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https://issues.apache.org/jira/browse/HBASE-3581?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13002281#comment-13002281
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Benoit Sigoure commented on HBASE-3581:
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-1: Can we *please* find a way of making this change such that clients can
still support the "old" protocol and the new one at the same time?
For instance, after sending the "hello" header ("hrpc3" + creds) maybe the
server could reply (right now it doesn't) and say "hey, here's my version
info". Because you can't use the {{getProtocolVersion}} RPC to find about this
incompatibility.
Other possibility: swap the errorFlag and the size, and use an extra bit in the
error flag, not to indicate an error but to indicate that the size follows. If
we do this, we should refer to "errorFlag" as just "flag" since it's not going
to be only about errors anymore.
> hbase rpc should send size of response
> --------------------------------------
>
> Key: HBASE-3581
> URL: https://issues.apache.org/jira/browse/HBASE-3581
> Project: HBase
> Issue Type: Improvement
> Reporter: ryan rawson
> Assignee: ryan rawson
> Fix For: 0.92.0
>
> Attachments: HBASE-rpc-response.txt
>
>
> The RPC reply from Server->Client does not include the size of the payload,
> it is framed like so:
> <i32> callId
> <byte> errorFlag
> <byte[]> data
> The data segment would contain enough info about how big the response is so
> that it could be decoded by a writable reader.
> This makes it difficult to write buffering clients, who might read the entire
> 'data' then pass it to a decoder. While less memory efficient, if you want to
> easily write block read clients (eg: nio) it would be necessary to send the
> size along so that the client could snarf into a local buf.
> The new proposal is:
> <i32> callId
> <i32> size
> <byte> errorFlag
> <byte[]> data
> the size being sizeof(data) + sizeof(errorFlag).
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