my personal opinion - a log compacted topic is basically a kv-store, so a
map API.
map.put(key, null) is not the same as map.remove(key), which to me means a
null value should not represent a delete. a delete should be explicit
(meaning flag).


On Wed, Nov 9, 2016 at 11:01 AM, Mayuresh Gharat <gharatmayures...@gmail.com
> wrote:

> I see the reasoning and might be inclined to agree a bit :
> If we go to stage 2, the only difference is that we can theoretically
> support a null value non-tombstone message in a log compacted topic, but I
> am not sure if that has any use case.
>
> But as an end goal I see that kafka should clearly specify what it means by
> a tombstone : is it the attribute flag OR is it the null value. If we just
> do stage 1, I don't think we are defining the end-goal completely.
> Again this is more about semantics of correctness of end state.
>
> Thanks,
>
> Mayuresh
>
> On Wed, Nov 9, 2016 at 10:49 AM, Becket Qin <becket....@gmail.com> wrote:
>
> > I am not sure if we need the second stage. Wouldn't it be enough to say
> > that a message is a tombstone if one of the following is true?
> > 1. tombstone flag is set.
> > 2. value is null.
> >
> > If we go to stage 2, the only difference is that we can theoretically
> > support a null value non-tombstone message in a log compacted topic, but
> I
> > am not sure if that has any use case.
> >
> > Thanks,
> >
> > Jiangjie (Becket) Qin
> >
> >
> > On Wed, Nov 9, 2016 at 9:23 AM, Mayuresh Gharat <
> > gharatmayures...@gmail.com>
> > wrote:
> >
> > > I think it will be a good idea. +1
> > >
> > > Thanks,
> > >
> > > Mayuresh
> > >
> > > On Wed, Nov 9, 2016 at 9:13 AM, Michael Pearce <michael.pea...@ig.com>
> > > wrote:
> > >
> > > > +1 Mayuresh, I think this is a good solution/strategy.
> > > >
> > > > Shall we update the KIP with this? Becket/Jun/Joel any comments to
> add
> > > > before we do?
> > > >
> > > > On 08/11/2016, 17:29, "Mayuresh Gharat" <gharatmayures...@gmail.com>
> > > > wrote:
> > > >
> > > >     I think the migration can be done in 2 stages :
> > > >
> > > >     1) In first stage the broker should understand the attribute flag
> > as
> > > > well
> > > >     as Null for the value for log compaction.
> > > >     2) In second stage we move on to supporting only the attribute
> flag
> > > > for log
> > > >     compaction.
> > > >
> > > >     I agree with Becket that for older clients (consumers) the broker
> > > might
> > > >     have to down convert a message that has the attribute flag set
> for
> > > log
> > > >     compacting but has a non null value. But this should be in first
> > > stage.
> > > >     Once all the clients have upgraded (clients start recognizing the
> > > > attribute
> > > >     flag), we can move the broker to stage 2.
> > > >
> > > >     Thanks,
> > > >
> > > >     Mayuresh
> > > >
> > > >     On Tue, Nov 8, 2016 at 12:06 AM, Michael Pearce <
> > > michael.pea...@ig.com
> > > > >
> > > >     wrote:
> > > >
> > > >     > Also we can add further guidance:
> > > >     >
> > > >     > To  avoid the below caveat to organisations by promoting of
> > > > upgrading all
> > > >     > consumers first before relying on producing tombstone messages
> > with
> > > > data
> > > >     >
> > > >     > Sent using OWA for iPhone
> > > >     > ________________________________________
> > > >     > From: Michael Pearce
> > > >     > Sent: Tuesday, November 8, 2016 8:03:32 AM
> > > >     > To: dev@kafka.apache.org
> > > >     > Subject: Re: [DISCUSS] KIP-87 - Add Compaction Tombstone Flag
> > > >     >
> > > >     > Thanks Jun on the feedback, I think I understand the
> issue/point
> > > now.
> > > >     >
> > > >     > We def can add that on older client version if tombstone marker
> > > make
> > > > the
> > > >     > value null to preserve behaviour.
> > > >     >
> > > >     > There is one caveats to this:
> > > >     >
> > > >     > * we have to be clear that data is lost if reading via old
> > > > client/message
> > > >     > format - I don't think this is a big issue as mostly the
> idea/use
> > > > case is
> > > >     > around meta data transport as such would only be as bad as
> > current
> > > > situation
> > > >     >
> > > >     > Re having configurable broker this was to handle cases like you
> > > > described
> > > >     > but in another way by allowing organisation choose the
> behaviour
> > of
> > > > the
> > > >     > compaction per broker or per topic so they could manage their
> > > > transition to
> > > >     > using tombstone markers.
