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From Jay Kreps <...@confluent.io>
Subject Re: [DISCUSS] KIP-98: Exactly Once Delivery and Transactional Messaging
Date Fri, 09 Dec 2016 18:08:07 GMT
Hey Michael,

Doesn't that example have more to do with applying the update against two
rows in a single transaction? That is, clearly the write to Kafka needs to
be "transactional" and the write to the destination needs to be
transactional, but it's not clear to me that you need isolation that spans
both operations. Can you dive into the system architecture a bit more and
explain why Kafka needs to participate in the same transaction as the
destination system?

-Jay

On Thu, Dec 8, 2016 at 10:19 PM, Michael Pearce <Michael.Pearce@ig.com>
wrote:

> Usecase in IG:
>
> Fund transfer between accounts. When we debit one account and fund another
> we must ensure the records to both occur as an acid action, and as a single
> transaction.
>
> Today we achieve this because we have jms, as such we can do the actions
> needed in an xa transaction across both the accounts. To move this flow to
> Kafka we would need support of XA transaction.
>
>
>
> Sent using OWA for iPhone
> ________________________________________
> From: Michael Pearce <Michael.Pearce@ig.com>
> Sent: Friday, December 9, 2016 6:09:06 AM
> To: dev@kafka.apache.org
> Subject: Re: [DISCUSS] KIP-98: Exactly Once Delivery and Transactional
> Messaging
>
> Hi Jay,
>
> For me having an XA transaction allows for ensuring ACID across my
> application.
>
> I believe it is part of the JMS api, and obviously JMS still is in
> enterprise very widely adopted for Messaging transport , so obviously to
> say it isn't widely used i think is ignoring a whole range of users. Like
> wise I believe frameworks like spring etc fully support it more evidence of
> its wide adoption.
>
> On this note personally we try to avoid transactions entirely in our flows
> for performance and simplicity. but we do alas unfortunately have one or
> two places we cannot ignore it.
>
> Cheers
> Mike
>
> Sent using OWA for iPhone
> ________________________________________
> From: Jay Kreps <jay@confluent.io>
> Sent: Thursday, December 8, 2016 11:25:53 PM
> To: dev@kafka.apache.org
> Subject: Re: [DISCUSS] KIP-98: Exactly Once Delivery and Transactional
> Messaging
>
> Hey Edoardo,
>
> For (3) can you outline what you think the benefit and use cases for a more
> general cross-system XA feature would be an what changes to the proposal
> would be required to enable it? When I have asked people who wanted
> cross-system XA in the past what they wanted it for, I haven't really
> gotten any answers that made sense. Every person really wanted something
> that would be better solved by a transactional (or idempotent) write to
> Kafka followed by an independent transactional (or idempotent) consumption
> (which this proposal enables). For the use cases they described tying these
> two things together had no advantage and many disadvantages.
>
> I have one use case which would be accomplished by cross-system XA which is
> allowing the producer to block on the synchronous processing of the message
> by (all? some?) consumers. However I'm not convinced that cross-system XA
> is the best solution to this problem, and I'm also not convinced this is an
> important problem to solve. But maybe you have something in mind here.
>
> -Jay
>
>
>
> On Thu, Dec 8, 2016 at 1:15 PM, Edoardo Comar <ECOMAR@uk.ibm.com> wrote:
>
> > Hi,
> > thanks, very interesting KIP ... I haven't fully digested it yet.
> >
> > We have many users who choose not to use the Java client,  so I have
> > concerns about the added complexity in developing the clients.
> > A few questions.
> >
> > 1 - is mixing transactional and non transactional messages on the *same
> > topic-partition* really a requirement ?
> > What use case does it satisfy?
> >
> > 2 - I guess some clients may only be interested to implement the producer
> > idempotency.
> > It's not clear how they could be implemented without having to add the
> > transaction capabilities.
> > As others on this list have said, I too would like to see idempotency as
> a
> > more basic feature, on top which txns can be built.
> >
> > 3 - The KIP seems focused on a use case where consumption from a topic
> and
> > subsequent production are part of the producer transaction.
> >
> > It'd be great to see a way to extend the producer transaction to include
> > additional transactional resources,
> > so that the consumption from another topic just becomes a special case of
> > a more general "distributed" txn.
> >
> > Edo
> > --------------------------------------------------
> > Edoardo Comar
> > IBM MessageHub
> > ecomar@uk.ibm.com
> > IBM UK Ltd, Hursley Park, SO21 2JN
> >
> > IBM United Kingdom Limited Registered in England and Wales with number
> > 741598 Registered office: PO Box 41, North Harbour, Portsmouth, Hants.
> PO6
> > 3AU
> >
> >
> >
> > From:   Guozhang Wang <wangguoz@gmail.com>
> > To:     "dev@kafka.apache.org" <dev@kafka.apache.org>
> > Date:   30/11/2016 22:20
> > Subject:        [DISCUSS] KIP-98: Exactly Once Delivery and Transactional
> > Messaging
> >
> >
> >
> > 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
> >
> >
> >
> > Unless stated otherwise above:
> > IBM United Kingdom Limited - Registered in England and Wales with number
> > 741598.
> > Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6
> 3AU
> >
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