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 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 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.
> > >
> > >
