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https://issues.apache.org/jira/browse/HDFS-2691?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13193442#comment-13193442
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Eli Collins commented on HDFS-2691:
-----------------------------------
Sorry for chiming in late. I think solution #1 is preferable. It shouldn't be
much additional overhead, and it's important to minimize the amount of state
the standby needs to learn about when it becomes active, which makes the
failover less buggy (ie less risk that we fail over to something that's not up
to speed, and potentially faster).
The latest patch needs to be updated on the latest 2742/2791. Would be helpful
for DataNode.proto to comment that RECEIVING is for pipeline creation and
RECEIVED is for block completion/replacement, otherwise looks good.
> HA: Tests and fixes for pipeline targets and replica recovery
> -------------------------------------------------------------
>
> Key: HDFS-2691
> URL: https://issues.apache.org/jira/browse/HDFS-2691
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ha
> Affects Versions: HA branch (HDFS-1623)
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Critical
> Attachments: hdfs-2691.txt, hdfs-2691.txt, hdfs-2691.txt
>
>
> Currently there are some TODOs around pipeline/recovery code in the HA
> branch. For example, commitBlockSynchronization only gets sent to the active
> NN which may have failed over by that point. So, we need to write some tests
> here and figure out what the correct behavior is.
> Another related area is the treatment of targets in the pipeline. When a
> pipeline is created, the active NN adds the "expected locations" to the
> BlockInfoUnderConstruction, but the DN identifiers aren't logged with the
> OP_ADD. So after a failover, the BlockInfoUnderConstruction will have no
> targets and I imagine replica recovery would probably trigger some issues.
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