Hi all,
sorry for joining late in the game, the carribean got in the way.
My thoughts:
There is no way around the chicken&egg problem, so the sooner we can
add protocol versioning functionality the better and we'll add heuristics
in clients to
handle the migration period (e.g, what Dana has done in kafka-python).
The focus at this point should be to mitigate the core issue (allow clients
to know what is supported)
in the least intrusive way. Hopefully we can redesign the protocol in the
future to add proper
response headers, etc.
I'm with Data that reusing the broker version as a protocol version will
work just fine and
saves us from administrating another version.
>From a client's perspective an explicit protocol version doesn't really add
any value.
I'd rather maintain a mapping of actual broker versions to supported
protocol requests rather than
some independent protocol version that still needs to be translated to a
broker version for
proper code maintainability / error messages / etc.
Thus my suggestion is in line with some of the previous speakers, that is
is to keep things
simple and bump the MetadataRequest version to 1 by adding a VersionString
("0.9.1.0")
and VersionInt (0x00090100) field to the response.
These fields return version information for the current connection's broker
only, not for other broker's
in the cluster:
Providing version information for other brokers doesn't really serve any
purpose:
a) the information is cached by the responding broker so it might be
outdated ( = cant be trusted)
b) by the time the client connects to a given broker it might have upgraded
This means that a client (that is interested in protocol versioning) will
need to query each
connection's version any way. Since MetadataRequets are typically already
sent on connection set up
this seems to be the proper place to put it.
The MetadataRequest semantics should also be extended to allow asking only
for cluster and version information,
but not the topic list since this might have negative performance impact on
large clusters with many topics.
One way to achieve this would be to provide one single Null topic in the
request (length=-1).
Sending a new Metadata V1 request to an old broker will cause the
connection to be closed and
the client will need to use this as a heuristic to downgrade its protocol
ambitions to an older version
(either by some default value or by user configuration).
/Magnus
2016-03-10 20:04 GMT+01:00 Ashish Singh <asi...@cloudera.com>:
> @Magnus,
>
> Does the latest suggestion sound OK to you. I am planning to update PR
> based on latest suggestion.
>
> On Mon, Mar 7, 2016 at 10:58 AM, Ashish Singh <asi...@cloudera.com> wrote:
>
> >
> >
> > On Fri, Mar 4, 2016 at 5:46 PM, Jay Kreps <j...@confluent.io> wrote:
> >
> >> Hey Ashish,
> >>
> >> Both good points.
> >>
> >> I think the issue with the general metadata request is the same as the
> >> issue with a version-specific metadata request from the other
> >> proposal--basically it's a chicken and egg problem, to find out anything
> >> about the cluster you have to be able to communicate something in a
> format
> >> the server can understand without knowing a priori what version it's
> on. I
> >> guess the question is how can you continue to evolve the metadata
> request
> >> (whether it is the existing metadata or a protocol-version specific
> >> metadata request) given that you need this information to bootstrap you
> >> have to be more careful in how that request evolves.
> >>
> > You are correct. It's just that protocol version request would be very
> > specific to retrieve the protocol versions. Changes to protocol version
> > request itself should be very rare, if at all. However, the general
> > metadata request carries a lot more information and its format is more
> > probable to evolve. This boils down to higher probability of change vs a
> > definite network round-trip for each re/connect. It does sound like, it
> is
> > better to avoid a definite penalty than to avoid a probable rare issue.
> >
> >>
> >> I think deprecation/removal may be okay. Ultimately clients will always
> >> use
> >> the highest possible version of the protocol the server supports so if
> >> we've already deprecated and removed your highest version then you are
> >> screwed and you're going to get an error no matter what, right?
> Basically
> >> there is nothing dynamic you can do in that case.
> >>
> > Sure, this should be expected. Just wanted to make sure deprecation is
> > still on the table.
> >
> >>
> >> -Jay
> >>
> >> On Fri, Mar 4, 2016 at 4:05 PM, Ashish Singh <asi...@cloudera.com>
> wrote:
> >>
> >> > Hello Jay,
> >> >
> >> > The overall approach sounds good. I do realize that this discussion
> has
> >> > gotten too lengthy and is starting to shoot tangents. Maybe a KIP call
> >> will
> >> > help us getting to a decision faster. I do have a few questions
> though.
> >> >
> >> > On Fri, Mar 4, 2016 at 9:52 AM, Jay Kreps <j...@confluent.io> wrote:
> >> >
> >> > > Yeah here is my summary of my take:
> >> > >
> >> > > 1. Negotiating a per-connection protocol actually does add a lot of
> >> > > complexity to clients (many more failure states to get right).
> >> > >
> >> > > 2. Having the client configure the protocol version manually is
> doable
> >> > now
> >> > > but probably a worse state. I suspect this will lead to more not
> less
> >> > > confusion.
> >> > >
> >> > > 3. I don't think the current state is actually that bad. Integrators
> >> > pick a
> >> > > conservative version and build against that. There is a tradeoff
> >> between
> >> > > getting the new features and being compatible with old Kafka
> versions.
> >> > But
> >> > > a large part of this tradeoff is essential since new features aren't
> >> > going
> >> > > to magically appear on old servers, so even if you upgrade your
> client
> >> > you
> >> > > likely aren't going to get the new stuff (since we will end up
> >> > dynamically
> >> > > turning it off). Having client features that are there but don't
> work
> >> > > because you're on an old cluster may actually be a worse experience
> if
> >> > not
> >> > > handled very carefully..
> >> > >
> >> > > 4. The problems Dana brought up are totally orthogonal to the
> problem
> >> of
> >> > > having per-api versions or overall versions. The problem was that we
> >> > > changed behavior subtly without changing the version. This will be
> an
> >> > issue
> >> > > regardless of whether the version is global or not.
> >> > >
> >> > > 5. Using the broker release as the version is strictly worse than
> >> using a
> >> > > global protocol version (0, 1, 2, ...) that increments any time any
> >> api
> >> > > changes but doesn't increment just because non-protocol code is
> >> changed.
> >> > > The problem with using the broker release version is we want to be
> >> able
> >> > to
> >> > > keep Kafka releasable from any commit which means there isn't as
> >> clear a
> >> > > sequencing of releases as you would think.
> >> > >
> >> > > 6. We need to consider the case of mixed version clusters during the
> >> time
> >> > > period when you are upgrading Kafka.
> >> > >
> >> > > So overall I think this is not a critical thing to do right now, but
> >> if
> >> > we
> >> > > are going to do it we should do it in a way that actually improves
> >> > things.
> >> > >
> >> > > Here would be one proposal for that:
> >> > > a. Add a global protocol version that increments with any api
> version
> >> > > update. Move the documentation so that the docs are by version. This
> >> is
> >> > > basically just a short-hand for a complete set of supported api
> >> versions.
> >> > > b. Include a field in the metadata response for each broker that
> adds
> >> the
> >> > > protocol version.
> >> > >
> >> > There might be an issue here where the metadata request version sent
> by
> >> > client is not supported by broker, an older broker. However, if we are
> >> > clearly stating that a client is not guaranteed to work with an older
> >> > broker then this becomes expected. This will potentially limit us in
> >> terms
> >> > of supporting downgrades though, if we ever want to.
> >> >
> >> > > c. To maintain the protocol version this information will have to
> get
> >> > > propagated with the rest of the broker metadata like host, port, id,
> >> etc.
> >> > >
> >> > > The instructions to clients would be:
> >> > > - By default you build against a single conservative Kafka protocol
> >> > version
> >> > > and we carry that support forward, as today
> >> > >
> >> > If I am getting this correct, this will mean we will never
> >> deprecate/remove
> >> > any protocol version in future. Having some way to deprecate/remove
> >> older
> >> > protocol versions will probably be a good idea. It is possible with
> the
> >> > global protocol version approach, it could be as simple as marking a
> >> > protocol deprecated in protocol doc before removing it. Just want to
> >> make
> >> > sure deprecation is still on the table.
> >> >
> >> > > - If you want to get fancy you can use the protocol version field in
> >> the
> >> > > metadata request to more dynamically chose what features are
> available
> >> > and
> >> > > select api versions appropriately. This is purely optional.
> >> > >
> >> > > -Jay
> >> > >
> >> > > On Thu, Mar 3, 2016 at 9:38 PM, Jason Gustafson <ja...@confluent.io
> >
> >> > > wrote:
> >> > >
> >> > > > I talked with Jay about this KIP briefly this morning, so let me
> >> try to
> >> > > > summarize the discussion (I'm sure he'll jump in if I get anything
> >> > > wrong).
> >> > > > Apologies in advance for the length.
> >> > > >
> >> > > > I think we both share some skepticism that a request with all the
> >> > > supported
> >> > > > versions of all the request APIs is going to be a useful primitive
> >> to
> >> > try
> >> > > > and build client compatibility around. In practice I think people
> >> would
> >> > > end
> >> > > > up checking for particular request versions in order to determine
> if
> >> > the
> >> > > > broker is 0.8 or 0.9 or whatever, and then change behavior
> >> accordingly.
