>From offline discussion, the eventual conclusion is to use a top-level
Consumer#getMetadata() API to fetch the latest group metadata information
for offset fencing, so that we only call initTransaction once in lifetime.
Since no further question is raised on this thread, I will start vote
today. In the meantime, still feel free to make comments on the discussion
thread, thank you!
Boyang
On Sun, Aug 25, 2019 at 11:43 PM Boyang Chen <reluctanthero...@gmail.com>
wrote:
> Hey Guozhang and Jason,
>
> I'm ok with either way. Thinking of Guozhang's approach, it is simpler to
> implement a consumer-producer if we avoid callback pattern and only do the
> group metadata initialization once, however the access pattern of consumer
> rebalance state is scattered, which means we get both rebalance listener
> and metadata getter. Jason's approach overloaded the initTransactions API,
> which could be more confusing as it already has been today. Comparing the
> two here, I'm inclined to Guozhang's approach as it is not conclusive to
> say a new metadata getter class will confuse any user, with a sacrifice in
> the cleanness of future implementation around consumer state. WDYT?
>
> Boyang
>
> On Wed, Aug 14, 2019 at 10:45 AM Guozhang Wang <wangg...@gmail.com> wrote:
>
>> My main concern is to require the overloaded `initTransactions` to be
>> called repeatedly while the original `initTransactions` still called once
>> throughout the life time, which is a bit confusing.
>>
>> Looking into the current POC PR, we actually only need the latest
>> generation id when fetching offsets, so we can just make the GroupMetadata
>> returned from the consumer a wrapper of the underlying values, and the
>> getters of this object would always return the latest value.
>> The values would be reset internally within the rebalances; and then the
>> new `initTransactions` would still only be called once.
>>
>> Guozhang
>>
>>
>> On Wed, Aug 14, 2019 at 9:53 AM Jason Gustafson <ja...@confluent.io>
>> wrote:
>>
>> > Yeah, my reasoning is that the group metadata is only relevant to the
>> > subscription API. So it makes sense to only expose it to the rebalance
>> > listener.
>> >
>> > One option we could consider is bring back the `initTransactions`
>> overload.
>> > Then usage looks something like this:
>> >
>> > consumer.subscribe(topics, new RebalanceListener() {
>> > void onGroupJoined(GroupMetadata metadata) {
>> > producer.initTransactions(metadata);
>> > }
>> > }
>> >
>> > That seems pretty clean. What do you think?
>> >
>> > -Jason
>> >
>> > On Tue, Aug 13, 2019 at 6:07 PM Boyang Chen <reluctanthero...@gmail.com
>> >
>> > wrote:
>> >
>> > > Hey Guozhang,
>> > >
>> > > thanks for the suggestion. Could you elaborate more on why defining a
>> > > direct consumer API would be easier? The benefit of reusing consumer
>> > > rebalance listener is to consolidate the entry point of consumer
>> internal
>> > > states. Compared with letting consumer generate a deep-copy of
>> metadata
>> > > every time we call #sendOffsetsToTransactions, using a callback seems
>> > > reducing unnecessary updates towards the metadata. WDYT?
>> > >
>> > > Boyang
>> > >
>> > > On Tue, Aug 13, 2019 at 2:14 PM Guozhang Wang <wangg...@gmail.com>
>> > wrote:
>> > >
>> > > > Hi Boyang, Jason,
>> > > >
>> > > > If we are going to expose the generation id / group.instance id etc
>> > > anyways
>> > > > I think its slightly better to just add a new API on KafkaConsumer
>> > > > returning the ConsumerGroupMetadata (option 3) than passing it in
>> on an
>> > > > additional callback of ConsumerRebalanceListener.
>> > > > It feels easier to leverage, than requiring users to pass in the
>> > > listener.
>> > > >
>> > > > Guozhang
>> > > >
>> > > > On Mon, Aug 12, 2019 at 3:41 PM Boyang Chen <
>> > reluctanthero...@gmail.com>
>> > > > wrote:
>> > > >
>> > > > > Thanks Jason, the intuition behind defining a separate callback
>> > > function
>> > > > is
>> > > > > that, with KIP-429 we no longer guarantee to call
>> > > OnPartitionsAssigned()
>> > > > or
>> > > > > OnPartitionsRevoked() with each rebalance. Our requirement is to
>> be
>> > > > > up-to-date with group metadata such as generation information, so
>> > > > callback
>> > > > > like onGroupJoined() would make more sense as it should be invoked
>> > > after
>> > > > > every successful rebalance.
>> > > > >
>> > > > > Best,
>> > > > > Boyang
>> > > > >
>> > > > > On Mon, Aug 12, 2019 at 2:02 PM Jason Gustafson <
>> ja...@confluent.io>
>> > > > > wrote:
>> > > > >
>> > > > > > Hey Boyang,
>> > > > > >
>> > > > > > I favor option 4 as well. It's a little more cumbersome than 3
>> for
>> > > this
>> > > > > use
>> > > > > > case, but it seems like a cleaner separation of concerns. The
>> > > rebalance
>> > > > > > listener is already concerned with events affecting the
>> assignment
>> > > > > > lifecycle and group membership. I think the only thing I'm
>> > wondering
>> > > is
>> > > > > > whether it should be a separate callback as you've suggested,
>> or if
>> > > it
>> > > > > > would make sense to overload `onPartitionsAssigned`. If it's
>> > > separate,
>> > > > > > maybe a name like `onGroupJoined` would be clearer?
>> > > > > >
>> > > > > > Thanks,
>> > > > > > Jason
>> > > > > >
>> > > > > >
>> > > > > >
>> > > > > > On Thu, Aug 8, 2019 at 10:59 PM Boyang Chen <
>> > > > reluctanthero...@gmail.com>
>> > > > > > wrote:
>> > > > > >
>> > > > > > > Thank you Jason. We had some offline discussion on properly
>> > keeping
>> > > > > group
>> > > > > > > metadata up to date, and here are some of our options
>> > brainstormed:
>> > > > > > > 1. Let the caller of `sendOffsetsToTransaction(offset,
>> metadata)`
>> > > > > > maintain
>> > > > > > > the ever-changing group metadata. This could be done on stream
>> > > side,
>> > > > > but
>> > > > > > > for non-stream EOS the sample code will become complicated as
>> the
>> > > > user
>> > > > > > > needs to implement the partition assignor interface to get the
>> > > update
>> > > > > > from
>> > > > > > > `onAssignment`
>> > > > > > >
>> > > > > > > 2. Get a new API on producer like
>> > `refreshGroupMetadata(metadata)`.
>> > > > > This
>> > > > > > is
>> > > > > > > similar to option 1 except that now in the partition assignor
>> > > > callback
>> > > > > we
>> > > > > > > could straightly pass in the producer instance, which
>> simplifies
>> > > the
>> > > > > > > non-stream EOS, however this new API seems weird to define on
>> > > > producer.
>> > > > > > >
>> > > > > > > 3. Make an accessing interface to group metadata, or just
>> expose
>> > > the
>> > > > > > group
>> > > > > > > metadata through a consumer API like
>> `consumer.GroupMetadata()`.
>> > > This
>> > > > > is
>> > > > > > > the old way which avoids the users’ effort to implement
>> partition
>> > > > > > assignor
>> > > > > > > directly.
>> > > > > > >
>> > > > > > > 4. Expose the group metadata through rebalance listener, which
>> > is a
>> > > > > more
>> > > > > > > well-known and adopted callback interface. We could do sth
>> like
>> > > > > > > `onGroupMetadataUpdated(ConsumerGroupMetadata metadata)`
>> > > > > > >
>> > > > > > > To simplify the code logic, we believe option 3 & 4 are better
>> > > > > solutions,
>> > > > > > > and of which I slightly prefer option 4 as it is the most
>> clean
>> > > > > solution
>> > > > > > > with less intrusion to both consumer and producer APIs.
>> > > > > > >
>> > > > > > > WDYT?
>> > > > > > >
>> > > > > > > Boyang
>> > > > > > >
>> > > > > > >
>> > > > > > >
>> > > > > > >
>> > > > > > > On Wed, Aug 7, 2019 at 9:20 AM Jason Gustafson <
>> > ja...@confluent.io
>> > > >
>> > > > > > wrote:
>> > > > > > >
>> > > > > > > > Hi Boyang,
>> > > > > > > >
>> > > > > > > > > We already persist member.id, instance.id and
>> generation.id
>> > in
>> > > > the
>> > > > > > > > offset
>> > > > > > > > topic, what extra fields we need to store?
>> > > > > > > >
>> > > > > > > > Yeah, you're right. I was a little confused and thought this
>> > > > > > information
>> > > > > > > > was needed by the transaction coordinator.
>> > > > > > > >
>> > > > > > > > > This should be easily done on the stream side as we have
>> > > > > > > > StreamsPartitionAssignor to reflect metadata changes upon
>> > > > > > > #onAssignment(),
>> > > > > > > > but non-stream user has to code the callback by hand, do you
>> > > think
>> > > > > the
>> > > > > > > > convenience we sacrifice here worth the simplification
>> benefit?
>> > > > > > > >
>> > > > > > > > Either way, you need a reference to the consumer. I was
>> mostly
>> > > just
>> > > > > > > > thinking it would be better to reduce the integration point
>> to
>> > > its
>> > > > > > > minimum.
>> > > > > > > > Have you thought through the implications of needing to keep
>> > > > around a
>> > > > > > > > reference to the consumer in the producer? What if it gets
>> > > closed?
>> > > > It
>> > > > > > > seems
>> > > > > > > > better not to have to think about these cases.
>> > > > > > > >
>> > > > > > > > -Jason
>> > > > > > > >
>> > > > > > > > On Tue, Aug 6, 2019 at 9:53 PM Boyang Chen <
>> > > > > reluctanthero...@gmail.com
>> > > > > > >
>> > > > > > > > wrote:
>> > > > > > > >
>> > > > > > > > > Thank you for the suggestions Jason. And a side note for
>> > > > Guozhang,
>> > > > > I
>> > > > > > > > > updated the KIP to reflect the dependency on 447.
>> > > > > > > > >
>> > > > > > > > > On Tue, Aug 6, 2019 at 11:35 AM Jason Gustafson <
>> > > > > ja...@confluent.io>
>> > > > > > > > > wrote:
>> > > > > > > > >
>> > > > > > > > > > Hi Boyang, thanks for the updates. I have a few more
>> > > comments:
>> > > > > > > > > >
>> > > > > > > > > > 1. We are adding some new fields to TxnOffsetCommit to
>> > > support
>> > > > > > > > > group-based
>> > > > > > > > > > fencing. Do we need these fields to be persisted in the
>> > > offsets
>> > > > > > topic
>> > > > > > > > to
>> > > > > > > > > > ensure that the fencing still works after a coordinator
>> > > > failover?
>> > > > > > > > > >
>> > > > > > > > > > We already persist member.id, instance.id and
>> > generation.id
>> > > in
>> > > > > the
>> > > > > > > > > offset
>> > > > > > > > > topic, what extra fields we need to store?
>> > > > > > > > >
>> > > > > > > > >
>> > > > > > > > > > 2. Since you are proposing a new `groupMetadata` API,
>> have
>> > > you
>> > > > > > > > considered
>> > > > > > > > > > whether we still need the `initTransactions` overload?
>> > > Another
>> > > > > way
>> > > > > > > > would
>> > > > > > > > > be
>> > > > > > > > > > to pass it through the `sendOffsetsToTransaction` API:
>> > > > > > > > > >
>> > > > > > > > > > void sendOffsetsToTransaction(Map<TopicPartition,
>> > > > > > OffsetAndMetadata>
>> > > > > > > > > > offsets, GroupMetadata groupMetadata) throws
>> > > > > > > > > > ProducerFencedException, IllegalGenerationException;
>> > > > > > > > > >
>> > > > > > > > > > This seems a little more consistent with the current API
>> > and
>> > > > > avoids
>> > > > > > > the
>> > > > > > > > > > direct dependence on the Consumer in the producer.
>> > > > > > > > > >
>> > > > > > > > > > Note that although we avoid one dependency to consumer,
>> > > > producer
>> > > > > > > needs
>> > > > > > > > to
>> > > > > > > > > periodically update
>> > > > > > > > > its group metadata, or in this case the caller of
>> > > > > > > > > *sendOffsetsToTransaction(Map<TopicPartition,
>> > > > > > > > > OffsetAndMetadata>*
>> > > > > > > > > *offsets, GroupMetadata groupMetadata) *is responsible for
>> > > > getting
>> > > > > > the
>> > > > > > > > > latest value of group metadata.
>> > > > > > > > > This should be easily done on the stream side as we have
>> > > > > > > > > StreamsPartitionAssignor to reflect metadata changes upon
>> > > > > > > > #onAssignment(),
>> > > > > > > > > but non-stream user has to code the callback by hand, do
>> you
>> > > > think
>> > > > > > the
>> > > > > > > > > convenience we sacrifice here worth the simplification
>> > benefit?
>> > > > > > > > >
>> > > > > > > > >
>> > > > > > > > > > 3. Can you clarify the behavior of the clients when the
>> > > brokers
>> > > > > do
>> > > > > > > not
>> > > > > > > > > > support the latest API versions? This is both for the
>> new
>> > > > > > > > TxnOffsetCommit
>> > > > > > > > > > and the OffsetFetch APIs. I guess the high level idea in
>> > > > streams
>> > > > > is
>> > > > > > > to
>> > > > > > > > > > detect broker support before instantiating the producer
>> and
>> > > > > > > consumer. I
>> > > > > > > > > > think that's reasonable, but we might need some approach
>> > for
>> > > > > > > > non-streams
>> > > > > > > > > > use cases. One option I was considering is enforcing the
>> > > latest
>> > > > > > > version
>> > > > > > > > > > through the new `sendOffsetsToTransaction` API.
>> Basically
>> > > when
>> > > > > you
>> > > > > > > use
>> > > > > > > > > the
>> > > > > > > > > > new API, we require support for the latest
>> TxnOffsetCommit
>> > > > > version.
