Hi Jun
do we have your vote on this now?
Any other concerns?
Cheers
Mike
Sent using OWA for iPhone
________________________________________
From: Michael Pearce <michael.pea...@ig.com>
Sent: Saturday, December 3, 2016 1:37:45 AM
To: dev@kafka.apache.org
Subject: Re: [VOTE] KIP-87 - Add Compaction Tombstone Flag
Hi Jun,
Have updated. Thanks again for the feedback.
Agree yes we should align up when it gets to that, I assume you’ve flagged the
same in the other KIP?
I think for now let’s get this KIP approved, then we can start the work to get
an initial PR, then we can discuss how to align the two if needed.
Cheers,
Mike
On 02/12/2016, 18:26, "Jun Rao" <j...@confluent.io> wrote:
Hi, Michael,
For 2), this is fine. Could you update the KIP wiki to make this and other
points clearer? Other than that, the KIP looks good to me.
An orthogonal thing is that there are other KIPs such as KIP-98 that also
intend to change the message format. If they all get approved, we should
think about whether it's better to just bump up the magic byte once to
incorporate multiple format changes like we did in KIP-31/KIP-32.
Thanks,
Jun
On Fri, Dec 2, 2016 at 3:19 AM, Michael Pearce <michael.pea...@ig.com>
wrote:
> Hi Jao
>
> Thanks for the response. Sorry for slow reply, both with personal sickness
> and also battling some critical issues encountered since upgrading to
> 0.10.1.0
>
> 1) Thans for spotting, Document error where we branched this KIP from
> KIP-82, will get that removed.
> 2) Intent is to do this just at the record message level.
> 3) Thanks for spotting, Will ensure this is corrected.
> 4) As per discussion thread we will support tombstone + null value,
> tombstone + non null value, no tombstone + null value.
> 5) I believe this was in the discussion thread, @Mayuresh is this
> something we’ve overlooked? I thought we would down convert and remove the
> value so the old consumer had existing behavior, or is there something we
> haven’t thought about?
>
> Cheers
> Mike
>
> On 30/11/2016, 18:12, "Jun Rao" <j...@confluent.io> wrote:
>
> Hi, Michael,
>
> Thanks for the KIP. A few comments below.
>
> 1. The message format change contains "HeadersLength Headers". Is that
> intended?
>
> 2. For compressed messageset, is the tombstone bit only set at the
> shallow
> level? Do we always leave that bit in the wrapper message unset? An
> alternative is to set the tombstone bit in the wrapper if at least one
> inner message has the tombstone bit set. This makes things a bit more
> complicated, but we could potentially exploit that for optimizing down
> conversion. For example, we only need to convert messages with magic 2
> to
> magic 1 if the wrapper's tombstone bit is set (conversion is always
> needed
> from magic 2 to magic 0). Not sure if the optimization is worth the
> complexity though.
>
> 3. The referencing of the new version of ProducerRequest/FetchRequest
> is
> inconsistent (v4 vs v3). Since our convention starts at version at 0,
I
> think the new version would be 3.
>
> 4. "If the magic byte on message is 2, the broker should use the
> tombstone
> bit for log compaction." What about null value? My understanding is
> that
> null value will be treated the same as setting the tombstone bit.
>
> 5. For the migration path, it would be useful to describe the down
> conversion path to consumers (i.e., brokers on message format 0.10.2
> and
> consumers on older version).
>
> Thanks,
>
> Jun
>
>
> On Tue, Nov 29, 2016 at 3:18 AM, Michael Pearce <michael.pea...@ig.com
> >
> wrote:
>
> > Hi All,
> >
> > We have been discussing in the below thread and final changes have
> been
> > made to the KIP wiki based on these discussions.
> >
> > We would now like to put to the vote the following KIP:
> > https://cwiki.apache.org/confluence/display/KAFKA/KIP-87+-+
> > Add+Compaction+Tombstone+Flag
> >
> > This kip is for having a distinct compaction attribute “tombstone”
> flag
> > instead of relying on null value, allowing non-null value delete
> messages.