> >> > > I'm
> >> > > > wondering if there's a reasonable way to handle the version
> >> responses
> >> > > that
> >> > > > doesn't amount to that. Maybe you could try to capture feature
> >> > > > compatibility by checking the versions for a subset of request
> >> types?
> >> > For
> >> > > > example, to ensure that you can use the new consumer API, you
> check
> >> > that
> >> > > > the group coordinator request is present, the offset commit
> request
> >> > > version
> >> > > > is greater than 2, the offset fetch request is greater than 1, and
> >> the
> >> > > join
> >> > > > group request is present. And to ensure compatibility with KIP-32,
> >> > maybe
> >> > > > you only need to check the appropriate versions of the fetch and
> >> > produce
> >> > > > requests. That sounds kind of complicated to keep track of and you
> >> > > probably
> >> > > > end up trying to handle combinations which aren't even possible in
> >> > > > practice.
> >> > > >
> >> > > > The alternative is to use a single API version. It could be the
> >> Kafka
> >> > > > release version, but then you need to figure out how to handle
> users
> >> > who
> >> > > > are running off of trunk since multiple API versions will
> typically
> >> > > change
> >> > > > between releases. Perhaps it makes more sense to keep a separate
> API
> >> > > > version number which is incremented every time any one of the API
> >> > > versions
> >> > > > increases? This also decouples the protocol from the Kafka
> >> > distribution.
> >> > > >
> >> > > > As far as whether there should be a separate request or not, I get
> >> > > Becket's
> >> > > > point that you would only need to do the version check once when a
> >> > > > connection is established, but another round trip still
> complicates
> >> the
> >> > > > picture quite a bit. Before you just need to send a metadata
> >> request to
> >> > > > bootstrap yourself to the cluster, but now you need to do version
> >> > > > negotiation before you can even do that, and then you need to try
> >> adapt
> >> > > to
> >> > > > the versions reported. Jay brought up the point that you probably
> >> > > wouldn't
> >> > > > design a protocol from scratch to work this way. Using the
> metadata
> >> > > request
> >> > > > would be better if it's possible, but you need a way to handle the
> >> fact
> >> > > > that a broker's version might be stale by the time you connect to
> >> it.
> >> > And
> >> > > > even then you're going to have to deal internally with the
> >> complexity
> >> > > > involved in trying to upgrade/downgrade dynamically, which sounds
> >> to me
> >> > > > like it would have a ton of edge cases.
> >> > > >
> >> > > > Taking a bit of a step back, any solution is probably going to be
> >> > painful
> >> > > > since the Kafka protocol was not designed for this use case.
> >> Currently
> >> > > what
> >> > > > that means for clients that /want/ to support compatibility across
> >> > broker
> >> > > > versions is that they need to have the user tell them the broker
> >> > version
> >> > > > through configuration (e.g. librdkafka has a "protocol.version"
> >> field
> >> > for
> >> > > > this purpose). The only real problem with this in my mind is that
> we
> >> > > don't
> >> > > > have a graceful way to detect request incompatibility, which is
> why
> >> > there
> >> > > > are so many questions on the user list which basically amount to
> the
> >> > > client
> >> > > > hanging because the broker refuses to respond to a request it
> >> doesn't
> >> > > > understand. If you solve this problem, then depending on
> >> configuration
> >> > > > seems totally reasonable and we can skip trying to implement
> request
> >> > > > version negotiation. Magnus's solution in this KIP may seem a
> little
> >> > > hacky,
> >> > > > but it also seems like the only way to do it without changing the
> >> > header.
> >> > > >
> >> > > > The Spark problem mentioned above is interesting and I agree that
> it
> >> > > sucks
> >> > > > for frameworks that need to ship the kafka client library since
> they
> >> > have
> >> > > > to figure out how to bundle multiple versions. Ultimately if we
> >> want to
> >> > > > solve this problem, then it sounds like we need to commit to
> >> > maintaining
> >> > > > compatibility with older versions of Kafka in the client going
> >> forward.
> >> > > > That's a lot bigger decision and it matters less whether the
> broker
> >> > > version
> >> > > > is found through configuration, topic metadata, or a new request
> >> type.
> >> > > >
> >> > > > -Jason
> >> > > >
> >> > > >
> >> > > > On Thu, Mar 3, 2016 at 3:59 PM, Becket Qin <becket....@gmail.com>
> >> > wrote:
> >> > > >
> >> > > > > Hi Ashish,
> >> > > > >
> >> > > > > In approach (1), the clients will still be able to talked to
> >> multiple
> >> > > > > versions of Kafka brokers as long as the clients version is not
> >> > higher
> >> > > > than
> >> > > > > the broker version, right?
> >> > > > >
> >> > > > > From Spark's point of view, it seems the difference is whether
> >> Spark
> >> > > can
> >> > > > > independently update their Kafka clients dependency or not. More
> >> > > > > specifically, consider the following three scenarios:
> >> > > > > A. Spark has some new features that do not rely on clients or
> >> brokers
> >> > > in
> >> > > > a
> >> > > > > new Kafka release.
> >> > > > > B. Spark has some new features that only rely on the clients in
> a
> >> new
> >> > > > Kafka
> >> > > > > release, but not rely on the brokers in a new Kafka release.
> e.g.
> >> New
> >> > > > > client provides a listTopic() method.
> >> > > > > C. Spark has some new features that rely on both the clients and
> >> > > brokers
> >> > > > in
> >> > > > > a new Kafka release. e.g timestamp field.
> >> > > > >
> >> > > > > For A, Spark does not need to update the Kafka dependency
> because
> >> > there
> >> > > > is
> >> > > > > no need and the old clients can talk to both new and old Kafka
> >> > brokers.
> >> > > > > For C, Spark has to wait for broker upgrade anyways.
> >> > > > > So in the above two scenarios, there is not much difference
> >> between
> >> > > > > approach (1) and (2).
> >> > > > >
> >> > > > > B is a tricky scenario. Because it is possible that we introduce
> >> both
> >> > > > > listTopic() and the timestamp field in the same Kafka release,
> >> and we
> >> > > > don't
> >> > > > > know if Spark needs both or only uses listTopic().
> >> > > > > This indicates the client should work fine if a method is
> >> supported
> >> > and
> >> > > > > should throw exception when a method is not supported. I think
> we
> >> can
> >> > > do
> >> > > > > the following:
> >> > > > > 0. Clients always use its highest request version. The clients
> >> keeps
> >> > a
> >> > > > > static final map recording the minimum required ApiVersion for
> >> each
> >> > > > > request.
> >> > > > > 1. When connect to a broker, the clients always send an
> >> > > ApiVersionRequest
> >> > > > > to the broker.
> >> > > > > 2. The broker replies with the its highest supported ApiVersion.
> >> > > > > 3. Before sending a request, the clients checks the minimum
> >> required
> >> > > > > ApiVersion for that request. If the broker returned ApiVersion
> is
> >> > > higher
> >> > > > > than this minimum required ApiVersion, then we can proceed.
> >> Otherwise
> >> > > we
> >> > > > > throw something like NotSupportedOperationException.
> >> > > > >
> >> > > > > With this approach, scenario B will also work unless Spark calls
> >> some
> >> > > > > function that is not supported by the Kafka broker, which makes
> it
> >> > > become
> >> > > > > scenario C.
> >> > > > >
> >> > > > > Thoughts?
> >> > > > >
> >> > > > > Thanks,
> >> > > > >
> >> > > > > Jiangjie (Becket) Qin
> >> > > > >
> >> > > > > On Thu, Mar 3, 2016 at 11:24 AM, Ashish Singh <
> >> asi...@cloudera.com>
> >> > > > wrote:
> >> > > > >
> >> > > > > > On Wed, Mar 2, 2016 at 8:29 PM, Becket Qin <
> >> becket....@gmail.com>
> >> > > > wrote:
> >> > > > > >
> >> > > > > > > Hi Jason,
> >> > > > > > >
> >> > > > > > > I was thinking that every time when we connect to a broker,
> we
> >> > > first
> >> > > > > send
> >> > > > > > > the version check request. (The version check request itself
> >> > should
> >> > > > be
> >> > > > > > very
> >> > > > > > > simple and never changes across all server releases.) This
> >> does
> >> > add
> >> > > > an
> >> > > > > > > additional round trip, but given reconnect is rare, it is
> >> > probably
> >> > > > > fine.
> >> > > > > > On
> >> > > > > > > the client side, the client will always send request using
> the
> >> > > lowest
> >> > > > > > > supported version across all brokers. That means if a Kafka
> >> > cluster
> >> > > > is
> >> > > > > > > downgrading, we will use the downgraded protocol as soon as
> >> the
> >> > > > client
> >> > > > > > > connected to an older broker.
