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Kafka, mail # dev - Troubles with compressed message set


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David Arthur 2013-01-30, 15:27
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Re: Troubles with compressed message set
Jay Kreps 2013-01-30, 16:19
Hi David,

MessageSets aren't size delimited because that format is shared with
producer/consumer and the kafka log itself. The log itself is just a big
sequence of messages and any subset that begins and ends at valid message
boundaries is a valid message set. This means that message sets are size
prefixed only as part of the request/response. Not sure if that is what you
are asking?

It's hard to see the cause of the error you describe. I don't suppose you
could send me a snapshot of your client to reproduce locally?

-Jay
On Wed, Jan 30, 2013 at 7:26 AM, David Arthur <[EMAIL PROTECTED]> wrote:

> I'm working on a client and I'm running into difficulties with compressed
> message sets. I am able to produce them fine, but when I go to fetch them,
> things seem strange.
>
> I am sending a message who's value is a compressed message set. The inner
> message set contains a single message. Specifically what looks weird is
> that the key of the top message looks corrupt. Here is a trace of my
> payloads:
>
> https://gist.github.com/**bf134906f6559b0f54ad<https://gist.github.com/bf134906f6559b0f54ad>
>
> See the "???" down in the FetchResponse for what I mean. Also the magic
> byte and attributes are wrong
>
> The data in the Kafka log for this partition matches what I get back for
> the MessageSet in the FetchResponse:
>
> \x00\x00\x00\x00\x00\x00\x00\**x00\x00\x00\x00;\xf5#\xc2N\**
> x00\x01\xff\xff\xff\xff\x00\**x00\x00-\x1f\x8b\x08\x00\x00\**
> x00\x00\x00\x00\x00c`\x80\x03\**x89P\xf7\xef\xccL
> \x16sZ~>\x90bw\x8f\xf2\x0c\**x08HM\x01\x00\xc5\x93\xd3<$\**x00\x00\x00
>
> Another bit of weirdness here is how MessageSets are encoded. Everywhere
> else in the API, we prefix a repeated element with a size of int32. When
> encoding MessageSets, if I follow this convention, Kafka rejects the
> produce request - if I exclude that int32 it works fine. I don't know if
> this was intentional or not, but it is somewhat annoying and inconsistent.
> When decoding MessageSets, I have to do-while instead of iterate a known
> number of times.
>
> Cheers
> -David
>

 
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David Arthur 2013-01-30, 21:00
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Jay Kreps 2013-01-30, 21:17
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David Arthur 2013-01-30, 21:23
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David Arthur 2013-01-30, 21:07