance and better to abort
> than be incorrect.
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