> >> > > > > > >
> >> > > > > > This sounds interesting and very similar to current
> suggestion.
> >> > > > However,
> >> > > > > > just to make sure I am getting it right, you are suggesting
> >> send a
> >> > > > > separate
> >> > > > > > request only for release version?
> >> > > > > >
> >> > > > > > >
> >> > > > > > > @Ashish,
> >> > > > > > > Can you help me understand the pain points from other open
> >> source
> >> > > > > > projects
> >> > > > > > > that you mentioned a little more? There are two different
> >> levels
> >> > of
> >> > > > > > > requirements:
> >> > > > > > > 1. User wants to know if the client is compatible with the
> >> broker
> >> > > or
> >> > > > > not.
> >> > > > > > > 2. User wants the client and the broker to negotiate the
> >> protocol
> >> > > on
> >> > > > > > their
> >> > > > > > > own.
> >> > > > > > >
> >> > > > > > Not sure which category it falls in, but below is the excerpt
> >> from
> >> > > > Mark,
> >> > > > > a
> >> > > > > > spark dev, who has been trying to upgrade spark kafka
> >> integration
> >> > to
> >> > > > use
> >> > > > > > 0.9 clients.
> >> > > > > >
> >> > > > > > Based on what I understand, users of Kafka need to upgrade
> their
> >> > > > brokers
> >> > > > > to
> >> > > > > > Kafka 0.9.x first, before they upgrade their clients to Kafka
> >> > 0.9.x.
> >> > > > > >
> >> > > > > > > However, that presents a problem to other projects that
> >> integrate
> >> > > > with
> >> > > > > > Kafka (Spark, Flume, Storm, etc.). From here on, I will speak
> >> for
> >> > > > Spark +
> >> > > > > > Kafka, since that's the one I am most familiar with.
> >> > > > > > In the light of compatibility (or the lack thereof) between
> >> 0.8.x
> >> > and
> >> > > > > > 0.9.x, Spark is faced with a problem of what version(s) of
> >> Kafka to
> >> > > be
> >> > > > > > compatible with, and has 2 options (discussed in this PR
> >> > > > > > <https://github.com/apache/spark/pull/11143>):
> >> > > > > > 1. We either upgrade to Kafka 0.9, dropping support for 0.8.
> >> Storm
> >> > > and
> >> > > > > > Flume are already on this path.
> >> > > > > > 2. We introduce complexity in our code to support both 0.8 and
> >> 0.9
> >> > > for
> >> > > > > the
> >> > > > > > entire duration of our next major release (Apache Spark 2.x).
> >> > > > > > I'd love to hear your thoughts on which option, you recommend.
> >> > > > > > Long term, I'd really appreciate if Kafka could do something
> >> that
> >> > > > doesn't
> >> > > > > > make Spark having to support two, or even more versions of
> >> Kafka.
> >> > > And,
> >> > > > if
> >> > > > > > there is something that I, personally, and Spark project can
> do
> >> in
> >> > > your
> >> > > > > > next release candidate phase to make things easier, please do
> >> let
> >> > us
> >> > > > > know.
> >> > > > > >
> >> > > > > > This issue has made other projects worry about how they are
> >> going
> >> > to
> >> > > > keep
> >> > > > > > up with Kafka releases. Last I heard, take this with a pinch
> of
> >> > salt,
> >> > > > > Spark
> >> > > > > > folks are discussing about using Maven profiles to build
> against
> >> > > > multiple
> >> > > > > > Kafka versions at compile time, etc. Also, there are clients
> who
> >> > are
> >> > > > > > relying on class-loading tricks with custom implementation of
> >> OSGi
> >> > to
> >> > > > > solve
> >> > > > > > such issues. Don't quote me on the stuff I just mentioned, as
> >> this
> >> > is
> >> > > > > what
> >> > > > > > I have heard during casual discussions. The point I am trying
> to
> >> > make
> >> > > > is
> >> > > > > > that Kafka clients are worried about being able to support
> >> multiple
> >> > > > Kafka
> >> > > > > > broker versions. I am sure we all agree on that.
> >> > > > > >
> >> > > > > > I think the second requirement makes more sense from a client
> >> > > > > perspective.
> >> > > > > > First req will just tell them that there is a problem, but no
> >> way
> >> > to
> >> > > > work
> >> > > > > > around it.
> >> > > > > >
> >> > > > > > >
> >> > > > > > > Currently in Kafka the principle we are following is to let
> >> > clients
> >> > > > > stick
> >> > > > > > > to a certain version and server will adapt to the clients
> >> > > > accordingly.
> >> > > > > > > If this KIP doesn't want to break this rule, it seems we
> >> should
> >> > > > simply
> >> > > > > > let
> >> > > > > > > the clients send the ApiVersion it is using to the brokers
> and
> >> > the
> >> > > > > > brokers
> >> > > > > > > will decide whether to accept or reject the clients. This
> >> means
> >> > > user
> >> > > > > have
> >> > > > > > > to upgrade broker before they upgrade clients. This
> satisfies
> >> (1)
> >> > > so
> >> > > > > > that a
> >> > > > > > > newer client will know it does not compatible with an older
> >> > server
> >> > > > > > > immediately.
> >> > > > > > > If this KIP will change that to let the newer clients adapt
> to
> >> > the
> >> > > > > older
> >> > > > > > > brokers, compatibility wise it is a good thing to have.
> With
> >> > this
> >> > > > now
> >> > > > > > > users are able to upgrade clients before they upgrade Kafka
> >> > > brokers.
> >> > > > > This
> >> > > > > > > means user can upgrade clients even before upgrade servers.
> >> This
> >> > > > > > satisfies
> >> > > > > > > (2) as the newer clients can also talk to the older servers.
> >> > > > > > >
> >> > > > > > More importantly, this will allow a client to talk to multiple
> >> > > versions
> >> > > > > of
> >> > > > > > Kafka.
> >> > > > >
> >> > > > >
> >> > > > > > >
> >> > > > > > > If we decide to go with (2). The benefit is that a newer
> >> client
> >> > > won't
> >> > > > > > break
> >> > > > > > > when talking to an older broker. But functionality wise, it
> >> might
> >> > > be
> >> > > > > the
> >> > > > > > > same as an older clients.
> >> > > > > > > In the downgrading case, we probably still have to notify
> all
> >> the
> >> > > > > users.
> >> > > > > > > For example, if application is sending messages with
> timestamp
> >> > and
> >> > > > the
> >> > > > > > > broker got downgraded to an older version that does not
> >> support
> >> > > > > > timestamp.
> >> > > > > > > The clients will suddenly start to throw away timestamps.
> This
> >> > > might
> >> > > > > > affect
> >> > > > > > > the application logic. In this case even if we have clients
> >> > > > > automatically
> >> > > > > > > adapted to a lower version broker, the applications might
> >> still
> >> > > > break.
> >> > > > > > > Hence we still need to notify the users about the case when
> >> the
> >> > > > clients
> >> > > > > > is
> >> > > > > > > newer than the brokers. This is the same for both (1) and
> (2).
> >> > > > > > > Supporting (2) will introduce more complication on the
> client
> >> > side.
> >> > > > And
> >> > > > > > we
> >> > > > > > > may also have to communicate with users about what function
> is
> >> > > > > supported
> >> > > > > > in
> >> > > > > > > the new clients and what is not supported after the protocol
> >> > > > > negotiation
> >> > > > > > > finishes.
> >> > > > > > >
> >> > > > > > Totally agreed, however only if clients want to support
> multiple
> >> > > broker
> >> > > > > > versions. If they want to, then I am sure they are willing to
> >> add
> >> > > some
> >> > > > > > logic on their end.
> >> > > > > >
> >> > > > > > >
> >> > > > > > > Thanks,
> >> > > > > > >
> >> > > > > > > Jiangjie (Becket) Qin
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > > >
> >> > > > > > > On Wed, Mar 2, 2016 at 5:58 PM, Dana Powers <
> >> > dana.pow...@gmail.com
> >> > > >
> >> > > > > > wrote:
> >> > > > > > >
> >> > > > > > > > In kafka-python we've been doing something like:
> >> > > > > > > >
> >> > > > > > > > if version >= (0, 9):
> >> > > > > > > > Do cool new stuff
> >> > > > > > > > elif version >= (0, 8, 2):
> >> > > > > > > > Do some older stuff
> >> > > > > > > > ....
> >> > > > > > > > else:
> >> > > > > > > > raise UnsupportedVersionError
> >> > > > > > > >
> >> > > > > > > > This will break if / when the new 0.9 apis are completely
> >> > removed
> >> > > > > from
> >> > > > > > > some
> >> > > > > > > > future release, but should handle intermediate broker
> >> upgrades.
