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From Jay Kreps <jay.kr...@gmail.com>
Subject Re: versionId in responses (and general API versioning questions)
Date Wed, 13 Feb 2013 21:08:22 GMT
Hey David,

We ended up not versioning the response, instead the version must
correspond to the request version.

This makes sense from the client point of view. If you send a request
using version X of the protocol you know you will get a response in
format X. Separately versioning the response would seem to indicate
that the server is allowed to send back a different version of the
response. This means the client has to check this and handle old
response versions (and what would it even do with newer versions?).
Instead we thought it makes more sense to make the server deal with
compatibility only. So the versioning is at the request/response pair
and the server is required to always send the correct version of the
response for all supported request versions.

I just noticed that your responses for the offset apis actually have a
version. We should probably remove that before the release.


On Wed, Feb 13, 2013 at 12:48 PM, David Arthur <mumrah@gmail.com> wrote:
> Just noticed that most of the API response structs do not include the
> ApiVersion. This will make it hard for clients to determine how to handle
> responses once the APIs start getting updated (which is pretty much
> inevitable).
> I'd propose we update the standard response envelope to include it
> Response => ApiVersion CorrelationId ResponseMessage
>   ApiVersion => int16
>   CorrelationId => int32
>   ResponseMessage => ...
> Otherwise, it seems we must freeze the response formats forever.
> Another thought is that the server should return the same version of the API
> that was requested (if a client sends in v1, then presumably it does know
> about any future versions...). How will this work? This seems to imply
> backwards compat for the APIs like Avro.
> Thoughts?
> -David

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