>> > > > > > > > This
>> > > > > > > > > > puts some burden on users, but it avoids breaking
>> > correctness
>> > > > > > > > assumptions
>> > > > > > > > > > when the new APIs are in use. What do you think?
>> > > > > > > > > >
>> > > > > > > > > Yes, I think we haven't covered this case, so the plan is
>> to
>> > > > crash
>> > > > > > the
>> > > > > > > > > non-stream application when the job is using new
>> sendOffsets
>> > > API.
>> > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > > > -Jason
>> > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > > > On Mon, Aug 5, 2019 at 6:06 PM Boyang Chen <
>> > > > > > > reluctanthero...@gmail.com
>> > > > > > > > >
>> > > > > > > > > > wrote:
>> > > > > > > > > >
>> > > > > > > > > > > Yep, Guozhang I think that would be best as passing
>> in an
>> > > > > entire
>> > > > > > > > > consumer
>> > > > > > > > > > > instance is indeed cumbersome.
>> > > > > > > > > > >
>> > > > > > > > > > > Just saw you updated KIP-429, I will follow-up to
>> change
>> > > 447
>> > > > as
>> > > > > > > well.
>> > > > > > > > > > >
>> > > > > > > > > > > Best,
>> > > > > > > > > > > Boyang
>> > > > > > > > > > >
>> > > > > > > > > > > On Mon, Aug 5, 2019 at 3:18 PM Guozhang Wang <
>> > > > > wangg...@gmail.com
>> > > > > > >
>> > > > > > > > > wrote:
>> > > > > > > > > > >
>> > > > > > > > > > > > okay I think I understand your concerns about
>> > > > > > > ConsumerGroupMetadata
>> > > > > > > > > > now:
>> > > > > > > > > > > if
>> > > > > > > > > > > > we still want to only call initTxns once, then we
>> > should
>> > > > > allow
>> > > > > > > the
>> > > > > > > > > > > whatever
>> > > > > > > > > > > > passed-in parameter to reflect the latest value of
>> > > > generation
>> > > > > > id
>> > > > > > > > > > whenever
>> > > > > > > > > > > > sending the offset fetch request.
>> > > > > > > > > > > >
>> > > > > > > > > > > > Whereas the current ConsumerGroupMetadata is a
>> static
>> > > > object.
>> > > > > > > > > > > >
>> > > > > > > > > > > > Maybe we can consider having an extended class of
>> > > > > > > > > ConsumerGroupMetadata
>> > > > > > > > > > > > whose values are updated from the consumer's
>> rebalance
>> > > > > > callback?
>> > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > > > Guozhang
>> > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > > > On Mon, Aug 5, 2019 at 9:26 AM Boyang Chen <
>> > > > > > > > > reluctanthero...@gmail.com
>> > > > > > > > > > >
>> > > > > > > > > > > > wrote:
>> > > > > > > > > > > >
>> > > > > > > > > > > > > Thank you Guozhang for the reply! I'm curious
>> whether
>> > > > > KIP-429
>> > > > > > > has
>> > > > > > > > > > > > reflected
>> > > > > > > > > > > > > the latest change on ConsumerGroupMetadata? Also
>> > > > regarding
>> > > > > > > > question
>> > > > > > > > > > > one,
>> > > > > > > > > > > > > the group metadata needs to be accessed via
>> callback,
>> > > > does
>> > > > > > that
>> > > > > > > > > mean
>> > > > > > > > > > we
>> > > > > > > > > > > > > need a separate producer API such like
>> > > > > > > > > > > > > "producer.refreshMetadata(groupMetadata)" to be
>> able
>> > to
>> > > > > > access
>> > > > > > > it
>> > > > > > > > > > > instead
>> > > > > > > > > > > > > of passing in the consumer instance?
>> > > > > > > > > > > > >
>> > > > > > > > > > > > > Boyang
>> > > > > > > > > > > > >
>> > > > > > > > > > > > > On Fri, Aug 2, 2019 at 4:36 PM Guozhang Wang <
>> > > > > > > wangg...@gmail.com
>> > > > > > > > >
>> > > > > > > > > > > wrote:
>> > > > > > > > > > > > >
>> > > > > > > > > > > > > > Thanks Boyang,
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > > > I've made another pass on KIP-447 as well as
>> > > > > > > > > > > > > > https://github.com/apache/kafka/pull/7078, and
>> > have
>> > > > some
>> > > > > > > minor
>> > > > > > > > > > > > comments
>> > > > > > > > > > > > > > about the proposed API:
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > > > 1. it seems instead of needing the whole
>> > > KafkaConsumer
>> > > > > > > object,
>> > > > > > > > > > you'd
>> > > > > > > > > > > > only
>> > > > > > > > > > > > > > need the "ConsumerGroupMetadata", in that case
>> can
>> > we
>> > > > > just
>> > > > > > > pass
>> > > > > > > > > in
>> > > > > > > > > > > that
>> > > > > > > > > > > > > > object into the initTxns call?
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > > > 2. the current trunk already has a public class
>> > named
>> > > > > > > > > > > > > > (ConsumerGroupMetadata)
>> > > > > > > > > > > > > > under o.a.k.clients.consumer created by
>> KIP-429. If
>> > > we
>> > > > > want
>> > > > > > > to
>> > > > > > > > > just
>> > > > > > > > > > > use
>> > > > > > > > > > > > > > that then maybe it makes less sense to declare a
>> > base
>> > > > > > > > > GroupMetadata
>> > > > > > > > > > > as
>> > > > > > > > > > > > we
>> > > > > > > > > > > > > > are already leaking such information on the
>> > assignor
>> > > > > > anyways.
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > > > Guozhang
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > > > On Tue, Jul 30, 2019 at 1:55 PM Boyang Chen <
>> > > > > > > > > > > > reluctanthero...@gmail.com>
>> > > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > Thank you Guozhang for the reply. We will
>> > consider
>> > > > the
>> > > > > > > > > interface
>> > > > > > > > > > > > change
>> > > > > > > > > > > > > > > from 429 as a backup plan for 447.
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > And bumping this thread for more discussion.
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > On Mon, Jul 22, 2019 at 6:28 PM Guozhang Wang
>> <
>> > > > > > > > > > wangg...@gmail.com>
>> > > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > On Sat, Jul 20, 2019 at 9:50 AM Boyang Chen
>> <
>> > > > > > > > > > > > > > reluctanthero...@gmail.com>
>> > > > > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > Thank you Guozhang for the suggestion! I
>> > would
>> > > > > > normally
>> > > > > > > > > > prefer
>> > > > > > > > > > > > > > naming a
>> > > > > > > > > > > > > > > > > flag corresponding to its functionality.
>> > Seems
>> > > to
>> > > > > me
>> > > > > > > > > > > > > > `isolation_level`
>> > > > > > > > > > > > > > > > > makes us another hop on information track.
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > Fair enough, let's use a separate flag
>> name
>> > > then
>> > > > :)
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > As for the generation.id exposure, I'm
>> fine
>> > > > > > leveraging
>> > > > > > > > the
>> > > > > > > > > > new
>> > > > > > > > > > > > API
>> > > > > > > > > > > > > > > from
>> > > > > > > > > > > > > > > > > 429, but however is that design finalized
>> > yet,
>> > > > and
>> > > > > > > > whether
>> > > > > > > > > > the
>> > > > > > > > > > > > API
>> > > > > > > > > > > > > > will
>> > > > > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > added on the generic Consumer<K, V>
>> > interface?
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > The current PartitionAssignor is inside
>> > > > `internals`
>> > > > > > > > package
>> > > > > > > > > > and
>> > > > > > > > > > > > in
>> > > > > > > > > > > > > > > > KIP-429
>> > > > > > > > > > > > > > > > we are going to create a new interface out
>> of
>> > > > > > `internals`
>> > > > > > > > to
>> > > > > > > > > > > really
>> > > > > > > > > > > > > > make
>> > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > public APIs, and as part of that we are
>> > > refactoring
>> > > > > > some
>> > > > > > > of
>> > > > > > > > > its
>> > > > > > > > > > > > > method
>> > > > > > > > > > > > > > > > signatures. I just feel some of the newly
>> > > > introduced
>> > > > > > > > classes
>> > > > > > > > > > can
>> > > > > > > > > > > be
>> > > > > > > > > > > > > > > reused
>> > > > > > > > > > > > > > > > in your KIP as well, i.e. just for code
>> > > > succinctness,
>> > > > > > but
>> > > > > > > > no
>> > > > > > > > > > > > > semantical
>> > > > > > > > > > > > > > > > indications.
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > Boyang
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > On Fri, Jul 19, 2019 at 3:57 PM Guozhang
>> > Wang <
>> > > > > > > > > > > > wangg...@gmail.com>
>> > > > > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > Boyang, thanks for the updated proposal!
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > 3.a. As Jason mentioned, with EOS
>> enabled
>> > we
>> > > > > still
>> > > > > > > need
>> > > > > > > > > to
>> > > > > > > > > > > > > augment
>> > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > offset fetch request with a boolean to
>> > > indicate
>> > > > > > "give
>> > > > > > > > me
>> > > > > > > > > an
>> > > > > > > > > > > > > > retriable
>> > > > > > > > > > > > > > > > > error
>> > > > > > > > > > > > > > > > > > code if there's pending offset, rather
>> than
>> > > > > sending
>> > > > > > > me
>> > > > > > > > > the
>> > > > > > > > > > > > > > committed
>> > > > > > > > > > > > > > > > > offset
>> > > > > > > > > > > > > > > > > > immediately". Personally I still feel
>> it is
>> > > > okay
>> > > > > to
>> > > > > > > > > > > piggy-back
>> > > > > > > > > > > > on
>> > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > ISOLATION_LEVEL boolean, but I'm also
>> fine
>> > > with
>> > > > > > > another
>> > > > > > > > > > > > > > > > > `await_transaction`
>> > > > > > > > > > > > > > > > > > boolean if you feel strongly about it.
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > 10. About the exposure of generation id,
>> > > there
>> > > > > may
>> > > > > > be
>> > > > > > > > > some
>> > > > > > > > > > > > > > > refactoring
>> > > > > > > > > > > > > > > > > work
>> > > > > > > > > > > > > > > > > > coming from KIP-429 that can benefit
>> > KIP-447
>> > > as
>> > > > > > well
>> > > > > > > > > since
>> > > > > > > > > > we
>> > > > > > > > > > > > are
>> > > > > > > > > > > > > > > > > wrapping
>> > > > > > > > > > > > > > > > > > the consumer subscription / assignment
>> data
>> > > in
>> > > > > new
>> > > > > > > > > classes.
>> > > > > > > > > > > > Note
>> > > > > > > > > > > > > > that
>> > > > > > > > > > > > > > > > > > current proposal does not `generationId`
>> > > since
>> > > > > with
>> > > > > > > the
>> > > > > > > > > > > > > cooperative
>> > > > > > > > > > > > > > > > > sticky
>> > > > > > > > > > > > > > > > > > assignor we think it is not necessary
>> for
>> > > > > > > correctness,
>> > > > > > > > > but
>> > > > > > > > > > > also
>> > > > > > > > > > > > > if
>> > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > agree
>> > > > > > > > > > > > > > > > > > it is okay to expose it we can
>> potentially
>> > > > > include
>> > > > > > it
>> > > > > > > > in
>> > > > > > > > > > > > > > > > > > `ConsumerAssignmentData` as well.
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > Guozhang
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > On Thu, Jul 18, 2019 at 3:55 PM Boyang
>> > Chen <
>> > > > > > > > > > > > > > > > reluctanthero...@gmail.com>
>> > > > > > > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > Thank you Jason for the ideas.
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > On Mon, Jul 15, 2019 at 5:28 PM Jason
>> > > > > Gustafson <
>> > > > > > > > > > > > > > > ja...@confluent.io>
>> > > > > > > > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > Hi Boyang,
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > Thanks for the updates. A few
>> comments
>> > > > below:
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > 1. The KIP mentions that `
>> > > > > > transaction.timeout.ms
>> > > > > > > `
>> > > > > > > > > > should
>> > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > reduced
>> > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > 10s.
>> > > > > > > > > > > > > > > > > > > > I think this makes sense for Kafka
>> > > Streams
>> > > > > > which
>> > > > > > > is
>> > > > > > > > > > tied
>> > > > > > > > > > > to
>> > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > consumer
>> > > > > > > > > > > > > > > > > > > > group semantics and uses a default
>> 10s
>> > > > > session
>> > > > > > > > > timeout.
>> > > > > > > > > > > > > > However,
>> > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > > > seems a
>> > > > > > > > > > > > > > > > > > > > bit dangerous to make this change
>> for
>> > the
>> > > > > > > producer
>> > > > > > > > > > > > generally.
>> > > > > > > > > > > > > > > Could
>> > > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > just
>> > > > > > > > > > > > > > > > > > > > change it for streams?
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > That sounds good to me.
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > 2. The new `initTransactions` API
>> > takes a
>> > > > > > > > `Consumer`
>> > > > > > > > > > > > > instance.
>> > > > > > > > > > > > > > I
>> > > > > > > > > > > > > > > > > think
>> > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > idea is to basically put in a
>> backdoor
>> > to
>> > > > > give
>> > > > > > > the
>> > > > > > > > > > > producer
>> > > > > > > > > > > > > > > access
>> > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > group generationId. It's not clear
>> to
>> > me
>> > > > how
>> > > > > > this
>> > > > > > > > > would
>> > > > > > > > > > > > work
>> > > > > > > > > > > > > > > given
>> > > > > > > > > > > > > > > > > > > package
>> > > > > > > > > > > > > > > > > > > > restrictions. I wonder if it would
>> be
>> > > > better
>> > > > > to
>> > > > > > > > just
>> > > > > > > > > > > expose
>> > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > state
>> > > > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > > need from the consumer. I know we
>> have
>> > > been
>> > > > > > > > reluctant
>> > > > > > > > > > to
>> > > > > > > > > > > do
>> > > > > > > > > > > > > > this
>> > > > > > > > > > > > > > > so
>> > > > > > > > > > > > > > > > > far
>> > > > > > > > > > > > > > > > > > > > because we treat the generationId
>> as an
>> > > > > > > > > implementation
>> > > > > > > > > > > > > detail.
