On points 1 and 2 I agree.
This also affects kip-98, I should expect this resolved before that vote also
passes. If it is accepted there (I’m assuming this is getting discussed on that
KIP? As you’re driving the move to VarInts), I am happy to make this KIP will
simply follow suit to whatever is agreed in KIP-98.
On 3) Agreed this is a simpler form, as long as no one is expecting hashmap
lookup performance ( O(1) ), I still would prefer an encapsulated class, so if
we find that holding it as an array in future is causing some perf issues, the
internals are not exposed to end users, allowing the internal structure to move
to a map.
Can we compromise on?
class ConsumerRecord<K, V> {
K key;
V value;
Headers headers;
}
class Headers {
Header[] headers;
add(String key, byte[] value)
Collection<byte[]> get(String key)
}
class Header {
String key;
byte[] value;
}
On 19/02/2017, 18:54, "Jason Gustafson" <ja...@confluent.io> wrote:
>
> headers dont "leak" into application code. they are useful to application
> code as well.
This is exactly what I have been trying to get at. The use cases documented
here are middleware:
https://cwiki.apache.org/confluence/display/KAFKA/A+Case+for+Kafka+Headers.
If headers are intended for the application space as well, the document
should be updated accordingly so that it is an explicit design goal and not
an unfortunate design byproduct. There may be some disagreement on whether
it _should_ be a design goal, but it may not matter much since the current
interceptor API is probably insufficient for middleware applications (I
haven't thought of a way to do this that isn't cumbersome).
That aside, the three unresolved points for me are the following:
1. The use of varints. As a one-off for use only with record headers, the
case was weak, but if we are using them throughout the message format, then
we should do so here as well. The additional complexity is minimal and
early performance testing fully justifies their use.
2. If varints are used, the case for using attributes to indicate null
headers also becomes weak. We only add one additional byte in each message
if there are no headers. Whatever the case, let us be consistent with how
we treat null keys and values.
3. We have apparently agreed that the broker will validate headers (please
add this to the KIP). That being the case, I would prefer to use Kafka's
conventional format for arrays. The downside is that it takes more work to
skip over the headers on the consumer, though it's unclear if the cost
would matter in practice. Some concern was previously expressed about the
allocation of maps. An alternative would be to use arrays, i.e.
class ConsumerRecord<K, V> {
K key;
V value;
Header[] headers;
}
class Header {
String key;
byte[] value;
}
This would work nicely with the conventional array format and my guess is
it would obviate the need do any lazy initialization. If we use the map as
is currently documented, then it is possible with either representation to
slice the headers and initialize them lazily. Either way, it might be a
good idea to use a separate object to represent the headers in case we need
to modify it in the future in some way.
(By the way, doesn't it feel a bit odd that we seem to be designing a
feature which is optimized for people not using?)
If we can resolve these points, then at least you will get my vote.
Thanks,
Jason
On Sun, Feb 19, 2017 at 7:30 AM, radai <radai.rosenbl...@gmail.com> wrote:
> headers dont "leak" into application code. they are useful to application
> code as well.
> IIUC samze currently has headers "in-V" and would just switch over to
kafka
> headers if they exist.
> im sure plenty of other users of kafka would have a use for headers.
> im pretty sure use cases exist around shuffling data into/out-of kafka
> (kafka connect or equivalent) where metadata from one end could copied
over
> to the other (S3, for example uses http headers for user-accessible
> metadata). it will be kafka client code getting/setting those headers. not
> an interceptor.
>
> On Fri, Feb 17, 2017 at 1:41 PM, Michael Pearce <michael.pea...@ig.com>
> wrote:
>
> > For APM single event tracing, need access to the header at the point of
> > processing on the processing thread.
> >
> > As such interceptors will not work/be suitable for these, due to the
fact
> > they act on the ConsumerRecords as a batch, before the handling thread
> can
> > split out and process per message which is the point these tools will
> need
> > to continue to transaction tracing.
> >
> > Like wise tools and infra pieces will need access to the message outside
> > the interceptor realm.
> >
> >
> >
> > On 17/02/2017, 21:26, "Jason Gustafson" <ja...@confluent.io> wrote:
> >
> > >
> > > That’s exactly what we’re doing the headers are a slice of bytes,
> > which
> > > then gets parsed later if needed, or can be parsed right away, the
> > headers
> > > is part of the protocol, so can still be validated if wanted.
> > > If you had a header count then you would have to go through each
> > header
> > > key and value length value to work out how much to skip to get to
> > say the
> > > value or any future component in the message after the headers.
> > Having it
> > > as a byte[] with length value makes this a lot easier to skip.
> >
> >
> > So the broker will parse the headers and validate them. Good. The
> only
> > reason remaining that I can see to leave the headers as a byte array
> > is to
> > make it easier for the client to skip past them. Are we sure this is
> > not
> > premature optimization? Are there any performance results which show
> > that
> > this is worthwhile?
> >
> > What’s the issue with exposing a method getHeaders on the
> > producer/consumer
> > > record? It doesn’t break anything. We don’t need any special
> version.
> >
> >
> > See my previous explanation. What I am trying to resist is the
> headers
> > becoming a general application-level facility. The primary use case
> as
> > far
> > as I can tell is middleware, which is the use case that the
> > interceptors
> > are providing.
> >
> > Current batch consumer model and consumer interceptors don’t work
> where
> > > headers need to be acted on at per message level at time of
> > processing,
> > > very case is APM (the core one), where the header value is used to
> > continue
> > > tracing.
> >
> >
> > I still don't understand the point about batching. The consumer
> > records are
> > exposed as a batch in the consumer interceptor, but you can still
> > iterate
> > them individually. It is no different for the consumer API itself.
> >
> > -Jason
> >
> > On Fri, Feb 17, 2017 at 12:48 PM, Michael Pearce <
> > michael.pea...@ig.com>
> > wrote:
> >
> > > Re:
> > >
> > > “ The point about creation of maps seems orthogonal. We can
> still
> > > represent
> > > the headers as a slice of bytes until the time it is
accessed.”
> > >
> > > That’s exactly what we’re doing the headers are a slice of bytes,
> > which
> > > then gets parsed later if needed, or can be parsed right away, the
> > headers
> > > is part of the protocol, so can still be validated if wanted.
> > >
> > > If you had a header count then you would have to go through each
> > header
> > > key and value length value to work out how much to skip to get to
> > say the
> > > value or any future component in the message after the headers.
> > Having it
> > > as a byte[] with length value makes this a lot easier to skip.
> > >
> > >
> > > On 17/02/2017, 20:37, "Michael Pearce" <michael.pea...@ig.com>
> > wrote:
> > >
> > > What’s the issue with exposing a method getHeaders on the
> > > producer/consumer record? It doesn’t break anything. We don’t need
> > any
> > > special version.
> > >
> > > Current batch consumer model and consumer interceptors don’t
> work
> > > where headers need to be acted on at per message level at time of
> > > processing, very case is APM (the core one), where the header
value
> > is used
> > > to continue tracing. JMS/HTTP etc all expose these, without
issues.
> > I would
> > > NOT want to lock this down to only be usable accessible via
> > interceptors,
> > > as we’d fail on one of the main goals.
> > >
> > > Regards
> > > Mike
> > >
> > >
> > >
> > >
> > > On 17/02/2017, 20:21, "Jason Gustafson" <ja...@confluent.io>
> > wrote:
> > >
> > > The point about creation of maps seems orthogonal. We can
> > still
> > > represent
> > > the headers as a slice of bytes until the time it is
> > accessed.
> > >
> > >
> > > > Yes exactly we have access to the records thus why the
> > header
> > > should be
> > > > accessible via it and not hidden for only interceptors
to
> > access.
> > >
> > >
> > > As explained above, the point is to make the intended
usage
> > clear.
> > > Applications should continue to rely on the key/value
> fields
> > to
> > > serialize
> > > their own headers, and it would be more ideal if we can
> avoid
> > > leaking
> > > third-party headers into applications. This is difficult
to
> > do
> > > with the
> > > current interceptors because they share the record objects
> > with
> > > the common
> > > API. What I had in mind is something like an extension of
> the
> > > current
> > > interceptors which exposed a different object (e.g.
> > > `RecordAndHeaders`).
> > > The challenge is for MM-like use cases. Let me see if I
can
> > come
> > > up with a
> > > concrete proposal for that problem.