> >> > > > > Because
> >> > > > > > > we
> >> > > > > > > > can't add support for future apis a priori, I think the
> >> best we
> >> > > > could
> >> > > > > > do
> >> > > > > > > > here is throw an error that request protocol version X is
> >> not
> >> > > > > > supported.
> >> > > > > > > > For now that comes through as a broken socket connection,
> so
> >> > > there
> >> > > > is
> >> > > > > > an
> >> > > > > > > > error - just not a super helpful one.
> >> > > > > > > >
> >> > > > > > > > For that reason I'm also in favor of a generic error
> >> response
> >> > > when
> >> > > > a
> >> > > > > > > > protocol req is not recognized.
> >> > > > > > > >
> >> > > > > > > > -Dana
> >> > > > > > > > On Mar 2, 2016 5:38 PM, "Jay Kreps" <j...@confluent.io>
> >> wrote:
> >> > > > > > > >
> >> > > > > > > > > But won't it be the case that what clients end up doing
> >> would
> >> > > be
> >> > > > > > > > something
> >> > > > > > > > > like
> >> > > > > > > > > if(version != 0.8.1)
> >> > > > > > > > > throw new UnsupportedVersionException()
> >> > > > > > > > > which then means the client is broken as soon as we
> >> release a
> >> > > new
> >> > > > > > > server
> >> > > > > > > > > version even though the protocol didn't change. I'm
> >> actually
> >> > > not
> >> > > > > sure
> >> > > > > > > how
> >> > > > > > > > > you could use that information in a forward compatible
> way
> >> > > since
> >> > > > > you
> >> > > > > > > > can't
> >> > > > > > > > > know a priori if you will work with the next release
> until
> >> > you
> >> > > > know
> >> > > > > > if
> >> > > > > > > > the
> >> > > > > > > > > protocol changed.
> >> > > > > > > > >
> >> > > > > > > > > -Jay
> >> > > > > > > > >
> >> > > > > > > > > On Wed, Mar 2, 2016 at 5:28 PM, Jason Gustafson <
> >> > > > > ja...@confluent.io>
> >> > > > > > > > > wrote:
> >> > > > > > > > >
> >> > > > > > > > > > Hey Jay,
> >> > > > > > > > > >
> >> > > > > > > > > > Yeah, I wasn't suggesting that we eliminate request
> API
> >> > > > versions.
> >> > > > > > > > They're
> >> > > > > > > > > > definitely needed on the broker to support
> >> compatibility. I
> >> > > was
> >> > > > > > just
> >> > > > > > > > > saying
> >> > > > > > > > > > that if a client wants to support multiple broker
> >> versions
> >> > > > (e.g.
> >> > > > > > 0.8
> >> > > > > > > > and
> >> > > > > > > > > > 0.9), then it makes more sense to me to make the kafka
> >> > > release
> >> > > > > > > version
> >> > > > > > > > > > available in order to determine which version of the
> >> > request
> >> > > > API
> >> > > > > > > should
> >> > > > > > > > > be
> >> > > > > > > > > > used rather than adding a new request type which
> exposes
> >> > all
> >> > > of
> >> > > > > the
> >> > > > > > > > > > different supported versions for all of the request
> >> types.
> >> > > > > Request
> >> > > > > > > API
> >> > > > > > > > > > versions all change in lockstep with Kafka releases
> >> anyway.
> >> > > > > > > > > >
> >> > > > > > > > > > -Jason
> >> > > > > > > > > >
> >> > > > > > > > > > On Wed, Mar 2, 2016 at 5:15 PM, Becket Qin <
> >> > > > becket....@gmail.com
> >> > > > > >
> >> > > > > > > > wrote:
> >> > > > > > > > > >
> >> > > > > > > > > > > I think using Kafka release version makes sense.
> More
> >> > > > > > particularly,
> >> > > > > > > > we
> >> > > > > > > > > > can
> >> > > > > > > > > > > use the ApiVersion and this will cover all the
> >> interval
> >> > > > version
> >> > > > > > as
> >> > > > > > > > > well.
> >> > > > > > > > > > In
> >> > > > > > > > > > > KAFKA-3025, we added the ApiVersion to message
> format
> >> > > version
> >> > > > > > > > mapping,
> >> > > > > > > > > We
> >> > > > > > > > > > > can add the ApiKey to version mapping to ApiVersion
> as
> >> > > well.
> >> > > > We
> >> > > > > > can
> >> > > > > > > > > move
> >> > > > > > > > > > > ApiVersion class to o.a.k.c package and use it for
> >> both
> >> > > > server
> >> > > > > > and
> >> > > > > > > > > > clients.
> >> > > > > > > > > > >
> >> > > > > > > > > > > @Jason, if we cache the release info in metadata and
> >> not
> >> > > > > > > re-validate
> >> > > > > > > > > the
> >> > > > > > > > > > > release on reconnect, would it still work if we do a
> >> > > rolling
> >> > > > > > > > downgrade?
> >> > > > > > > > > > >
> >> > > > > > > > > > > On Wed, Mar 2, 2016 at 3:16 PM, Jason Gustafson <
> >> > > > > > > ja...@confluent.io>
> >> > > > > > > > > > > wrote:
> >> > > > > > > > > > >
> >> > > > > > > > > > > > I think Dana's suggestion to include the Kafka
> >> release
> >> > > > > version
> >> > > > > > > > makes
> >> > > > > > > > > a
> >> > > > > > > > > > > lot
> >> > > > > > > > > > > > of sense. I'm actually wondering why you would
> need
> >> the
> >> > > > > > > individual
> >> > > > > > > > > API
> >> > > > > > > > > > > > versions if you have that? It sounds like keeping
> >> track
> >> > > of
> >> > > > > all
> >> > > > > > > the
> >> > > > > > > > > api
> >> > > > > > > > > > > > version information would add a lot of complexity
> to
> >> > > > clients
> >> > > > > > > since
> >> > > > > > > > > > > they'll
> >> > > > > > > > > > > > have to try to handle different version
> permutations
> >> > > which
> >> > > > > are
> >> > > > > > > not
> >> > > > > > > > > > > actually
> >> > > > > > > > > > > > possible in practice. Wouldn't it be simpler to
> know
> >> > that
> >> > > > > > you're
> >> > > > > > > > > > talking
> >> > > > > > > > > > > to
> >> > > > > > > > > > > > an 0.9 broker than that you're talking to a broker
> >> > which
> >> > > > > > supports
> >> > > > > > > > > > > version 2
> >> > > > > > > > > > > > of the group coordinator request, version 1 of
> fetch
> >> > > > request,
> >> > > > > > > etc?
> >> > > > > > > > > > Also,
> >> > > > > > > > > > > > the release version could be included in the
> broker
> >> > > > > information
> >> > > > > > > in
> >> > > > > > > > > the
> >> > > > > > > > > > > > topic metadata request which would save the need
> for
> >> > the
> >> > > > > > > additional
> >> > > > > > > > > > round
> >> > > > > > > > > > > > trip on every reconnect.
> >> > > > > > > > > > > >
> >> > > > > > > > > > > > -Jason
> >> > > > > > > > > > > >
> >> > > > > > > > > > > > On Tue, Mar 1, 2016 at 7:59 PM, Ashish Singh <
> >> > > > > > > asi...@cloudera.com>
> >> > > > > > > > > > > wrote:
> >> > > > > > > > > > > >
> >> > > > > > > > > > > > > On Tue, Mar 1, 2016 at 6:30 PM, Gwen Shapira <
> >> > > > > > > g...@confluent.io>
> >> > > > > > > > > > > wrote:
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > > > > One more thing, the KIP actually had 3 parts:
> >> > > > > > > > > > > > > > 1. The version protocol
> >> > > > > > > > > > > > > > 2. New response on messages of wrong API key
> or
> >> > wrong
> >> > > > > > version
> >> > > > > > > > > > > > > > 3. Protocol documentation
> >> > > > > > > > > > > > > >
> >> > > > > > > > > > > > > There is a WIP patch for adding protocol docs,
> >> > > > > > > > > > > > > https://github.com/apache/kafka/pull/970 . By
> >> > protocol
> >> > > > > > > > > > documentation,
> >> > > > > > > > > > > > you
> >> > > > > > > > > > > > > mean updating this, right?
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > I understand that you are offering to only
> >> > implement
> >> > > > part
> >> > > > > > 1?
> >> > > > > > > > > > > > > > But the KIP discussion and vote should still
> >> cover
> >> > > all
> >> > > > > > three
> >> > > > > > > > > parts,
> >> > > > > > > > > > > > > > they will just be implemented in separate
> JIRA?
> >> > > > > > > > > > > > > >
> >> > > > > > > > > > > > > The patch for KAFKA-3307,
> >> > > > > > > > https://github.com/apache/kafka/pull/986
> >> > > > > > > > > ,
> >> > > > > > > > > > > > covers
> >> > > > > > > > > > > > > 1 and 2. KAFKA-3309 tracks documentation part.