>> > > > > > > > > > > > > > > > > > However, I
>> > > > > > > > > > > > > > > > > > > > think we might just bite the bullet
>> and
>> > > > > expose
>> > > > > > it
>> > > > > > > > > > rather
>> > > > > > > > > > > > than
>> > > > > > > > > > > > > > > > coming
>> > > > > > > > > > > > > > > > > up
>> > > > > > > > > > > > > > > > > > > > with a messy hack. Concepts such as
>> > > > memberIds
>> > > > > > > have
>> > > > > > > > > > > already
>> > > > > > > > > > > > > been
>> > > > > > > > > > > > > > > > > exposed
>> > > > > > > > > > > > > > > > > > > in
>> > > > > > > > > > > > > > > > > > > > the AdminClient, so maybe it is not
>> too
>> > > > bad.
>> > > > > > > > > > > Alternatively,
>> > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > could
>> > > > > > > > > > > > > > > > > > use
>> > > > > > > > > > > > > > > > > > > an
>> > > > > > > > > > > > > > > > > > > > opaque type. For example:
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > // public
>> > > > > > > > > > > > > > > > > > > > interface GroupMetadata {}
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > // private
>> > > > > > > > > > > > > > > > > > > > interface ConsumerGroupMetadata {
>> > > > > > > > > > > > > > > > > > > > final int generationId;
>> > > > > > > > > > > > > > > > > > > > final String memberId;
>> > > > > > > > > > > > > > > > > > > > }
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > // Consumer API
>> > > > > > > > > > > > > > > > > > > > public GroupMetadata
>> groupMetadata();
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > I am probably leaning toward just
>> > > exposing
>> > > > > the
>> > > > > > > > state
>> > > > > > > > > we
>> > > > > > > > > > > > need.
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > Yes, also to mention that Kafka
>> Streams
>> > > use
>> > > > > > > generic
>> > > > > > > > > > > > Cosnumer
>> > > > > > > > > > > > > > API
>> > > > > > > > > > > > > > > > > which
>> > > > > > > > > > > > > > > > > > > doesn't have rich
>> > > > > > > > > > > > > > > > > > > states like a full `KafkaConsumer`.
>> The
>> > > hack
>> > > > > will
>> > > > > > > not
>> > > > > > > > > > work
>> > > > > > > > > > > as
>> > > > > > > > > > > > > > > > expected.
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > Instead, just exposing the consumer
>> > > > > > generation.id
>> > > > > > > > > seems
>> > > > > > > > > > a
>> > > > > > > > > > > > way
>> > > > > > > > > > > > > > > easier
>> > > > > > > > > > > > > > > > > > work.
>> > > > > > > > > > > > > > > > > > > We could consolidate
>> > > > > > > > > > > > > > > > > > > the API and make it
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > 3. Given that we are already
>> providing a
>> > > way
>> > > > to
>> > > > > > > > > propagate
>> > > > > > > > > > > > group
>> > > > > > > > > > > > > > > state
>> > > > > > > > > > > > > > > > > > from
>> > > > > > > > > > > > > > > > > > > > the consumer to the producer, I
>> wonder
>> > if
>> > > > we
>> > > > > > may
>> > > > > > > as
>> > > > > > > > > > well
>> > > > > > > > > > > > > > include
>> > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > memberId and groupInstanceId. This
>> > would
>> > > > make
>> > > > > > the
>> > > > > > > > > > > > validation
>> > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > do
>> > > > > > > > > > > > > > > > > for
>> > > > > > > > > > > > > > > > > > > > TxnOffsetCommit consistent with
>> > > > OffsetCommit.
>> > > > > > If
>> > > > > > > > for
>> > > > > > > > > no
>> > > > > > > > > > > > other
>> > > > > > > > > > > > > > > > > benefit,
>> > > > > > > > > > > > > > > > > > at
>> > > > > > > > > > > > > > > > > > > > least this may help with debugging.
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > Yes, we could put them into the
>> > > GroupMetadata
>> > > > > > > struct.
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > 4. I like the addition of
>> > isolation_level
>> > > > to
>> > > > > > the
>> > > > > > > > > offset
>> > > > > > > > > > > > > fetch.
>> > > > > > > > > > > > > > At
>> > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > same
>> > > > > > > > > > > > > > > > > > > > time, its behavior is a bit
>> > inconsistent
>> > > > with
>> > > > > > how
>> > > > > > > > it
>> > > > > > > > > is
>> > > > > > > > > > > > used
>> > > > > > > > > > > > > in
>> > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > consumer generally. There is no
>> reason
>> > > for
>> > > > > the
>> > > > > > > > group
>> > > > > > > > > > > > > > coordinator
>> > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > ever
>> > > > > > > > > > > > > > > > > > > > expose aborted data, so this is
>> mostly
>> > > > about
>> > > > > > > > awaiting
>> > > > > > > > > > > > pending
>> > > > > > > > > > > > > > > > offset
>> > > > > > > > > > > > > > > > > > > > commits, not reading uncommitted
>> data.
>> > > > > Perhaps
>> > > > > > > > > instead
>> > > > > > > > > > of
>> > > > > > > > > > > > > > calling
>> > > > > > > > > > > > > > > > > this
>> > > > > > > > > > > > > > > > > > > > "isolation level," it should be more
>> > like
>> > > > > > > > > > > > > > > > "await_pending_transaction"
>> > > > > > > > > > > > > > > > > > or
>> > > > > > > > > > > > > > > > > > > > something like that?
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > Also, just to be clear, the consumer
>> > > would
>> > > > > > treat
>> > > > > > > > this
>> > > > > > > > > > as
>> > > > > > > > > > > an
>> > > > > > > > > > > > > > > > optional
>> > > > > > > > > > > > > > > > > > > field,
>> > > > > > > > > > > > > > > > > > > > right? So if the broker does not
>> > support
>> > > > the
>> > > > > > > latest
>> > > > > > > > > > > > > OffsetFetch
>> > > > > > > > > > > > > > > > API,
>> > > > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > > > > would silently revert to reading the
>> > old
>> > > > > data.
>> > > > > > > > > > Basically
>> > > > > > > > > > > it
>> > > > > > > > > > > > > > would
>> > > > > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > up
>> > > > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > the streams version probing logic to
>> > > ensure
>> > > > > > that
>> > > > > > > > the
>> > > > > > > > > > > > > > expectation
>> > > > > > > > > > > > > > > on
>> > > > > > > > > > > > > > > > > > this
>> > > > > > > > > > > > > > > > > > > > API fits with the usage of `
>> > > > transctional.id
>> > > > > `.
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > Sounds like a better naming to me,
>> > while
>> > > I
>> > > > > > think
>> > > > > > > it
>> > > > > > > > > > could
>> > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > shortened
>> > > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > `await_transaction`.
>> > > > > > > > > > > > > > > > > > > I think the field should be optional,
>> > too.
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > Thanks,
>> > > > > > > > > > > > > > > > > > > > Jason
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > On Mon, Jul 8, 2019 at 3:19 PM
>> Boyang
>> > > Chen
>> > > > <
>> > > > > > > > > > > > > > > > > reluctanthero...@gmail.com
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > Hey Guozhang,
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > I will correct my statement from
>> last
>> > > > > email.
>> > > > > > I
>> > > > > > > > > don't
>> > > > > > > > > > > > think
>> > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > read_committed (3.a) is necessary
>> to
>> > be
>> > > > > added
>> > > > > > > to
>> > > > > > > > > the
>> > > > > > > > > > > > > > > OffsetFetch
>> > > > > > > > > > > > > > > > > > > request,
>> > > > > > > > > > > > > > > > > > > > > as if we are using EOS
>> application,
>> > the
>> > > > > > > > underlying
>> > > > > > > > > > > > > consumers
>> > > > > > > > > > > > > > > > within
>> > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > group should always back off when
>> > there
>> > > > is
>> > > > > > > > pending
>> > > > > > > > > > > > offsets.
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > Let me know if you think this is
>> > > correct.
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > On Tue, Jul 2, 2019 at 3:21 PM
>> Boyang
>> > > > Chen
>> > > > > <
>> > > > > > > > > > > > > > > > > > reluctanthero...@gmail.com
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > > Thank you Guozhang for the
>> > questions,
>> > > > > > inline
>> > > > > > > > > > answers
>> > > > > > > > > > > > are
>> > > > > > > > > > > > > > > below.
>> > > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > > On Tue, Jul 2, 2019 at 3:14 PM
>> > Boyang
>> > > > > Chen
>> > > > > > <
>> > > > > > > > > > > > > > > > > > > reluctanthero...@gmail.com
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >> Hey all,
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >> I have done a fundamental
>> polish
>> > of
>> > > > > > KIP-447
>> > > > > > > > > > > > > > > > > > > > > >> <
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > >
>> > > > > > > >
>> > > > > > >
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-447%3A+Producer+scalability+for+exactly+once+semantics
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > > > > >> written a design doc
>> > > > > > > > > > > > > > > > > > > > > >> <
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > >
>> > > > > > > >
>> > > > > > >
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>> https://docs.google.com/document/d/1LhzHGeX7_Lay4xvrEXxfciuDWATjpUXQhrEIkph9qRE/edit#
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > depicting
>> > > > > > > > > > > > > > > > > > > > > >> internal changes. We stripped
>> off
>> > > many
>> > > > > > > > > > > implementation
>> > > > > > > > > > > > > > > details
>> > > > > > > > > > > > > > > > > from
>> > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > KIP,
>> > > > > > > > > > > > > > > > > > > > > >> and simplified the public
>> changes
>> > > by a
>> > > > > > lot.
>> > > > > > > > For
>> > > > > > > > > > > > > reviewers,
>> > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > > > > > highly
>> > > > > > > > > > > > > > > > > > > > > >> recommended to fully understand
>> > EOS
>> > > > > design
>> > > > > > > in
>> > > > > > > > > > KIP-98
>> > > > > > > > > > > > and
>> > > > > > > > > > > > > > > read
>> > > > > > > > > > > > > > > > > its
>> > > > > > > > > > > > > > > > > > > > > >> corresponding design doc
>> > > > > > > > > > > > > > > > > > > > > >> <
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > >
>> > > > > > > >
>> > > > > > >
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>> https://docs.google.com/document/d/11Jqy_GjUGtdXJK94XGsEIK7CP1SnQGdp2eF0wSw9ra8/edit
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > if
>> > > > > > > > > > > > > > > > > > > > > >> you haven't done so already.
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >> Let me know if you found
>> anything
>> > > > > > confusing
>> > > > > > > > > around
>> > > > > > > > > > > the
>> > > > > > > > > > > > > KIP
>> > > > > > > > > > > > > > > or
>> > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > design.
>> > > > > > > > > > > > > > > > > > > > > >> Would be happy to discuss in
>> > depth.
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >> Best,
>> > > > > > > > > > > > > > > > > > > > > >> Boyang
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >> On Wed, Jun 26, 2019 at 11:00
>> AM
>> > > > > Guozhang
>> > > > > > > > Wang <
>> > > > > > > > > > > > > > > > > > wangg...@gmail.com>
>> > > > > > > > > > > > > > > > > > > > > >> wrote:
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> 2. The reason we did not
>> expose
>> > > > > > > > generation.id
>> > > > > > > > > > from
>> > > > > > > > > > > > > > > > > KafkaConsumer
>> > > > > > > > > > > > > > > > > > > > > public
>> > > > > > > > > > > > > > > > > > > > > >>> APIs directly is to abstract
>> this
>> > > > > notion
>> > > > > > > from
>> > > > > > > > > > users
>> > > > > > > > > > > > > > (since
>> > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > > > an
>> > > > > > > > > > > > > > > > > > > > > >>> implementation detail of the
>> > > > rebalance
>> > > > > > > > protocol
>> > > > > > > > > > > > itself,
>> > > > > > > > > > > > > > > e.g.
>> > > > > > > > > > > > > > > > if
>> > > > > > > > > > > > > > > > > > > user
>> > > > > > > > > > > > > > > > > > > > > >>> calls
>> > > > > > > > > > > > > > > > > > > > > >>> consumer.assign() they do not
>> > need
>> > > to
>> > > > > > > invoke
>> > > > > > > > > > > > > > > > > ConsumerCoordinator
>> > > > > > > > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > > > no
>> > > > > > > > > > > > > > > > > > > > > >>> need to be aware of
>> > generation.id
>> > > at
>> > > > > > all).
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>> On the other hand, with the
>> > current
>> > > > > > > proposal
>> > > > > > > > > the
>> > > > > > > > > > > > > > > > > txn.coordiantor
>> > > > > > > > > > > > > > > > > > > did
>> > > > > > > > > > > > > > > > > > > > > not
>> > > > > > > > > > > > > > > > > > > > > >>> know about the latest
>> generation
>> > > from
>> > > > > the
>> > > > > > > > > > > > > source-of-truth
>> > > > > > > > > > > > > > > > > > > > > >>> group.coordinator; instead, it
>> > will
>> > > > > only
>> > > > > > > bump
>> > > > > > > > > up
>> > > > > > > > > > > the
>> > > > > > > > > > > > > > > > generation
>> > > > > > > > > > > > > > > > > > > from
>> > > > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> producer's
>> InitProducerIdRequest
>> > > > only.
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>> The key here is that
>> > > > GroupCoordinator,
>> > > > > > when
>> > > > > > > > > > > handling
>> > > > > > > > > > > > > > > > > > > > > >>> `InitProducerIdRequest
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >> In the new design, we just pass
>> > the
>> > > > > entire
>> > > > > > > > > > consumer
>> > > > > > > > > > > > > > instance
>> > > > > > > > > > > > > > > > > into
>> > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > > producer through
>> > > > > > > > > > > > > > > > > > > > > > #initTransaction, so no public
>> API
>> > > will
>> > > > > be
>> > > > > > > > > created.
>> > > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >> 3. I agree that if we rely on
>> the
>> > > > group
>> > > > > > > > > > coordinator
>> > > > > > > > > > > to
>> > > > > > > > > > > > > > block
>> > > > > > > > > > > > > > > > on
>> > > > > > > > > > > > > > > > > > > > > returning
>> > > > > > > > > > > > > > > > > > > > > >>> offset-fetch-response if
>> > > > read-committed
>> > > > > > is
>> > > > > > > > > > enabled,
>> > > > > > > > > > > > > then
>> > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > do
>> > > > > > > > > > > > > > > > > > not
>> > > > > > > > > > > > > > > > > > > > need
>> > > > > > > > > > > > > > > > > > > > > >>> to
>> > > > > > > > > > > > > > > > > > > > > >>> store partition assignment on
>> txn
>> > > > > > > coordinator
>> > > > > > > > > and
>> > > > > > > > > > > > > > therefore
>> > > > > > > > > > > > > > > > > it's
>> > > > > > > > > > > > > > > > > > > > better
>> > > > > > > > > > > > > > > > > > > > > >>> to
>> > > > > > > > > > > > > > > > > > > > > >>> still decouple them. For that
>> > case
>> > > we
>> > > > > > still
>> > > > > > > > > need
>> > > > > > > > > > to
>> > > > > > > > > > > > > > update
>> > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > KIP
>> > > > > > > > > > > > > > > > > > > > wiki
>> > > > > > > > > > > > > > > > > > > > > >>> page that includes:
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>> 3.a. Augment
>> OffsetFetchRequest
>> > > with
>> > > > > the
>> > > > > > > > > > > > > ISOLATION_LEVEL
>> > > > > > > > > > > > > > as
>> > > > > > > > > > > > > > > > > well.
>> > > > > > > > > > > > > > > > > > > > > >>> 3.b. Add new error code in
>> > > > > > > > OffsetFetchResponse
>> > > > > > > > > to
>> > > > > > > > > > > let
>> > > > > > > > > > > > > > > client
>> > > > > > > > > > > > > > > > > > > backoff
>> > > > > > > > > > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > > > > >>> retry if there are pending
>> txns
>> > > > > including
>> > > > > > > the
>> > > > > > > > > > > > > interested
>> > > > > > > > > > > > > > > > > > > partitions.
>> > > > > > > > > > > > > > > > > > > > > >>> 3.c. Also in the worst case we
>> > > would
>> > > > > let
>> > > > > > > the
>> > > > > > > > > > client
>> > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > blocked
>> > > > > > > > > > > > > > > > > > for
>> > > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> txn.timeout period, and for
>> that
>> > > > > > rationale
>> > > > > > > we
>> > > > > > > > > may
>> > > > > > > > > > > > need
>> > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > consider
>> > > > > > > > > > > > > > > > > > > > > >>> reducing
>> > > > > > > > > > > > > > > > > > > > > >>> our default txn.timeout value
>> as
>> > > > well.
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>> Addressed 3.b and 3.c, will do
>> > 3.a.
>> > > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >> 4. According to Colin it seems
>> we
>> > do
>> > > > not
>> > > > > > > need
>> > > > > > > > to
>> > > > > > > > > > > > create
>> > > > > > > > > > > > > > > > another
>> > > > > > > > > > > > > > > > > > KIP
>> > > > > > > > > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > > > >>> can just complete it as part
>> of
>> > > > > KIP-117 /
>> > > > > > > > > > > KAFKA-5214;
>> > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > need
>> > > > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > do
>> > > > > > > > > > > > > > > > > > > > > >>> some cleanup to have
>> > > BrokerApiVersion
>> > > > > > > exposed
>> > > > > > > > > > from
>> > > > > > > > > > > > > > > > AdminClient
>> > > > > > > > > > > > > > > > > > > > (@Colin
>> > > > > > > > > > > > > > > > > > > > > >>> please let use know if you
>> have
>> > any
>> > > > > > > concerns
>> > > > > > > > > > > exposing
>> > > > > > > > > > > > > > it).
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >> I think we no longer need to
>> rely
>> > on
>> > > > api
>> > > > > > > > version
>> > > > > > > > > > for
>> > > > > > > > > > > > > > > > > > initialization,
>> > > > > > > > > > > > > > > > > > > > > > since we will be using the
>> > > upgrade.from
>> > > > > > > config
>> > > > > > > > > > > anyway.
>> > > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> Guozhang
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>> On Tue, Jun 25, 2019 at 6:43
>> PM
>> > > Jason
>> > > > > > > > > Gustafson <
>> > > > > > > > > > > > > > > > > > > ja...@confluent.io>
>> > > > > > > > > > > > > > > > > > > > > >>> wrote:
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>> > For reference, we have
>> > > > > > > > > BrokerApiVersionCommand
>> > > > > > > > > > > > > already
>> > > > > > > > > > > > > > > as a
>> > > > > > > > > > > > > > > > > > > public
>> > > > > > > > > > > > > > > > > > > > > >>> > interface. We have a bit of
>> > tech
>> > > > debt
>> > > > > > at
>> > > > > > > > the
>> > > > > > > > > > > moment
>> > > > > > > > > > > > > > > because
>> > > > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > > > > uses a
>> > > > > > > > > > > > > > > > > > > > > >>> > custom AdminClient. It
>> would be
>> > > > nice
>> > > > > to
>> > > > > > > > clean
>> > > > > > > > > > > that
>> > > > > > > > > > > > > up.
>> > > > > > > > > > > > > > In
>> > > > > > > > > > > > > > > > > > > general,
>> > > > > > > > > > > > > > > > > > > > I
>> > > > > > > > > > > > > > > > > > > > > >>> think
>> > > > > > > > > > > > > > > > > > > > > >>> > it is reasonable to expose
>> from
>> > > > > > > > AdminClient.
>> > > > > > > > > It
>> > > > > > > > > > > can
>> > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > used
>> > > > > > > > > > > > > > > > > by
>> > > > > > > > > > > > > > > > > > > > > >>> management
>> > > > > > > > > > > > > > > > > > > > > >>> > tools to inspect running
>> Kafka
>> > > > > versions
>> > > > > > > for
>> > > > > > > > > > > > example.
>> > > > > > > > > > > > > > > > > > > > > >>> >
>> > > > > > > > > > > > > > > > > > > > > >>> > -Jason
>> > > > > > > > > > > > > > > > > > > > > >>> >
>> > > > > > > > > > > > > > > > > > > > > >>> > On Tue, Jun 25, 2019 at
>> 4:37 PM
>> > > > > Boyang
>> > > > > > > > Chen <
>> > > > > > > > > > > > > > > > > > > > > >>> reluctanthero...@gmail.com>
>> > > > > > > > > > > > > > > > > > > > > >>> > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > Thank you for the context
>> > > Colin.
>> > > > > The
>> > > > > > > > > groupId
>> > > > > > > > > > > was
>> > > > > > > > > > > > > > > indeed a
>> > > > > > > > > > > > > > > > > > > > > copy-paste
>> > > > > > > > > > > > > > > > > > > > > >>> > error.
>> > > > > > > > > > > > > > > > > > > > > >>> > > Our use case here for 447
>> is
>> > > > > (Quoted
>> > > > > > > from
>> > > > > > > > > > > > > Guozhang):
>> > > > > > > > > > > > > > > > > > > > > >>> > > '''
>> > > > > > > > > > > > > > > > > > > > > >>> > > I think if we can do
>> > something
>> > > > else
>> > > > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > avoid this config though,
>> for
>> > > > > example
>> > > > > > > we
>> > > > > > > > > can
>> > > > > > > > > > > use
>> > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > embedded
>> > > > > > > > > > > > > > > > > > > > > >>> AdminClient
>> > > > > > > > > > > > > > > > > > > > > >>> > > to send the APIVersion
>> > request
>> > > > upon
>> > > > > > > > > starting
>> > > > > > > > > > > up,
>> > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > based
>> > > > > > > > > > > > > > > > > on
>> > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > returned
>> > > > > > > > > > > > > > > > > > > > > >>> > > value decides whether to
>> go
>> > to
>> > > > the
>> > > > > > old
>> > > > > > > > code
>> > > > > > > > > > > path
>> > > > > > > > > > > > or
>> > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > new
>> > > > > > > > > > > > > > > > > > > > > behavior.
>> > > > > > > > > > > > > > > > > > > > > >>> > > '''
>> > > > > > > > > > > > > > > > > > > > > >>> > > The benefit we get is to
>> > avoid
>> > > > > > adding a
>> > > > > > > > new
>> > > > > > > > > > > > > > > configuration
>> > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > make a
>> > > > > > > > > > > > > > > > > > > > > >>> > > decision simply base on
>> > broker
>> > > > > > version.
>> > > > > > > > If
>> > > > > > > > > > you
>> > > > > > > > > > > > have
>> > > > > > > > > > > > > > > > > concerns
>> > > > > > > > > > > > > > > > > > > with
>> > > > > > > > > > > > > > > > > > > > > >>> > exposing
>> > > > > > > > > > > > > > > > > > > > > >>> > > ApiVersion for client, we
>> > could
>> > > > > > > > > > > > > > > > > > > > > >>> > > try to think of
>> alternative
>> > > > > solutions
>> > > > > > > > too.
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > Boyang
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > On Tue, Jun 25, 2019 at
>> 4:20
>> > PM
>> > > > > Colin
>> > > > > > > > > McCabe
>> > > > > > > > > > <
>> > > > > > > > > > > > > > > > > > > cmcc...@apache.org
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > kafka.api.ApiVersion is
>> an
>> > > > > internal
>> > > > > > > > > class,
>> > > > > > > > > > > not
>> > > > > > > > > > > > > > > suitable
>> > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > > exposing
>> > > > > > > > > > > > > > > > > > > > > >>> > > > through AdminClient.
>> That
>> > > > class
>> > > > > is
>> > > > > > > not
>> > > > > > > > > > even
>> > > > > > > > > > > > > > > accessible
>> > > > > > > > > > > > > > > > > > > without
>> > > > > > > > > > > > > > > > > > > > > >>> having
>> > > > > > > > > > > > > > > > > > > > > >>> > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > broker jars on your
>> > > CLASSPATH.
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > Another question is,
>> what
>> > is
>> > > > the
>> > > > > > > > groupId
>> > > > > > > > > > > > > parameter
>> > > > > > > > > > > > > > > > doing
>> > > > > > > > > > > > > > > > > in
>> > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> call?
>> > > > > > > > > > > > > > > > > > > > > >>> > > The
>> > > > > > > > > > > > > > > > > > > > > >>> > > > API versions are the
>> same
>> > no
>> > > > > matter
>> > > > > > > > what
>> > > > > > > > > > > > consumer
>> > > > > > > > > > > > > > > group
>> > > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > use,
>> > > > > > > > > > > > > > > > > > > > > >>> right?
>> > > > > > > > > > > > > > > > > > > > > >>> > > > Perhaps this was a copy
>> and
>> > > > paste
>> > > > > > > > error?
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > This is not the first
>> time
>> > we
>> > > > > have
>> > > > > > > > > > discussed
>> > > > > > > > > > > > > > having a
>> > > > > > > > > > > > > > > > > > method
>> > > > > > > > > > > > > > > > > > > in
>> > > > > > > > > > > > > > > > > > > > > >>> > > > AdminClient to retrieve
>> API
>> > > > > version
>> > > > > > > > > > > > information.
>> > > > > > > > > > > > > > In
>> > > > > > > > > > > > > > > > > fact,
>> > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> original
>> > > > > > > > > > > > > > > > > > > > > >>> > > KIP
>> > > > > > > > > > > > > > > > > > > > > >>> > > > which created
>> > > KafkaAdminClient
>> > > > > > > > specified
>> > > > > > > > > an
>> > > > > > > > > > > API
>> > > > > > > > > > > > > for
>> > > > > > > > > > > > > > > > > > fetching
>> > > > > > > > > > > > > > > > > > > > > >>> version
>> > > > > > > > > > > > > > > > > > > > > >>> > > > information. It was
>> called
>> > > > > > > apiVersions
>> > > > > > > > > and
>> > > > > > > > > > > it
>> > > > > > > > > > > > is
>> > > > > > > > > > > > > > > still
>> > > > > > > > > > > > > > > > > > there
>> > > > > > > > > > > > > > > > > > > > on
>> > > > > > > > > > > > > > > > > > > > > >>> the
>> > > > > > > > > > > > > > > > > > > > > >>> > > wiki.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > See
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> > > > > > > > > > > > > > > > > > > > > >>> >
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > >
>> > > > > > > >
>> > > > > > >
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-117%3A+Add+a+public+AdminClient+API+for+Kafka+admin+operations
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > However, this API wasn't
>> > > ready
>> > > > in
>> > > > > > > time
>> > > > > > > > > for
>> > > > > > > > > > > > 0.11.0
>> > > > > > > > > > > > > > so
>> > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > shipped
>> > > > > > > > > > > > > > > > > > > > > >>> without
>> > > > > > > > > > > > > > > > > > > > > >>> > > > it. There was a JIRA to
>> > > > > implement
>> > > > > > it
>> > > > > > > > for
>> > > > > > > > > > > later
>> > > > > > > > > > > > > > > > versions,
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > https://issues.apache.org/jira/browse/KAFKA-5214
>> > > > > > > > > > > > > ,
>> > > > > > > > > > > > > > > as
>> > > > > > > > > > > > > > > > > well
>> > > > > > > > > > > > > > > > > > > as
>> > > > > > > > > > > > > > > > > > > > a
>> > > > > > > > > > > > > > > > > > > > > >>> PR,
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > https://github.com/apache/kafka/pull/3012
>> > > > > > > > > > .
>> > > > > > > > > > > > > > > However,
>> > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > > started
>> > > > > > > > > > > > > > > > > > > > > >>> to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > rethink whether this
>> > > > AdminClient
>> > > > > > > > function
>> > > > > > > > > > was
>> > > > > > > > > > > > > even
>> > > > > > > > > > > > > > > > > > necessary.