> > >
> > > -Jason
> > >
> > >
> > >
> > > On Fri, Feb 17, 2017 at 11:55 AM, Michael Pearce <
> > > michael.pea...@ig.com>
> > > wrote:
> > >
> > > > I am happy to move the definition of the header into the
> > message
> > > body, but
> > > > would cause us not to lazy initialise/parse the headers,
> as
> > > obviously, we
> > > > would have to traverse these reading the message.
> > > >
> > > > This was actually one of Jay’s requests:
> > > >
> > > > “ 2. I think we should think about creating the Map
> > lazily to
> > > avoid
> > > > parsing out all the headers into little objects.
> > HashMaps
> > > themselves
> > > > are
> > > > kind of expensive and the consumer is very perf
> > sensitive so
> > > and making
> > > > gazillions of hashmaps that may or may not get used
> is
> > > probably a bad
> > > > idea.”
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > On 17/02/2017, 19:44, "Michael Pearce" <
> > michael.pea...@ig.com>
> > > wrote:
> > > >
> > > > Yes exactly we have access to the records thus why
> the
> > > header should
> > > > be accessible via it and not hidden for only
interceptors
> > to
> > > access.
> > > >
> > > > Sent using OWA for iPhone
> > > > ________________________________________
> > > > From: Magnus Edenhill <mag...@edenhill.se>
> > > > Sent: Friday, February 17, 2017 7:34:49 PM
> > > > To: dev@kafka.apache.org
> > > > Subject: Re: [DISCUSS] KIP-82 - Add Record Headers
> > > >
> > > > Big +1 on VarInts.
> > > > CPUs are fast, memory is slow.
> > > >
> > > > I agree with Jason that we'll want to continue
> > verifying
> > > messages,
> > > > including their headers, so while I appreciate the
> > idea of
> > > the opaque
> > > > header blob it won't be useful in practice.
> > > >
> > > > /Magnus
> > > >
> > > > 2017-02-17 10:41 GMT-08:00 Jason Gustafson <
> > > ja...@confluent.io>:
> > > >
> > > > > Sorry, my mistake. The consumer interceptor is per
> > batch,
> > > though I'm
> > > > not
> > > > > sure that's an actual limitation since you still
> have
> > > access to the
> > > > > individual records.
> > > > >
> > > > > -Jason
> > > > >
> > > > > On Fri, Feb 17, 2017 at 10:39 AM, Jason Gustafson
<
> > > > ja...@confluent.io>
> > > > > wrote:
> > > > >
> > > > > > Re headers as byte array and future use by
> broker.
> > This
> > > doesn't
> > > > take away
> > > > > >> from that at all. Nor makes it difficult at all
> > in my
> > > opinion.
> > > > > >
> > > > > >
> > > > > > Yeah, I didn't say it was difficult, only
> awkward.
> > You
> > > wouldn't
> > > > write the
> > > > > > schema that way if you were planning to use it
on
> > the
> > > brokers from
> > > > the
> > > > > > beginning. Note also that one of the benefits of
> > letting
> > > the broker
> > > > > > understand headers is that it can validate that
> > they are
> > > properly
> > > > > > formatted. If cost is the only concern, we
should
> > > confirm its
> > > > impact
> > > > > > through performance testing.
> > > > > >
> > > > > > One of the key use cases requires access on
> > consume at
> > > per
> > > > event/message
> > > > > >> level at the point that message is being
> > processed, as
> > > such the
> > > > batch
> > > > > >> interceptors and batch consume api isn't
> > suitable. It
> > > needs to be
> > > > at the
> > > > > >> record level.
> > > > > >
> > > > > >
> > > > > > I'm not sure I understand the point about
> batching.
> > > Interceptors
> > > > are
> > > > > > applied per-message, right?
> > > > > >
> > > > > > My intent on interceptors is to keep the usage
of
> > headers
> > > > well-defined so
> > > > > > that they don't start leaking unnecessarily into
> > > applications. My
> > > > guess
> > > > > is
> > > > > > that it's probably inevitable, but isolating it
> in
> > the
> > > > interceptors would
> > > > > > at least give people a second thought before
> > deciding to
> > > use it.
> > > > The main
> > > > > > challenge in my mind is figuring out how an MM
> use
> > case
> > > would
> > > > work. It
> > > > > > would be more cumbersome to replicate headers
> > through an
> > > > interceptor,
> > > > > > though arguably MM should be working at a lower
> > level
> > > anyway.
> > > > > >
> > > > > > -Jason
> > > > > >
> > > > > > On Fri, Feb 17, 2017 at 10:16 AM, Michael Pearce
> <
> > > > michael.pea...@ig.com>
> > > > > > wrote:
> > > > > >
> > > > > >> Re headers available on the record va
> > interceptors only
> > > > > >>
> > > > > >> One of the key use cases requires access on
> > consume at
> > > per
> > > > event/message
> > > > > >> level at the point that message is being
> > processed, as
> > > such the
> > > > batch
> > > > > >> interceptors and batch consume api isn't
> > suitable. It
> > > needs to be
> > > > at the
> > > > > >> record level.
> > > > > >>
> > > > > >> This anyhow is similar to jms/http/amqp where
> > headers
> > > are
> > > > available to
> > > > > >> consuming applications.
> > > > > >>
> > > > > >> Re headers as byte array and future use by
> > broker. This
> > > doesn't
> > > > take
> > > > > away
> > > > > >> from that at all. Nor makes it difficult at all
> > in my
> > > opinion.
> > > > > >>
> > > > > >>
> > > > > >>
> > > > > >> Sent using OWA for iPhone
> > > > > >> ________________________________________
> > > > > >> From: Jason Gustafson <ja...@confluent.io>
> > > > > >> Sent: Friday, February 17, 2017 5:55:42 PM
> > > > > >> To: dev@kafka.apache.org
> > > > > >> Subject: Re: [DISCUSS] KIP-82 - Add Record
> Headers
> > > > > >>
> > > > > >> >
> > > > > >> > Would you be proposing in KIP-98 to convert
> the
> > other
> > > message
> > > > int’s
> > > > > (key
> > > > > >> > length, value length) also to varint to keep
> it
> > > uniform.
> > > > > >> > Also I assume there will be a static or
helper
> > method
> > > made to
> > > > > write/read
> > > > > >> > these in the client and server.
> > > > > >>
> > > > > >>
> > > > > >> Yes, that is what we are proposing, so using
> > varints
> > > for headers
> > > > would
> > > > > be
> > > > > >> consistent with the rest of the message. We
have
> > used
> > > static
> > > > helper
> > > > > >> methods
> > > > > >> in our prototype implementation.
> > > > > >>
> > > > > >> The cost of parsing, we want to parse/interpret
> > the
> > > headers
> > > > lazily (this
> > > > > >> is
> > > > > >> > a key point brought up earlier in
discussions)
> > > > > >>
> > > > > >>
> > > > > >> I'm a bit skeptical of this. Has anyone done
the
> > > performance
> > > > testing? I
> > > > > >> can
> > > > > >> probably implement it and test it if no one
else
> > has. I
> > > was also
> > > > under
> > > > > the
> > > > > >> impression that there may be use cases down the
> > road
> > > where the
> > > > broker
> > > > > >> would
> > > > > >> need to interpret headers. That wouldn't be off
> > the
> > > table in the
> > > > future
> > > > > if
> > > > > >> it's represented as bytes, but it would be
quite
> > a bit
> > > more
> > > > awkward,
> > > > > >> right?
> > > > > >>
> > > > > >> By the way, one question I have been wondering
> > about. My
> > > > understanding
> > > > > is
> > > > > >> that headers are primarily for use cases where
a
> > > third-party
> > > > components
> > > > > >> wants to enrich messages without needing to
> > understand
> > > or modify
> > > > the
> > > > > >> schema
> > > > > >> of the message key and value. For the
> applications
> > > which directly
> > > > > produce
> > > > > >> and consume the messages and control the
> key/value
> > > schema
> > > > directly, it
> > > > > >> seems we would rather have them implement
> headers
> > > directly in
> > > > their own
> > > > > >> schema. Supposing for the sake of argument that
> > it was
> > > possible,
> > > > my
> > > > > >> question is whether it be sufficient to expose
> the
> > > headers in the
> > > > > >> interceptor API and not in the common API?
