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https://issues.apache.org/jira/browse/HDFS-2983?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13250364#comment-13250364
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Konstantin Shvachko commented on HDFS-2983:
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Yes, ctime will prevent DNs from previous versions connecting to NN started
with -upgrade.
Can we add a condition to allow rolling-upgrades only if there are no
upgrades-snapshots in progress.
That is one should first finalize or rollback the upgrade-snapshot, then do
rolling upgrades.
The scenario that scares me is if somebody does a snapshot, then several
rolling upgrades, and then decides to rollback. This may be possible, but seems
to be very much error-prone.
Also that way we will have clear separation between snapshots and rolling
upgrades.
> 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, HDFS-2983.patch, HDFS-2983.patch,
> HDFS-2983.patch, HDFS-2983.patch, HDFS-2983.patch, 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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