> > > >     >
> > > >     > On hind sight it maybe easier to just upgrade and downgrade the
> > > > messages
> > > >     > on version as you propose.
> > > >     >
> > > >     >
> > > >     >
> > > >     >
> > > >     >
> > > >     >
> > > >     > Sent using OWA for iPhone
> > > >     > ________________________________________
> > > >     > From: Jun Rao <j...@confluent.io>
> > > >     > Sent: Tuesday, November 8, 2016 12:34:41 AM
> > > >     > To: dev@kafka.apache.org
> > > >     > Subject: Re: [DISCUSS] KIP-87 - Add Compaction Tombstone Flag
> > > >     >
> > > >     > For the use case, one potential use case is for schema
> > > registration.
> > > > For
> > > >     > example, in Avro, a null value corresponds to a Null schema.
> So,
> > if
> > > > you
> > > >     > want to be able to keep the schema id in a delete message, the
> > > value
> > > > can't
> > > >     > be null. We could get around this issue by specializing null
> > value
> > > > during
> > > >     > schema registration though.
> > > >     >
> > > >     > Now for the proposed changes. We probably should preserve
> client
> > > >     > compatibility. If a client application is sending a null value
> > to a
> > > >     > compacted topic, ideally, it should work the same after the
> > client
> > > >     > upgrades.
> > > >     >
> > > >     > I am not sure about making the tombstone marker configurable,
> > > > especially at
> > > >     > the topic level. Should we allow users to change the config
> > values
> > > > back and
> > > >     > forth, and what would be the implication?
> > > >     >
> > > >     > Thanks,
> > > >     >
> > > >     > Jun
> > > >     >
> > > >     > On Mon, Nov 7, 2016 at 10:48 AM, Becket Qin <
> > becket....@gmail.com>
> > > > wrote:
> > > >     >
> > > >     > > Hi Michael,
> > > >     > >
> > > >     > > Yes, changing the logic in the log cleaner makes sense. There
> > > > could be
> > > >     > some
> > > >     > > other thing worth thinking (e.g. the message size change
> after
> > > >     > conversion),
> > > >     > > though.
> > > >     > >
> > > >     > > The scenario I was thinking is the following:
> > > >     > > Imagine a distributed caching system built on top of Kafka. A
> > > user
> > > > is
> > > >     > > consuming from a topic and it is guaranteed that if the user
> > > > consume to
> > > >     > the
> > > >     > > log end it will get the latest value for all the keys.
> > Currently
> > > > if the
> > > >     > > consumer sees a null value it knows the key has been removed.
> > Now
> > > > let's
> > > >     > say
> > > >     > > we rolled out this change. And the producer applies a message
> > > with
> > > > the
> > > >     > > tombstone flag set, but the value was not null. When we
> append
> > > that
> > > >     > message
> > > >     > > to the log I suppose we will not do the down conversion if
> the
> > > > broker has
> > > >     > > set the message.format.version to the latest. Because the log
> > > > cleaner
> > > >     > won't
> > > >     > > touch the active log segment, so that message will be sitting
> > in
> > > > the
> > > >     > active
> > > >     > > segment as is. Now when a consumer that hasn't upgraded yet
> > > > consumes that
> > > >     > > tombstone message in the active segment, it seems that the
> > broker
> > > > will
> > > >     > need
> > > >     > > to down convert that message to remove the value, right? In
> > this
> > > > case, we
> > > >     > > cannot wait for the log cleaner to do the down conversion
> > because
> > > > that
> > > >     > > message may have already been consumed before the log
> > compaction
> > > > happens.
> > > >     > >
> > > >     > > Thanks,
> > > >     > >
> > > >     > > Jiangjie (Becket) Qin
> > > >     > >
> > > >     > >
> > > >     > >
> > > >     > > On Mon, Nov 7, 2016 at 9:59 AM, Michael Pearce <
> > > > michael.pea...@ig.com>
> > > >     > > wrote:
> > > >     > >
> > > >     > > > Hi Becket,
> > > >     > > >
> > > >     > > > We were thinking more about having the logic that’s in the
> > > method
> > > >     > > > shouldRetainMessage configurable via
> > http://kafka.apache.org/
> > > >     > > > documentation.html#brokerconfigs  at a broker/topic level.
> > And
> > > > then
> > > >     > > scrap
> > > >     > > > auto converting the message, and allow organisations to
> > manage
> > > > the
> > > >     > > rollout
> > > >     > > > of enabling of the feature.
> > > >     > > > (this isn’t in documentation but in response to the
> > discussion
> > > > thread
> > > >     > as
> > > >     > > > an alternative approach to roll out the feature)
> > > >     > > >
> > > >     > > > Does this make any more sense?