> >
> > Many thanks,
> > Michael
> >
> >
> >
> > On 22/11/2016, 15:52, "Michael Pearce" <michael.pea...@ig.com>
> wrote:
> >
> > Hi Mayuresh,
> >
> > LGTM. Ive just made one small adjustment updating the wire
> protocol to
> > show the magic byte bump.
> >
> > Do we think we’re good to put to a vote? Is there any other bits
> > needing discussion?
> >
> > Cheers
> > Mike
> >
> > On 21/11/2016, 18:26, "Mayuresh Gharat" <
> gharatmayures...@gmail.com>
> > wrote:
> >
> > Hi Michael,
> >
> > I have updated the migration section of the KIP. Can you
> please
> > take a look?
> >
> > Thanks,
> >
> > Mayuresh
> >
> > On Fri, Nov 18, 2016 at 9:07 AM, Mayuresh Gharat <
> > gharatmayures...@gmail.com
> > > wrote:
> >
> > > Hi Michael,
> > >
> > > That whilst sending tombstone and non null value, the
> consumer
> > can expect
> > > only to receive the non-null message only in step (3) is
> this
> > correct?
> > > ---> I do agree with you here.
> > >
> > > Becket, Ismael : can you guys review the migration plan
> listed
> > above using
> > > magic byte?
> > >
> > > Thanks,
> > >
> > > Mayuresh
> > >
> > > On Fri, Nov 18, 2016 at 8:58 AM, Michael Pearce <
> > michael.pea...@ig.com>
> > > wrote:
> > >
> > >> Many thanks for this Mayuresh. I don't have any
> objections.
> > >>
> > >> I assume we should state:
> > >>
> > >> That whilst sending tombstone and non null value, the
> consumer
> > can expect
> > >> only to receive the non-null message only in step (3) is
> this
> > correct?
> > >>
> > >> Cheers
> > >> Mike
> > >>
> > >>
> > >>
> > >> Sent using OWA for iPhone
> > >> ________________________________________
> > >> From: Mayuresh Gharat <gharatmayures...@gmail.com>
> > >> Sent: Thursday, November 17, 2016 5:18:41 PM
> > >> To: dev@kafka.apache.org
> > >> Subject: Re: [DISCUSS] KIP-87 - Add Compaction Tombstone
> Flag
> > >>
> > >> Hi Ismael,
> > >>
> > >> Thanks for the explanation.
> > >> Specially I like this part where in you mentioned we can
> get
> > rid of the
> > >> older null value support for log compaction later on,
> here :
> > >> We can't change semantics of the message format without
> having
> > a long
> > >> transition period. And we can't rely
> > >> on people reading documentation or acting on a warning
for
> > something so
> > >> fundamental. As such, my take is that we need to bump the
> magic
> > byte. The
> > >> good news is
> > >> that we don't have to support all versions forever. We
> have
> > said that we
> > >> will support direct upgrades for 2 years. That means that
> > message format
> > >> version n could, in theory, be removed 2 years after the
> it's
> > introduced.
> > >>
> > >> Just a heads up, I would like to mention that even
without
> > bumping magic
> > >> byte, we will *NOT* loose zero copy as in the client(x+1)
> in my
> > >> explanation
> > >> above will convert internally a null value to have a
> tombstone
> > bit set and
> > >> a tombstone bit set to have a null value automatically
> > internally and by
> > >> the time we move to version (x+2), the clients would have
> > upgraded.
> > >> Obviously if we support a request from consumer(x), we
> will
> > loose zero
> > >> copy
> > >> but that is the same case with magic byte.
> > >>
> > >> But if magic byte bump makes life easier for transition
> for the
> > above
> > >> reasons that you explained, I am OK with it since we are
> going
> > to meet the
> > >> end goal down the road :)
> > >>
> > >> On a side note can we update the doc here on magic byte
> to say
> > that "*it
> > >> should be bumped whenever the message format is changed
> or the
> > >> interpretation of message format (usage of the reserved
> bits as
> > well) is
> > >> changed*".