>> > > > > > > > > > > > > > > > > > > > > >>> Most of
>> > > > > > > > > > > > > > > > > > > > > >>> > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > use-cases we could
>> think of
>> > > > > seemed
>> > > > > > > like
>> > > > > > > > > > > > horrible
>> > > > > > > > > > > > > > > hacks.
>> > > > > > > > > > > > > > > > > So
>> > > > > > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > > > > > has
>> > > > > > > > > > > > > > > > > > > > > >>> > never
>> > > > > > > > > > > > > > > > > > > > > >>> > > > really been implemented
>> > > (yet?).
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > best,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > Colin
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > On Tue, Jun 25, 2019, at
>> > > 15:46,
>> > > > > > > Boyang
>> > > > > > > > > Chen
>> > > > > > > > > > > > > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > Actually, after a
>> second
>> > > > > > thought, I
>> > > > > > > > > think
>> > > > > > > > > > > it
>> > > > > > > > > > > > > > > actually
>> > > > > > > > > > > > > > > > > > makes
>> > > > > > > > > > > > > > > > > > > > > >>> sense to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > support auto upgrade
>> > > through
>> > > > > > admin
>> > > > > > > > > client
>> > > > > > > > > > > to
>> > > > > > > > > > > > > help
>> > > > > > > > > > > > > > > use
>> > > > > > > > > > > > > > > > > get
>> > > > > > > > > > > > > > > > > > > api
>> > > > > > > > > > > > > > > > > > > > > >>> version
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > from
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > broker.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > A draft KIP is here:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> > > > > > > > > > > > > > > > > > > > > >>> >
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > >
>> > > > > > > >
>> > > > > > >
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-483%3A++Add+Broker+Version+API+in+Admin+Client
>> > > > > > > > > > > > > > > > > > > > > >>> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > Boyang
>> > > > > > > > > > > > > > > > > > > > > >>> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > On Tue, Jun 25, 2019
>> at
>> > > 2:57
>> > > > PM
>> > > > > > > > Boyang
>> > > > > > > > > > > Chen <
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> reluctanthero...@gmail.com>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > Thank you Guozhang,
>> > some
>> > > of
>> > > > > my
>> > > > > > > > > > > > understandings
>> > > > > > > > > > > > > > are
>> > > > > > > > > > > > > > > > > > inline
>> > > > > > > > > > > > > > > > > > > > > below.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > On Tue, Jun 25,
>> 2019 at
>> > > > 11:05
>> > > > > > AM
>> > > > > > > > > Jason
>> > > > > > > > > > > > > > Gustafson
>> > > > > > > > > > > > > > > <
>> > > > > > > > > > > > > > > > > > > > > >>> > ja...@confluent.io
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > I think
>> co-locating
>> > > does
>> > > > > > have
>> > > > > > > > some
>> > > > > > > > > > > > merits
>> > > > > > > > > > > > > > > here,
>> > > > > > > > > > > > > > > > > i.e.
>> > > > > > > > > > > > > > > > > > > > > >>> letting the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> ConsumerCoordinator
>> > > > which
>> > > > > > has
>> > > > > > > > the
>> > > > > > > > > > > > > > > > source-of-truth
>> > > > > > > > > > > > > > > > > of
>> > > > > > > > > > > > > > > > > > > > > >>> assignment
>> > > > > > > > > > > > > > > > > > > > > >>> > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > act
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> as
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > the
>> TxnCoordinator
>> > as
>> > > > > well;
>> > > > > > > but
>> > > > > > > > I
>> > > > > > > > > > > agree
>> > > > > > > > > > > > > > > there's
>> > > > > > > > > > > > > > > > > also
>> > > > > > > > > > > > > > > > > > > > some
>> > > > > > > > > > > > > > > > > > > > > >>> cons
>> > > > > > > > > > > > > > > > > > > > > >>> > of
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> coupling
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > them together.
>> I'm
>> > > > still a
>> > > > > > bit
>> > > > > > > > > > > inclining
>> > > > > > > > > > > > > > > towards
>> > > > > > > > > > > > > > > > > > > > > colocation
>> > > > > > > > > > > > > > > > > > > > > >>> but
>> > > > > > > > > > > > > > > > > > > > > >>> > if
>> > > > > > > > > > > > > > > > > > > > > >>> > > > there
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > are good
>> rationales
>> > > not
>> > > > to
>> > > > > > do
>> > > > > > > > so I
>> > > > > > > > > > can
>> > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > convinced
>> > > > > > > > > > > > > > > > > > as
>> > > > > > > > > > > > > > > > > > > > > well.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> The good rationale
>> is
>> > > that
>> > > > > we
>> > > > > > > have
>> > > > > > > > > no
>> > > > > > > > > > > > > > mechanism
>> > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > colocate
>> > > > > > > > > > > > > > > > > > > > > >>> > > > partitions ;).
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> Are you suggesting
>> we
>> > > > store
>> > > > > > the
>> > > > > > > > > group
>> > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > transaction
>> > > > > > > > > > > > > > > > > > > > state
>> > > > > > > > > > > > > > > > > > > > > >>> in the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > same
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> log? Can you be
>> more
>> > > > > concrete
>> > > > > > > > about
>> > > > > > > > > > the
>> > > > > > > > > > > > > > benefit?
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> -Jason
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> On Tue, Jun 25,
>> 2019
>> > at
>> > > > > 10:51
>> > > > > > AM
>> > > > > > > > > > > Guozhang
>> > > > > > > > > > > > > > Wang <
>> > > > > > > > > > > > > > > > > > > > > >>> > wangg...@gmail.com>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > Hi Boyang,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > 1. One advantage
>> of
>> > > > retry
>> > > > > > > > against
>> > > > > > > > > > > > on-hold
>> > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > that
>> > > > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > > > > will
>> > > > > > > > > > > > > > > > > > > > > >>> not
>> > > > > > > > > > > > > > > > > > > > > >>> > > > tie-up a
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > handler thread
>> (of
>> > > > course
>> > > > > > the
>> > > > > > > > > latter
>> > > > > > > > > > > > could
>> > > > > > > > > > > > > > do
>> > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > same
>> > > > > > > > > > > > > > > > > > > > but
>> > > > > > > > > > > > > > > > > > > > > >>> that
>> > > > > > > > > > > > > > > > > > > > > >>> > > > involves
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > using a purgatory
>> > > which
>> > > > is
>> > > > > > > more
>> > > > > > > > > > > > > > complicated),
>> > > > > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > also
>> > > > > > > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > > > > > > >>> > less
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> likely to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > violate request
>> > > timeout.
>> > > > > So
>> > > > > > I
>> > > > > > > > > think
>> > > > > > > > > > > > there
>> > > > > > > > > > > > > > are
>> > > > > > > > > > > > > > > > some
>> > > > > > > > > > > > > > > > > > > > > >>> rationales to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > prefer
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > retries.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > That sounds fair to
>> > me,
>> > > > also
>> > > > > > we
>> > > > > > > > are
>> > > > > > > > > > > > avoiding
>> > > > > > > > > > > > > > > usage
>> > > > > > > > > > > > > > > > > of
>> > > > > > > > > > > > > > > > > > > > > another
>> > > > > > > > > > > > > > > > > > > > > >>> > > > purgatory
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > instance. Usually
>> for
>> > one
>> > > > > > > back-off
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > we are only delaying
>> > 50ms
>> > > > > > during
>> > > > > > > > > > startup
>> > > > > > > > > > > > > which
>> > > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > > > trivial
>> > > > > > > > > > > > > > > > > > > > > cost.
>> > > > > > > > > > > > > > > > > > > > > >>> > This
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > behavior shouldn't
>> be
>> > > > > changed.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > > 2. Regarding
>> > > > > > > > > > > "ConsumerRebalanceListener":
>> > > > > > > > > > > > > > both
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> ConsumerRebalanceListener
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > and
>> > PartitionAssignors
>> > > > are
>> > > > > > > > > > > > > user-customizable
>> > > > > > > > > > > > > > > > > > modules,
>> > > > > > > > > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > > > > >>> only
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> difference
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > is that the
>> former
>> > is
>> > > > > > > specified
>> > > > > > > > > via
>> > > > > > > > > > > code
>> > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > latter
>> > > > > > > > > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > > > > > > >>> > > > specified via
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > config.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > Regarding Jason's
>> > > > proposal
>> > > > > > of
>> > > > > > > > > > > > > > > > ConsumerAssignment,
>> > > > > > > > > > > > > > > > > > one
>> > > > > > > > > > > > > > > > > > > > > thing
>> > > > > > > > > > > > > > > > > > > > > >>> to
>> > > > > > > > > > > > > > > > > > > > > >>> > > note
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> though
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > with KIP-429 the
>> > > > > > > > > onPartitionAssigned
>> > > > > > > > > > > may
>> > > > > > > > > > > > > not
>> > > > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > > called
>> > > > > > > > > > > > > > > > > > > > if
>> > > > > > > > > > > > > > > > > > > > > >>> the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > assignment
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > does not change,
>> > > whereas
>> > > > > > > > > > onAssignment
>> > > > > > > > > > > > > would
>> > > > > > > > > > > > > > > > always
>> > > > > > > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > > > > > >>> called at
>> > > > > > > > > > > > > > > > > > > > > >>> > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > end
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> of
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > sync-group
>> response.
>> > > My
>> > > > > > > proposed
>> > > > > > > > > > > > semantics
>> > > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > that
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > `RebalanceListener#onPartitionsXXX`
>> > > > > > > > > > > are
>> > > > > > > > > > > > > used
>> > > > > > > > > > > > > > > for
>> > > > > > > > > > > > > > > > > > > > > >>> notifications
>> > > > > > > > > > > > > > > > > > > > > >>> > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > user,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> and
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > hence if there's
>> no
>> > > > > changes
>> > > > > > > > these
>> > > > > > > > > > will
>> > > > > > > > > > > > not
>> > > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > > called,
>> > > > > > > > > > > > > > > > > > > > > >>> whereas
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> `PartitionAssignor`
>> > is
>> > > > > used
>> > > > > > > for
>> > > > > > > > > > > assignor
>> > > > > > > > > > > > > > > logic,
>> > > > > > > > > > > > > > > > > > whose
>> > > > > > > > > > > > > > > > > > > > > >>> callback
>> > > > > > > > > > > > > > > > > > > > > >>> > > would
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> always
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > be called no
>> matter
>> > if
>> > > > the
>> > > > > > > > > > partitions
>> > > > > > > > > > > > have
>> > > > > > > > > > > > > > > > changed
>> > > > > > > > > > > > > > > > > > or
>> > > > > > > > > > > > > > > > > > > > not.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> I think a third
>> option
>> > > is
>> > > > to
>> > > > > > > > > > gracefully
>> > > > > > > > > > > > > expose
>> > > > > > > > > > > > > > > > > > > generation
>> > > > > > > > > > > > > > > > > > > > id
>> > > > > > > > > > > > > > > > > > > > > >>> as
>> > > > > > > > > > > > > > > > > > > > > >>> > part
>> > > > > > > > > > > > > > > > > > > > > >>> > > > of
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > consumer API, so
>> that
>> > we
>> > > > > don't
>> > > > > > > need
>> > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > bother overloading
>> > > various
>> > > > > > > > callbacks.
>> > > > > > > > > > Of
>> > > > > > > > > > > > > > course,
>> > > > > > > > > > > > > > > > this
>> > > > > > > > > > > > > > > > > > > > builds
>> > > > > > > > > > > > > > > > > > > > > >>> upon
>> > > > > > > > > > > > > > > > > > > > > >>> > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > assumption that
>> topic
>> > > > > > partitions
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > will not be
>> included in
>> > > new
>> > > > > > > > > > > initTransaction
>> > > > > > > > > > > > > > API.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > > 3. I feel it is a
>> bit
>> > > > > awkward
>> > > > > > > to
>> > > > > > > > > let
>> > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > TxnCoordinator
>> > > > > > > > > > > > > > > > > > > > > >>> keeping
>> > > > > > > > > > > > > > > > > > > > > >>> > > > partition
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > assignments
>> since it
>> > > is
>> > > > > sort
>> > > > > > > of
>> > > > > > > > > > taking
>> > > > > > > > > > > > > over
>> > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > job
>> > > > > > > > > > > > > > > > > > of
>> > > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> ConsumerCoordinator,
>> > > and
>> > > > > may
>> > > > > > > > > likely
>> > > > > > > > > > > > cause
>> > > > > > > > > > > > > a
>> > > > > > > > > > > > > > > > > > > split-brain
>> > > > > > > > > > > > > > > > > > > > > >>> problem
>> > > > > > > > > > > > > > > > > > > > > >>> > as
>> > > > > > > > > > > > > > > > > > > > > >>> > > > two
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > coordinators
>> keep a
>> > > copy
>> > > > > of
>> > > > > > > this
>> > > > > > > > > > > > > assignment
>> > > > > > > > > > > > > > > > which
>> > > > > > > > > > > > > > > > > > may
>> > > > > > > > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > > > > > >>> > > different.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > I think
>> co-locating
>> > > does
>> > > > > > have
>> > > > > > > > some
>> > > > > > > > > > > > merits
>> > > > > > > > > > > > > > > here,
>> > > > > > > > > > > > > > > > > i.e.
>> > > > > > > > > > > > > > > > > > > > > >>> letting the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> ConsumerCoordinator
>> > > > which
>> > > > > > has
>> > > > > > > > the
>> > > > > > > > > > > > > > > > source-of-truth
>> > > > > > > > > > > > > > > > > of
>> > > > > > > > > > > > > > > > > > > > > >>> assignment
>> > > > > > > > > > > > > > > > > > > > > >>> > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > act
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> as
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > the
>> TxnCoordinator
>> > as
>> > > > > well;
>> > > > > > > but
>> > > > > > > > I
>> > > > > > > > > > > agree
>> > > > > > > > > > > > > > > there's
>> > > > > > > > > > > > > > > > > also
>> > > > > > > > > > > > > > > > > > > > some
>> > > > > > > > > > > > > > > > > > > > > >>> cons
>> > > > > > > > > > > > > > > > > > > > > >>> > of
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> coupling
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > them together.