> > > >     > > >
> > > >     > > > Thanks
> > > >     > > > Mike
> > > >     > > >
> > > >     > > > On 11/3/16, 2:27 PM, "Becket Qin" <becket....@gmail.com>
> > > wrote:
> > > >     > > >
> > > >     > > >     Hi Michael,
> > > >     > > >
> > > >     > > >     Do you mean using a new configuration it is just the
> > > exiting
> > > >     > > >     message.format.version config? It seems the
> > > > message.format.version
> > > >     > > > config
> > > >     > > >     is enough in this case. And the default value would
> > always
> > > > be the
> > > >     > > > latest
> > > >     > > >     version.
> > > >     > > >
> > > >     > > >     > Message version migration would be handled as like in
> > > > KIP-32
> > > >     > > >
> > > >     > > >     Also just want to confirm on this. Today if an old
> > consumer
> > > >     > consumes
> > > >     > > a
> > > >     > > > log
> > > >     > > >     compacted topic and sees an empty value, it knows that
> > is a
> > > >     > > tombstone.
> > > >     > > >     After we start to use the attribute bit, a tombstone
> > > message
> > > > can
> > > >     > > have a
> > > >     > > >     non-empty value. So by "like in KIP-32" you mean we
> will
> > > > remove the
> > > >     > > > value
> > > >     > > >     to down convert the message if the consumer version is
> > old,
> > > > right?
> > > >     > > >
> > > >     > > >     Thanks.
> > > >     > > >
> > > >     > > >     Jiangjie (Becket) Qin
> > > >     > > >
> > > >     > > >     On Wed, Nov 2, 2016 at 1:37 AM, Michael Pearce <
> > > >     > > michael.pea...@ig.com>
> > > >     > > >     wrote:
> > > >     > > >
> > > >     > > >     > Hi Joel , et al.
> > > >     > > >     >
> > > >     > > >     > Any comments on the below idea to handle roll out /
> > > > compatibility
> > > >     > > of
> > > >     > > > this
> > > >     > > >     > feature, using a configuration?
> > > >     > > >     >
> > > >     > > >     > Does it make sense/clear?
> > > >     > > >     > Does it add value?
> > > >     > > >     > Do we want to enforce flag by default, or value by
> > > > default, or
> > > >     > > both?
> > > >     > > >     >
> > > >     > > >     > Cheers
> > > >     > > >     > Mike
> > > >     > > >     >
> > > >     > > >     >
> > > >     > > >     > On 10/27/16, 4:47 PM, "Michael Pearce" <
> > > > michael.pea...@ig.com>
> > > >     > > > wrote:
> > > >     > > >     >
> > > >     > > >     >     Thanks, James, I think this is a really good
> > addition
> > > > to the
> > > >     > > KIP
> > > >     > > >     > details, please feel free to amend the wiki/add the
> use
> > > > cases,
> > > >     > also
> > > >     > > > if any
> > > >     > > >     > others you think of. I definitely think its
> worthwhile
> > > >     > documenting.
> > > >     > > > If you
> > > >     > > >     > can’t let me know ill add them next week (just
> leaving
> > > for
> > > > a long
> > > >     > > > weekend
> > > >     > > >     > off)
> > > >     > > >     >
> > > >     > > >     >     Re Joel and others comments about upgrade and
> > > > compatibility.
> > > >     > > >     >
> > > >     > > >     >     Rather than trying to auto manage this.
> > > >     > > >     >
> > > >     > > >     >     Actually maybe we make a configuration option,
> both
> > > at
> > > > server
> > > >     > > > and per
> > > >     > > >     > topic level to control the behavior of how the server
> > > logic
> > > >     > should
> > > >     > > > work out
> > > >     > > >     > if the record, is a tombstone record .
> > > >     > > >     >
> > > >     > > >     >     e.g.
> > > >     > > >     >
> > > >     > > >     >     key = compation.tombstone.marker
> > > >     > > >     >
> > > >     > > >     >     value options:
> > > >     > > >     >
> > > >     > > >     >     value   (continues to use null value as tombstone
> > > > marker)
> > > >     > > >     >     flag (expects to use the tombstone flag)
> > > >     > > >     >     value_or_flag (if either is true it treats the
> > record
> > > > as a
> > > >     > > > tombstone)
> > > >     > > >     >
> > > >     > > >     >     This way on upgrade users can keep current
> > behavior,
> > > > and
> > > >     > slowly
> > > >     > > >     > migrate to the new. Having a transition period of
> using
> > > >     > > > value_or_flag,
> > > >     > > >     > finally having flag only if an organization wishes to
> > use
> > > > null
> > > >     > > values
> > > >     > > >     > without it being treated as a tombstone marker (use
> > case
> > > > noted
> > > >     > > below)
> > > >     > > >     >
> > > >     > > >     >     Having it both global broker level and topic
> > override
> > > > also
> > > >     > > > allows some
> > > >     > > >     > flexibility here.