> > >>
> > >>
> > >> Hi Michael,
> > >>
> > >> Here is the update plan that we discussed offline
> yesterday :
> > >>
> > >> Currently the magic-byte which corresponds to the
> > "message.format.version"
> > >> is set to 1.
> > >>
> > >> 1) On broker it will be set to 1 initially.
> > >>
> > >> 2) When a producer client sends a message with magic-byte
> = 2,
> > since the
> > >> broker is on magic-byte = 1, we will down convert it,
> which
> > means if the
> > >> tombstone bit is set, the value will be set to null. A
> consumer
> > >> understanding magic-byte = 1, will still work with this.
A
> > consumer
> > >> working
> > >> with magic-byte =2 will also be able to understand this,
> since
> > it
> > >> understands the tombstone.
> > >> Now there is still the question of supporting a
> non-tombstone
> > and null
> > >> value from producer client with magic-byte = 2.* (I am
> not sure
> > if we
> > >> should support this. Ismael/Becket can comment here)*
> > >>
> > >> 3) When almost all the clients have upgraded, the
> > message.format.version
> > >> on
> > >> the broker can be changed to 2, where in the down
> conversion in
> > the above
> > >> step will not happen. If at this point we get a consumer
> > request from a
> > >> older consumer, we might have to down convert where in we
> loose
> > zero copy,
> > >> but these cases should be rare.
> > >>
> > >> Becket can you review this plan and add more details if I
> have
> > >> missed/wronged something, before we put it on KIP.
> > >>
> > >> Thanks,
> > >>
> > >> Mayuresh
> > >>
> > >> On Wed, Nov 16, 2016 at 11:07 PM, Michael Pearce <
> > michael.pea...@ig.com>
> > >> wrote:
> > >>
> > >> > Thanks guys, for discussing this offline and getting
> some
> > consensus.
> > >> >
> > >> > So its clear for myself and others what is proposed now
> (i
> > think i
> > >> > understand, but want to make sure)
> > >> >
> > >> > Could i ask either directly update the kip to detail
the
> > migration
> > >> > strategy, or (re-)state your offline discussed and
> agreed
> > migration
> > >> > strategy based on a magic byte is in this thread.
> > >> >
> > >> >
> > >> > The main original driver for the KIP was to support
> > compaction where
> > >> value
> > >> > isn't null, based off the discussions on KIP-82 thread.
> > >> >
> > >> > We should be able to support non-tombstone + null value
> by the
> > >> completion
> > >> > of the KIP, as we noted when discussing this kip,
having
> > logic based on
> > >> a
> > >> > null value isn't very clean and also separates the
> concerns.
> > >> >
> > >> > As discussed already though we can split this into
> KIP-87a
> > and KIP-87b
> > >> >
> > >> > Where we look to deliver KIP-87a on a compacted topic
> (to
> > address the
> > >> > immediate issues)
> > >> > * tombstone + null value
> > >> > * tombstone + non-null value
> > >> > * non-tombstone + non-null value
> > >> >
> > >> > Then we can discuss once KIP-87a is completed options
> later
> > and how we
> > >> > support the second part KIP-87b to deliver:
> > >> > * non-tombstone + null value
> > >> >
> > >> > Cheers
> > >> > Mike
> > >> >
> > >> >
> > >> >
> > >> > ________________________________________
> > >> > From: Becket Qin <becket....@gmail.com>
> > >> > Sent: Thursday, November 17, 2016 1:43 AM
> > >> > To: dev@kafka.apache.org
> > >> > Subject: Re: [DISCUSS] KIP-87 - Add Compaction
> Tombstone Flag
> > >> >
> > >> > Renu, Mayuresh and I had an offline discussion, and
> following
> > is a brief
> > >> > summary.