>> I'm
>> > > > still a
>> > > > > > bit
>> > > > > > > > > > > inclining
>> > > > > > > > > > > > > > > towards
>> > > > > > > > > > > > > > > > > > > > > colocation
>> > > > > > > > > > > > > > > > > > > > > >>> but
>> > > > > > > > > > > > > > > > > > > > > >>> > if
>> > > > > > > > > > > > > > > > > > > > > >>> > > > there
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > are good
>> rationales
>> > > not
>> > > > to
>> > > > > > do
>> > > > > > > > so I
>> > > > > > > > > > can
>> > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > convinced
>> > > > > > > > > > > > > > > > > > as
>> > > > > > > > > > > > > > > > > > > > > well.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > The purpose of
>> > > co-location
>> > > > is
>> > > > > > to
>> > > > > > > > let
>> > > > > > > > > > txn
>> > > > > > > > > > > > > > > > coordinator
>> > > > > > > > > > > > > > > > > > see
>> > > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> group
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > assignment. This
>> > priority
>> > > > is
>> > > > > > > > weakened
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > when we already have
>> > > > defense
>> > > > > on
>> > > > > > > the
>> > > > > > > > > > > > consumer
>> > > > > > > > > > > > > > > offset
>> > > > > > > > > > > > > > > > > > > fetch,
>> > > > > > > > > > > > > > > > > > > > > so I
>> > > > > > > > > > > > > > > > > > > > > >>> > guess
>> > > > > > > > > > > > > > > > > > > > > >>> > > > it's
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > not super important
>> > > > anymore.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > 4. I guess I'm
>> > > > preferring
>> > > > > > the
>> > > > > > > > > > > philosophy
>> > > > > > > > > > > > > of
>> > > > > > > > > > > > > > > > "only
>> > > > > > > > > > > > > > > > > > add
>> > > > > > > > > > > > > > > > > > > > > >>> configs if
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> there's no
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > other ways",
>> since
>> > > more
>> > > > > and
>> > > > > > > more
>> > > > > > > > > > > configs
>> > > > > > > > > > > > > > would
>> > > > > > > > > > > > > > > > > make
>> > > > > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > > > > > less
>> > > > > > > > > > > > > > > > > > > > > >>> and
>> > > > > > > > > > > > > > > > > > > > > >>> > > less
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > intuitive out of
>> the
>> > > box
>> > > > > to
>> > > > > > > use.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > I think it's a
>> valid
>> > > > point
>> > > > > > > that
>> > > > > > > > > > checks
>> > > > > > > > > > > > > upon
>> > > > > > > > > > > > > > > > > starting
>> > > > > > > > > > > > > > > > > > > up
>> > > > > > > > > > > > > > > > > > > > > >>> does not
>> > > > > > > > > > > > > > > > > > > > > >>> > > > cope
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> with
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > brokers
>> downgrading
>> > > but
>> > > > > even
>> > > > > > > > with
>> > > > > > > > > a
>> > > > > > > > > > > > > config,
>> > > > > > > > > > > > > > > but
>> > > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > > > > > > still
>> > > > > > > > > > > > > > > > > > > > > >>> hard
>> > > > > > > > > > > > > > > > > > > > > >>> > > for
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> users
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > to determine when
>> > they
>> > > > can
>> > > > > > be
>> > > > > > > > > > ensured
>> > > > > > > > > > > > the
>> > > > > > > > > > > > > > > broker
>> > > > > > > > > > > > > > > > > > would
>> > > > > > > > > > > > > > > > > > > > > never
>> > > > > > > > > > > > > > > > > > > > > >>> > > > downgrade
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > anymore and hence
>> > can
>> > > > > safely
>> > > > > > > > > switch
>> > > > > > > > > > > the
>> > > > > > > > > > > > > > > config.
>> > > > > > > > > > > > > > > > So
>> > > > > > > > > > > > > > > > > > my
>> > > > > > > > > > > > > > > > > > > > > >>> feeling is
>> > > > > > > > > > > > > > > > > > > > > >>> > > > that
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> this
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > config would not
>> be
>> > > > > helping
>> > > > > > > too
>> > > > > > > > > much
>> > > > > > > > > > > > > still.
>> > > > > > > > > > > > > > If
>> > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > want
>> > > > > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> be at
>> > > > > > > > > > > > > > > > > > > > > >>> > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> safer
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > side, then I'd
>> > suggest
>> > > > we
>> > > > > > > modify
>> > > > > > > > > the
>> > > > > > > > > > > > > > > Coordinator
>> > > > > > > > > > > > > > > > > ->
>> > > > > > > > > > > > > > > > > > > > > >>> > NetworkClient
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> hierarchy
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > to allow the
>> > > > NetworkClient
>> > > > > > > being
>> > > > > > > > > > able
>> > > > > > > > > > > to
>> > > > > > > > > > > > > > pass
>> > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > APIVersion
>> > > > > > > > > > > > > > > > > > > > > >>> > > > metadata to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > Coordinator, so
>> that
>> > > > > > > Coordinator
>> > > > > > > > > can
>> > > > > > > > > > > > rely
>> > > > > > > > > > > > > on
>> > > > > > > > > > > > > > > > that
>> > > > > > > > > > > > > > > > > > > logic
>> > > > > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> > change
>> > > > > > > > > > > > > > > > > > > > > >>> > > > its
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > behavior
>> > dynamically.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > The stream thread
>> init
>> > > > could
>> > > > > > not
>> > > > > > > be
>> > > > > > > > > > > > supported
>> > > > > > > > > > > > > > by
>> > > > > > > > > > > > > > > a
>> > > > > > > > > > > > > > > > > > client
>> > > > > > > > > > > > > > > > > > > > > >>> > coordinator
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > behavior change on
>> the
>> > > fly,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > we are only losing
>> > > > > > possibilities
>> > > > > > > > > after
>> > > > > > > > > > we
>> > > > > > > > > > > > > > > > > initialized.
>> > > > > > > > > > > > > > > > > > > > (main
>> > > > > > > > > > > > > > > > > > > > > >>> thread
>> > > > > > > > > > > > > > > > > > > > > >>> > > > gets
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > exit and no thread
>> has
>> > > > global
>> > > > > > > > picture
>> > > > > > > > > > > > > anymore)
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > If we do want to
>> > support
>> > > > auto
>> > > > > > > > version
>> > > > > > > > > > > > > > detection,
>> > > > > > > > > > > > > > > > > admin
>> > > > > > > > > > > > > > > > > > > > client
>> > > > > > > > > > > > > > > > > > > > > >>> > request
>> > > > > > > > > > > > > > > > > > > > > >>> > > > in
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > this sense shall be
>> > > easier.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > 5. I do not have
>> a
>> > > > > concrete
>> > > > > > > idea
>> > > > > > > > > > about
>> > > > > > > > > > > > how
>> > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > impact
>> > > > > > > > > > > > > > > > > > > on
>> > > > > > > > > > > > > > > > > > > > > >>> Connect
>> > > > > > > > > > > > > > > > > > > > > >>> > > > would
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > make, maybe
>> Randall
>> > or
>> > > > > > > > Konstantine
>> > > > > > > > > > can
>> > > > > > > > > > > > > help
>> > > > > > > > > > > > > > > > here?
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > > Sounds good, let's
>> see
>> > > > their
>> > > > > > > > > thoughts.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > Guozhang
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > On Mon, Jun 24,
>> 2019
>> > > at
>> > > > > > 10:26
>> > > > > > > PM
>> > > > > > > > > > > Boyang
>> > > > > > > > > > > > > > Chen <
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > reluctanthero...@gmail.com>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > Hey Jason,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > thank you for
>> the
>> > > > > proposal
>> > > > > > > > here.
>> > > > > > > > > > > Some
>> > > > > > > > > > > > of
>> > > > > > > > > > > > > > my
>> > > > > > > > > > > > > > > > > > thoughts
>> > > > > > > > > > > > > > > > > > > > > >>> below.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > On Mon, Jun 24,
>> > 2019
>> > > > at
>> > > > > > 8:58
>> > > > > > > > PM
>> > > > > > > > > > > Jason
>> > > > > > > > > > > > > > > > Gustafson
>> > > > > > > > > > > > > > > > > <
>> > > > > > > > > > > > > > > > > > > > > >>> > > > ja...@confluent.io>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > Hi Boyang,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > Thanks for
>> > picking
>> > > > > this
>> > > > > > > up!
>> > > > > > > > > > Still
>> > > > > > > > > > > > > > reading
>> > > > > > > > > > > > > > > > > > through
>> > > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > updates,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > but
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> here
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > are
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > a couple
>> initial
>> > > > > > comments
>> > > > > > > on
>> > > > > > > > > the
>> > > > > > > > > > > > APIs:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > 1. The
>> > > > > > > `TxnProducerIdentity`
>> > > > > > > > > > class
>> > > > > > > > > > > > is
>> > > > > > > > > > > > > a
>> > > > > > > > > > > > > > > bit
>> > > > > > > > > > > > > > > > > > > > awkward. I
>> > > > > > > > > > > > > > > > > > > > > >>> think
>> > > > > > > > > > > > > > > > > > > > > >>> > > we
>> > > > > > > > > > > > > > > > > > > > > >>> > > > are
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > trying
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > to
>> encapsulate
>> > > state
>> > > > > > from
>> > > > > > > > the
>> > > > > > > > > > > > current
>> > > > > > > > > > > > > > > group
>> > > > > > > > > > > > > > > > > > > > > assignment.
>> > > > > > > > > > > > > > > > > > > > > >>> > Maybe
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> something
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > like
>> > > > > > `ConsumerAssignment`
>> > > > > > > > > would
>> > > > > > > > > > be
>> > > > > > > > > > > > > > > clearer?
>> > > > > > > > > > > > > > > > If
>> > > > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > > make
>> > > > > > > > > > > > > > > > > > > > > >>> the
>> > > > > > > > > > > > > > > > > > > > > >>> > > usage
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > consistent
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > across the
>> > > consumer
>> > > > > and
>> > > > > > > > > > producer,
>> > > > > > > > > > > > then
>> > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > can
>> > > > > > > > > > > > > > > > > > > avoid
>> > > > > > > > > > > > > > > > > > > > > >>> exposing
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> internal
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > state
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > like the
>> > > > generationId.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > For example:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > // Public API
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > interface
>> > > > > > > > ConsumerAssignment {
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > Set<TopicPartition>
>> > > > > > > > > > > partittions();
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > }
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > // Not a
>> public
>> > > API
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > class
>> > > > > > > > > InternalConsumerAssignment
>> > > > > > > > > > > > > > > implements
>> > > > > > > > > > > > > > > > > > > > > >>> > > ConsumerAssignment {
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > Set<TopicPartition>
>> > > > > > > > > > partittions;
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > int
>> > > generationId;
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > }
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > Then we can
>> > change
>> > > > the
>> > > > > > > > > rebalance
>> > > > > > > > > > > > > > listener
>> > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > something
>> > > > > > > > > > > > > > > > > > > > > >>> like
>> > > > > > > > > > > > > > > > > > > > > >>> > > > this:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > onPartitionsAssigned(ConsumerAssignment
>> > > > > > > > > > > > > > > > > > > assignment)
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > And on the
>> > > producer:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > void
>> > > > > > > initTransactions(String
>> > > > > > > > > > > > groupId,
>> > > > > > > > > > > > > > > > > > > > > ConsumerAssignment
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> assignment);
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > 2. Another
>> bit
>> > of
>> > > > > > > > awkwardness
>> > > > > > > > > is
>> > > > > > > > > > > the
>> > > > > > > > > > > > > > fact
>> > > > > > > > > > > > > > > > that
>> > > > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > > have
>> > > > > > > > > > > > > > > > > > > > > >>> to
>> > > > > > > > > > > > > > > > > > > > > >>> > pass
>> > > > > > > > > > > > > > > > > > > > > >>> > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > groupId
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > through both
>> > > > > > > > > initTransactions()
>> > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> sendOffsetsToTransaction().
>> > > > > > > > > > > > > > > > > > > > > >>> > > > We
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > could
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > consider a
>> > config
>> > > > > > instead.
>> > > > > > > > > Maybe
>> > > > > > > > > > > > > > something
>> > > > > > > > > > > > > > > > > like
>> > > > > > > > > > > > > > > > > > `
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > transactional.group.id
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > `?
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > Then we could
>> > > > simplify
>> > > > > > the
>> > > > > > > > > > > producer
>> > > > > > > > > > > > > > APIs,
>> > > > > > > > > > > > > > > > > > > > potentially
>> > > > > > > > > > > > > > > > > > > > > >>> even
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> deprecating
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > current
>> > > > > > > > > > sendOffsetsToTransaction.
>> > > > > > > > > > > In
>> > > > > > > > > > > > > > fact,
>> > > > > > > > > > > > > > > > for
>> > > > > > > > > > > > > > > > > > > this
>> > > > > > > > > > > > > > > > > > > > > new
>> > > > > > > > > > > > > > > > > > > > > >>> > usage,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > the `
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> transational.id
>> > `
>> > > > > config
>> > > > > > > is
>> > > > > > > > > not
>> > > > > > > > > > > > > needed.
>> > > > > > > > > > > > > > It
>> > > > > > > > > > > > > > > > > would
>> > > > > > > > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > > > > > >>> nice if
>> > > > > > > > > > > > > > > > > > > > > >>> > we
>> > > > > > > > > > > > > > > > > > > > > >>> > > > don't
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > have
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > provide it.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > I like the
>> idea
>> > of
>> > > > > > > > combining 1
>> > > > > > > > > > and
>> > > > > > > > > > > > 2.