> > > >     > > >     >
> > > >     > > >     >     Cheers
> > > >     > > >     >     Mike
> > > >     > > >     >
> > > >     > > >     >
> > > >     > > >     >
> > > >     > > >     >
> > > >     > > >     >
> > > >     > > >     >
> > > >     > > >     >     On 10/27/16, 8:03 AM, "James Cheng" <
> > > > wushuja...@gmail.com>
> > > >     > > > wrote:
> > > >     > > >     >
> > > >     > > >     >         This KIP would definitely address a gap in
> the
> > > > current
> > > >     > > >     > functionality, where you currently can't have a
> > tombstone
> > > > with
> > > >     > any
> > > >     > > >     > associated content.
> > > >     > > >     >
> > > >     > > >     >         That said, I'd like to talk about use cases,
> to
> > > > make sure
> > > >     > > > that
> > > >     > > >     > this is in fact useful. The KIP should be updated
> with
> > > > whatever
> > > >     > use
> > > >     > > > cases
> > > >     > > >     > we come up with.
> > > >     > > >     >
> > > >     > > >     >         First of all, an observation: When we speak
> > about
> > > > log
> > > >     > > > compaction,
> > > >     > > >     > we typically think of "the latest message for a key
> is
> > > > retained".
> > > >     > > In
> > > >     > > > that
> > > >     > > >     > respect, a delete tombstone (i.e. a message with a
> null
> > > > payload)
> > > >     > is
> > > >     > > > treated
> > > >     > > >     > the same as any other Kafka message: the latest
> message
> > > is
> > > >     > > retained.
> > > >     > > > It
> > > >     > > >     > doesn't matter whether the latest message is null, or
> > if
> > > > the
> > > >     > latest
> > > >     > > > message
> > > >     > > >     > has actual content. In all cases, the last message is
> > > > retained.
> > > >     > > >     >
> > > >     > > >     >         The only way a delete tombstone is treated
> > > > differently
> > > >     > from
> > > >     > > > other
> > > >     > > >     > Kafka messages is that it automatically disappears
> > after
> > > a
> > > > while.
> > > >     > > > The time
> > > >     > > >     > of deletion is specified using delete.retention.ms.
> > > >     > > >     >
> > > >     > > >     >         So what we're really talking about is, do we
> > want
> > > > to
> > > >     > > support
> > > >     > > >     > messages in a log-compacted topic that auto-delete
> > > > themselves
> > > >     > after
> > > >     > > > a while?
> > > >     > > >     >
> > > >     > > >     >         In a thread from 2015, there was a discussion
> > on
> > > >     > > first-class
> > > >     > > >     > support of headers between Roger Hoover, Felix GV,
> Jun
> > > > Rao, and
> > > >     > I.
> > > >     > > > See
> > > >     > > >     > thread at https://groups.google.com/d/
> > > > msg/confluent-platform/
> > > >     > > >     > 8xPbjyUE_7E/yQ1AeCufL_gJ <
> https://groups.google.com/d/
> > > >     > > >     > msg/confluent-platform/8xPbjyUE_7E/yQ1AeCufL_gJ> .
> In
> > > that
> > > >     > thread,
> > > >     > > > Jun
> > > >     > > >     > raised a good question that I didn't have a good
> answer
> > > > for at
> > > >     > the
> > > >     > > > time: If
> > > >     > > >     > a message is going to auto-delete itself after a
> while,
> > > how
> > > >     > > > important was
> > > >     > > >     > the message? That is, what information did the
> message
> > > > contain
> > > >     > that
> > > >     > > > was
> > > >     > > >     > important *for a while* but not so important that it
> > > > needed to be
> > > >     > > > kept
> > > >     > > >     > around forever?
> > > >     > > >     >
> > > >     > > >     >         Some use cases that I can think of:
> > > >     > > >     >
> > > >     > > >     >         1) Tracability. I would like to know who
> issued
> > > > this
> > > >     > delete
> > > >     > > >     > tombstone. It might include the hostname, IP of the
> > > > producer of
> > > >     > the
> > > >     > > > delete.
> > > >     > > >     >         2) Timestamps. I would like to know when this
> > > > delete was
> > > >     > > > issued.