> >> Yes,
> >> > we
> >> > > > > should
> >> > > > > > > > > include
> >> > > > > > > > > > > all
> >> > > > > > > > > > > > > the three points you mentioned while discussing
> or
> >> > > voting
> >> > > > > for
> >> > > > > > > > > KIP-35.
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > On Tue, Mar 1, 2016 at 5:25 PM, Ashish Singh <
> >> > > > > > > > > asi...@cloudera.com>
> >> > > > > > > > > > > > > wrote:
> >> > > > > > > > > > > > > > > On Tue, Mar 1, 2016 at 5:11 PM, Gwen
> Shapira <
> >> > > > > > > > > g...@confluent.io>
> >> > > > > > > > > > > > > wrote:
> >> > > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > >> I don't see a use for the name - clients
> >> should
> >> > be
> >> > > > > able
> >> > > > > > to
> >> > > > > > > > > > > translate
> >> > > > > > > > > > > > > > >> ApiKey to name for any API they support,
> and
> >> I'm
> >> > > not
> >> > > > > > sure
> >> > > > > > > > why
> >> > > > > > > > > > > would
> >> > > > > > > > > > > > a
> >> > > > > > > > > > > > > > >> client need to log anything about APIs it
> >> does
> >> > not
> >> > > > > > > support.
> >> > > > > > > > > Am I
> >> > > > > > > > > > > > > > >> missing something?
> >> > > > > > > > > > > > > > >>
> >> > > > > > > > > > > > > > > Yea, it is a fair assumption that client
> would
> >> > know
> >> > > > > about
> >> > > > > > > > APIs
> >> > > > > > > > > it
> >> > > > > > > > > > > > > > supports.
> >> > > > > > > > > > > > > > > It could have been helpful for client users
> to
> >> > see
> >> > > > new
> >> > > > > > APIs
> >> > > > > > > > > > though,
> >> > > > > > > > > > > > > > however
> >> > > > > > > > > > > > > > > users can always refer to protocol doc of
> new
> >> > > version
> >> > > > > to
> >> > > > > > > find
> >> > > > > > > > > > > > > > corresponding
> >> > > > > > > > > > > > > > > names of the new APIs.
> >> > > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > >>
> >> > > > > > > > > > > > > > >> On a related note, Magnus is currently on
> >> > > vacation,
> >> > > > > but
> >> > > > > > he
> >> > > > > > > > > > should
> >> > > > > > > > > > > be
> >> > > > > > > > > > > > > > >> back at the end of next week. I'd like to
> >> hold
> >> > off
> >> > > > on
> >> > > > > > the
> >> > > > > > > > vote
> >> > > > > > > > > > > until
> >> > > > > > > > > > > > > > >> he gets back since his experience in
> >> > implementing
> >> > > > > > clients
> >> > > > > > > > and
> >> > > > > > > > > > his
> >> > > > > > > > > > > > > > >> opinions will be very valuable for this
> >> > > discussion.
> >> > > > > > > > > > > > > > >>
> >> > > > > > > > > > > > > > > That is great. It will be valuable to have
> his
> >> > > > > feedback.
> >> > > > > > I
> >> > > > > > > > will
> >> > > > > > > > > > > hold
> >> > > > > > > > > > > > > off
> >> > > > > > > > > > > > > > on
> >> > > > > > > > > > > > > > > removing "api_name" and
> >> "api_deprecated_versions"
> >> > > or
> >> > > > > > adding
> >> > > > > > > > > > release
> >> > > > > > > > > > > > > > version.
> >> > > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > >>
> >> > > > > > > > > > > > > > >> Gwen
> >> > > > > > > > > > > > > > >>
> >> > > > > > > > > > > > > > >> On Tue, Mar 1, 2016 at 4:24 PM, Ashish
> Singh
> >> <
> >> > > > > > > > > > asi...@cloudera.com
> >> > > > > > > > > > > >
> >> > > > > > > > > > > > > > wrote:
> >> > > > > > > > > > > > > > >> > Works with me. I will update PR to remove
> >> > this.
> >> > > > > > > > > > > > > > >> >
> >> > > > > > > > > > > > > > >> > Also, "api_name" have been pointed out
> as a
> >> > > > concern.
> >> > > > > > > > > However,
> >> > > > > > > > > > it
> >> > > > > > > > > > > > can
> >> > > > > > > > > > > > > > be
> >> > > > > > > > > > > > > > >> > handy for logging and similar purposes.
> Any
> >> > take
> >> > > > on
> >> > > > > > > that?
> >> > > > > > > > > > > > > > >> >
> >> > > > > > > > > > > > > > >> > On Tue, Mar 1, 2016 at 3:46 PM, Gwen
> >> Shapira <
> >> > > > > > > > > > g...@confluent.io
> >> > > > > > > > > > > >
> >> > > > > > > > > > > > > > wrote:
> >> > > > > > > > > > > > > > >> >
> >> > > > > > > > > > > > > > >> >> Jay also mentioned:
> >> > > > > > > > > > > > > > >> >> "Or, alternately, since deprecation has
> no
> >> > > > > functional
> >> > > > > > > > > impact
> >> > > > > > > > > > > and
> >> > > > > > > > > > > > is
> >> > > > > > > > > > > > > > >> >> just a message
> >> > > > > > > > > > > > > > >> >> to developers, we could just leave it
> out
> >> of
> >> > > the
> >> > > > > > > protocol
> >> > > > > > > > > and
> >> > > > > > > > > > > > just
> >> > > > > > > > > > > > > > have
> >> > > > > > > > > > > > > > >> it
> >> > > > > > > > > > > > > > >> >> in release notes etc."
> >> > > > > > > > > > > > > > >> >>
> >> > > > > > > > > > > > > > >> >> I'm in favor of leaving it out of the
> >> > > protocol. I
> >> > > > > > can't
> >> > > > > > > > > > really
> >> > > > > > > > > > > > see
> >> > > > > > > > > > > > > a
> >> > > > > > > > > > > > > > >> >> use-case.
> >> > > > > > > > > > > > > > >> >>
> >> > > > > > > > > > > > > > >> >> Gwen
> >> > > > > > > > > > > > > > >> >>
> >> > > > > > > > > > > > > > >> >> On Mon, Feb 29, 2016 at 3:55 PM, Ashish
> >> > Singh <
> >> > > > > > > > > > > > asi...@cloudera.com
> >> > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > >> wrote:
> >> > > > > > > > > > > > > > >> >>
> >> > > > > > > > > > > > > > >> >> > I hope it is OK for me to make some
> >> > progress
> >> > > > > here.
> >> > > > > > I
> >> > > > > > > > have
> >> > > > > > > > > > > made
> >> > > > > > > > > > > > > the
> >> > > > > > > > > > > > > > >> >> > following changes.
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >> > 1. Updated KIP-35, to adopt Jay's
> >> > suggestion
> >> > > on
> >> > > > > > > > > maintaining
> >> > > > > > > > > > > > > > separate
> >> > > > > > > > > > > > > > >> list
> >> > > > > > > > > > > > > > >> >> > of deprecated versions, instead of
> >> using a
> >> > > > > version
> >> > > > > > of
> >> > > > > > > > -1.
> >> > > > > > > > > > > > > > >> >> > 2. Added information on required
> >> > permissions,
> >> > > > > > > Describe
> >> > > > > > > > > > action
> >> > > > > > > > > > > > on
> >> > > > > > > > > > > > > > >> Cluster
> >> > > > > > > > > > > > > > >> >> > resource, to be able to retrieve
> >> protocol
> >> > > > > versions
> >> > > > > > > > from a
> >> > > > > > > > > > > auth
> >> > > > > > > > > > > > > > enabled
> >> > > > > > > > > > > > > > >> >> > Kafka cluster.
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >> > Created
> >> > > > > > > > https://issues.apache.org/jira/browse/KAFKA-3304
> >> > > > > > > > > .
