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Kafka, mail # dev - Troubles with compressed message set


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Re: Troubles with compressed message set
David Arthur 2013-01-30, 21:23

On 1/30/13 4:17 PM, Jay Kreps wrote:
> Ah, yes, the decision since we were making a breaking change to the
> protocol to just reset all the versions to 0.
Excellent, I shall purge my 0.7x compatible code at once :)
> But if you are trying to
> handle both cases from the same code that will be hard.
>
> -Jay
>
>
> On Wed, Jan 30, 2013 at 12:59 PM, David Arthur <[EMAIL PROTECTED]> wrote:
>
>> Jay,
>>
>> Figured it out.
>>
>> In Message.scala, CurrentMagicValue is set to 0; should be 2. This was
>> causing my client to attempt to decode it as a v0 message. Changing the
>> value to 2 solved my problem. Seems like a trivial change, so I'll let you
>> decided if you want a Jira or not.
>>
>>  From my previous example, https://gist.github.com/**
>> bf134906f6559b0f54ad#file-**gistfile1-txt-L71<https://gist.github.com/bf134906f6559b0f54ad#file-gistfile1-txt-L71>should be 2
>>
>> -David
>>
>> messages to set their offsets
>>
>> On 1/30/13 11:18 AM, Jay Kreps wrote:
>>
>>> 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>
>>>> <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
>>>>
>>>>