> > >> >
> > >> > 1. We agreed that not bumping up magic value may result
> in
> > losing zero
> > >> copy
> > >> > during migration.
> > >> > 2. Given that bumping up magic value is almost free and
> has
> > benefit of
> > >> > avoiding potential performance issue. It is probably
> worth
> > doing.
> > >> >
> > >> > One issue we still need to think about is whether we
> want to
> > support a
> > >> > non-tombstone message with null value.
> > >> > Currently it is not supported by Kafka. If we allow a
> > non-tombstone null
> > >> > value message to exist after KIP-87. The problem is
> that such
> > message
> > >> will
> > >> > not be supported by the consumers prior to KIP-87.
> Because a
> > null value
> > >> > will always be interpreted to a tombstone.
> > >> >
> > >> > One option is that we keep the current way, i.e. do not
> > support such
> > >> > message. It would be good to know if there is a
> concrete use
> > case for
> > >> such
> > >> > message. If there is not, we can probably just not
> support it.
> > >> >
> > >> > Thanks,
> > >> >
> > >> > JIangjie (Becket) Qin
> > >> >
> > >> >
> > >> >
> > >> > On Wed, Nov 16, 2016 at 1:28 PM, Mayuresh Gharat <
> > >> > gharatmayures...@gmail.com
> > >> > > wrote:
> > >> >
> > >> > > Hi Ismael,
> > >> > >
> > >> > > This is something I can think of for migration plan:
> > >> > > So the migration plan can look something like this,
> with up
> > >> conversion :
> > >> > >
> > >> > > 1) Currently lets say we have Broker at version x.
> > >> > > 2) Currently we have clients at version x.
> > >> > > 3) a) We move the version to Broker(x+1) : supports
> both
> > tombstone and
> > >> > null
> > >> > > for log compaction.
> > >> > > b) We upgrade the client to version client(x+1) :
> if in
> > the
> > >> producer
> > >> > > client(x+1) the value is set to null, we will
> automatically
> > set the
> > >> > > Tombstone bit internally. If the producer client(x+1)
> sets
> > the
> > >> tombstone
> > >> > > itself, well and good. For producer client(x), the
> broker
> > will up
> > >> convert
> > >> > > to have the tombstone bit. Broker(x+1) is supporting
> both.
> > Consumer
> > >> > > client(x+1) will be aware of this and should be able
> to
> > handle this.
> > >> For
> > >> > > consumer client(x) we will down convert the message
> on the
> > broker
> > >> side.
> > >> > > c) At this point we will have to specify a
> warning or
> > clearly
> > >> specify
> > >> > > in docs that this behavior is about to be changed for
> log
> > compaction.
> > >> > > 4) a) In next release of the Broker(x+2), we say that
> only
> > Tombstone
> > >> is
> > >> > > used for log compaction on the Broker side.
> Clients(x+1)
> > still is
> > >> > > supported.
> > >> > > b) We upgrade the client to version client(x+2) :
> if
> > value is set
> > >> to
> > >> > > null, tombstone will not be set automatically. The
> client
> > will have to
> > >> > call
> > >> > > setTombstone() to actually set the tombstone.
> > >> > >
> > >> > > We should compare this migration plan with the
> migration
> > plan for
> > >> magic
> > >> > > byte bump and do whatever looks good.
> > >> > > I am just worried that if we go down magic byte
route,
> > unless I am
> > >> > missing
> > >> > > something, it sounds like kafka will be stuck with
> > supporting both
> > >> null
> > >> > > value and tombstone bit for log compaction for life
> long,
> > which does
> > >> not
> > >> > > look like a good end state.
> > >> > >
> > >> > > Thanks,
> > >> > >
> > >> > > Mayuresh
> > >> > >
> > >> > >
> > >> > >
> > >> > >
> > >> > > On Wed, Nov 16, 2016 at 9:32 AM, Mayuresh Gharat <
> > >> > > gharatmayures...@gmail.com
> > >> > > > wrote:
> > >> > >
> > >> > > > Hi Ismael,
> > >> > > >
> > >> > > > That's a very good point which I might have not
> > considered earlier.