> > > > > >>
> > > > > >> -Jason
> > > > > >>
> > > > > >> On Fri, Feb 17, 2017 at 3:26 AM, Michael Pearce
> <
> > > > michael.pea...@ig.com>
> > > > > >> wrote:
> > > > > >>
> > > > > >> > On the point of varInts
> > > > > >> >
> > > > > >> > Would you be proposing in KIP-98 to convert
> the
> > other
> > > message
> > > > int’s
> > > > > (key
> > > > > >> > length, value length) also to varint to keep
> it
> > > uniform.
> > > > > >> > Also I assume there will be a static or
helper
> > method
> > > made to
> > > > > write/read
> > > > > >> > these in the client and server.
> > > > > >> >
> > > > > >> > Cheers
> > > > > >> > Mike
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> > On 17/02/2017, 11:22, "Michael Pearce" <
> > > michael.pea...@ig.com>
> > > > wrote:
> > > > > >> >
> > > > > >> > On the point re: headers in the message
> > protocol
> > > being a
> > > > byte
> > > > > array
> > > > > >> > and not a count of elements followed by the
> > elements.
> > > Again
> > > > this was
> > > > > >> > discussed/argued previously.
> > > > > >> >
> > > > > >> > It was agreed on for a few reasons some
of
> > which
> > > you have
> > > > > obviously
> > > > > >> > picked up on:
> > > > > >> >
> > > > > >> > Broker is able to pass it through
opaquely
> > > > > >> > The cost of parsing, we want to
> > parse/interpret
> > > the headers
> > > > lazily
> > > > > >> > (this is a key point brought up earlier in
> > > discussions)
> > > > > >> > Headers can be copied from consumer
record
> > to
> > > producer
> > > > record (aka
> > > > > >> > mirror makers etc) without parsing if no
> > changes are
> > > being made
> > > > or
> > > > > being
> > > > > >> > looked at.
> > > > > >> > Keeps the broker agnostic to the format
> > > > > >> > You need an int32 either for the byte
size
> > of the
> > > headers,
> > > > or for
> > > > > >> the
> > > > > >> > count of elements, so overheads are the same,
> > but
> > > with going
> > > > with an
> > > > > >> opaque
> > > > > >> > byte array has the above advantages.
> > > > > >> >
> > > > > >> > Cheers
> > > > > >> > Mike
> > > > > >> >
> > > > > >> >
> > > > > >> > On 17/02/2017, 02:50, "Jason Gustafson" <
> > > ja...@confluent.io
> > > > >
> > > > > wrote:
> > > > > >> >
> > > > > >> > Sorry, should have noted that the
> > performance
> > > testing
> > > > was done
> > > > > >> > using the
> > > > > >> > producer performance tool shipped
with
> > Kafka.
> > > > > >> >
> > > > > >> > -Jason
> > > > > >> >
> > > > > >> > On Thu, Feb 16, 2017 at 6:44 PM,
Jason
> > > Gustafson <
> > > > > >> > ja...@confluent.io> wrote:
> > > > > >> >
> > > > > >> > > Hey Nacho,
> > > > > >> > >
> > > > > >> > > I've compared performance of our
> > KIP-98
> > > > implementation with
> > > > > >> and
> > > > > >> > without
> > > > > >> > > varints. For messages around 128
> > bytes, we
> > > see an
> > > > increase
> > > > > in
> > > > > >> > throughput of
> > > > > >> > > about 30% using the default
> > configuration
> > > settings.
> > > > At 256
> > > > > >> > bytes, the
> > > > > >> > > increase is around 16%. Obviously
> the
> > > performance
> > > > converge
> > > > > as
> > > > > >> > messages get
> > > > > >> > > larger, but it seems well worth the
> > cost.
> > > Note that
> > > > we are
> > > > > >> also
> > > > > >> > seeing a
> > > > > >> > > substantial performance increase
> > against
> > > trunk
> > > > primarily
> > > > > >> because
> > > > > >> > of the
> > > > > >> > > much more efficient packing that
> > varints
> > > provide us.
> > > > > Anything
> > > > > >> > adding to
> > > > > >> > > message overhead, such as record
> > headers,
> > > would only
> > > > > increase
> > > > > >> > the relative
> > > > > >> > > difference. (Of course take these
> > numbers
> > > with a
> > > > grain of
> > > > > salt
> > > > > >> > since I have
> > > > > >> > > only used the default settings with
> > both
> > > the producer
> > > > and
> > > > > >> broker
> > > > > >> > on my
> > > > > >> > > local machine. We intend to provide
> > more
> > > extensive
> > > > > performance
> > > > > >> > details as
> > > > > >> > > part of the work for KIP-98.)
> > > > > >> > >
> > > > > >> > > The implementation we are using is
> > from
> > > protobuf (
> > > > > >> > > https://developers.google.com/
> > > > > protocol-buffers/docs/encoding
> > > > > >> ),
> > > > > >> > which is
> > > > > >> > > also used in HBase. It is trivial
to
> > > implement and as
> > > > far
> > > > > as I
> > > > > >> > know doesn't
> > > > > >> > > suffer from the aliasing problem
you
> > are
> > > describing. I
> > > > > checked
> > > > > >> > with Magnus
> > > > > >> > > (the author of librdkafka) and he
> > agreed
> > > that the
> > > > savings
> > > > > >> seemed
> > > > > >> > worth the
> > > > > >> > > cost of implementation.
> > > > > >> > >
> > > > > >> > > -Jason
> > > > > >> > >
> > > > > >> > > On Thu, Feb 16, 2017 at 4:32 PM,
> > Ignacio
> > > Solis <
> > > > > >> iso...@igso.net>
> > > > > >> > wrote:
> > > > > >> > >
> > > > > >> > >> -VarInts
> > > > > >> > >>
> > > > > >> > >> I'm one of the people (if not the
> > most)
> > > opposed to
> > > > VarInts.
> > > > > >> > VarInts
> > > > > >> > >> have a place, but this is not it.
> > (We
> > > had a large
> > > > > >> discussion
> > > > > >> > about
> > > > > >> > >> them at the beginning of KIP-82
> time)
> > > > > >> > >>
> > > > > >> > >> If anybody has real life
> performance
> > > numbers of
> > > > VarInts
> > > > > >> > improving
> > > > > >> > >> things or significantly reducing
> > resources
> > > I would
> > > > like to
> > > > > >> know
> > > > > >> > what
> > > > > >> > >> that case may be. Yes, you can
save
> > some
> > > bytes here
> > > > and
> > > > > >> there,
> > > > > >> > but
> > > > > >> > >> this is probably insignificant to
> the
> > > overall system
> > > > > behavior
> > > > > >> > and
> > > > > >> > >> storage requirements. -- I say
> this
> > with
> > > respect to
> > > > using
> > > > > >> > VarInts in
> > > > > >> > >> the protocol itself, not as part
of
> > the
> > > data.
> > > > > >> > >>
> > > > > >> > >> VarInts require you to parse the
> Int
> > > before using it
> > > > and
> > > > > >> > depending on
> > > > > >> > >> the encoding they can suffer from
> > aliasing
> > > (multiple
> > > > > >> > representations
> > > > > >> > >> for the same value).
> > > > > >> > >>
> > > > > >> > >> Why add complexity?
> > > > > >> > >>
> > > > > >> > >> Nacho
> > > > > >> > >>
> > > > > >> > >>
> > > > > >> > >> On Thu, Feb 16, 2017 at 10:29 AM,
> > Colin
> > > McCabe <
> > > > > >> > cmcc...@apache.org>
> > > > > >> > >> wrote:
> > > > > >> > >> > +1 for varints here-- it would
> save
> > > quite a bit of
> > > > space.
> > > > > >> > They are
> > > > > >> > >> > pretty quick to implement as
> well.
> > > > > >> > >> >
> > > > > >> > >> > I think it makes sense for
values
> > to be
> > > byte
> > > > arrays.
> > > > > Users
> > > > > >> > might want
> > > > > >> > >> > to attach arbitrary payloads;
> they
> > > shouldn't be
> > > > forced to
> > > > > >> > serialize
> > > > > >> > >> > everything to Java strings.
> > > > > >> > >> >
> > > > > >> > >> > best,
> > > > > >> > >> > Colin
> > > > > >> > >> >
> > > > > >> > >> >
> > > > > >> > >> > On Thu, Feb 16, 2017, at 09:52,
> > Jason
> > > Gustafson
> > > > wrote:
> > > > > >> > >> >> Hey Michael,
> > > > > >> > >> >>
> > > > > >> > >> >> Hmm, I guess the point of
> > representing
> > > it as
> > > > bytes is to
> > > > > >> > allow the
> > > > > >> > >> broker
> > > > > >> > >> >> to pass it through opaquely? Is
> > the
> > > cost of
> > > > parsing
> > > > > them a
> > > > > >> > concern, or
> > > > > >> > >> >> are
> > > > > >> > >> >> we simply trying to ensure that
> > the
> > > broker stays
> > > > > agnostic
> > > > > >> to
> > > > > >> > the
> > > > > >> > >> format?