> >> > > > > > > > > > > > > Primary
> >> > > > > > > > > > > > > > >> patch
> >> > > > > > > > > > > > > > >> >> is
> >> > > > > > > > > > > > > > >> >> > available to review,
> >> > > > > > > > > > > https://github.com/apache/kafka/pull/986
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >> > On Thu, Feb 25, 2016 at 1:27 PM,
> Ashish
> >> > > Singh <
> >> > > > > > > > > > > > > asi...@cloudera.com
> >> > > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > >> >> wrote:
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >> > > Kafka clients in Hadoop ecosystem,
> >> Flume,
> >> > > > > Spark,
> >> > > > > > > etc,
> >> > > > > > > > > > have
> >> > > > > > > > > > > > > found
> >> > > > > > > > > > > > > > it
> >> > > > > > > > > > > > > > >> >> > really
> >> > > > > > > > > > > > > > >> >> > > difficult to cope up with Kafka
> >> releases
> >> > as
> >> > > > > they
> >> > > > > > > want
> >> > > > > > > > > to
> >> > > > > > > > > > > > > support
> >> > > > > > > > > > > > > > >> users
> >> > > > > > > > > > > > > > >> >> on
> >> > > > > > > > > > > > > > >> >> > > different Kafka versions. Capability
> >> to
> >> > > > > retrieve
> >> > > > > > > > > protocol
> >> > > > > > > > > > > > > version
> >> > > > > > > > > > > > > > >> will
> >> > > > > > > > > > > > > > >> >> > go a
> >> > > > > > > > > > > > > > >> >> > > long way to ease out those pain
> >> points. I
> >> > > > will
> >> > > > > be
> >> > > > > > > > happy
> >> > > > > > > > > > to
> >> > > > > > > > > > > > help
> >> > > > > > > > > > > > > > out
> >> > > > > > > > > > > > > > >> >> with
> >> > > > > > > > > > > > > > >> >> > > the work on this KIP. @Magnus,
> thanks
> >> for
> >> > > > > driving
> >> > > > > > > > this,
> >> > > > > > > > > > is
> >> > > > > > > > > > > it
> >> > > > > > > > > > > > > OK
> >> > > > > > > > > > > > > > if
> >> > > > > > > > > > > > > > >> I
> >> > > > > > > > > > > > > > >> >> > carry
> >> > > > > > > > > > > > > > >> >> > > forward the work from here. It will
> be
> >> > > ideal
> >> > > > to
> >> > > > > > > have
> >> > > > > > > > > this
> >> > > > > > > > > > > in
> >> > > > > > > > > > > > > > >> 0.10.0.0.
> >> > > > > > > > > > > > > > >> >> > >
> >> > > > > > > > > > > > > > >> >> > > On Mon, Oct 12, 2015 at 9:29 PM, Jay
> >> > Kreps
> >> > > <
> >> > > > > > > > > > > j...@confluent.io
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > > > > >> wrote:
> >> > > > > > > > > > > > > > >> >> > >
> >> > > > > > > > > > > > > > >> >> > >> I wonder if we need to solve the
> >> error
> >> > > > > problem?
> >> > > > > > I
> >> > > > > > > > > think
> >> > > > > > > > > > > this
> >> > > > > > > > > > > > > KIP
> >> > > > > > > > > > > > > > >> >> gives a
> >> > > > > > > > > > > > > > >> >> > >> descent work around.
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >> Probably we should have included an
> >> > error
> >> > > in
> >> > > > > the
> >> > > > > > > > > > response
> >> > > > > > > > > > > > > > header,
> >> > > > > > > > > > > > > > >> but
> >> > > > > > > > > > > > > > >> >> we
> >> > > > > > > > > > > > > > >> >> > >> debated it at the time decided not
> to
> >> > and
> >> > > > now
> >> > > > > it
> >> > > > > > > is
> >> > > > > > > > > > pretty
> >> > > > > > > > > > > > > hard
> >> > > > > > > > > > > > > > to
> >> > > > > > > > > > > > > > >> add
> >> > > > > > > > > > > > > > >> >> > >> because the headers aren't
> versioned
> >> > > (d'oh).
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >> It seems like any other solution is
> >> > going
> >> > > to
> >> > > > > be
> >> > > > > > > kind
> >> > > > > > > > > of
> >> > > > > > > > > > a
> >> > > > > > > > > > > > > hack,
> >> > > > > > > > > > > > > > >> right?
> >> > > > > > > > > > > > > > >> >> > >> Sending malformed responses back
> >> seems
> >> > > like
> >> > > > > not
> >> > > > > > a
> >> > > > > > > > > clean
> >> > > > > > > > > > > > > > solution...
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >> (Not sure if I was pro- having a
> >> > top-level
> >> > > > > error
> >> > > > > > > or
> >> > > > > > > > > not,
> >> > > > > > > > > > > but
> >> > > > > > > > > > > > > in
> >> > > > > > > > > > > > > > any
> >> > > > > > > > > > > > > > >> >> case
> >> > > > > > > > > > > > > > >> >> > >> the rationale for the decision was
> >> that
> >> > so
> >> > > > > many
> >> > > > > > of
> >> > > > > > > > the
> >> > > > > > > > > > > > > requests
> >> > > > > > > > > > > > > > >> were
> >> > > > > > > > > > > > > > >> >> > >> per-partition or per-topic or
> >> whatever
> >> > and
> >> > > > > hence
> >> > > > > > > > fail
> >> > > > > > > > > or
> >> > > > > > > > > > > > > > succeed at
> >> > > > > > > > > > > > > > >> >> that
> >> > > > > > > > > > > > > > >> >> > >> level and this makes it hard to
> know
> >> > what
> >> > > > the
> >> > > > > > > right
> >> > > > > > > > > > > > top-level
> >> > > > > > > > > > > > > > error
> >> > > > > > > > > > > > > > >> >> code
> >> > > > > > > > > > > > > > >> >> > >> is
> >> > > > > > > > > > > > > > >> >> > >> and hard for the client to figure
> out
> >> > what
> >> > > > to
> >> > > > > do
> >> > > > > > > > with
> >> > > > > > > > > > the
> >> > > > > > > > > > > > top
> >> > > > > > > > > > > > > > level
> >> > > > > > > > > > > > > > >> >> > error
> >> > > > > > > > > > > > > > >> >> > >> if some of the partitions succeed
> but
> >> > > there
> >> > > > > is a
> >> > > > > > > > > > top-level
> >> > > > > > > > > > > > > > error).
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >> I think actually this new API
> >> actually
> >> > > > gives a
> >> > > > > > way
> >> > > > > > > > to
> >> > > > > > > > > > > handle
> >> > > > > > > > > > > > > > this
> >> > > > > > > > > > > > > > >> >> > >> gracefully on the client side by
> just
> >> > > having
> >> > > > > > > clients
> >> > > > > > > > > > that
> >> > > > > > > > > > > > want
> >> > > > > > > > > > > > > > to
> >> > > > > > > > > > > > > > >> be
> >> > > > > > > > > > > > > > >> >> > >> graceful check for support for
> their
> >> > > > version.
> >> > > > > > > > Clients
> >> > > > > > > > > > that
> >> > > > > > > > > > > > do
> >> > > > > > > > > > > > > > that
> >> > > > > > > > > > > > > > >> >> will
> >> > > > > > > > > > > > > > >> >> > >> have a graceful message.
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >> At some point if we're ever
> reworking
> >> > the
> >> > > > > > headers
> >> > > > > > > we
> >> > > > > > > > > > > should
> >> > > > > > > > > > > > > > really
> >> > > > > > > > > > > > > > >> >> > >> consider
> >> > > > > > > > > > > > > > >> >> > >> (a) versioning them and (b) adding
> a
> >> > > > top-level
> >> > > > > > > error
> >> > > > > > > > > > code
> >> > > > > > > > > > > in
> >> > > > > > > > > > > > > the
> >> > > > > > > > > > > > > > >> >> > response.
> >> > > > > > > > > > > > > > >> >> > >> But given this would be a big
> >> breaking
> >> > > > change
> >> > > > > > and
> >> > > > > > > > this
> >> > > > > > > > > > is
> >> > > > > > > > > > > > > really
> >> > > > > > > > > > > > > > >> just
> >> > > > > > > > > > > > > > >> >> to
> >> > > > > > > > > > > > > > >> >> > >> give a nicer error message seems
> >> like it
> >> > > > > > probably
> >> > > > > > > > > isn't
> >> > > > > > > > > > > > worth
> >> > > > > > > > > > > > > > it to
> >> > > > > > > > > > > > > > >> >> try
> >> > > > > > > > > > > > > > >> >> > to
> >> > > > > > > > > > > > > > >> >> > >> do something now.
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >> -Jay
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >> On Mon, Oct 12, 2015 at 8:11 PM,
> >> > Jiangjie
> >> > > > Qin
> >> > > > > > > > > > > > > > >> >> <j...@linkedin.com.invalid
> >> > > > > > > > > > > > > > >> >> > >
> >> > > > > > > > > > > > > > >> >> > >> wrote:
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >> > I am thinking instead of
> returning
> >> an
> >> > > > empty
> >> > > > > > > > > response,
> >> > > > > > > > > > it
> >> > > > > > > > > > > > > > would be
> >> > > > > > > > > > > > > > >> >> > >> better to
> >> > > > > > > > > > > > > > >> >> > >> > return an explicit
> >> > > > > UnsupportedVersionException
> >> > > > > > > > code.
