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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:
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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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