My apologies, my computer is auto spellchecking and I didn’t notice before
sending.
*@Sriram
Thanks
Mike
On 08/12/2016, 08:35, "Michael Pearce" <michael.pea...@ig.com> wrote:
@Shiram,
I would like to be able to have though exactly once delivery without the
need to use more heavy weight transactions, this is why I’m proposing separate
KIP these are not entirely orthogonal.
Agreed the uuid could be re-used in supporting transactionality, but I
wouldn’t want to have to have full transactions and the additional performance
costs. Note this on activemq/artemis implementation, that I can get/achieve the
dedupe, but it is not tied into having a full transaction the solutions are
de-coupled.
On 06/12/2016, 19:01, "Sriram Subramanian" <r...@confluent.io> wrote:
@Jay
1. I totally agree on the naming. The appid for transactions is really
an
instance id. Any recommendation for a name is appreciated. We had
thought
of instance id, session id or app id and went with app id.
2. We also discussed about init() method but that could add its own set
of
confusion to existing users (should I update my existing usage to call
init()? Why should I have this extra step instead of the constructor
doing
it?). Transactions is going to be used by a subset of users (probably
small) and it made sense to add the burden of calling
initTransactions/recoverTransactions to only that subset. We are
actually
open to suggestions here in terms of naming as well.
@Jonathan
I am not sure it adds more complexity unless you use them. We have
explicitly named them for transactions and the current usage of the
producer remains unchanged.
@Michael
If you look at our idempotent producer implementation in the kip/design,
this is exactly what we do except that the deduplication happens on the
server. We started with separate KIPs but it made it very confusing to
read
since there were interdependencies between the concepts.
On Tue, Dec 6, 2016 at 9:04 AM, Michael Pearce <michael.pea...@ig.com>
wrote:
> For dealing with exactly once delivery.
>
> As an alternative option has it been considered to have a message
uuid in
> the record, that then is deduped on consumption?
>
> Similar to
>
https://activemq.apache.org/artemis/docs/1.0.0/duplicate-detection.html
>
> Agreed this does not deal with transaction support.
>
> But should the two concerns be separated anyhow into two kips?
>
> Cheers
> Mike
>
>
> Sent using OWA for iPhone
> ________________________________________
> From: Jay Kreps <j...@confluent.io>
> Sent: Tuesday, December 6, 2016 4:47:55 PM
> To: dev@kafka.apache.org
> Subject: Re: [DISCUSS] KIP-98: Exactly Once Delivery and Transactional
> Messaging
>
> Hey Guozhang,
>
>
> 1. My point is that it is a bit confusing to have two things called
> application id that have different meanings, right? Won't the
streams
> user
> end up specifying two different application ids?
> 2. Makes sense. My two complaints are
> 1. At this point we've jumped through quite a lot of hoops to
make
> the producer lazily initialize, seems sad to get rid of that
now.
> 2. The call initTransactions doesn't really make sense to the
user
> unless they understand the details of the protocol (which they
> won't). When
> do i call this? How many times? etc. Maybe two additional
> options would be
> to just add a general init() call that could cover metadata
> initialization
> as well as this and potentially future things or continue to do
it
> lazily.
> 3. Yeah I get that you need an expiry scheme to limit it to 4
bytes. Is
> there a mechanism to expire them, and hence shrink it?
>
> -Jay
>
> On Fri, Dec 2, 2016 at 12:04 PM, Guozhang Wang <wangg...@gmail.com>
wrote:
>
> > @Jay
> >
> > 1. Stream's applicationId is shared among all instances for the
app, and
> is
> > used as part of the consumer group id, while "app.id" is per
producer
> > instance. So a Streams app that has a single "applicationID" config
will
> > likely contain multiple producers each with a different appID based
on
> > their corresponding taskIDs.
> >
> > 2. Another motivation besides the one pointed out by Jason for
making
> sure
> > transaction-involved offsets have been committed before resuming,
is that
> > we also want to separate the "app.id" config with the transactional
> > mechanism. More concretely, if a user does specify the "app.id"
config
> and
> > without using transaction functions (i.e. initTransactions,
beginTxn,
> etc),
> > they can still get idempotency guarantee across multiple sessions
of the
> > producer identified by the app.id.