> > > >     > > >     > This use case is already addressed by the
> availability
> > of
> > > >     > > per-message
> > > >     > > >     > timestamps that came in 0.10.0
> > > >     > > >     >         3) Data provenance. I hope I'm using this
> > phrase
> > > >     > correctly,
> > > >     > > > but
> > > >     > > >     > what I mean is, where did this delete come from? What
> > > > processing
> > > >     > > job
> > > >     > > >     > emitted it? What input to the processing job caused
> > this
> > > > delete
> > > >     > to
> > > >     > > be
> > > >     > > >     > produced? For example, if a record in topic A was
> > > > processed and
> > > >     > > > caused a
> > > >     > > >     > delete tombstone to be emitted to topic B, I might
> like
> > > the
> > > >     > offset
> > > >     > > > of the
> > > >     > > >     > topic A message to be attached to the topic B
> message.
> > > >     > > >     >         4) Distributed tracing for stream topologies.
> > > This
> > > > might
> > > >     > > be a
> > > >     > > >     > slight repeat of the above use cases. In the
> > > microservices
> > > > world,
> > > >     > > we
> > > >     > > > can
> > > >     > > >     > generate call-graphs of webservices using tools like
> > > > Zipkin/
> > > >     > > > opentracing.io
> > > >     > > >     > <http://opentracing.io/>, or something homegrown
> like
> > > >     > > >     > https://engineering.linkedin.
> > > com/distributed-service-call-
> > > >     > > >     > graph/real-time-distributed-
> > tracing-website-performance-
> > > >     > > and-efficiency
> > > >     > > > <
> > > >     > > >     > https://engineering.linkedin.
> > > com/distributed-service-call-
> > > >     > > >     > graph/real-time-distributed-
> > tracing-website-performance-
> > > >     > > > and-efficiency>.
> > > >     > > >     > I can imagine that you might want to do something
> > similar
> > > > for
> > > >     > > stream
> > > >     > > >     > processing topologies, where stream processing jobs
> > carry
> > > > along
> > > >     > and
> > > >     > > > forward
> > > >     > > >     > along a globally unique identifier, and a distributed
> > > > topology
> > > >     > > graph
> > > >     > > > is
> > > >     > > >     > generated.
> > > >     > > >     >         5) Cases where processing a delete requires
> > data
> > > > that is
> > > >     > > not
> > > >     > > >     > available in the message key. I'm not sure I have a
> > good
> > > > example
> > > >     > of
> > > >     > > > this,
> > > >     > > >     > though. One hand-wavy example might be where I am
> > > > publishing
> > > >     > > > documents into
> > > >     > > >     > Kafka where the documentId is the message key, and
> the
> > > text
> > > >     > > contents
> > > >     > > > of the
> > > >     > > >     > document are in the message body. And I have a
> > consuming
> > > > job that
> > > >     > > > does some
> > > >     > > >     > analytics on the message body. If that document gets
> > > > deleted,
> > > >     > then
> > > >     > > > the
> > > >     > > >     > consuming job might need the original message body in
> > > > order to
> > > >     > > > "delete"
> > > >     > > >     > that message's impact from the analytics. But I'm not
> > > sure
> > > > that
> > > >     > is
> > > >     > > a
> > > >     > > > great
> > > >     > > >     > example. If the consumer was worried about that, the
> > > > consumer
> > > >     > would
> > > >     > > >     > probably keep the original message around, stored by
> > > > primary key.
> > > >     > > > And then
> > > >     > > >     > all it would need from a delete message would be the
> > > > primary key
> > > >     > of
> > > >     > > > the
> > > >     > > >     > message.
> > > >     > > >     >
> > > >     > > >     >         Do people think these are valid use cases?
> > > >     > > >     >
> > > >     > > >     >         What are other use cases that people can
> think
> > > of?
> > > >     > > >     >
> > > >     > > >     >         -James
> > > >     > > >     >
> > > >     > > >     >         > On Oct 26, 2016, at 3:46 PM, Mayuresh
> Gharat
> > <
> > > >     > > >     > gharatmayures...@gmail.com> wrote:
> > > >     > > >     >         >
> > > >     > > >     >         > +1 @Joel.
> > > >     > > >     >         > I think a clear migration plan of upgrading
> > and
> > > >     > > > downgrading of
> > > >     > > >     > server and
> > > >     > > >     >         > clients along with handling of issues that
> > Joel
> > > >     > > mentioned,
> > > >     > > > on
> > > >     > > >     > the KIP would
> > > >     > > >     >         > be really great.
