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https://issues.apache.org/jira/browse/HDFS-2983?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13249182#comment-13249182
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Todd Lipcon commented on HDFS-2983:
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bq. The proposal seems to suggest that the NN does not need to be updated if
desired. Correct?
Yes, I think that's correct, and desired. Sometimes upgrades only address the
slave nodes, so there's no sense having to change the NN. Of course, with HA,
upgrading the NN isn't as big a problem, but even so it is a more
complicated/delicate operation.
bq. I see why it is desirable but does can we simplify things or make upgrades
safer if we drop that requirement?
I don't know if it makes things much simpler. I think adding a requirement that
the NN upgrade before the DNs is quite inconvenient for operators. But I am not
100% sure of this, and willing to be convinced :)
> Relax the build version check to permit rolling upgrades within a release
> -------------------------------------------------------------------------
>
> Key: HDFS-2983
> URL: https://issues.apache.org/jira/browse/HDFS-2983
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.0.0
> Reporter: Eli Collins
> Assignee: Aaron T. Myers
> Attachments: HDFS-2983.patch
>
>
> Currently the version check for DN/NN communication is strict (it checks the
> exact svn revision or git hash, Storage#getBuildVersion calls
> VersionInfo#getRevision), which prevents rolling upgrades across any
> releases. Once we have the PB-base RPC in place (coming soon to branch-23)
> we'll have the necessary pieces in place to loosen this restriction, though
> perhaps it takes another 23 minor release or so before we're ready to commit
> to making the minor versions compatible.
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