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https://issues.apache.org/jira/browse/HBASE-9681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13788255#comment-13788255
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Andrew Purtell commented on HBASE-9681:
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So to modify the OP with Elliot's suggestion:
The client can optionally send a message, a manufactured "call" that would
otherwise be invalid in some way, to the server asking for a list of supported
cell codecs, and also optionally a preference ordered list of the codecs it
wants. An older server should simply send back an error because the request is
invalid except to servers supporting this feature.
If the preference ordered list was provided, the server should enable the most
preferred codec available for all further communication on the connection and
send back a call response acknowledging the change and indicating which codec
is in use, or an error indication if something went wrong.
If a preference ordered list was not provided, or if no codec on the client's
list was available, the server should send back a list of available codecs. The
client can optionally send another message, a manufactured "call" that would
otherwise be invalid in some way, to the server asking for it to use one of the
codecs from the server supplied list for all further communication. Otherwise
the server will continue to use the default codec. The server will send back a
call response acknowledging the change or an error indication if the request
cannot be honored.
Suggestions for error handling:
- Once codec negotiation is initiated by the client, if the client and server
can't agree on a codec then the connection setup should fail with a big fat
ERROR in the logs on the server and client sides both.
- We should not do anything about incompatible default codecs if codec
negotiation is disabled (either due to older servers, or older clients, or a
configuration toggle). Connection setup should proceed, but there will be
failures later.
> Basic codec negotiation
> -----------------------
>
> Key: HBASE-9681
> URL: https://issues.apache.org/jira/browse/HBASE-9681
> Project: HBase
> Issue Type: Sub-task
> Affects Versions: 0.98.0
> Reporter: Andrew Purtell
>
> Basic codec negotiation:
> There should be a default codec used for cell encoding over the RPC
> connection. This should be configurable in the site file.
> The client can optionally send a message, a manufactured "call" that would
> otherwise be invalid in some way, to the server asking for a list of
> supported cell codecs. An older server should simply send back an error
> because the request is invalid except to servers supporting this feature. A
> server supporting this feature should send back the requested information or
> an error indication if something went wrong.
> The client can optionally send a message, a manufactured "call" that would
> otherwise be invalid in some way, to the server asking for it to use a given
> codec for all further communication. Otherwise the server will continue to
> use the default codec. The server will send back a call response
> acknowledging the change or an error indication if the request cannot be
> honored.
> Server configuration should support mappings from one codec type to another.
> We need to handle the case where the server has a codec available that
> extends the requested type but overrides some behavior in the base class, and
> this is what should be used in lieu of the base type. It must also be
> possible to choose an alternate default codec which stands in for the default
> codec, is compatible with client expectations, but changes the server side
> behavior as needed in the absence of negotiation.
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