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > Today KafkaApis handles the error
> >> in
> >> > the
> >> > > > > > > following
> >> > > > > > > > > > way:
> >> > > > > > > > > > > > > > >> >> > >> > 1. For requests/responses using
> old
> >> > > Scala
> >> > > > > > > classes,
> >> > > > > > > > > > > > KafkaApis
> >> > > > > > > > > > > > > > uses
> >> > > > > > > > > > > > > > >> >> > >> > RequestOrResponse.handleError()
> to
> >> > > return
> >> > > > an
> >> > > > > > > error
> >> > > > > > > > > > > > response.
> >> > > > > > > > > > > > > > >> >> > >> > 2. For requests/response using
> Java
> >> > > > classes
> >> > > > > > > (only
> >> > > > > > > > > > > > > > >> JoinGroupRequest
> >> > > > > > > > > > > > > > >> >> and
> >> > > > > > > > > > > > > > >> >> > >> > Heartbeat now), KafkaApis calls
> >> > > > > > > > > > > > > > >> AbstractRequest.getErrorResponse()
> >> > > > > > > > > > > > > > >> >> to
> >> > > > > > > > > > > > > > >> >> > >> > return an error response.
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > In KAFKA-2512, I am returning an
> >> > > > > > > > > > > > UnsupportedVersionException
> >> > > > > > > > > > > > > > for
> >> > > > > > > > > > > > > > >> >> case
> >> > > > > > > > > > > > > > >> >> > >> [1]
> >> > > > > > > > > > > > > > >> >> > >> > when see an unsupported version.
> >> This
> >> > > will
> >> > > > > put
> >> > > > > > > the
> >> > > > > > > > > > error
> >> > > > > > > > > > > > > code
> >> > > > > > > > > > > > > > per
> >> > > > > > > > > > > > > > >> >> > topic
> >> > > > > > > > > > > > > > >> >> > >> or
> >> > > > > > > > > > > > > > >> >> > >> > partition for most of the
> requests,
> >> > but
> >> > > > > might
> >> > > > > > > not
> >> > > > > > > > > work
> >> > > > > > > > > > > all
> >> > > > > > > > > > > > > the
> >> > > > > > > > > > > > > > >> time.
> >> > > > > > > > > > > > > > >> >> > >> e.g.
> >> > > > > > > > > > > > > > >> >> > >> > TopicMetadataRequest with an
> empty
> >> > topic
> >> > > > > set.
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > Case [2] does not quite work for
> >> > > > unsupported
> >> > > > > > > > > version,
> >> > > > > > > > > > > > > because
> >> > > > > > > > > > > > > > we
> >> > > > > > > > > > > > > > >> >> will
> >> > > > > > > > > > > > > > >> >> > >> > thrown an uncaught exception when
> >> > > version
> >> > > > is
> >> > > > > > not
> >> > > > > > > > > > > > recognized
> >> > > > > > > > > > > > > > (BTW
> >> > > > > > > > > > > > > > >> >> this
> >> > > > > > > > > > > > > > >> >> > >> is a
> >> > > > > > > > > > > > > > >> >> > >> > bug). Part of the reason is that
> >> for
> >> > > some
> >> > > > > > > response
> >> > > > > > > > > > > types,
> >> > > > > > > > > > > > > > error
> >> > > > > > > > > > > > > > >> code
> >> > > > > > > > > > > > > > >> >> > is
> >> > > > > > > > > > > > > > >> >> > >> not
> >> > > > > > > > > > > > > > >> >> > >> > part of the response level field.
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > Maybe it worth checking how each
> >> > > response
> >> > > > is
> >> > > > > > > > dealing
> >> > > > > > > > > > > with
> >> > > > > > > > > > > > > > error
> >> > > > > > > > > > > > > > >> code
> >> > > > > > > > > > > > > > >> >> > >> today.
> >> > > > > > > > > > > > > > >> >> > >> > A scan of the response formats
> >> gives
> >> > the
> >> > > > > > > following
> >> > > > > > > > > > > result:
> >> > > > > > > > > > > > > > >> >> > >> > 1. TopicMetadataResponse - per
> >> topic
> >> > > error
> >> > > > > > code,
> >> > > > > > > > > does
> >> > > > > > > > > > > not
> >> > > > > > > > > > > > > work
> >> > > > > > > > > > > > > > >> when
> >> > > > > > > > > > > > > > >> >> > the
> >> > > > > > > > > > > > > > >> >> > >> > topic set is empty in the
> request.
> >> > > > > > > > > > > > > > >> >> > >> > 2. ProduceResonse - per partition
> >> > error
> >> > > > > code.
> >> > > > > > > > > > > > > > >> >> > >> > 3. OffsetCommitResponse - per
> >> > partition.
> >> > > > > > > > > > > > > > >> >> > >> > 4. OffsetFetchResponse - per
> >> > partition.
> >> > > > > > > > > > > > > > >> >> > >> > 5. OffsetResponse - per
> partition.
> >> > > > > > > > > > > > > > >> >> > >> > 6. FetchResponse - per partition
> >> > > > > > > > > > > > > > >> >> > >> > 7. ConsumerMetadataResponse -
> >> response
> >> > > > level
> >> > > > > > > > > > > > > > >> >> > >> > 8. ControlledShutdownResponse -
> >> > response
> >> > > > > level
> >> > > > > > > > > > > > > > >> >> > >> > 9. JoinGroupResponse - response
> >> level
> >> > > > > > > > > > > > > > >> >> > >> > 10. HearbeatResponse - response
> >> level
> >> > > > > > > > > > > > > > >> >> > >> > 11. LeaderAndIsrResponse -
> response
> >> > > level
> >> > > > > > > > > > > > > > >> >> > >> > 12. StopReplicaResponse -
> response
> >> > level
> >> > > > > > > > > > > > > > >> >> > >> > 13. UpdateMetadataResponse -
> >> response
> >> > > > level
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > So from the list above it looks
> for
> >> > each
> >> > > > > > > response
> >> > > > > > > > we
> >> > > > > > > > > > are
> >> > > > > > > > > > > > > > actually
> >> > > > > > > > > > > > > > >> >> able
> >> > > > > > > > > > > > > > >> >> > >> to
> >> > > > > > > > > > > > > > >> >> > >> > return an error code, as long as
> we
> >> > make
> >> > > > > sure
> >> > > > > > > the
> >> > > > > > > > > > topic
> >> > > > > > > > > > > or
> >> > > > > > > > > > > > > > >> partition
> >> > > > > > > > > > > > > > >> >> > >> won't
> >> > > > > > > > > > > > > > >> >> > >> > be empty when the error code is
> at
> >> > topic
> >> > > > or
> >> > > > > > > > > partition
> >> > > > > > > > > > > > level.
> >> > > > > > > > > > > > > > >> Luckily
> >> > > > > > > > > > > > > > >> >> > in
> >> > > > > > > > > > > > > > >> >> > >> the
> >> > > > > > > > > > > > > > >> >> > >> > above list we only need to worry
> >> about
> >> > > > > > > > > > > > > TopicMetadataResponse.
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > Maybe error handling is out of
> the
> >> > scope
> >> > > > of
> >> > > > > > this
> >> > > > > > > > > KIP,
> >> > > > > > > > > > > but
> >> > > > > > > > > > > > I
> >> > > > > > > > > > > > > > >> prefer
> >> > > > > > > > > > > > > > >> >> we
> >> > > > > > > > > > > > > > >> >> > >> think
> >> > > > > > > > > > > > > > >> >> > >> > through how to deal with error
> code
> >> > for
> >> > > > the
> >> > > > > > > > > requests,
> >> > > > > > > > > > > > > because
> >> > > > > > > > > > > > > > >> there
> >> > > > > > > > > > > > > > >> >> > are
> >> > > > > > > > > > > > > > >> >> > >> > more request types to be added in
> >> > > > KAFKA-2464
> >> > > > > > and
> >> > > > > > > > > > future
> >> > > > > > > > > > > > > > patches.
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > Thanks,
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > Jiangjie (Becket) Qin
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > On Mon, Oct 12, 2015 at 6:04 PM,
> >> Jay
> >> > > > Kreps <
> >> > > > > > > > > > > > > j...@confluent.io>
> >> > > > > > > > > > > > > > >> >> wrote:
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >> > > Two quick pieces of feedback:
> >> > > > > > > > > > > > > > >> >> > >> > > 1. The use of a version of -1
> as
> >> > > magical
> >> > > > > > entry
> >> > > > > > > > > > > dividing
> >> > > > > > > > > > > > > > between
> >> > > > > > > > > > > > > > >> >> > >> > deprecated
> >> > > > > > > > > > > > > > >> >> > >> > > versions is a bit hacky. What
> >> about
> >> > > > > instead
> >> > > > > > > > having
> >> > > > > > > > > > an
> >> > > > > > > > > > > > > array
> >> > > > > > > > > > > > > > of
> >> > > > > > > > > > > > > > >> >> > >> supported
> >> > > > > > > > > > > > > > >> >> > >> > > versions and a separate array
> of
> >> > > > > deprecated
> >> > > > > > > > > > versions.
