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From "David S. Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6009) Changes for HBASE-5209 are technically incompatible
Date Fri, 18 May 2012 18:41:08 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6009?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13279067#comment-13279067
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David S. Wang commented on HBASE-6009:
--------------------------------------

The immediate issue here is that HBASE-5209 was committed in 0.92.1, and that broke compatibility
with 0.92.0.  I suppose anyone who cares about 0.92 branch has moved to 0.92.1 so that there
is no practical hit.

You are right that adding a size would be another incompatible change, hence my later comment
about "let's just not make any more changes until 0.96".  :D

Anyway in the absence of any changes, I can at least add a release note to 0.92.1 stating
this incompatibility with 0.92.0.  I'll use this JIRA to track that.
                
> Changes for HBASE-5209 are technically incompatible
> ---------------------------------------------------
>
>                 Key: HBASE-6009
>                 URL: https://issues.apache.org/jira/browse/HBASE-6009
>             Project: HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 0.92.1, 0.94.0
>            Reporter: David S. Wang
>
> The additions to add backup masters to ClusterStatus are technically incompatible between
clients and servers.  Older clients will basically not read the extra bits that the newer
server pushes for the backup masters, thus screwing up the serialization for the next blob
in the pipe.
> For the Writable, we can add a total size field for ClusterStatus at the beginning, or
we can have start and end markers.  I can make a patch for either approach; interested in
whatever folks have to suggest.  Would be good to get this in soon to limit the damage to
0.92.1 (don't know if we can get this in in time for 0.94.0).
> Either change will make us forward-compatible starting with when the change goes in,
but will not fix the backwards incompatibility, which we will have to mark with a release
note as there have already been releases with this change.
> Hopefully we can do this in a cleaner way when wire compat rolls around in 0.96.

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