>> > > > > > > > > > > > > We
>> > > > > > > > > > > > > > > > could
>> > > > > > > > > > > > > > > > > > > > > >>> definitely
>> > > > > > > > > > > > > > > > > > > > > >>> > pass
>> > > > > > > > > > > > > > > > > > > > > >>> > > > in a
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > group.id
>> config
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > so that we
>> could
>> > > avoid
>> > > > > > > > exposing
>> > > > > > > > > > that
>> > > > > > > > > > > > > > > > information
>> > > > > > > > > > > > > > > > > > in
>> > > > > > > > > > > > > > > > > > > a
>> > > > > > > > > > > > > > > > > > > > > >>> public
>> > > > > > > > > > > > > > > > > > > > > >>> > > API.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > The
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > question I have
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > is that
>> whether we
>> > > > > should
>> > > > > > > name
>> > > > > > > > > the
>> > > > > > > > > > > > > > interface
>> > > > > > > > > > > > > > > > > > > > > >>> `GroupAssignment`
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> instead,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > so
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > that Connect
>> later
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > could also
>> extend
>> > on
>> > > > the
>> > > > > > > same
>> > > > > > > > > > > > interface,
>> > > > > > > > > > > > > > > just
>> > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > echo
>> > > > > > > > > > > > > > > > > > > > > >>> > Guozhang's
>> > > > > > > > > > > > > > > > > > > > > >>> > > > point
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > here, Also the
>> > base
>> > > > > > > interface
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > is better to be
>> > > > defined
>> > > > > > > empty
>> > > > > > > > > for
>> > > > > > > > > > > easy
>> > > > > > > > > > > > > > > > > extension,
>> > > > > > > > > > > > > > > > > > or
>> > > > > > > > > > > > > > > > > > > > > >>> define an
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> abstract
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > type called
>> > > `Resource`
>> > > > > to
>> > > > > > be
>> > > > > > > > > > > shareable
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > later IMHO.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > By the way,
>> I'm
>> > a
>> > > > bit
>> > > > > > > > confused
>> > > > > > > > > > > about
>> > > > > > > > > > > > > > > > > discussion
>> > > > > > > > > > > > > > > > > > > > above
>> > > > > > > > > > > > > > > > > > > > > >>> about
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> colocating
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > txn and group
>> > > > > > > coordinators.
>> > > > > > > > > That
>> > > > > > > > > > > is
>> > > > > > > > > > > > > not
>> > > > > > > > > > > > > > > > > actually
>> > > > > > > > > > > > > > > > > > > > > >>> necessary,
>> > > > > > > > > > > > > > > > > > > > > >>> > is
>> > > > > > > > > > > > > > > > > > > > > >>> > > > it?
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > Yes, this is
>> > not a
>> > > > > > > > requirement
>> > > > > > > > > > for
>> > > > > > > > > > > > > this
>> > > > > > > > > > > > > > > KIP,
>> > > > > > > > > > > > > > > > > > > because
>> > > > > > > > > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > > > > > > >>> is
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> inherently
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > impossible to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > achieve
>> > co-locating
>> > > > > topic
>> > > > > > > > > > partition
>> > > > > > > > > > > > of
>> > > > > > > > > > > > > > > > > > transaction
>> > > > > > > > > > > > > > > > > > > > log
>> > > > > > > > > > > > > > > > > > > > > >>> and
>> > > > > > > > > > > > > > > > > > > > > >>> > > > consumed
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > offset
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > topics.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > Thanks,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > Jason
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > On Mon, Jun 24,
>> > 2019
>> > > > at
>> > > > > > > 10:07
>> > > > > > > > AM
>> > > > > > > > > > > > Boyang
>> > > > > > > > > > > > > > > Chen <
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > reluctanthero...@gmail.com
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > Thank you
>> > Ismael
>> > > > for
>> > > > > > the
>> > > > > > > > > > > > suggestion.
>> > > > > > > > > > > > > > We
>> > > > > > > > > > > > > > > > will
>> > > > > > > > > > > > > > > > > > > > attempt
>> > > > > > > > > > > > > > > > > > > > > >>> to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > address
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> it by
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > giving more
>> > > > details
>> > > > > to
>> > > > > > > > > > rejected
>> > > > > > > > > > > > > > > > alternative
>> > > > > > > > > > > > > > > > > > > > section.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > Thank you
>> for
>> > > the
>> > > > > > > comment
>> > > > > > > > > > > > Guozhang!
>> > > > > > > > > > > > > > > > Answers
>> > > > > > > > > > > > > > > > > > are
>> > > > > > > > > > > > > > > > > > > > > inline
>> > > > > > > > > > > > > > > > > > > > > >>> > > below.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > On Sun, Jun
>> > 23,
>> > > > 2019
>> > > > > > at
>> > > > > > > > 6:33
>> > > > > > > > > > PM
>> > > > > > > > > > > > > > Guozhang
>> > > > > > > > > > > > > > > > > Wang
>> > > > > > > > > > > > > > > > > > <
>> > > > > > > > > > > > > > > > > > > > > >>> > > > wangg...@gmail.com
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > Hello
>> > Boyang,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > Thanks
>> for
>> > the
>> > > > > KIP,
>> > > > > > I
>> > > > > > > > have
>> > > > > > > > > > > some
>> > > > > > > > > > > > > > > comments
>> > > > > > > > > > > > > > > > > > > below:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > 1. "Once
>> > > > > > transactions
>> > > > > > > > are
>> > > > > > > > > > > > > complete,
>> > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > call
>> > > > > > > > > > > > > > > > > > > > will
>> > > > > > > > > > > > > > > > > > > > > >>> > return."
>> > > > > > > > > > > > > > > > > > > > > >>> > > > This
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > seems
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > different
>> > from
>> > > > the
>> > > > > > > > > existing
>> > > > > > > > > > > > > > behavior,
>> > > > > > > > > > > > > > > in
>> > > > > > > > > > > > > > > > > > which
>> > > > > > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > > > >>> would
>> > > > > > > > > > > > > > > > > > > > > >>> > > > return a
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > retriable
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > CONCURRENT_TRANSACTIONS
>> > > > > > > > > and
>> > > > > > > > > > > let
>> > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > client
>> > > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> retry, is
>> > > > > > > > > > > > > > > > > > > > > >>> > > this
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > intentional?
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > I don’t
>> think
>> > it
>> > > > is
>> > > > > > > > > > intentional,
>> > > > > > > > > > > > > and I
>> > > > > > > > > > > > > > > > will
>> > > > > > > > > > > > > > > > > > > defer
>> > > > > > > > > > > > > > > > > > > > > this
>> > > > > > > > > > > > > > > > > > > > > >>> > > > question to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > Jason
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > when he got
>> > time
>> > > > to
>> > > > > > > answer
>> > > > > > > > > > since
>> > > > > > > > > > > > > from
>> > > > > > > > > > > > > > > > what I
>> > > > > > > > > > > > > > > > > > > > > >>> understood
>> > > > > > > > > > > > > > > > > > > > > >>> > > retry
>> > > > > > > > > > > > > > > > > > > > > >>> > > > and
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> on
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > hold
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > seem both
>> > valid
>> > > > > > > > approaches.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > 2. "an
>> > > overload
>> > > > to
>> > > > > > > > > > > > > > > onPartitionsAssigned
>> > > > > > > > > > > > > > > > in
>> > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > consumer's
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> rebalance
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > listener
>> > > > > interface":
>> > > > > > > as
>> > > > > > > > > part
>> > > > > > > > > > > of
>> > > > > > > > > > > > > > > KIP-341
>> > > > > > > > > > > > > > > > > > we've
>> > > > > > > > > > > > > > > > > > > > > >>> already
>> > > > > > > > > > > > > > > > > > > > > >>> > add
>> > > > > > > > > > > > > > > > > > > > > >>> > > > this
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > information
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > to the
>> > > > > onAssignment
>> > > > > > > > > > callback.
>> > > > > > > > > > > > > Would
>> > > > > > > > > > > > > > > this
>> > > > > > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > > > > > >>> sufficient?
>> > > > > > > > > > > > > > > > > > > > > >>> > Or
>> > > > > > > > > > > > > > > > > > > > > >>> > > > more
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > generally
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > speaking,
>> > > which
>> > > > > > > > > information
>> > > > > > > > > > > have
>> > > > > > > > > > > > > to
>> > > > > > > > > > > > > > be
>> > > > > > > > > > > > > > > > > > passed
>> > > > > > > > > > > > > > > > > > > > > >>> around in
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> rebalance
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > callback
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > while
>> others
>> > > can
>> > > > > be
>> > > > > > > > passed
>> > > > > > > > > > > > around
>> > > > > > > > > > > > > in
>> > > > > > > > > > > > > > > > > > > > > >>> PartitionAssignor
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> callback? In
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > Streams
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > for
>> example
>> > > both
>> > > > > > > > callbacks
>> > > > > > > > > > are
>> > > > > > > > > > > > > used
>> > > > > > > > > > > > > > > but
>> > > > > > > > > > > > > > > > > most
>> > > > > > > > > > > > > > > > > > > > > >>> critical
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> information
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > is
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > passed
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > via
>> > > > onAssignment.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > We still
>> need
>> > to
>> > > > > > extend
>> > > > > > > > > > > > > > > > > > > ConsumerRebalanceListener
>> > > > > > > > > > > > > > > > > > > > > >>> because
>> > > > > > > > > > > > > > > > > > > > > >>> > > > it’s the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > interface
>> we
>> > > could
>> > > > > > have
>> > > > > > > > > public
>> > > > > > > > > > > > > access
>> > > > > > > > > > > > > > > to.
>> > > > > > > > > > > > > > > > > The
>> > > > > > > > > > > > > > > > > > > > > >>> > #onAssignment
>> > > > > > > > > > > > > > > > > > > > > >>> > > > call
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> is
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > defined
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > on
>> > > > PartitionAssignor
>> > > > > > > level
>> > > > > > > > > > which
>> > > > > > > > > > > > is
>> > > > > > > > > > > > > > not
>> > > > > > > > > > > > > > > > easy
>> > > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > work
>> > > > > > > > > > > > > > > > > > > > > >>> with
>> > > > > > > > > > > > > > > > > > > > > >>> > > > external
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > producers.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > 3. "We
>> > propose
>> > > > to
>> > > > > > use
>> > > > > > > a
>> > > > > > > > > > > separate
>> > > > > > > > > > > > > > > record
>> > > > > > > > > > > > > > > > > type
>> > > > > > > > > > > > > > > > > > > in
>> > > > > > > > > > > > > > > > > > > > > >>> order to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > store
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > group
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > assignment.":
>> > > > > hmm, I
>> > > > > > > > > thought
>> > > > > > > > > > > > with
>> > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > third
>> > > > > > > > > > > > > > > > > > > > typed
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> FindCoordinator,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > same
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > broker
>> that
>> > > act
>> > > > as
>> > > > > > the
>> > > > > > > > > > > consumer
>> > > > > > > > > > > > > > > > > coordinator
>> > > > > > > > > > > > > > > > > > > > would
>> > > > > > > > > > > > > > > > > > > > > >>> > always
>> > > > > > > > > > > > > > > > > > > > > >>> > > be
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > selected
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > as
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > the txn
>> > > > > coordinator,
>> > > > > > > in
>> > > > > > > > > > which
>> > > > > > > > > > > > case
>> > > > > > > > > > > > > > it
>> > > > > > > > > > > > > > > > can
>> > > > > > > > > > > > > > > > > > > access
>> > > > > > > > > > > > > > > > > > > > > its
>> > > > > > > > > > > > > > > > > > > > > >>> > local
>> > > > > > > > > > > > > > > > > > > > > >>> > > > cache
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > metadata /
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > offset
>> topic
>> > > to
>> > > > > get
>> > > > > > > this
>> > > > > > > > > > > > > information
>> > > > > > > > > > > > > > > > > > already?
>> > > > > > > > > > > > > > > > > > > We
>> > > > > > > > > > > > > > > > > > > > > >>> just
>> > > > > > > > > > > > > > > > > > > > > >>> > need
>> > > > > > > > > > > > > > > > > > > > > >>> > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> think
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > about
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > how to
>> make
>> > > > these
>> > > > > > two
>> > > > > > > > > > modules
>> > > > > > > > > > > > > > directly
>> > > > > > > > > > > > > > > > > > > exchange
>> > > > > > > > > > > > > > > > > > > > > >>> > > information
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> without
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > messing
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > up the
>> code
>> > > > > > hierarchy.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > These two
>> > > > > coordinators
>> > > > > > > > will
>> > > > > > > > > be
>> > > > > > > > > > > on
>> > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > same
>> > > > > > > > > > > > > > > > > > > broker
>> > > > > > > > > > > > > > > > > > > > > only
>> > > > > > > > > > > > > > > > > > > > > >>> > when
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> number of
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > partitions
>> for
>> > > > > > > transaction
>> > > > > > > > > > state
>> > > > > > > > > > > > > topic
>> > > > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > > > consumer
>> > > > > > > > > > > > > > > > > > > > > >>> offset
>> > > > > > > > > > > > > > > > > > > > > >>> > > > topic
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> are
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > same. This
>> > > > normally
>> > > > > > > holds
>> > > > > > > > > > true,
>> > > > > > > > > > > > but
>> > > > > > > > > > > > > > I'm
>> > > > > > > > > > > > > > > > > afraid
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > we couldn't
>> > make
>> > > > > this
>> > > > > > > > > > > assumption?
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > 4. The
>> config
>> > of
>> > > > > > > > > > > > > > > > > > > > "CONSUMER_GROUP_AWARE_TRANSACTION":
>> > > > > > > > > > > > > > > > > > > > > >>> it
>> > > > > > > > > > > > > > > > > > > > > >>> > > seems
>> > > > > > > > > > > > > > > > > > > > > >>> > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > goal
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > of
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > this
>> config
>> > is
>> > > > > just
>> > > > > > to
>> > > > > > > > > avoid
>> > > > > > > > > > > > > > > > old-versioned
>> > > > > > > > > > > > > > > > > > > > broker
>> > > > > > > > > > > > > > > > > > > > > >>> to not
>> > > > > > > > > > > > > > > > > > > > > >>> > > be
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> able to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > recognize
>> > > newer
>> > > > > > > > versioned
>> > > > > > > > > > > > client.