> > > > > >> > >> >>
> > > > > >> > >> >> On varints, I think adding
> > support for
> > > them makes
> > > > less
> > > > > >> sense
> > > > > >> > for an
> > > > > >> > >> >> isolated use case, but as part
> of
> > a
> > > more holistic
> > > > change
> > > > > >> > (such as what
> > > > > >> > >> we
> > > > > >> > >> >> have proposed in KIP-98), I
> think
> > they
> > > are
> > > > justifiable.
> > > > > If
> > > > > >> > we add them,
> > > > > >> > >> >> then the need to use attributes
> > becomes
> > > quite a
> > > > bit
> > > > > >> weaker,
> > > > > >> > right? The
> > > > > >> > >> >> other thing I find slightly odd
> > is the
> > > fact that
> > > > null
> > > > > >> > headers has no
> > > > > >> > >> >> actual
> > > > > >> > >> >> semantic meaning for the
message
> > > (unlike null
> > > > keys and
> > > > > >> > values). It is
> > > > > >> > >> >> just
> > > > > >> > >> >> a space optimization. It seems
a
> > bit
> > > better to
> > > > always
> > > > > use
> > > > > >> > size 0 to
> > > > > >> > >> >> indicate having no headers.
> > > > > >> > >> >>
> > > > > >> > >> >> Overall, the main point is
> > ensuring
> > > that the
> > > > message
> > > > > >> schema
> > > > > >> > remains
> > > > > >> > >> >> consistent, either within the
> > larger
> > > protocol, or
> > > > at a
> > > > > >> > minimum within
> > > > > >> > >> the
> > > > > >> > >> >> message itself.
> > > > > >> > >> >>
> > > > > >> > >> >> -Jason
> > > > > >> > >> >>
> > > > > >> > >> >> On Thu, Feb 16, 2017 at 6:39
AM,
> > > Michael Pearce <
> > > > > >> > michael.pea...@ig.com
> > > > > >> > >> >
> > > > > >> > >> >> wrote:
> > > > > >> > >> >>
> > > > > >> > >> >> > Hi Jason,
> > > > > >> > >> >> >
> > > > > >> > >> >> > On point 1) in the message
> > protocol
> > > the headers
> > > > are
> > > > > >> simply
> > > > > >> > a byte
> > > > > >> > >> array,
> > > > > >> > >> >> > as like the key or value,
this
> > is to
> > > clearly
> > > > demarcate
> > > > > >> the
> > > > > >> > header in
> > > > > >> > >> the
> > > > > >> > >> >> > core message. Then the header
> > byte
> > > array in the
> > > > core
> > > > > >> > message is an
> > > > > >> > >> array of
> > > > > >> > >> >> > key, value pairs. This is
what
> > it is
> > > denoting.
> > > > > >> > >> >> >
> > > > > >> > >> >> > Then this would be I guess in
> > the
> > > given
> > > > notation:
> > > > > >> > >> >> >
> > > > > >> > >> >> > Headers => [KeyLength, Key,
> > > ValueLength, Value]
> > > > > >> > >> >> > KeyLength => int32
> > > <-----------------NEW
> > > > size of
> > > > > the
> > > > > >> > byte[] of
> > > > > >> > >> the
> > > > > >> > >> >> > serialised key value
> > > > > >> > >> >> > Key => bytes
> > > <---------------------- NEW
> > > > > serialised
> > > > > >> > string (UTF8)
> > > > > >> > >> >> > bytes of the header key
> > > > > >> > >> >> > ValueLength => int32
> > > <-------------- NEW
> > > > size of
> > > > > the
> > > > > >> > byte[] of
> > > > > >> > >> the
> > > > > >> > >> >> > serialised header value
> > > > > >> > >> >> > Value => bytes
> > > <-------------------- NEW
> > > > > serialised
> > > > > >> > form of the
> > > > > >> > >> header
> > > > > >> > >> >> > value
> > > > > >> > >> >> >
> > > > > >> > >> >> > The key length and value
> length
> > is
> > > matching the
> > > > way
> > > > > the
> > > > > >> > protocol is
> > > > > >> > >> >> > defined in the core message
> > currently.
> > > > > >> > >> >> >
> > > > > >> > >> >> >
> > > > > >> > >> >> >
> > > > > >> > >> >> >
> > > > > >> > >> >> > On point 2)
> > > > > >> > >> >> > Var sized ints, this was
> > discussed
> > > much earlier
> > > > on, in
> > > > > >> > fact I had
> > > > > >> > >> >> > suggested it myself (with
> Hadoop
> > > references),
> > > > the
> > > > > >> > complexity of this
> > > > > >> > >> >> > compared to having a simpler
> > protocol
> > > was
> > > > argued and
> > > > > >> > agreed it
> > > > > >> > >> wasn’t worth
> > > > > >> > >> >> > the complexity as all other
> > clients
> > > in other
> > > > languages
> > > > > >> > would need to
> > > > > >> > >> ensure
> > > > > >> > >> >> > theyre using the right var
> size
> > > algorithm, as
> > > > there
> > > > > is a
> > > > > >> > few.
> > > > > >> > >> >> >
> > > > > >> > >> >> > On point 3)
> > > > > >> > >> >> > We did the attributes,
> optional
> > > approach as
> > > > originally
> > > > > >> > there was
> > > > > >> > >> marked
> > > > > >> > >> >> > concern that headers would
> > cause a
> > > message size
> > > > > overhead
> > > > > >> > for others,
> > > > > >> > >> who
> > > > > >> > >> >> > don’t want them. As such this
> > is the
> > > clean
> > > > solution to
> > > > > >> > achieve that.
> > > > > >> > >> If
> > > > > >> > >> >> > that no longer holds, and we
> > don’t
> > > care that we
> > > > add
> > > > > >> 4bytes
> > > > > >> > overhead,
> > > > > >> > >> then
> > > > > >> > >> >> > im happy to remove.
> > > > > >> > >> >> >
> > > > > >> > >> >> > I’m personally in favour of
> > keeping
> > > the message
> > > > as
> > > > > small
> > > > > >> > as possible
> > > > > >> > >> so
> > > > > >> > >> >> > people don’t get shocks in
> perf
> > and
> > > throughputs
> > > > dues
> > > > > to
> > > > > >> > message size,
> > > > > >> > >> >> > unless they actively use the
> > feature,
> > > as such I
> > > > do
> > > > > >> prefer
> > > > > >> > the
> > > > > >> > >> attribute bit
> > > > > >> > >> >> > wise feature flag approach
> > myself.
> > > > > >> > >> >> >
> > > > > >> > >> >> >
> > > > > >> > >> >> >
> > > > > >> > >> >> >
> > > > > >> > >> >> > On 16/02/2017, 05:40, "Jason
> > > Gustafson" <
> > > > > >> > ja...@confluent.io> wrote:
> > > > > >> > >> >> >
> > > > > >> > >> >> > We have proposed a few
> > > significant changes
> > > > to the
> > > > > >> > message format
> > > > > >> > >> in
> > > > > >> > >> >> > KIP-98
> > > > > >> > >> >> > which now seems likely to
> > pass
> > > (perhaps
> > > > with some
> > > > > >> > iterations on
> > > > > >> > >> >> > implementation details).
> It
> > would
> > > be good
> > > > to try
> > > > > and
> > > > > >> > coordinate
> > > > > >> > >> the
> > > > > >> > >> >> > changes
> > > > > >> > >> >> > in both of the proposals
> to
> > make
> > > sure they
> > > > are
> > > > > >> > consistent and
> > > > > >> > >> >> > compatible.
> > > > > >> > >> >> >
> > > > > >> > >> >> > I think using the
> > attributes to
> > > indicate
> > > > null
> > > > > >> headers
> > > > > >> > is a
> > > > > >> > >> reasonable
> > > > > >> > >> >> > approach. We have
proposed
> > to do
> > > the same
> > > > thing
> > > > > for
> > > > > >> > the message
> > > > > >> > >> key and
> > > > > >> > >> >> > value. That said, I
> > sympathize
> > > with Jay's
> > > > > argument.