> > > >     > > >     >         >
> > > >     > > >     >         > Thanks,
> > > >     > > >     >         >
> > > >     > > >     >         > Mayuresh
> > > >     > > >     >         >
> > > >     > > >     >         > On Wed, Oct 26, 2016 at 3:31 PM, Joel
> Koshy <
> > > >     > > > jjkosh...@gmail.com>
> > > >     > > >     > wrote:
> > > >     > > >     >         >
> > > >     > > >     >         >> I'm not sure why it would be useful, but
> it
> > > > should be
> > > >     > > >     > theoretically
> > > >     > > >     >         >> possible if the attribute bit alone is
> > enough
> > > > to mark
> > > >     > a
> > > >     > > >     > tombstone. OTOH, we
> > > >     > > >     >         >> could consider that as invalid if we wish.
> > > > These are
> > > >     > > > relevant
> > > >     > > >     > details that
> > > >     > > >     >         >> I think should be added to the KIP.
> > > >     > > >     >         >>
> > > >     > > >     >         >> Also, in the few odd scenarios that I
> > > mentioned
> > > > we
> > > >     > > should
> > > >     > > > also
> > > >     > > >     > consider
> > > >     > > >     >         >> that fetches could be coming from other
> > > >     > > yet-to-be-upgraded
> > > >     > > >     > brokers in a
> > > >     > > >     >         >> cluster that is being upgraded. So we
> would
> > > > probably
> > > >     > > want
> > > >     > > > to
> > > >     > > >     > continue to
> > > >     > > >     >         >> support nulls as tombstones or
> down-convert
> > in
> > > > a way
> > > >     > > that
> > > >     > > > we
> > > >     > > >     > are sure works
> > > >     > > >     >         >> with least surprise to fetchers.
> > > >     > > >     >         >>
> > > >     > > >     >         >> There is a slightly vague statement under
> > > >     > > "Compatibility,
> > > >     > > >     > Deprecation, and
> > > >     > > >     >         >> Migration Plan" that could benefit more
> > > details:
> > > >     > *Logic
> > > >     > > > would
> > > >     > > >     > base on
> > > >     > > >     >         >> current behavior of null value or if
> > tombstone
> > > > flag
> > > >     > set
> > > >     > > to
> > > >     > > >     > true, as such
> > > >     > > >     >         >> wouldn't impact any existing flows simply
> > > allow
> > > > new
> > > >     > > > producers
> > > >     > > >     > to make use
> > > >     > > >     >         >> of the feature*. It is unclear to me based
> > on
> > > > that
> > > >     > > > whether you
> > > >     > > >     > would
> > > >     > > >     >         >> interpret null as a tombstone if the
> > tombstone
> > > >     > attribute
> > > >     > > > bit is
> > > >     > > >     > off.
> > > >     > > >     >         >>
> > > >     > > >     >         >> On Wed, Oct 26, 2016 at 3:10 PM, Xavier
> > > Léauté <
> > > >     > > >     > xav...@confluent.io>
> > > >     > > >     >         >> wrote:
> > > >     > > >     >         >>
> > > >     > > >     >         >>> Does this mean that starting with V4
> > requests
> > > > we
> > > >     > would
> > > >     > > > allow
> > > >     > > >     > storing null
> > > >     > > >     >         >>> messages in compacted topics? The KIP
> > should
> > > > probably
> > > >     > > > clarify
> > > >     > > >     > the
> > > >     > > >     >         >> behavior
> > > >     > > >     >         >>> for null messages where the tombstone
> flag
> > is
> > > > not
> > > >     > net.
> > > >     > > >     >         >>>
> > > >     > > >     >         >>> On Wed, Oct 26, 2016 at 1:32 AM Magnus
> > > > Edenhill <
> > > >     > > >     > mag...@edenhill.se>
> > > >     > > >     >         >>> wrote:
> > > >     > > >     >         >>>
> > > >     > > >     >         >>>> 2016-10-25 21:36 GMT+02:00 Nacho Solis
> > > >     > > >     > <nso...@linkedin.com.invalid>:
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>>> I think you probably require a
> MagicByte
> > > > bump if
> > > >     > you
> > > >     > > > expect
> > > >     > > >     > correct
> > > >     > > >     >         >>>>> behavior of the system as a whole.
> > > >     > > >     >         >>>>>
> > > >     > > >     >         >>>>> From a client perspective you want to
> > make
> > > > sure
> > > >     > that
> > > >     > > > when you
> > > >     > > >     >         >> deliver a
> > > >     > > >     >         >>>>> message that the broker supports the
> > > feature
> > > > you're
> > > >     > > > expecting
> > > >     > > >     >         >>>>> (compaction).  So, depending on the
> > > behavior
> > > > of the
> > > >     > > > broker on
> > > >     > > >     >         >>>> encountering
> > > >     > > >     >         >>>>> a previously undefined bit flag I would
> > > > suggest
> > > >     > > making
> > > >     > > > some
> > > >     > > >     > change to
> > > >     > > >     >         >>>> make
> > > >     > > >     >         >>>>> certain that flag-based compaction is
> > > > supported.
