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From Joe Stein <joe.st...@stealth.ly>
Subject Re: New Producer - ONLY sync mode?
Date Wed, 04 Feb 2015 15:19:08 GMT
Now that 0.8.2.0 is in the wild I look forward to working with more and
seeing what folks start to-do with this function
https://dist.apache.org/repos/dist/release/kafka/0.8.2.0/javadoc/org/apache/kafka/clients/producer/KafkaProducer.html#send(org.apache.kafka.clients.producer.ProducerRecord,
org.apache.kafka.clients.producer.Callback) and keeping it fully non
blocking.

One sprint I know of coming up is going to have the new producer as a
component in their reactive calls and handling bookkeeping and retries
through that type of call back approach. Should work well (haven't tried
but don't see why not) with Akka, ScalaZ, RxJava, Finagle, etc, etc, etc in
functional languages and frameworks.

I think as JDK 8 starts to get out in the wild too more (may after jdk7
eol) the use of .get will be reduced (imho) and folks will be thinking more
about non-blocking vs blocking and not as so much sync vs async but my
crystal ball just back from the shop so well see =8^)

/*******************************************
 Joe Stein
 Founder, Principal Consultant
 Big Data Open Source Security LLC
 http://www.stealth.ly
 Twitter: @allthingshadoop <http://www.twitter.com/allthingshadoop>
********************************************/

On Tue, Feb 3, 2015 at 10:45 PM, Jay Kreps <jay.kreps@gmail.com> wrote:

> Hey guys,
>
> I guess the question is whether it really matters how many underlying
> network requests occur? It is very hard for an application to depend on
> this even in the old producer since it depends on the partitions placement
> (a send to two partitions may go to either one machine or two and so it
> will send either one or two requests). So when you send a batch in one call
> you may feel that is "all at once", but that is only actually guaranteed if
> all messages have the same partition.
>
> The challenge is allowing even this in the presence of bounded request
> sizes which we have in the new producer. The user sends a list of objects
> and the serialized size that will result is not very apparent to them. If
> you break it up into multiple requests then that is kind of further ruining
> the illusion of a single send. If you don't then you have to just error out
> which is equally annoying to have to handle.
>
> But I'm not sure if from your description you are saying you actually care
> how many physical requests are issued. I think it is more like it is just
> syntactically annoying to send a batch of data now because it needs a for
> loop.
>
> Currently to do this you would do:
>
> List responses = new ArrayList();
> for(input: recordBatch)
>     responses.add(producer.send(input));
> for(response: responses)
>     response.get
>
> If you don't depend on the offset/error info we could add a flush call so
> you could instead do
> for(input: recordBatch)
>     producer.send(input);
> producer.flush();
>
> But if you do want the error/offset then you are going to be back to the
> original case.
>
> Thoughts?
>
> -Jay
>
> On Mon, Feb 2, 2015 at 1:48 PM, Gwen Shapira <gshapira@cloudera.com>
> wrote:
>
> > I've been thinking about that too, since both Flume and Sqoop rely on
> > send(List) API of the old API.
> >
> > I'd like to see this API come back, but I'm debating how we'd handle
> > errors. IIRC, the old API would fail an entire batch on a single
> > error, which can lead to duplicates. Having N callbacks lets me retry
> > / save / whatever just the messages that had issues.
> >
> > If messages had identifiers from the producer side, we could have the
> > API call the callback with a list of message-ids and their status. But
> > they don't :)
> >
> > Any thoughts on how you'd like it to work?
> >
> > Gwen
> >
> >
> > On Mon, Feb 2, 2015 at 1:38 PM, Pradeep Gollakota <pradeepg26@gmail.com>
> > wrote:
> > > This is a great question Otis. Like Gwen said, you can accomplish Sync
> > mode
> > > by setting the batch size to 1. But this does highlight a shortcoming
> of
> > > the new producer API.
> > >
> > > I really like the design of the new API and it has really great
> > properties
> > > and I'm enjoying working with it. However, once API that I think we're
> > > lacking is a "batch" API. Currently, I have to iterate over a batch and
> > > call .send() on each record, which returns n callbacks instead of 1
> > > callback for the whole batch. This significantly complicates recovery
> > logic
> > > where we need to commit a batch as opposed 1 record at a time.
> > >
> > > Do you guys have any plans to add better semantics around batches?
> > >
> > > On Mon, Feb 2, 2015 at 1:34 PM, Gwen Shapira <gshapira@cloudera.com>
> > wrote:
> > >
> > >> If I understood the code and Jay correctly - if you wait for the
> > >> future it will be a similar delay to that of the old sync producer.
> > >>
> > >> Put another way, if you test it out and see longer delays than the
> > >> sync producer had, we need to find out why and fix it.
> > >>
> > >> Gwen
> > >>
> > >> On Mon, Feb 2, 2015 at 1:27 PM, Otis Gospodnetic
> > >> <otis.gospodnetic@gmail.com> wrote:
> > >> > Hi,
> > >> >
> > >> > Nope, unfortunately it can't do that.  X is a remote app, doesn't
> > listen
> > >> to
> > >> > anything external, calls Y via HTTPS.  So X has to decide what to
do
> > with
> > >> > its data based on Y's synchronous response.  It has to block until
Y
> > >> > responds.  And it wouldn't be pretty, I think, because nobody wants
> to
> > >> run
> > >> > apps that talk to remove servers and hang on to connections more
> than
> > >> they
> > >> > have to.  But perhaps that is the only way?  Or maybe the answer to
> > "I'm
> > >> > guessing the delay would be more or less the same as if the Producer
> > was
> > >> > using SYNC mode?" is YES, in which case the connection from X to Y
> > would
> > >> be
> > >> > open for just as long as with a SYNC producer running in Y?
> > >> >
> > >> > Thanks,
> > >> > Otis
> > >> > --
> > >> > Monitoring * Alerting * Anomaly Detection * Centralized Log
> Management
> > >> > Solr & Elasticsearch Support * http://sematext.com/
> > >> >
> > >> >
> > >> > On Mon, Feb 2, 2015 at 4:03 PM, Gwen Shapira <gshapira@cloudera.com
> >
> > >> wrote:
> > >> >
> > >> >> Can Y have a callback that will handle the notification to X?