> > > > > >> > Having
> > > > > >> > >> multiple
> > > > > >> > >> >> > ways to
> > > > > >> > >> >> > specify a null value
> > increases
> > > the overall
> > > > > >> complexity
> > > > > >> > of the
> > > > > >> > >> protocol.
> > > > > >> > >> >> > You
> > > > > >> > >> >> > can see this just from
the
> > fact
> > > that you
> > > > need the
> > > > > >> > extra verbiage
> > > > > >> > >> in the
> > > > > >> > >> >> > protocol specification in
> > this
> > > KIP and in
> > > > KIP-98
> > > > > to
> > > > > >> > describe the
> > > > > >> > >> >> > dependence
> > > > > >> > >> >> > between the fields and
the
> > > attributes. It
> > > > seems
> > > > > >> like a
> > > > > >> > slippery
> > > > > >> > >> slope
> > > > > >> > >> >> > if
> > > > > >> > >> >> > you start allowing
> different
> > > request types
> > > > to
> > > > > >> > implement the
> > > > > >> > >> protocol
> > > > > >> > >> >> > specification
differently.
> > > > > >> > >> >> >
> > > > > >> > >> >> > You can also argue that
> the
> > > messages
> > > > already are
> > > > > and
> > > > > >> > are likely
> > > > > >> > >> to
> > > > > >> > >> >> > remain a
> > > > > >> > >> >> > special case. For
example,
> > there
> > > is
> > > > currently no
> > > > > >> > generality in
> > > > > >> > >> how
> > > > > >> > >> >> > compressed message sets
> are
> > > represented
> > > > that would
> > > > > >> be
> > > > > >> > applicable
> > > > > >> > >> for
> > > > > >> > >> >> > other
> > > > > >> > >> >> > request types. Some might
> > see this
> > > > divergence as
> > > > > an
> > > > > >> > unfortunate
> > > > > >> > >> >> > protocol
> > > > > >> > >> >> > deficiency which should
be
> > fixed;
> > > others
> > > > might see
> > > > > >> it
> > > > > >> > as sort of
> > > > > >> > >> the
> > > > > >> > >> >> > inevitability of needing
> to
> > > optimize where
> > > > it
> > > > > counts
> > > > > >> > most. I'm
> > > > > >> > >> probably
> > > > > >> > >> >> > somewhere in between, but
> I
> > think
> > > we
> > > > probably all
> > > > > >> > share the
> > > > > >> > >> intuition
> > > > > >> > >> >> > that
> > > > > >> > >> >> > the protocol should be
> kept
> > as
> > > consistent as
> > > > > >> possible.
> > > > > >> > With that
> > > > > >> > >> in
> > > > > >> > >> >> > mind,
> > > > > >> > >> >> > here are a few comments:
> > > > > >> > >> >> >
> > > > > >> > >> >> > 1. One thing I found a
> > little odd
> > > when
> > > > reading the
> > > > > >> > current
> > > > > >> > >> proposal is
> > > > > >> > >> >> > that
> > > > > >> > >> >> > the headers are both
> > represented
> > > as an
> > > > array of
> > > > > >> bytes
> > > > > >> > and as an
> > > > > >> > >> array
> > > > > >> > >> >> > of
> > > > > >> > >> >> > key/value pairs. I'd
> > probably
> > > suggest
> > > > something
> > > > > like
> > > > > >> > this:
> > > > > >> > >> >> >
> > > > > >> > >> >> > Headers => [HeaderKey
> > HeaderValue]
> > > > > >> > >> >> > HeaderKey => String
> > > > > >> > >> >> > HeaderValue => Bytes
> > > > > >> > >> >> >
> > > > > >> > >> >> > An array in the Kafka
> > protocol is
> > > > represented as a
> > > > > >> > 4-byte integer
> > > > > >> > >> >> > indicating the number of
> > elements
> > > in the
> > > > array
> > > > > >> > followed by the
> > > > > >> > >> >> > serialization of the
> > elements.
> > > Unless I'm
> > > > > >> > misunderstanding, what
> > > > > >> > >> you
> > > > > >> > >> >> > have
> > > > > >> > >> >> > instead is the total size
> > of the
> > > headers in
> > > > bytes
> > > > > >> > followed by the
> > > > > >> > >> >> > elements.
> > > > > >> > >> >> > I'm not sure I see any
> > reason for
> > > this
> > > > > >> inconsistency.
> > > > > >> > >> >> >
> > > > > >> > >> >> > 2. In KIP-98, we've
> > introduced
> > > > variable-length
> > > > > >> integer
> > > > > >> > fields.
> > > > > >> > >> >> > Effectively,
> > > > > >> > >> >> > we've enriched (or
> > "complicated"
> > > as Jay
> > > > might say
> > > > > ;)
> > > > > >> > the protocol
> > > > > >> > >> >> > specification to include
> the
> > > following
> > > > types:
> > > > > >> VarInt,
> > > > > >> > VarLong,
> > > > > >> > >> >> > UnsignedVarInt and
> > > UnsignedVarLong.
> > > > > >> > >> >> >
> > > > > >> > >> >> > Along with these
> > primitives, we
> > > could
> > > > introduce
> > > > > the
> > > > > >> > following
> > > > > >> > >> types:
> > > > > >> > >> >> >
> > > > > >> > >> >> > VarSizeArray =>
> > NumberOfItems
> > > Item1 Item2
> > > > .. ItemN
> > > > > >> > >> >> > NumberOfItems =>
> > UnsignedVarInt
> > > > > >> > >> >> >
> > > > > >> > >> >> > VarSizeNullableArray =>
> > > NumberOfItemsOrNull
> > > > Item1
> > > > > >> > Item2 .. ItemN
> > > > > >> > >> >> > NumberOfItemsOrNull =>
> > VarInt
> > > (-1 means
> > > > null)
> > > > > >> > >> >> >
> > > > > >> > >> >> > And similarly for the
> > `String`
> > > and `Bytes`
> > > > types.
> > > > > >> > These types
> > > > > >> > >> can save
> > > > > >> > >> >> > a
> > > > > >> > >> >> > considerable amount of
> > space in
> > > this
> > > > proposal
> > > > > >> because
> > > > > >> > they can
> > > > > >> > >> be used
> > > > > >> > >> >> > for
> > > > > >> > >> >> > both the number of
headers
> > > included in the
> > > > message
> > > > > >> and
> > > > > >> > the
> > > > > >> > >> lengths of
> > > > > >> > >> >> > the
> > > > > >> > >> >> > header keys and values.
We
> > could
> > > do this
> > > > instead:
> > > > > >> > >> >> >
> > > > > >> > >> >> > Headers =>
> > VarSizeArray[HeaderKey
> > > > HeaderValue]
> > > > > >> > >> >> > HeaderKey =>
> VarSizeString
> > > > > >> > >> >> > HeaderValue =>
> > VarSizeBytes
> > > > > >> > >> >> >
> > > > > >> > >> >> > Combining the savings
from
> > the
> > > use of
> > > > variable
> > > > > >> length
> > > > > >> > fields, the
> > > > > >> > >> >> > benefit
> > > > > >> > >> >> > of using the attributes
to
> > > represent null
> > > > seems
> > > > > >> pretty
> > > > > >> > small.
> > > > > >> > >> >> >
> > > > > >> > >> >> > 3. Whichever way we go
> > (whether
> > > we use the
> > > > > >> attributes
> > > > > >> > or not), we
> > > > > >> > >> >> > should at
> > > > > >> > >> >> > least be consistent
> between
> > this
> > > KIP and
> > > > KIP-98.
> > > > > It
> > > > > >> > would be very
> > > > > >> > >> >> > strange
> > > > > >> > >> >> > to have two ways to
> > represent
> > > null values
> > > > in the
> > > > > >> same
> > > > > >> > schema.
> > > > > >> > >> Either
> > > > > >> > >> >> > way is
> > > > > >> > >> >> > OK with me. I think some
> > > message-level
> > > > > optimizations
> > > > > >> > are
> > > > > >> > >> justifiable,
> > > > > >> > >> >> > but
> > > > > >> > >> >> > the savings here seem
> > minimal (a
> > > few bytes
> > > > per
> > > > > >> > message), so
> > > > > >> > >> maybe it's
> > > > > >> > >> >> > not
> > > > > >> > >> >> > worth the cost of letting
> > the
> > > message
> > > > diverge even
> > > > > >> > further from
> > > > > >> > >> the
> > > > > >> > >> >> > rest of
> > > > > >> > >> >> > the protocol.