> > > >     > I'm
> > > >     > > > going
> > > >     > > >     > to guess
> > > >     > > >     >         >>> that
> > > >     > > >     >         >>>>> the MagicByte would do this.
> > > >     > > >     >         >>>>>
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>> I dont believe this is needed since it
> is
> > > > already
> > > >     > > > attributed
> > > >     > > >     > through
> > > >     > > >     >         >> the
> > > >     > > >     >         >>>> request's API version.
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>> Producer:
> > > >     > > >     >         >>>> * if a client sends ProduceRequest V4
> then
> > > >     > > > attributes.bit5
> > > >     > > >     > indicates a
> > > >     > > >     >         >>>> tombstone
> > > >     > > >     >         >>>> * if a clients sends ProduceRequest <V4
> > then
> > > >     > > > attributes.bit5
> > > >     > > >     > is
> > > >     > > >     >         >> ignored
> > > >     > > >     >         >>>> and value==null indicates a tombstone
> > > >     > > >     >         >>>> * in both cases the on-disk messages are
> > > > stored with
> > > >     > > >     > attributes.bit5
> > > >     > > >     >         >> (I
> > > >     > > >     >         >>>> assume?)
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>> Consumer:
> > > >     > > >     >         >>>> * if a clients sends FetchRequest V4
> > > messages
> > > > are
> > > >     > > >     > sendfile():ed
> > > >     > > >     >         >> directly
> > > >     > > >     >         >>>> from disk (with attributes.bit5)
> > > >     > > >     >         >>>> * if a client sends FetchRequest <V4
> > > messages
> > > > are
> > > >     > > > slowpathed
> > > >     > > >     > and
> > > >     > > >     >         >>>> translated from attributes.bit5 to
> > > value=null
> > > > as
> > > >     > > > required.
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>> That's my understanding anyway, please
> > > > correct me if
> > > >     > > I'm
> > > >     > > >     > wrong.
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>> /Magnus
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>>> On Tue, Oct 25, 2016 at 10:17 AM,
> Magnus
> > > > Edenhill <
> > > >     > > >     >         >> mag...@edenhill.se>
> > > >     > > >     >         >>>>> wrote:
> > > >     > > >     >         >>>>>
> > > >     > > >     >         >>>>>> It is safe to assume that a previously
> > > > undefined
> > > >     > > > attributes
> > > >     > > >     > bit
> > > >     > > >     >         >> will
> > > >     > > >     >         >>> be
> > > >     > > >     >         >>>>>> unset in protocol requests from
> existing
> > > > clients,
> > > >     > if
> > > >     > > > not,
> > > >     > > >     > such a
> > > >     > > >     >         >>> client
> > > >     > > >     >         >>>>> is
> > > >     > > >     >         >>>>>> already violating the protocol and
> needs
> > > to
> > > > be
> > > >     > > fixed.
> > > >     > > >     >         >>>>>>
> > > >     > > >     >         >>>>>> So I dont see a need for a MagicByte
> > bump,
> > > > both
> > > >     > > > broker and
> > > >     > > >     > client
> > > >     > > >     >         >> has
> > > >     > > >     >         >>>> the
> > > >     > > >     >         >>>>>> information it needs to construct or
> > parse
> > > > the
> > > >     > > message
> > > >     > > >     > according to
> > > >     > > >     >         >>>>> request
> > > >     > > >     >         >>>>>> version.
> > > >     > > >     >         >>>>>>
> > > >     > > >     >         >>>>>>
> > > >     > > >     >         >>>>>> 2016-10-25 18:48 GMT+02:00 Michael
> > Pearce
> > > <
> > > >     > > >     > michael.pea...@ig.com>:
> > > >     > > >     >         >>>>>>
> > > >     > > >     >         >>>>>>> Hi Magnus,
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>> I was wondering if I even needed to
> > > change
> > > > those
> > > >     > > > also, as
> > > >     > > >     >         >>> technically
> > > >     > > >     >         >>>>>>> we’re just making use of a non used
> > > > attribute
> > > >     > bit,
> > > >     > > > but im
> > > >     > > >     > not
> > > >     > > >     >         >> 100%
> > > >     > > >     >         >>>> that
> > > >     > > >     >         >>>>>> it
> > > >     > > >     >         >>>>>>> be always false currently.
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>> If someone can say 100% it will
> already
> > > be
> > > > set
> > > >     > > false
> > > >     > > > with
> > > >     > > >     > current
> > > >     > > >     >         >>> and
> > > >     > > >     >         >>>>>>> historic bit wise masking techniques
> > used
> > > > over
> > > >     > the
> > > >     > > > time,
> > > >     > > >     > we could
> > > >     > > >     >         >>> do
> > > >     > > >     >         >>>>> away
> > > >     > > >     >         >>>>>>> with both, and simply just start to
> use
> > > it.
