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 <jjkosh...@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 <jjkosh...@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 > > > > > > > >