> > > > > >> > >> >> >
> > > > > >> > >> >> > -Jason
> > > > > >> > >> >> >
> > > > > >> > >> >> >
> > > > > >> > >> >> > On Wed, Feb 15, 2017 at
> > 8:52 AM,
> > > radai <
> > > > > >> > >> radai.rosenbl...@gmail.com>
> > > > > >> > >> >> > wrote:
> > > > > >> > >> >> >
> > > > > >> > >> >> > > I've trimmed the inline
> > > contents as this
> > > > mail is
> > > > > >> > getting too
> > > > > >> > >> big for
> > > > > >> > >> >> > the
> > > > > >> > >> >> > > apache mailing list
> > software to
> > > deliver
> > > > :-(
> > > > > >> > >> >> > >
> > > > > >> > >> >> > > 1. the important thing
> for
> > > > interoperability is
> > > > > for
> > > > > >> > different
> > > > > >> > >> >> > "interested
> > > > > >> > >> >> > > parties" (plugins,
infra
> > > layers/wrappers,
> > > > > >> user-code)
> > > > > >> > to be
> > > > > >> > >> able to
> > > > > >> > >> >> > stick
> > > > > >> > >> >> > > pieces of metadata onto
> > msgs
> > > without
> > > > getting in
> > > > > >> each
> > > > > >> > other's
> > > > > >> > >> way. a
> > > > > >> > >> >> > common
> > > > > >> > >> >> > > key scheme (Strings, as
> > of the
> > > time of
> > > > this
> > > > > >> > writing?) is all
> > > > > >> > >> thats
> > > > > >> > >> >> > required
> > > > > >> > >> >> > > for that. it is assumed
> > that
> > > the other end
> > > > > >> > interested in any
> > > > > >> > >> such
> > > > > >> > >> >> > piece of
> > > > > >> > >> >> > > metadata knows the
> > encoding,
> > > and byte[]
> > > > provides
> > > > > >> for
> > > > > >> > the most
> > > > > >> > >> >> > flexibility.
> > > > > >> > >> >> > > i believe this is the
> same
> > > logic behind
> > > > core
> > > > > kafka
> > > > > >> > being
> > > > > >> > >> >> > byte[]/byte[] -
> > > > > >> > >> >> > > Strings are more
> "usable"
> > but
> > > bytes are
> > > > flexible
> > > > > >> and
> > > > > >> > so were
> > > > > >> > >> chosen.
> > > > > >> > >> >> > > Also - core kafka
doesnt
> > even
> > > do that
> > > > good of a
> > > > > >> job
> > > > > >> > on
> > > > > >> > >> usability of
> > > > > >> > >> >> > the
> > > > > >> > >> >> > > payload (example - i
> have
> > to
> > > specify the
> > > > nop
> > > > > >> byte[]
> > > > > >> > "decoders"
> > > > > >> > >> >> > explicitly
> > > > > >> > >> >> > > in conf), and again
> > sacrificies
> > > usability
> > > > for
> > > > > the
> > > > > >> > sake of
> > > > > >> > >> >> > performance (no
> > > > > >> > >> >> > > convenient
single-record
> > > processing as
> > > > poll is a
> > > > > >> > batch, lots of
> > > > > >> > >> >> > obscure
> > > > > >> > >> >> > > little config details
> > exposing
> > > internals
> > > > of the
> > > > > >> > batching
> > > > > >> > >> mechanism,
> > > > > >> > >> >> > etc)
> > > > > >> > >> >> > >
> > > > > >> > >> >> > > this is also why i
> really
> > > dislike the
> > > > idea of a
> > > > > >> > "type system"
> > > > > >> > >> for
> > > > > >> > >> >> > header
> > > > > >> > >> >> > > values, it further
> > degrades the
> > > > usability, adds
> > > > > >> > complexity and
> > > > > >> > >> will
> > > > > >> > >> >> > > eventually get in
> > people's way,
> > > also, it
> > > > would
> > > > > be
> > > > > >> > the 2nd/3rd
> > > > > >> > >> >> > home-group
> > > > > >> > >> >> > > serialization mechanism
> > in core
> > > kafka
> > > > (counting
> > > > > 2
> > > > > >> > iterations
> > > > > >> > >> of the
> > > > > >> > >> >> > "type
> > > > > >> > >> >> > > definition DSL")
> > > > > >> > >> >> > >
> > > > > >> > >> >> > > 2. this is an
> > implementation
> > > detail, and
> > > > not
> > > > > even
> > > > > >> a
> > > > > >> > very "user
> > > > > >> > >> >> > facing" one?
> > > > > >> > >> >> > > to the best of my
> > understanding
> > > the vote
> > > > process
> > > > > >> is
> > > > > >> > on proposed
> > > > > >> > >> >> > > API/behaviour. also -
> > since
> > > we're willing
> > > > to go
> > > > > >> with
> > > > > >> > strings
> > > > > >> > >> just
> > > > > >> > >> >> > serialize
> > > > > >> > >> >> > > a 0-sized header blob
> and
> > IIUC
> > > you dont
> > > > need any
> > > > > >> > optionals
> > > > > >> > >> anymore.
> > > > > >> > >> >> > >
> > > > > >> > >> >> > > 3. yes, we can :-)
> > > > > >> > >> >> > >
> > > > > >> > >> >> > > On Tue, Feb 14, 2017 at
> > 11:56
> > > PM, Michael
> > > > > Pearce <
> > > > > >> > >> >> > michael.pea...@ig.com>
> > > > > >> > >> >> > > wrote:
> > > > > >> > >> >> > >
> > > > > >> > >> >> > > > Hi Jay,
> > > > > >> > >> >> > > >
> > > > > >> > >> >> > > > 1) There was some
> > initial
> > > debate on the
> > > > value
> > > > > >> > part, as youll
> > > > > >> > >> note
> > > > > >> > >> >> > String,
> > > > > >> > >> >> > > > String headers were
> > > discounted early
> > > > on. The
> > > > > >> > reason for this
> > > > > >> > >> is
> > > > > >> > >> >> > > flexibility
> > > > > >> > >> >> > > > and keeping in line
> > with the
> > > > flexibility of
> > > > > key,
> > > > > >> > value of the
> > > > > >> > >> >> > message
> > > > > >> > >> >> > > > object itself. I
don’t
> > think
> > > it takes
> > > > away
> > > > > from
> > > > > >> an
> > > > > >> > ecosystem
> > > > > >> > >> as
> > > > > >> > >> >> > each
> > > > > >> > >> >> > > plugin
> > > > > >> > >> >> > > > will care for their
> own
> > key,
> > > this way
> > > > ints,
> > > > > >> > booleans , exotic
> > > > > >> > >> >> > custom
> > > > > >> > >> >> > > binary
> > > > > >> > >> >> > > > can all be catered
> for=.
> > > > > >> > >> >> > > > a. If you really
> wanted
> > to
> > > push for a
> > > > typed
> > > > > >> value
> > > > > >> > interface,
> > > > > >> > >> I
> > > > > >> > >> >> > wouldn’t
> > > > > >> > >> >> > > > want just String
> values
> > > supported, but
> > > > the the
> > > > > >> > primatives
> > > > > >> > >> plus
> > > > > >> > >> >> > string and
> > > > > >> > >> >> > > > also still keeping
the
> > > ability to have a
> > > > > binary
> > > > > >> > for custom
> > > > > >> > >> >> > binaries that
> > > > > >> > >> >> > > > some organisations
may
> > have.
> > > > > >> > >> >> > > > i. I have written
this
> > slight
> > > > alternative
> > > > > here,
> > > > > >> > >> >> > >
> https://cwiki.apache.org/
> > > > > >> > >> >> > > >
> > confluence/display/KAFKA/KIP-
> > > > > >> > 82+-+Add+Record+Headers+-+Typed
> > > > > >> > >> >> > > > ii. Essentially the
> > value
> > > bytes, has a
> > > > leading
> > > > > >> > byte overhead.
> > > > > >> > >> >> > > > 1. This tells you
> what
> > type
> > > the value
> > > > is,
> > > > > >> before
> > > > > >> > reading
> > > > > >> > >> the rest
> > > > > >> > >> >> > of the
> > > > > >> > >> >> > > > bytes, allowing
> > > > serialisation/deserialization
> > > > > to
> > > > > >> > and from the
> > > > > >> > >> >> > primitives,
> > > > > >> > >> >> > > > string and byte[].
