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From Dana Powers <dana.pow...@rd.io>
Subject Re: Consumer and offset management support in 0.8.2 and 0.9
Date Mon, 05 Jan 2015 17:33:05 GMT
Hi Gwen, I am using/writing kafka-python to construct api requests and have
not dug too deeply into the server source code.  But I believe it is
kafka/api/OffsetCommitRequest.scala and specifically the readFrom method
used to decode the wire protocol.

-Dana
OffsetCommitRequest has two constructors now:

For version 0:
 OffsetCommitRequest(String groupId, Map<TopicPartition,
PartitionData> offsetData)

And version 1:
OffsetCommitRequest(String groupId, int generationId, String
consumerId, Map<TopicPartition, PartitionData> offsetData)

None of them seem to require timestamps... so I'm not sure where you
see that this is required. Can you share an example?

Gwen

On Sun, Jan 4, 2015 at 11:15 PM, Dana Powers <dana.powers@rd.io> wrote:
> Hi Joel,
>
> I'm looking more closely at the OffsetCommitRequest wire protocol change
> you mentioned below, and I cannot figure out how to explicitly construct a
> request with the earlier version.  Should the api version be different for
> requests that do not include it and/or servers that do not support the
> timestamp field?  It looks like 0.8.1.1 did not include the timestamp
field
> and used api version 0.  But 0.8.2-beta seems to now require timestamps
> even when I explicitly encode OffsetCommitRequest api version 0 (server
> logs a BufferUnderflowException).
>
> Is this the expected server behavior?  Can you provide any tips on how
> third-party clients should manage the wire-protocol change for this api
> method (I'm working on kafka-python)?
>
> Thanks,
>
> -Dana
>
> On Tue, Nov 18, 2014 at 1:27 PM, Joel Koshy <jjkoshy.w@gmail.com> wrote:
>
>> Yes it should be backwards compatible. So for e.g., you should be able
>> to use an 0.8.1 client with an 0.8.2 broker. In general, you should
>> not upgrade your clients until after the brokers have been upgraded.
>> However, you can point an 0.8.2 client at an 0.8.1 broker. One wire
>> protocol change I'm aware of is the OffsetCommitRequest.  There is a
>> change in the OffsetCommitRequest format (KAFKA-1634) although you can
>> explicitly construct an OffsetCommitRequest with the earlier version.
>>
>> Thanks,
>>
>> Joel
>>
>> On Tue, Nov 18, 2014 at 03:39:41PM -0500, Marius Bogoevici wrote:
>> > Hi Joel,
>> >
>> > Thanks for all the clarifications!  Just another question on this: will
>> > 0.8.2 be backwards compatible with 0.8.1, just as 0.8.1 was with 0.8?
>> > Generally speaking, would there be any concerns with using the 0.8.2
>> > consumer with a 0.8.1 broker, for instance?
>> >
>> > Marius
>> >
>> > On Tue, Nov 18, 2014 at 2:55 PM, Joel Koshy <jjkoshy.w@gmail.com>
wrote:
>> >
>> > > Inline..
>> > >
>> > > On Tue, Nov 18, 2014 at 04:26:04AM -0500, Marius Bogoevici wrote:
>> > > > Hello everyone,
>> > > >
>> > > > I have a few questions about the current status and future of the
>> Kafka
>> > > > consumers.
>> > > >
>> > > > We have been working to adding Kafka support in Spring XD [1],
>> currently
>> > > > using the high level consumer via Spring Integration Kafka [2]. We
>> are
>> > > > working on adding features such as:
>> > > > - the ability to control offsets/replay topics;
>> > > > - the ability to control partition allocation across multiple
>> consumers;
>> > > >
>> > > > We are currently at version 0.8.1.1, so using the simple consumer
is
>> a
>> > > > pretty straightforward choice right now. However, in the light of
the
>> > > > upcoming consumer changes for 0.8.2 and 0.9, I have a few
questions:
>> > > >
>> > > > 1) With respect to the consumer redesign for 0.9, what is the
future
>> of
>> > > the
>> > > > Simple Consumer and High Level Consumer? To my best understanding,
>> the
>> > > > existing high level consumer API will be deprecated in favour of
the
>> new
>> > > > consumer API. What is the future of the Simple Consumer, in this
>> case? it
>> > > > will continue to exist as a low-level API implementing the Kafka