> > >> >> In this case, perhaps Y can be async and X can buffer the data
> until
> > >> >> the callback triggers and says "all good" (or resend if the
> callback
> > >> >> indicates an error)
> > >> >>
> > >> >> On Mon, Feb 2, 2015 at 12:56 PM, Otis Gospodnetic
> > >> >> <otis.gospodnetic@gmail.com> wrote:
> > >> >> > Hi,
> > >> >> >
> > >> >> > Thanks for the info.  Here's the use case.  We have something
up
> > >> stream
> > >> >> > sending data, say a log shipper called X.  It sends it to
some
> > remote
> > >> >> > component Y.  Y is the Kafka Producer and it puts data into
> Kafka.
> > >> But Y
> > >> >> > needs to send a reply to X and tell it whether it successfully
> put
> > all
> > >> >> its
> > >> >> > data into Kafka.  If it did not, Y wants to tell X to buffer
data
> > >> locally
> > >> >> > and resend it later.
> > >> >> >
> > >> >> > If producer is ONLY async, Y can't easily do that.  Or maybe
Y
> > would
> > >> just
> > >> >> > need to wait for the Future to come back and only then send
the
> > >> response
> > >> >> > back to X?  If so, I'm guessing the delay would be more or
less
> the
> > >> same
> > >> >> as
> > >> >> > if the Producer was using SYNC mode?
> > >> >> >
> > >> >> > Thanks,
> > >> >> > Otis
> > >> >> > --
> > >> >> > Monitoring * Alerting * Anomaly Detection * Centralized Log
> > Management
> > >> >> > Solr & Elasticsearch Support * http://sematext.com/
> > >> >> >
> > >> >> >
> > >> >> > On Mon, Feb 2, 2015 at 3:13 PM, Jay Kreps <jay.kreps@gmail.com>
> > >> wrote:
> > >> >> >
> > >> >> >> Yeah as Gwen says there is no sync/async mode anymore.
There is
> a
> > new
> > >> >> >> configuration which does a lot of what async did in terms
of
> > allowing
> > >> >> >> batching:
> > >> >> >>
> > >> >> >> batch.size - This is the target amount of data per partition
the
> > >> server
> > >> >> >> will attempt to batch together.
> > >> >> >> linger.ms - This is the time the producer will wait for
more
> data
> > >> to be
> > >> >> >> sent to better batch up writes. The default is 0 (send
> > immediately).
> > >> So
> > >> >> if
> > >> >> >> you set this to 50 ms the client will send immediately
if it has
> > >> already
> > >> >> >> filled up its batch, otherwise it will wait to accumulate
the
> > number
> > >> of
> > >> >> >> bytes given by batch.size.
> > >> >> >>
> > >> >> >> To send asynchronously you do
> > >> >> >>    producer.send(record)
> > >> >> >> whereas to block on a response you do
> > >> >> >>    producer.send(record).get();
> > >> >> >> which will wait for acknowledgement from the server.
> > >> >> >>
> > >> >> >> One advantage of this model is that the client will do
it's best
> > to
> > >> >> batch
> > >> >> >> under the covers even if linger.ms=0. It will do this
by
> batching
> > >> any
> > >> >> data
> > >> >> >> that arrives while another send is in progress into a
single
> > >> >> >> request--giving a kind of "group commit" effect.
> > >> >> >>
> > >> >> >> The hope is that this will be both simpler to understand
(a
> single
> > >> api
> > >> >> that
> > >> >> >> always works the same) and more powerful (you always
get a
> > response
> > >> with
> > >> >> >> error and offset information whether or not you choose
to use
> it).
> > >> >> >>
> > >> >> >> -Jay
> > >> >> >>
> > >> >> >>
> > >> >> >> On Mon, Feb 2, 2015 at 11:15 AM, Gwen Shapira <
> > gshapira@cloudera.com
> > >> >
> > >> >> >> wrote:
> > >> >> >>
> > >> >> >> > If you want to emulate the old sync producer behavior,
you
> need
> > to
> > >> set
> > >> >> >> > the batch size to 1  (in producer config) and wait
on the
> future
> > >> you
> > >> >> >> > get from Send (i.e. future.get)
> > >> >> >> >
> > >> >> >> > I can't think of good reasons to do so, though.
> > >> >> >> >
> > >> >> >> > Gwen
> > >> >> >> >
> > >> >> >> >
> > >> >> >> > On Mon, Feb 2, 2015 at 11:08 AM, Otis Gospodnetic
> > >> >> >> > <otis.gospodnetic@gmail.com> wrote:
> > >> >> >> > > Hi,
> > >> >> >> > >
> > >> >> >> > > Is the plan for New Producer to have ONLY async
mode?  I'm
> > asking
> > >> >> >> because
> > >> >> >> > > of this info from the Wiki:
> > >> >> >> > >
> > >> >> >> > >
> > >> >> >> > >    - The producer will always attempt to batch
data and will
> > >> always
> > >> >> >> > >    immediately return a SendResponse which
acts as a Future
> to
> > >> allow
> > >> >> >> the
> > >> >> >> > >    client to await the completion of the request.
> > >> >> >> > >
> > >> >> >> > >
> > >> >> >> > > The word "always" makes me think there will
be no sync mode.
> > >> >> >> > >
> > >> >> >> > > Thanks,
> > >> >> >> > > Otis
> > >> >> >> > > --
> > >> >> >> > > Monitoring * Alerting * Anomaly Detection *
Centralized Log
> > >> >> Management
> > >> >> >> > > Solr & Elasticsearch Support * http://sematext.com/
> > >> >> >> >
> > >> >> >>
> > >> >>
> > >>
> >
>

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