> This
> > is
> > > akin to some
> > > > other
> > > > > >> > messaging
> > > > > >> > >> systems.
> > > > > >> > >> >> > > > 2) We are making it
> > optional,
> > > so that
> > > > for
> > > > > those
> > > > > >> > not wanting
> > > > > >> > >> >> > headers have
> > > > > >> > >> >> > > 0
> > > > > >> > >> >> > > > bytes overhead (think
> > of it
> > > as a feature
> > > > > flag),
> > > > > >> I
> > > > > >> > don’t
> > > > > >> > >> think this
> > > > > >> > >> >> > is
> > > > > >> > >> >> > > > complex, especially
if
> > > comparing to
> > > > changes
> > > > > >> > proposed in
> > > > > >> > >> other kips
> > > > > >> > >> >> > like
> > > > > >> > >> >> > > > kip-98.
> > > > > >> > >> >> > > > a. If you really
> really
> > don’t
> > > like
> > > > this, we
> > > > > can
> > > > > >> > drop it, but
> > > > > >> > >> it
> > > > > >> > >> >> > would
> > > > > >> > >> >> > > mean
> > > > > >> > >> >> > > > buying into 4 bytes
> > extra
> > > overhead for
> > > > users
> > > > > who
> > > > > >> > do not want
> > > > > >> > >> to use
> > > > > >> > >> >> > > headers.
> > > > > >> > >> >> > > > 3) In the summary
yes,
> > it is
> > > at a higher
> > > > > level,
> > > > > >> > but I think
> > > > > >> > >> this
> > > > > >> > >> >> > is well
> > > > > >> > >> >> > > > documented in the
> > proposed
> > > changes
> > > > section.
> > > > > >> > >> >> > > > a. Added getHeaders
> > method to
> > > > > Producer/Consumer
> > > > > >> > record (that
> > > > > >> > >> is it)
> > > > > >> > >> >> > > > b. We’ve also
detailed
> > the
> > > new Headers
> > > > class
> > > > > >> that
> > > > > >> > this method
> > > > > >> > >> >> > returns
> > > > > >> > >> >> > > that
> > > > > >> > >> >> > > > encapsulates the
> headers
> > > protocol and
> > > > logic.
> > > > > >> > >> >> > > >
> > > > > >> > >> >> > > > Best,
> > > > > >> > >> >> > > > Mike
> > > > > >> > >> >> > > >
> > > > > >> > >> >> > > > ==Original questions
> > from the
> > > vote
> > > > thread from
> > > > > >> > Jay.==
> > > > > >> > >> >> > > >
> > > > > >> > >> >> > > > Couple of things I
> > think we
> > > still need
> > > > to work
> > > > > >> out:
> > > > > >> > >> >> > > >
> > > > > >> > >> >> > > > 1. I think we
agree
> > about
> > > the key,
> > > > but I
> > > > > >> think
> > > > > >> > we haven't
> > > > > >> > >> >> > talked about
> > > > > >> > >> >> > > > the value yet. I
> > think if
> > > our goal
> > > > is an
> > > > > open
> > > > > >> > ecosystem
> > > > > >> > >> of these
> > > > > >> > >> >> > > header
> > > > > >> > >> >> > > > spread across many
> > plugins
> > > from many
> > > > > systems
> > > > > >> we
> > > > > >> > should
> > > > > >> > >> consider
> > > > > >> > >> >> > making
> > > > > >> > >> >> > > > this
> > > > > >> > >> >> > > > a string as well
so
> > it can
> > > be
> > > > printed, set
> > > > > >> via
> > > > > >> > a UI, set
> > > > > >> > >> in
> > > > > >> > >> >> > config,
> > > > > >> > >> >> > > etc.
> > > > > >> > >> >> > > > Basically
> encouraging
> > > pluggable
> > > > > serialization
> > > > > >> > formats
> > > > > >> > >> here will
> > > > > >> > >> >> > lead
> > > > > >> > >> >> > > to
> > > > > >> > >> >> > > > a
> > > > > >> > >> >> > > > bit of a tower of
> > babel.
> > > > > >> > >> >> > > > 2. This proposal
> > still
> > > includes a
> > > > pretty
> > > > > big
> > > > > >> > change to our
> > > > > >> > >> >> > > serialization
> > > > > >> > >> >> > > > and protocol
> > definition
> > > layer.
> > > > Essentially
> > > > > >> it is
> > > > > >> > >> introducing an
> > > > > >> > >> >> > > optional
> > > > > >> > >> >> > > > type, where the
> > format is
> > > data
> > > > dependent. I
> > > > > >> > think this is
> > > > > >> > >> >> > actually a
> > > > > >> > >> >> > > big
> > > > > >> > >> >> > > > change though it
> > doesn't
> > > seem like
> > > > it. It
> > > > > >> means
> > > > > >> > you can no
> > > > > >> > >> >> > longer
> > > > > >> > >> >> > > > specify
> > > > > >> > >> >> > > > this type with our
> > type
> > > definition
> > > > DSL, and
> > > > > >> > likewise it
> > > > > >> > >> requires
> > > > > >> > >> >> > > custom
> > > > > >> > >> >> > > > handling in client
> > libs.
> > > This isn't
> > > > a huge
> > > > > >> > thing, since
> > > > > >> > >> the
> > > > > >> > >> >> > Record
> > > > > >> > >> >> > > > definition is
> custom
> > > anyway, but I
> > > > think
> > > > > this
> > > > > >> > kind of
> > > > > >> > >> protocol
> > > > > >> > >> >> > > > inconsistency is
> very
> > > non-desirable
> > > > and
> > > > > ties
> > > > > >> > you to
> > > > > >> > >> hand-coding
> > > > > >> > >> >> > > things.
> > > > > >> > >> >> > > > I
> > > > > >> > >> >> > > > think the type
> should
> > > instead by [Key
> > > > > Value]
> > > > > >> in
> > > > > >> > our BNF,
> > > > > >> > >> where
> > > > > >> > >> >> > key and
> > > > > >> > >> >> > > > value are both
> short
> > > strings as used
> > > > > >> elsewhere.
> > > > > >> > This
> > > > > >> > >> brings it
> > > > > >> > >> >> > in line
> > > > > >> > >> >> > > > with
> > > > > >> > >> >> > > > the rest of the
> > protocol.
> > > > > >> > >> >> > > > 3. Could we get
> more
> > > specific about
> > > > the
> > > > > exact
> > > > > >> > Java API
> > > > > >> > >> change to
> > > > > >> > >> >> > > > ProducerRecord,
> > > ConsumerRecord,
> > > > Record,
> > > > > etc?
> > > > > >> > >> >> > > >
> > > > > >> > >> >> > > > -Jay
> > > > > >> > >> >> > > >
> > > > > >> > >> >> > >
> > > > > >> > >> >> >
> > > > > >> > >> >> >
> > > > > >> > >> >> > The information contained in
> > this
> > > email is
> > > > strictly
> > > > > >> > confidential and
> > > > > >> > >> for
> > > > > >> > >> >> > the use of the addressee
only,
> > unless
> > > otherwise
> > > > > >> indicated.
> > > > > >> > If you
> > > > > >> > >> are not
> > > > > >> > >> >> > the intended recipient,
please
> > do not
> > > read,
> > > > copy, use
> > > > > or
> > > > > >> > disclose to
> > > > > >> > >> others
> > > > > >> > >> >> > this message or any
> attachment.
> > > Please also
> > > > notify the
> > > > > >> > sender by
> > > > > >> > >> replying
> > > > > >> > >> >> > to this email or by telephone
> > > (+44(020 7896
> > > > 0011) and
> > > > > >> then
> > > > > >> > delete
> > > > > >> > >> the email
> > > > > >> > >> >> > and any copies of it.
