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https://issues.apache.org/jira/browse/HDFS-2742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13190222#comment-13190222
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Todd Lipcon commented on HDFS-2742:
-----------------------------------
I should also note that this test modifies
TestHASafeMode.testEnterSafeModeInANNShouldNotThrowNPE - previously it had an
incorrect assertion, that the NN would be in safemode after startup, even
though the namesystem was empty. This is not supposed to be the case and was
actually a prior bug which got fixed along the way of this patch. I added a new
non-HA test case for this behavior in HDFS-2817.
> HA: observed dataloss in replication stress test
> ------------------------------------------------
>
> Key: HDFS-2742
> URL: https://issues.apache.org/jira/browse/HDFS-2742
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: data-node, ha, name-node
> Affects Versions: HA branch (HDFS-1623)
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Blocker
> Attachments: hdfs-2742.txt, hdfs-2742.txt, hdfs-2742.txt,
> hdfs-2742.txt, log-colorized.txt
>
>
> The replication stress test case failed over the weekend since one of the
> replicas went missing. Still diagnosing the issue, but it seems like the
> chain of events was something like:
> - a block report was generated on one of the nodes while the block was being
> written - thus the block report listed the block as RBW
> - when the standby replayed this queued message, it was replayed after the
> file was marked complete. Thus it marked this replica as corrupt
> - it asked the DN holding the corrupt replica to delete it. And, I think,
> removed it from the block map at this time.
> - That DN then did another block report before receiving the deletion. This
> caused it to be re-added to the block map, since it was "FINALIZED" now.
> - Replication was lowered on the file, and it counted the above replica as
> non-corrupt, and asked for the other replicas to be deleted.
> - All replicas were lost.
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