> > > >     > > > Unfortunately
> > > >     > > >     > I don’t
> > > >     > > >     >         >>>> have
> > > >     > > >     >         >>>>>> that
> > > >     > > >     >         >>>>>>> historic knowledge so was hoping it
> > would
> > > > be
> > > >     > > flagged
> > > >     > > > up in
> > > >     > > >     > this
> > > >     > > >     >         >>>>>> discussion
> > > >     > > >     >         >>>>>>> thread ?
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>> Cheers
> > > >     > > >     >         >>>>>>> Mike
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>> On 10/25/16, 5:36 PM, "Magnus
> > Edenhill" <
> > > >     > > >     > mag...@edenhill.se>
> > > >     > > >     >         >>> wrote:
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>>    Hi Michael,
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>>    With the version bumps for Produce
> > and
> > > > Fetch
> > > >     > > > requests,
> > > >     > > >     > do you
> > > >     > > >     >         >>>>> really
> > > >     > > >     >         >>>>>>> need
> > > >     > > >     >         >>>>>>>    to bump MagicByte too?
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>>    Regards,
> > > >     > > >     >         >>>>>>>    Magnus
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>>    2016-10-25 18:09 GMT+02:00 Michael
> > > > Pearce <
> > > >     > > >     >         >>> michael.pea...@ig.com
> > > >     > > >     >         >>>>> :
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>>> Hi All,
> > > >     > > >     >         >>>>>>>>
> > > >     > > >     >         >>>>>>>> I would like to discuss the
> following
> > > KIP
> > > >     > > proposal:
> > > >     > > >     >         >>>>>>>> https://cwiki.apache.org/
> > > >     > > > confluence/display/KAFKA/KIP-
> > > >     > > >     >         >>>>>>>> 87+-+Add+Compaction+Tombstone+Flag
> > > >     > > >     >         >>>>>>>>
> > > >     > > >     >         >>>>>>>> This is off the back of the
> discussion
> > > on
> > > > KIP-82
> > > >     > > /
> > > >     > > > KIP
> > > >     > > >     >         >>> meeting
> > > >     > > >     >         >>>>>>> where it
> > > >     > > >     >         >>>>>>>> was agreed to separate this issue
> and
> > > > feature.
> > > >     > > See:
> > > >     > > >     >         >>>>>>>> http://mail-archives.apache.
> > > >     > > > org/mod_mbox/kafka-dev/201610
> > > >     > > >     > .
> > > >     > > >     >         >>>>>>>> mbox/%3cCAJS3ho8OcR==
> > > > EcxsJ8OP99pD2hz=iiGecWsv-
> > > >     > > >     >         >>>>>>>> EZsBsNyDcKr=g...@mail.gmail.com%3e
> > > >     > > >     >         >>>>>>>>
> > > >     > > >     >         >>>>>>>> Thanks
> > > >     > > >     >         >>>>>>>> Mike
> > > >     > > >     >         >>>>>>>>
> > > >     > > >     >         >>>>>>>> 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.
> > > >     > > >     >         >>>>>>>
> > > >     > > >     >         >>>>>>
> > > >     > > >     >         >>>>>
> > > >     > > >     >         >>>>>
> > > >     > > >     >         >>>>>
> > > >     > > >     >         >>>>> --
> > > >     > > >     >         >>>>> Nacho (Ignacio) Solis
> > > >     > > >     >         >>>>> Kafka
> > > >     > > >     >         >>>>> nso...@linkedin.com
> > > >     > > >     >         >>>>>
> > > >     > > >     >         >>>>
> > > >     > > >     >         >>>
> > > >     > > >     >         >>
> > > >     > > >     >         >
> > > >     > > >     >         >
> > > >     > > >     >         >
> > > >     > > >     >         > --
> > > >     > > >     >         > -Regards,
> > > >     > > >     >         > Mayuresh R. Gharat
> > > >     > > >     >         > (862) 250-7125
> > > >     > > >     >
> > > >     > > >     >
> > > >     > > >     >
> > > >     > > >     >     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.
> > > >     >
> > > >
> > > >
> > > >
> > > >     --
> > > >     -Regards,
> > > >     Mayuresh R. Gharat
> > > >     (862) 250-7125
> > > >
> > > >
> > > > 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.
> > > >
> > >
> > >
> > >
> > > --
> > > -Regards,
> > > Mayuresh R. Gharat
> > > (862) 250-7125
> > >
> >
>
>
>
> --
> -Regards,
> Mayuresh R. Gharat
> (862) 250-7125
>

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