> Opinions,
> > > conclusion
> > > > (etc) that
> > > > > do
> > > > > >> > not relate
> > > > > >> > >> to the
> > > > > >> > >> >> > official business of this
> > company
> > > shall be
> > > > understood
> > > > > as
> > > > > >> > neither
> > > > > >> > >> given nor
> > > > > >> > >> >> > endorsed by it. IG is a
> trading
> > name
> > > of IG
> > > > Markets
> > > > > >> Limited
> > > > > >> > (a company
> > > > > >> > >> >> > registered in England and
> Wales,
> > > company number
> > > > > >> 04008957)
> > > > > >> > and IG
> > > > > >> > >> Index
> > > > > >> > >> >> > Limited (a company registered
> in
> > > England and
> > > > Wales,
> > > > > >> > company number
> > > > > >> > >> >> > 01190902). Registered address
> at
> > > Cannon Bridge
> > > > House,
> > > > > 25
> > > > > >> > Dowgate
> > > > > >> > >> Hill,
> > > > > >> > >> >> > London EC4R 2YA. Both IG
> Markets
> > > Limited
> > > > (register
> > > > > >> number
> > > > > >> > 195355)
> > > > > >> > >> and IG
> > > > > >> > >> >> > Index Limited (register
number
> > > 114059) are
> > > > authorised
> > > > > >> and
> > > > > >> > regulated
> > > > > >> > >> by the
> > > > > >> > >> >> > Financial Conduct Authority.
> > > > > >> > >> >> >
> > > > > >> > >>
> > > > > >> > >>
> > > > > >> > >>
> > > > > >> > >> --
> > > > > >> > >> Nacho - Ignacio Solis -
> > iso...@igso.net
> > > > > >> > >>
> > > > > >> > >
> > > > > >> > >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> >
> > > > > >> > The information contained in this email is
> > strictly
> > > > confidential and
> > > > > for
> > > > > >> > the use of the addressee only, unless
> otherwise
> > > indicated. If
> > > > you are
> > > > > >> not
> > > > > >> > the intended recipient, please do not read,
> > copy, use
> > > or
> > > > disclose to
> > > > > >> others
> > > > > >> > this message or any attachment. Please also
> > notify
> > > the sender by
> > > > > >> replying
> > > > > >> > to this email or by telephone (+44(020 7896
> > 0011) and
> > > then
> > > > delete the
> > > > > >> email
> > > > > >> > and any copies of it. Opinions, conclusion
> > (etc) that
> > > do not
> > > > relate to
> > > > > >> the
> > > > > >> > official business of this company shall be
> > understood
> > > as
> > > > neither given
> > > > > >> nor
> > > > > >> > endorsed by it. IG is a trading name of IG
> > Markets
> > > Limited (a
> > > > company
> > > > > >> > registered in England and Wales, company
> number
> > > 04008957) and
> > > > IG Index
> > > > > >> > Limited (a company registered in England and
> > Wales,
> > > company
> > > > number
> > > > > >> > 01190902). Registered address at Cannon
Bridge
> > House,
> > > 25
> > > > Dowgate Hill,
> > > > > >> > London EC4R 2YA. Both IG Markets Limited
> > (register
> > > number
> > > > 195355) and
> > > > > IG
> > > > > >> > Index Limited (register number 114059) are
> > authorised
> > > and
> > > > regulated by
> > > > > >> the
> > > > > >> > Financial Conduct Authority.
> > > > > >> >
> > > > > >> The information contained in this email is
> > strictly
> > > confidential
> > > > and for
> > > > > >> the use of the addressee only, unless otherwise
> > > indicated. If you
> > > > are
> > > > > not
> > > > > >> the intended recipient, please do not read,
> copy,
> > use
> > > or disclose
> > > > to
> > > > > others
> > > > > >> this message or any attachment. Please also
> > notify the
> > > sender by
> > > > > replying
> > > > > >> to this email or by telephone (+44(020 7896
> 0011)
> > and
> > > then delete
> > > > the
> > > > > email
> > > > > >> and any copies of it. Opinions, conclusion
(etc)
> > that
> > > do not
> > > > relate to
> > > > > the
> > > > > >> official business of this company shall be
> > understood
> > > as neither
> > > > given
> > > > > nor
> > > > > >> endorsed by it. IG is a trading name of IG
> Markets
> > > Limited (a
> > > > company
> > > > > >> registered in England and Wales, company number
> > > 04008957) and IG
> > > > Index
> > > > > >> Limited (a company registered in England and
> > Wales,
> > > company number
> > > > > >> 01190902). Registered address at Cannon Bridge
> > House,
> > > 25 Dowgate
> > > > Hill,
> > > > > >> London EC4R 2YA. Both IG Markets Limited
> (register
> > > number 195355)
> > > > and IG
> > > > > >> Index Limited (register number 114059) are
> > authorised
> > > and
> > > > regulated by
> > > > > the
> > > > > >> Financial Conduct Authority.
> > > > > >>
> > > > > >
> > > > > >
> > > > >
> > > > The information contained in this email is strictly
> > > confidential and
> > > > for the use of the addressee only, unless otherwise
> > indicated.
> > > If you are
> > > > not the intended recipient, please do not read, copy,
use
> > or
> > > disclose to
> > > > others this message or any attachment. Please also
notify
> > the
> > > sender by
> > > > replying to this email or by telephone (+44(020 7896
> 0011)
> > and
> > > then delete
> > > > the email and any copies of it. Opinions, conclusion
> (etc)
> > that
> > > do not
> > > > relate to the official business of this company shall be
> > > understood as
> > > > neither given nor endorsed by it. IG is a trading name
of
> > IG
> > > Markets
> > > > Limited (a company registered in England and Wales,
> company
> > > number
> > > > 04008957) and IG Index Limited (a company registered in
> > England
> > > and Wales,
> > > > company number 01190902). Registered address at Cannon
> > Bridge
> > > House, 25
> > > > Dowgate Hill, London EC4R 2YA. Both IG Markets Limited
> > (register
> > > number
> > > > 195355) and IG Index Limited (register number 114059)
are
> > > authorised and
> > > > regulated by the Financial Conduct Authority.
> > > >
> > > >
> > > >
> > > >
> > >
> > >
> > > The information contained in this email is strictly
> confidential
> > and
> > > for the use of the addressee only, unless otherwise indicated. If
> > you are
> > > not the intended recipient, please do not read, copy, use or
> > disclose to
> > > others this message or any attachment. Please also notify the
> sender
> > by
> > > replying to this email or by telephone (+44(020 7896 0011) and
then
> > delete
> > > the email and any copies of it. Opinions, conclusion (etc) that do
> > not
> > > relate to the official business of this company shall be
understood
> > as
> > > neither given nor endorsed by it. IG is a trading name of IG
> Markets
> > > Limited (a company registered in England and Wales, company number
> > > 04008957) and IG Index Limited (a company registered in England
and
> > Wales,
> > > company number 01190902). Registered address at Cannon Bridge
> House,
> > 25
> > > Dowgate Hill, London EC4R 2YA. Both IG Markets Limited (register
> > number
> > > 195355) and IG Index Limited (register number 114059) are
> authorised
> > and
> > > regulated by the Financial Conduct Authority.
> > >
> > >
> > >
> >
> >
> > The information contained in this email is strictly confidential and for
> > the use of the addressee only, unless otherwise indicated. If you are
not
> > the intended recipient, please do not read, copy, use or disclose to
> others
> > this message or any attachment. Please also notify the sender by
replying
> > to this email or by telephone (+44(020 7896 0011) and then delete the
> email
> > and any copies of it. Opinions, conclusion (etc) that do not relate to
> the
> > official business of this company shall be understood as neither given
> nor
> > endorsed by it. IG is a trading name of IG Markets Limited (a company
> > registered in England and Wales, company number 04008957) and IG Index
> > Limited (a company registered in England and Wales, company number
> > 01190902). Registered address at Cannon Bridge House, 25 Dowgate Hill,
> > London EC4R 2YA. Both IG Markets Limited (register number 195355) and IG
> > Index Limited (register number 114059) are authorised and regulated by
> the
> > Financial Conduct Authority.
> >
>
The information contained in this email is strictly confidential and for the
use of the addressee only, unless otherwise indicated. If you are not the
intended recipient, please do not read, copy, use or disclose to others this
message or any attachment. Please also notify the sender by replying to this
email or by telephone (+44(020 7896 0011) and then delete the email and any
copies of it. Opinions, conclusion (etc) that do not relate to the official
business of this company shall be understood as neither given nor endorsed by
it. IG is a trading name of IG Markets Limited (a company registered in England
and Wales, company number 04008957) and IG Index Limited (a company registered
in England and Wales, company number 01190902). Registered address at Cannon
Bridge House, 25 Dowgate Hill, London EC4R 2YA. Both IG Markets Limited
(register number 195355) and IG Index Limited (register number 114059) are
authorised and regulated by the Financial Conduct Authority.
