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https://issues.apache.org/jira/browse/HBASE-5204?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13190357#comment-13190357
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Benoit Sigoure commented on HBASE-5204:
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I agree with Zhihong. Either this makes it into 0.92, or we just forget about
it.
I talked to Stack and tried to argue that including this *completely harmless*
change in 0.92 wouldn't require a new RC. But apparently there's an Apache
rule that you can't change a single byte of the code without going through a
new RC, so I gave up on the idea.
Including this change in trunk will cause confusion for future versions and
will make my asynchbase's life even more miserable than it is. Yes Stack in
theory I can rejigger the codes based on what version of HBase I'm talking to,
but in practice this I'd rather not do this.
It was a mistake to break the codes in the first place. Either this mistake
gets fixed right now, in 0.92.0, or we just accept it and live with it and
promise not to break them again in the future.
> Backward compatibility fixes for 0.92
> -------------------------------------
>
> Key: HBASE-5204
> URL: https://issues.apache.org/jira/browse/HBASE-5204
> Project: HBase
> Issue Type: Bug
> Components: ipc
> Reporter: Benoit Sigoure
> Assignee: Benoit Sigoure
> Priority: Blocker
> Labels: backwards-compatibility
> Fix For: 0.92.0
>
> Attachments:
> 0001-Add-some-backward-compatible-support-for-reading-old.patch,
> 0002-Make-sure-that-a-connection-always-uses-a-protocol.patch,
> 0003-Change-the-code-used-when-serializing-HTableDescript.patch, 5204-92.txt,
> 5204-trunk.txt, 5204.addendum
>
>
> Attached are 3 patches that are necessary to allow compatibility between
> HBase 0.90.x (and previous releases) and HBase 0.92.0.
> First of all, I'm well aware that 0.92.0 RC4 has been thumbed up by a lot of
> people and would probably wind up being released as 0.92.0 tomorrow, so I
> sincerely apologize for creating this issue so late in the process. I spent
> a lot of time trying to work around the quirks of 0.92 but once I realized
> that with a few very quasi-trivial changes compatibility would be made
> significantly easier, I immediately sent these 3 patches to Stack, who
> suggested I create this issue.
> The first patch is required as without it clients sending a 0.90-style RPC to
> a 0.92-style server causes the server to die uncleanly. It seems that 0.92
> ships with {{\-XX:OnOutOfMemoryError="kill \-9 %p"}}, and when a 0.92 server
> fails to deserialize a 0.90-style RPC, it attempts to allocate a large buffer
> because it doesn't read fields of 0.90-style RPCs properly. This allocation
> attempt immediately triggers an OOME, which causes the JVM to die abruptly of
> a {{SIGKILL}}. So whenever a 0.90.x client attempts to connect to HBase, it
> kills whichever RS is hosting the {{\-ROOT-}} region.
> The second patch fixes a bug introduced by HBASE-2002, which added support
> for letting clients specify what "protocol" they want to speak. If a client
> doesn't properly specify what protocol to use, the connection's {{protocol}}
> field will be left {{null}}, which causes any subsequent RPC on that
> connection to trigger an NPE in the server, even though the connection was
> successfully established from the client's point of view. The fix is to
> simply give the connection a default protocol, by assuming the client meant
> to speak to a RegionServer.
> The third patch fixes an oversight that slipped in HBASE-451, where a change
> to {{HbaseObjectWritable}} caused all the codes used to serialize
> {{Writables}} to shift by one. This was carefully avoided in other changes
> such as HBASE-1502, which cleanly removed entries for {{HMsg}} and
> {{HMsg[]}}, so I don't think this breakage in HBASE-451 was intended.
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