>> > > > > > > > > > > > > I
>> > > > > > > > > > > > > > > > think
>> > > > > > > > > > > > > > > > > if
>> > > > > > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > > > can
>> > > > > > > > > > > > > > > > > > > > > >>> do
>> > > > > > > > > > > > > > > > > > > > > >>> > > > something
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > else
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > avoid
>> this
>> > > > config
>> > > > > > > > though,
>> > > > > > > > > > for
>> > > > > > > > > > > > > > example
>> > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > can
>> > > > > > > > > > > > > > > > > > > use
>> > > > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > embedded
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > AdminClient
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > to send
>> the
>> > > > > > APIVersion
>> > > > > > > > > > request
>> > > > > > > > > > > > > upon
>> > > > > > > > > > > > > > > > > starting
>> > > > > > > > > > > > > > > > > > > up,
>> > > > > > > > > > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > > > > >>> > based
>> > > > > > > > > > > > > > > > > > > > > >>> > > > on
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > returned
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > value
>> > decides
>> > > > > > whether
>> > > > > > > to
>> > > > > > > > > go
>> > > > > > > > > > to
>> > > > > > > > > > > > the
>> > > > > > > > > > > > > > old
>> > > > > > > > > > > > > > > > > code
>> > > > > > > > > > > > > > > > > > > path
>> > > > > > > > > > > > > > > > > > > > > or
>> > > > > > > > > > > > > > > > > > > > > >>> the
>> > > > > > > > > > > > > > > > > > > > > >>> > > new
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > behavior.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> Admittedly
>> > > > asking
>> > > > > a
>> > > > > > > > random
>> > > > > > > > > > > > broker
>> > > > > > > > > > > > > > > about
>> > > > > > > > > > > > > > > > > > > > APIVersion
>> > > > > > > > > > > > > > > > > > > > > >>> does
>> > > > > > > > > > > > > > > > > > > > > >>> > > not
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > guarantee
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > whole
>> > > cluster's
>> > > > > > > > versions,
>> > > > > > > > > > but
>> > > > > > > > > > > > what
>> > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > can
>> > > > > > > > > > > > > > > > > do
>> > > > > > > > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> first
>> > > > > > > > > > > > > > > > > > > > > >>> > > 1)
>> > > > > > > > > > > > > > > > > > > > > >>> > > > find
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> coordinator
>> > > (and
>> > > > > if
>> > > > > > > the
>> > > > > > > > > > random
>> > > > > > > > > > > > > > broker
>> > > > > > > > > > > > > > > > does
>> > > > > > > > > > > > > > > > > > not
>> > > > > > > > > > > > > > > > > > > > > even
>> > > > > > > > > > > > > > > > > > > > > >>> > > > recognize
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > new
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > discover
>> > type,
>> > > > > fall
>> > > > > > > back
>> > > > > > > > > to
>> > > > > > > > > > > old
>> > > > > > > > > > > > > path
>> > > > > > > > > > > > > > > > > > > directly),
>> > > > > > > > > > > > > > > > > > > > > and
>> > > > > > > > > > > > > > > > > > > > > >>> then
>> > > > > > > > > > > > > > > > > > > > > >>> > > 2)
>> > > > > > > > > > > > > > > > > > > > > >>> > > > ask
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> discovered
>> > > > > > coordinator
>> > > > > > > > > about
>> > > > > > > > > > > its
>> > > > > > > > > > > > > > > > supported
>> > > > > > > > > > > > > > > > > > > > > >>> APIVersion.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > The caveat
>> > here
>> > > is
>> > > > > > that
>> > > > > > > we
>> > > > > > > > > > have
>> > > > > > > > > > > to
>> > > > > > > > > > > > > > make
>> > > > > > > > > > > > > > > > sure
>> > > > > > > > > > > > > > > > > > > both
>> > > > > > > > > > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > group
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > coordinator
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > and
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > transaction
>> > > > > > coordinator
>> > > > > > > > are
>> > > > > > > > > on
>> > > > > > > > > > > the
>> > > > > > > > > > > > > > > latest
>> > > > > > > > > > > > > > > > > > > version
>> > > > > > > > > > > > > > > > > > > > > >>> during
>> > > > > > > > > > > > > > > > > > > > > >>> > > init
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> stage.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > This
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > is
>> potentially
>> > > > > doable
>> > > > > > as
>> > > > > > > > we
>> > > > > > > > > > only
>> > > > > > > > > > > > > need
>> > > > > > > > > > > > > > a
>> > > > > > > > > > > > > > > > > > consumer
>> > > > > > > > > > > > > > > > > > > > > >>> group.id
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > to check
>> that.
>> > > In
>> > > > > the
>> > > > > > > > > > meantime,
>> > > > > > > > > > > a
>> > > > > > > > > > > > > > > > hard-coded
>> > > > > > > > > > > > > > > > > > > > config
>> > > > > > > > > > > > > > > > > > > > > is
>> > > > > > > > > > > > > > > > > > > > > >>> > > still a
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > favorable
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > backup in
>> case
>> > > the
>> > > > > > > server
>> > > > > > > > > has
>> > > > > > > > > > > > > > > downgraded,
>> > > > > > > > > > > > > > > > so
>> > > > > > > > > > > > > > > > > > you
>> > > > > > > > > > > > > > > > > > > > > will
>> > > > > > > > > > > > > > > > > > > > > >>> want
>> > > > > > > > > > > > > > > > > > > > > >>> > > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > use
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> a
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > new
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > version
>> client
>> > > > > without
>> > > > > > > > > > `consumer
>> > > > > > > > > > > > > > group`
>> > > > > > > > > > > > > > > > > > > > > transactional
>> > > > > > > > > > > > > > > > > > > > > >>> > > support.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > 5. This is
>> a
>> > > meta
>> > > > > > > > question:
>> > > > > > > > > > have
>> > > > > > > > > > > > you
>> > > > > > > > > > > > > > > > > > considered
>> > > > > > > > > > > > > > > > > > > > how
>> > > > > > > > > > > > > > > > > > > > > >>> this
>> > > > > > > > > > > > > > > > > > > > > >>> > can
>> > > > > > > > > > > > > > > > > > > > > >>> > > > be
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > applied
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > Kafka
>> > Connect
>> > > as
>> > > > > > well?
>> > > > > > > > For
>> > > > > > > > > > > > > example,
>> > > > > > > > > > > > > > > for
>> > > > > > > > > > > > > > > > > > source
>> > > > > > > > > > > > > > > > > > > > > >>> > connectors,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > assignment
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > is not by
>> > > > > > > "partitions",
>> > > > > > > > > but
>> > > > > > > > > > by
>> > > > > > > > > > > > > some
>> > > > > > > > > > > > > > > > other
>> > > > > > > > > > > > > > > > > > sort
>> > > > > > > > > > > > > > > > > > > > of
>> > > > > > > > > > > > > > > > > > > > > >>> > > > "resources"
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> based
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > on
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > source
>> > > systems,
>> > > > > how
>> > > > > > > > > KIP-447
>> > > > > > > > > > > > would
>> > > > > > > > > > > > > > > affect
>> > > > > > > > > > > > > > > > > > Kafka
>> > > > > > > > > > > > > > > > > > > > > >>> > Connectors
>> > > > > > > > > > > > > > > > > > > > > >>> > > > that
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > implemented
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > EOS as
>> well?
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > No, it's
>> not
>> > > > > currently
>> > > > > > > > > > included
>> > > > > > > > > > > in
>> > > > > > > > > > > > > the
>> > > > > > > > > > > > > > > > > scope.
>> > > > > > > > > > > > > > > > > > > > Could
>> > > > > > > > > > > > > > > > > > > > > >>> you
>> > > > > > > > > > > > > > > > > > > > > >>> > > point
>> > > > > > > > > > > > > > > > > > > > > >>> > > > me
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> to a
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > sample
>> source
>> > > > > > connector
>> > > > > > > > who
>> > > > > > > > > > uses
>> > > > > > > > > > > > > EOS?
>> > > > > > > > > > > > > > > > Could
>> > > > > > > > > > > > > > > > > > > always
>> > > > > > > > > > > > > > > > > > > > > >>> > > piggy-back
>> > > > > > > > > > > > > > > > > > > > > >>> > > > into
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > the
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > TxnProducerIdentity
>> > > > > > > struct
>> > > > > > > > > > with
>> > > > > > > > > > > > more
>> > > > > > > > > > > > > > > > > > information
>> > > > > > > > > > > > > > > > > > > > > such
>> > > > > > > > > > > > > > > > > > > > > >>> as
>> > > > > > > > > > > > > > > > > > > > > >>> > > > tasks. If
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > this is
>> > > something
>> > > > to
>> > > > > > > > support
>> > > > > > > > > > in
>> > > > > > > > > > > > near
>> > > > > > > > > > > > > > > term,
>> > > > > > > > > > > > > > > > > an
>> > > > > > > > > > > > > > > > > > > > > abstract
>> > > > > > > > > > > > > > > > > > > > > >>> > type
>> > > > > > > > > > > > > > > > > > > > > >>> > > > called
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > "Resource"
>> > could
>> > > > be
>> > > > > > > > provided
>> > > > > > > > > > and
>> > > > > > > > > > > > let
>> > > > > > > > > > > > > > > topic
>> > > > > > > > > > > > > > > > > > > > partition
>> > > > > > > > > > > > > > > > > > > > > >>> and
>> > > > > > > > > > > > > > > > > > > > > >>> > > > connect
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> task
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > implement
>> it.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > Guozhang
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > On Sat,
>> Jun
>> > > 22,
>> > > > > 2019
>> > > > > > > at
>> > > > > > > > > 8:40
>> > > > > > > > > > > PM
>> > > > > > > > > > > > > > Ismael
>> > > > > > > > > > > > > > > > > Juma
>> > > > > > > > > > > > > > > > > > <
>> > > > > > > > > > > > > > > > > > > > > >>> > > > ism...@juma.me.uk>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > Hi
>> Boyang,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > Thanks
>> for
>> > > the
>> > > > > > KIP.
>> > > > > > > > It's
>> > > > > > > > > > > good
>> > > > > > > > > > > > > that
>> > > > > > > > > > > > > > > we
>> > > > > > > > > > > > > > > > > > > listed a
>> > > > > > > > > > > > > > > > > > > > > >>> number
>> > > > > > > > > > > > > > > > > > > > > >>> > of
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> rejected
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > >
>> > > alternatives.
>> > > > It
>> > > > > > > would
>> > > > > > > > > be
>> > > > > > > > > > > > > helpful
>> > > > > > > > > > > > > > to
>> > > > > > > > > > > > > > > > > have
>> > > > > > > > > > > > > > > > > > an
>> > > > > > > > > > > > > > > > > > > > > >>> > explanation
>> > > > > > > > > > > > > > > > > > > > > >>> > > > of
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> why
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > they
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > were
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > >
>> rejected.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > Ismael
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > On Sat,
>> > Jun
>> > > > 22,
>> > > > > > 2019
>> > > > > > > > at
>> > > > > > > > > > 8:31
>> > > > > > > > > > > > PM
>> > > > > > > > > > > > > > > Boyang
>> > > > > > > > > > > > > > > > > > Chen
>> > > > > > > > > > > > > > > > > > > <
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> bche...@outlook.com
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > wrote:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > > Hey
>> all,
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > > I
>> would
>> > > like
>> > > > > to
>> > > > > > > > start
>> > > > > > > > > a
>> > > > > > > > > > > > > > discussion
>> > > > > > > > > > > > > > > > for
>> > > > > > > > > > > > > > > > > > > > > KIP-447:
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> > > > > > > > > > > > > > > > > > > > > >>> >
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > >
>> > > > > > > >
>> > > > > > >
>> > > > > >
>> > > > >
>> > > >
>> > >
>> >
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-447%3A+Producer+scalability+for+exactly+once+semantics
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > > this
>> is
>> > a
>> > > > work
>> > > > > > > > > > originated
>> > > > > > > > > > > by
>> > > > > > > > > > > > > > Jason
>> > > > > > > > > > > > > > > > > > > Gustafson
>> > > > > > > > > > > > > > > > > > > > > >>> and we
>> > > > > > > > > > > > > > > > > > > > > >>> > > > would
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> like
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > to
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > proceed
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > > into
>> > > > > discussion
>> > > > > > > > stage.
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > > Let
>> me
>> > > know
>> > > > > your
>> > > > > > > > > > thoughts,
>> > > > > > > > > > > > > > thanks!
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > >
>> Boyang
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > --
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > > --
>> Guozhang
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > --
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> > -- Guozhang
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >> >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >>
>> > > > > > > > > > > > > > > > > > > > > >>> > > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > > >
>> > > > > > > > > > > > > > > > > > > > > >>> > >
>> > > > > > > > > > > > > > > > > > > > > >>> >
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>> --
>> > > > > > > > > > > > > > > > > > > > > >>> -- Guozhang
>> > > > > > > > > > > > > > > > > > > > > >>>
>> > > > > > > > > > > > > > > > > > > > > >>
>> > > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > > > --
>> > > > > > > > > > > > > > > > > > -- Guozhang
>> > > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > > > --
>> > > > > > > > > > > > > > > > -- Guozhang
>> > > > > > > > > > > > > > > >
>> > > > > > > > > > > > > > >
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > > > --
>> > > > > > > > > > > > > > -- Guozhang
>> > > > > > > > > > > > > >
>> > > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > > >
>> > > > > > > > > > > > --
>> > > > > > > > > > > > -- Guozhang
>> > > > > > > > > > > >
>> > > > > > > > > > >
>> > > > > > > > > >
>> > > > > > > > >
>> > > > > > > >
>> > > > > > >
>> > > > > >
>> > > > >
>> > > >
>> > > >
>> > > > --
>> > > > -- Guozhang
>> > > >
>> > >
>> >
>>
>>
>> --
>> -- Guozhang
>>
>