> > >> > > >
> > >> > > > Here is a plan that I can think of:
> > >> > > >
> > >> > > > Stage 1) The broker from now on, up converts the
> message
> > to have the
> > >> > > > tombstone marker. The log compaction thread does
log
> > compaction
> > >> based
> > >> > on
> > >> > > > both null and tombstone marker. This is our
> transition
> > period.
> > >> > > > Stage 2) The next release we only say that log
> compaction
> > is based
> > >> on
> > >> > > > tombstone marker. (Open source kafka makes this as
a
> > policy). By
> > >> this
> > >> > > time,
> > >> > > > the organization which is moving to this release
> will be
> > sure that
> > >> they
> > >> > > > have gone through the entire transition period.
> > >> > > >
> > >> > > > My only goal of doing this is that Kafka clearly
> > specifies the end
> > >> > state
> > >> > > > about what log compaction means (is it null value
> or a
> > tombstone
> > >> > marker,
> > >> > > > but not both).
> > >> > > >
> > >> > > > What do you think?
> > >> > > >
> > >> > > > Thanks,
> > >> > > >
> > >> > > > Mayuresh
> > >> > > > .
> > >> > > >
> > >> > > > On Wed, Nov 16, 2016 at 9:17 AM, Ismael Juma <
> > ism...@juma.me.uk>
> > >> > wrote:
> > >> > > >
> > >> > > >> One comment below.
> > >> > > >>
> > >> > > >> On Wed, Nov 16, 2016 at 5:08 PM, Mayuresh Gharat <
> > >> > > >> gharatmayures...@gmail.com
> > >> > > >> > wrote:
> > >> > > >>
> > >> > > >> > - If we don't bump up the magic byte, on the
> broker
> > side, the
> > >> > > broker
> > >> > > >> > will always have to look at both tombstone
> bit and
> > the value
> > >> when
> > >> > > do
> > >> > > >> the
> > >> > > >> > compaction. Assuming we do not bump up the
> magic
> > byte,
> > >> > > >> > imagine the broker sees a message which does
> not
> > have a
> > >> tombstone
> > >> > > bit
> > >> > > >> > set. The broker does not know when the
> message was
> > produced
> > >> (i.e.
> > >> > > >> > whether
> > >> > > >> > the message has been up converted or not), it
> has
> > to take a
> > >> > further
> > >> > > >> > look at
> > >> > > >> > the value to see if it is null or not in
> order to
> > determine
> > >> if it
> > >> > > is
> > >> > > >> a
> > >> > > >> > tombstone. The same logic has to be put on
the
> > consumer as
> > >> well
> > >> > > >> because
> > >> > > >> > the
> > >> > > >> > consumer does not know if the message has
> been up
> > converted or
> > >> > not.
> > >> > > >> > - If we upconvert while appending, this is
> not
> > the case,
> > >> > right?
> > >> > > >>
> > >> > > >>
> > >> > > >> If I understand you correctly, this is not
> sufficient
> > because the
> > >> log
> > >> > > may
> > >> > > >> have messages appended before it was upgraded to
> include
> > KIP-87.
> > >> > > >>
> > >> > > >> Ismael
> > >> > > >>
> > >> > > >
> > >> > > >
> > >> > > >
> > >> > > > --
> > >> > > > -Regards,
> > >> > > > Mayuresh R. Gharat
> > >> > > > (862) 250-7125
> > >> > > >
> > >> > >
> > >> > >
> > >> > >
> > >> > > --
> > >> > > -Regards,
> > >> > > Mayuresh R. Gharat
> > >> > > (862) 250-7125
> > >> > >
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> > >> (862) 250-7125
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> > > (862) 250-7125
> > >
> >
> >
> >
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> > (862) 250-7125
> >
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> 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.