>> protocol
>> > > > [3] and providing the building blocks for the new consumer, or will
>> it be
>> > > > deprecated as well?
>> > >
>> > > The new consumer will subsume both use-cases (simple and high-level).
>> > > You can still use the old SimpleConsumer if you wish - i.e., the wire
>> > > protocol for fetch and other requests will still be supported.
>> > >
>> > > >
>> > > > 2) Regarding the new consumer: the v0.8.2 codebase contains an
early
>> > > > implementation of it, but since this a feature scheduled only for
>> 0.9,
>> > > what
>> > > > is its status as well? Is it included only as a future reference
and
>> for
>> > > > stabilizing the API?
>> > >
>> > > It is a WIP so you cannot really use it.
>> > >
>> > > > 3) Obviously, offset management is a concern if using the simple
>> > > consumer,
>> > > > so - wondering about the Offset Management API as well. The Kafka
>> > > protocol
>> > > > document specifically indicates that it will be fully functional in
>> 0.8.2
>> > > > [4] - however, a functional implementation is already available in
>> > > 0.8.1.1
>> > > > (accessible via the SimpleConsumer API but not documented in [5]).
>> Again,
>> > > > trying to understand the extent of what 0.8.1.1 already supports
>> > > > (ostensibly, the offset manager support seems to have been added
>> only in
>> > > > 0.8.2 - please correct me if I am wrong), and whether if it is
>> > > recommended
>> > > > for use in production in any form (with the caveats that accompany
>> the
>> > > use
>> > > > of ZooKeeper).
>> > >
>> > > In 0.8.2 the OffsetCommitRequest and OffsetFetchRequest will use
Kafka
>> > > as the offsets storage mechanism (not zookeeper). High-level Java
>> > > consumers can choose to store offsets in ZooKeeper instead by setting
>> > > offsets.storage=zookeeper
>> > >
>> > > However, if you are using the simple consumer and wish to store
>> > > offsets in ZooKeeper you will need to commit to ZooKeeper directly.
>> > > You can use ZkUtils in the kafka.utils package for this.
>> > >
>> > > If you wish to move to Kafka-based offsets we will be adding a new
>> > > OffsetsClient that can be used to commit/fetch offsets to/from Kafka.
>> > > This is currently not listed as a blocker for 0.8.2 but I think we
>> > > should include it. I will update that ticket.
>> > >
>> > > > 4) Trying to interpret the existing examples in [6] and the
comments
>> on
>> > > [7]
>> > > > - the version of the Offset Management API that exists in 0.8.1.1
is
>> > > using
>> > > > ZooKeeper - whereas ZooKeeper will be optional in 0.8.2 - to be
>> replaced
>> > > by
>> > > > Kafka, and phased out if possible. To my understanding, the switch
>> > > between
>> > > > the two will be controlled by the broker configuration (along with
>> other
>> > > > parameters that control the performance of offset queues. Is that
>> > > correct?
>> > >
>> > > The switch is a client-side configuration. That wiki is not
>> > > up-to-date. The most current documentation is available as a patch in
>> > > https://issues.apache.org/jira/browse/KAFKA-1729
>> > >
>> > > > 5) Also, wondering about the timeline of 0.8.2 - according to the
>> > > roadmaps
>> > > > it should be released relatively shortly. Is that correct?
>> > >
>> > > Yes - once the blockers are ironed out.
>> > >
>> > > >
>> > > > Thanks,
>> > > > Marius
>> > > >
>> > > > [1] http://projects.spring.io/spring-xd/
>> > > > [2] https://github.com/spring-projects/spring-integration-kafka
>> > > > [3]
>> > > >
>> > >
>>
https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol
>> > > > [4]
>> > > >
>> > >
>>
https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol#AGuideToTheKafkaProtocol-OffsetCommit/FetchAPI
>> > > > [5]
http://kafka.apache.org/082/documentation.html#simpleconsumerapi
>> > > > [6]
>> > > >
>> > >
>>
https://cwiki.apache.org/confluence/display/KAFKA/Committing+and+fetching+consumer+offsets+in+Kafka
>> > > > [7] https://issues.apache.org/jira/browse/KAFKA-1729
>> > >
>> > >
>>
>>

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