> >
> > 4. We thought about the PID length, note that since we do not expire
> PIDs,
> > we are expecting it to cover all possible producers that we have
ever
> seen,
> > and producers without an "app.id" can come and go with different
PIDs.
> > That
> > is why we feel 4 billion may not be sufficient.
> >
> >
> >
> > Guozhang
> >
> >
> > On Thu, Dec 1, 2016 at 11:10 PM, Jason Gustafson
<ja...@confluent.io>
> > wrote:
> >
> > > Hey Jay,
> > >
> > > Thanks for the questions! Let me take a couple of them.
> > >
> > > 2. The initTransactions() call is a little annoying. Can we get
rid of
> > > > that and call it automatically if you set a
transaction.app.id
> when
> > > we
> > > > do the first message send as we do with metadata? Arguably we
> should
> > > > have
> > > > included a general connect() or init() call in the producer,
but
> > given
> > > > that
> > > > we didn't do this it seems weird that the cluster metadata
> > initializes
> > > > automatically on demand and the transaction metadata doesn't.
> > >
> > >
> > > The purpose of this call is to fence off any producer with the
same
> AppID
> > > and await the completion of any pending transactions. When it
returns,
> > you
> > > know that your producer is safe to resume work. Take the the
"consume
> and
> > > produce" use case as an example. We send the offset commits as
part of
> > the
> > > producer's transaction (approximating the idea that it is "just
another
> > > write to a partition"). When you first initialize the
application, you
> > have
> > > to determine when it's safe for the consumer to read those
offsets.
> > > Otherwise, you may read stale offsets before a transaction which
is
> > rolling
> > > forward is able to write the marker to __consumer_offsets. So we
can't
> do
> > > the initialization in send() because that would assume that we had
> > already
> > > read data from the consumer, which we can't do until we've
initialized
> > the
> > > producer. Does that make sense?
> > >
> > > (For what it's worth, we're not married to this name or any of the
> > others,
> > > so anyone can feel free to suggest alternatives.)
> > >
> > >
> > > 5. One implication of factoring out the message set seems to be
you
> > > > can't ever "repack" messages to improve compression beyond
what is
> > > done
> > > > by
> > > > the producer. We'd talked about doing this either by
buffering
> when
> > > > writing
> > > > or during log cleaning. This isn't a show stopper but I
think one
> > > > implication is that we won't be able to do this. Furthermore
with
> > log
> > > > cleaning you'd assume that over time ALL messages would
collapse
> > down
> > > > to a
> > > > single wrapper as compaction removes the others.
> > >
> > >
> > > Yeah, that's a fair point. You may still be able to do some
merging if
> > > adjacent message sets have the same PID, but the potential savings
> might
> > > not be worth the cost of implementation. My gut feeling is that
merging
> > > message sets from different producers may not be a great idea
anyway
> > (you'd
> > > have to accept the fact that you always need "deep iteration" to
find
> the
> > > PIDs contained within the message set), but I haven't thought a
ton
> about
> > > it. Ultimately we'll have to decide if the potential for savings
in the
> > > future is worth some loss in efficiency now (for what it's worth,
I
> think
> > > the work that Ben has been looking at also hopes to bundle some
more
> > > information into the message set header).
> > >
> > > On a purely pragmatic development level, after spending a ton of
recent
> > > time working with that code, I can say that the benefit of having
a
> > > conceptually simpler message format is huge. It allows you to
converge
> > the
> > > paths for validation of message sets on the broker, for example.
> > Currently,
> > > we pretty much need two separate paths everywhere we process
messages.
> It
> > > can be tricky just to tell if the message you're dealing with is
the
> > inner
> > > or outer message, and whether it matters or not. Also, the fact
that
> the
> > > inner and outer messages share common fields makes bugs like
KAFKA-4298
> > > <https://issues.apache.org/jira/browse/KAFKA-4298> possible. The
risk
> of
> > > these bugs is much smaller when you can clearly separate the
fields
> > allowed
> > > in the message set header and those in the messages.