> >> > > > > > > > > > > > The
> >> > > > > > > > > > > > > > >> >> deprecated
> >> > > > > > > > > > > > > > >> >> > >> > > versions would always be a
> >> subset of
> >> > > the
> >> > > > > > > > supported
> >> > > > > > > > > > > > > versions.
> >> > > > > > > > > > > > > > >> Or,
> >> > > > > > > > > > > > > > >> >> > >> > > alternately, since deprecation
> >> has
> >> > no
> >> > > > > > > functional
> >> > > > > > > > > > > impact
> >> > > > > > > > > > > > > and
> >> > > > > > > > > > > > > > is
> >> > > > > > > > > > > > > > >> >> just
> >> > > > > > > > > > > > > > >> >> > a
> >> > > > > > > > > > > > > > >> >> > >> > > message to developers, we could
> >> just
> >> > > > leave
> >> > > > > > it
> >> > > > > > > > out
> >> > > > > > > > > of
> >> > > > > > > > > > > the
> >> > > > > > > > > > > > > > >> protocol
> >> > > > > > > > > > > > > > >> >> > and
> >> > > > > > > > > > > > > > >> >> > >> > just
> >> > > > > > > > > > > > > > >> >> > >> > > have it in release notes etc.
> >> > > > > > > > > > > > > > >> >> > >> > > 2. I think including the api
> name
> >> > may
> >> > > > > cause
> >> > > > > > > some
> >> > > > > > > > > > > > problems.
> >> > > > > > > > > > > > > > >> >> Currently
> >> > > > > > > > > > > > > > >> >> > >> the
> >> > > > > > > > > > > > > > >> >> > >> > > api key is the primary key that
> >> we
> >> > > keep
> >> > > > > > > > consistent
> >> > > > > > > > > > but
> >> > > > > > > > > > > > we
> >> > > > > > > > > > > > > > have
> >> > > > > > > > > > > > > > >> >> > >> actually
> >> > > > > > > > > > > > > > >> >> > >> > > evolved the english description
> >> of
> >> > the
> >> > > > > apis
> >> > > > > > as
> >> > > > > > > > > they
> >> > > > > > > > > > > have
> >> > > > > > > > > > > > > > >> changed.
> >> > > > > > > > > > > > > > >> >> > The
> >> > > > > > > > > > > > > > >> >> > >> > only
> >> > > > > > > > > > > > > > >> >> > >> > > use I can think of for the name
> >> > would
> >> > > be
> >> > > > > if
> >> > > > > > > > people
> >> > > > > > > > > > > used
> >> > > > > > > > > > > > > the
> >> > > > > > > > > > > > > > >> >> logical
> >> > > > > > > > > > > > > > >> >> > >> name
> >> > > > > > > > > > > > > > >> >> > >> > > and tried to resolve the api
> key,
> >> > but
> >> > > > that
> >> > > > > > > would
> >> > > > > > > > > be
> >> > > > > > > > > > > > wrong.
> >> > > > > > > > > > > > > > Not
> >> > > > > > > > > > > > > > >> >> sure
> >> > > > > > > > > > > > > > >> >> > >> if we
> >> > > > > > > > > > > > > > >> >> > >> > > actually need the english name,
> >> if
> >> > > there
> >> > > > > is
> >> > > > > > a
> >> > > > > > > > use
> >> > > > > > > > > > > case I
> >> > > > > > > > > > > > > > guess
> >> > > > > > > > > > > > > > >> >> we'll
> >> > > > > > > > > > > > > > >> >> > >> just
> >> > > > > > > > > > > > > > >> >> > >> > > have to be very clear that the
> >> name
> >> > is
> >> > > > > just
> >> > > > > > > > > > > > documentation
> >> > > > > > > > > > > > > > and
> >> > > > > > > > > > > > > > >> can
> >> > > > > > > > > > > > > > >> >> > >> change
> >> > > > > > > > > > > > > > >> >> > >> > > any time.
> >> > > > > > > > > > > > > > >> >> > >> > >
> >> > > > > > > > > > > > > > >> >> > >> > > -Jay
> >> > > > > > > > > > > > > > >> >> > >> > >
> >> > > > > > > > > > > > > > >> >> > >> > > On Fri, Sep 25, 2015 at 2:53
> PM,
> >> > > Magnus
> >> > > > > > > > Edenhill <
> >> > > > > > > > > > > > > > >> >> > mag...@edenhill.se>
> >> > > > > > > > > > > > > > >> >> > >> > > wrote:
> >> > > > > > > > > > > > > > >> >> > >> > >
> >> > > > > > > > > > > > > > >> >> > >> > > > Good evening,
> >> > > > > > > > > > > > > > >> >> > >> > > >
> >> > > > > > > > > > > > > > >> >> > >> > > > KIP-35 was created to address
> >> > > current
> >> > > > > and
> >> > > > > > > > future
> >> > > > > > > > > > > > > > >> broker-client
> >> > > > > > > > > > > > > > >> >> > >> > > > compatibility.
> >> > > > > > > > > > > > > > >> >> > >> > > >
> >> > > > > > > > > > > > > > >> >> > >> > > >
> >> > > > > > > > > > > > > > >> >> > >> > > >
> >> > > > > > > > > > > > > > >> >> > >> > >
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >>
> >> > > > > > > > > > > > > > >>
> >> > > > > > > > > > > > > >
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > >
> >> > > > > > > > > > >
> >> > > > > > > > > >
> >> > > > > > > > >
> >> > > > > > > >
> >> > > > > > >
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-35+-+Retrieving+protocol+version
> >> > > > > > > > > > > > > > >> >> > >> > > >
> >> > > > > > > > > > > > > > >> >> > >> > > > Summary:
> >> > > > > > > > > > > > > > >> >> > >> > > > * allow clients to retrieve
> >> the
> >> > > > > broker's
> >> > > > > > > > > protocol
> >> > > > > > > > > > > > > version
> >> > > > > > > > > > > > > > >> >> > >> > > > * make broker handle unknown
> >> > > protocol
> >> > > > > > > > requests
> >> > > > > > > > > > > > > gracefully
> >> > > > > > > > > > > > > > >> >> > >> > > >
> >> > > > > > > > > > > > > > >> >> > >> > > > Feedback and comments
> welcome!
> >> > > > > > > > > > > > > > >> >> > >> > > >
> >> > > > > > > > > > > > > > >> >> > >> > > > Regards,
> >> > > > > > > > > > > > > > >> >> > >> > > > Magnus
> >> > > > > > > > > > > > > > >> >> > >> > > >
> >> > > > > > > > > > > > > > >> >> > >> > >
> >> > > > > > > > > > > > > > >> >> > >> >
> >> > > > > > > > > > > > > > >> >> > >>
> >> > > > > > > > > > > > > > >> >> > >
> >> > > > > > > > > > > > > > >> >> > >
> >> > > > > > > > > > > > > > >> >> > >
> >> > > > > > > > > > > > > > >> >> > > --
> >> > > > > > > > > > > > > > >> >> > >
> >> > > > > > > > > > > > > > >> >> > > Regards,
> >> > > > > > > > > > > > > > >> >> > > Ashish
> >> > > > > > > > > > > > > > >> >> > >
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >> > --
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >> > Regards,
> >> > > > > > > > > > > > > > >> >> > Ashish
> >> > > > > > > > > > > > > > >> >> >
> >> > > > > > > > > > > > > > >> >>
> >> > > > > > > > > > > > > > >> >
> >> > > > > > > > > > > > > > >> >
> >> > > > > > > > > > > > > > >> >
> >> > > > > > > > > > > > > > >> > --
> >> > > > > > > > > > > > > > >> >
> >> > > > > > > > > > > > > > >> > Regards,
> >> > > > > > > > > > > > > > >> > Ashish
> >> > > > > > > > > > > > > > >>
> >> > > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > > --
> >> > > > > > > > > > > > > > >
> >> > > > > > > > > > > > > > > Regards,
> >> > > > > > > > > > > > > > > Ashish
> >> > > > > > > > > > > > > >
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > > > --
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > > > Regards,
> >> > > > > > > > > > > > > Ashish
> >> > > > > > > > > > > > >
> >> > > > > > > > > > > >
> >> > > > > > > > > > >
> >> > > > > > > > > >
> >> > > > > > > > >
> >> > > > > > > >
> >> > > > > > >
> >> > > > > >
> >> > > > > >
> >> > > > > >
> >> > > > > > --
> >> > > > > >
> >> > > > > > Regards,
> >> > > > > > Ashish
> >> > > > > >
> >> > > > >
> >> > > >
> >> > >
> >> >
> >> >
> >> >
> >> > --
> >> >
> >> > Regards,
> >> > Ashish
> >> >
> >>
> >
> >
> >
> > --
> >
> > Regards,
> > Ashish
> >
>
>
>
> --
>
> Regards,
> Ashish
>
