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From "Konstantin Shvachko (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2983) Relax the build version check to permit rolling upgrades within a release
Date Tue, 10 Apr 2012 18:37:14 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2983?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13250943#comment-13250943
] 

Konstantin Shvachko commented on HDFS-2983:
-------------------------------------------

The scenario is not different if you do rolling or non-rolling upgrades. The difference is
that the patch *removes build version verification*, which means that after 3 upgrades (rolling
or not) you are guaranteed to have 3 sets of nodes running different version of hadoop talking
to your NameNode.
While in today's world the strict version verification guarantees that un-upgraded nodes never
talk to NN. If you add to this snapshots, block pools, HA NameNodes it becomes an operability
horror.
Separating snapshots from upgrades straightens things up, imho.

Todd, your proposal to add DN versions to the Web UI is also very important. Otherwise it
is hard to monitor cluster consistency.
                
> 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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