> > >
> > >
> > > Thanks,
> > > Jason
> > >
> > > On Thu, Dec 1, 2016 at 8:19 PM, Jay Kreps <j...@confluent.io>
wrote:
> > >
> > > > Looks great!
> > > >
> > > > A few questions:
> > > >
> > > > 1. What is the relationship between transaction.app.id and
the
> > > existing
> > > > config application.id in streams?
> > > > 2. The initTransactions() call is a little annoying. Can we
get
> rid
> > of
> > > > that and call it automatically if you set a
transaction.app.id
> when
> > > we
> > > > do the first message send as we do with metadata? Arguably we
> should
> > > > have
> > > > included a general connect() or init() call in the producer,
but
> > given
> > > > that
> > > > we didn't do this it seems weird that the cluster metadata
> > initializes
> > > > automatically on demand and the transaction metadata doesn't.
> > > > 3. The equivalent concept of what we call "fetch.mode" in
> databases
> > is
> > > > called "isolation level" and takes values like
"serializable",
> "read
> > > > committed", "read uncommitted". Since we went with
transaction as
> > the
> > > > name
> > > > for the thing in between the begin/commit might make sense
to use
> > this
> > > > terminology for the concept and levels? I think the behavior
we
> are
> > > > planning is "read committed" and the alternative re-ordering
> > behavior
> > > is
> > > > equivalent to "serializable"?
> > > > 4. Can the PID be made 4 bytes if we handle roll-over
gracefully?
> 2
> > > > billion concurrent producers should be enough for anyone,
right?
> > > > 5. One implication of factoring out the message set seems to
be
> you
> > > > can't ever "repack" messages to improve compression beyond
what is
> > > done
> > > > by
> > > > the producer. We'd talked about doing this either by
buffering
> when
> > > > writing
> > > > or during log cleaning. This isn't a show stopper but I
think one
> > > > implication is that we won't be able to do this. Furthermore
with
> > log
> > > > cleaning you'd assume that over time ALL messages would
collapse
> > down
> > > > to a
> > > > single wrapper as compaction removes the others.
> > > >
> > > > -Jay
> > > >
> > > > On Wed, Nov 30, 2016 at 2:19 PM, Guozhang Wang
<wangg...@gmail.com>
> > > wrote:
> > > >
> > > > > Hi all,
> > > > >
> > > > > I have just created KIP-98 to enhance Kafka with exactly once
> > delivery
> > > > > semantics:
> > > > >
> > > > > *https://cwiki.apache.org/confluence/display/KAFKA/KIP-
> > > > > 98+-+Exactly+Once+Delivery+and+Transactional+Messaging
> > > > > <https://cwiki.apache.org/confluence/display/KAFKA/KIP-
> > > > > 98+-+Exactly+Once+Delivery+and+Transactional+Messaging>*
> > > > >
> > > > > This KIP adds a transactional messaging mechanism along with
an
> > > > idempotent
> > > > > producer implementation to make sure that 1) duplicated
messages
> sent
> > > > from
> > > > > the same identified producer can be detected on the broker
side,
> and
> > > 2) a
> > > > > group of messages sent within a transaction will atomically be
> either
> > > > > reflected and fetchable to consumers or not as a whole.
> > > > >
> > > > > The above wiki page provides a high-level view of the proposed
> > changes
> > > as
> > > > > well as summarized guarantees. Initial draft of the detailed
> > > > implementation
> > > > > design is described in this Google doc:
> > > > >
> > > > > https://docs.google.com/document/d/11Jqy_
> > > GjUGtdXJK94XGsEIK7CP1SnQGdp2eF
> > > > > 0wSw9ra8
> > > > >
> > > > >
> > > > > We would love to hear your comments and suggestions.
> > > > >
> > > > > Thanks,
> > > > >
> > > > > -- Guozhang
> > > > >
> > > >
> > >
> >
> >
> >
> > --
> > -- Guozhang
> >
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