Kane,
If you set message.send.max.retries to 0 it should be at-most-once, and I
saw your props have the right config. What are the exceptions you got from
the send() call?
Guozhang
On Fri, Oct 25, 2013 at 12:54 PM, Steve Morin <st...@stevemorin.com> wrote:
> Kane and Aniket,
> I am interested in knowing what the pattern/solution that people usually
> use to implement exactly once as well.
> -Steve
>
>
> On Fri, Oct 25, 2013 at 11:39 AM, Kane Kane <kane.ist...@gmail.com> wrote:
>
> > Guozhang, but i've posted a piece from kafka documentation above:
> > So effectively Kafka guarantees at-least-once delivery by default and
> > allows the user to implement at most once delivery by disabling retries
> on
> > the producer.
> >
> > What i want is at-most-once and docs claim it's possible with certain
> > settings. Did i miss anything here?
> >
> >
> > On Fri, Oct 25, 2013 at 11:35 AM, Guozhang Wang <wangg...@gmail.com>
> > wrote:
> >
> > > Aniket is exactly right. In general, Kafka provides "at least once"
> > > guarantee instead of "exactly once".
> > >
> > > Guozhang
> > >
> > >
> > > On Fri, Oct 25, 2013 at 11:13 AM, Aniket Bhatnagar <
> > > aniket.bhatna...@gmail.com> wrote:
> > >
> > > > As per my understanding, if the broker says the msg is committed,
> its
> > > > guaranteed to have been committed as per ur ack config. If it says it
> > did
> > > > not get committed, then its very hard to figure out if this was just
> a
> > > > false error. Since there is concept of unique ids for messages, a
> > replay
> > > of
> > > > the same message will result in duplication. I think its a reasonable
> > > > behaviour considering kafka prefers to append data to partitions fot
> > > > performance reasons.
> > > > The best way to right now deal with duplicate msgs is to build the
> > > > processing engine (layer where your consumer sits) to deal with at
> > least
> > > > once semantics of the broker.
> > > > On 25 Oct 2013 23:23, "Kane Kane" <kane.ist...@gmail.com> wrote:
> > > >
> > > > > Or, to rephrase it more generally, is there a way to know exactly
> if
> > > > > message was committed or no?
> > > > >
> > > > >
> > > > > On Fri, Oct 25, 2013 at 10:43 AM, Kane Kane <kane.ist...@gmail.com
> >
> > > > wrote:
> > > > >
> > > > > > Hello Guozhang,
> > > > > >
> > > > > > My partitions are split almost evenly between broker, so, yes -
> > > broker
> > > > > > that I shutdown is the leader for some of them. Does it mean i
> can
> > > get
> > > > an
> > > > > > exception and data is still being written? Is there any setting
> on
> > > the
> > > > > > broker where i can control this? I.e. can i make broker
> replication
> > > > > timeout
> > > > > > shorter than producer timeout, so i can ensure if i get an
> > exception
> > > > data
> > > > > > is not being committed?
> > > > > >
> > > > > > Thanks.
> > > > > >
> > > > > >
> > > > > > On Fri, Oct 25, 2013 at 10:36 AM, Guozhang Wang <
> > wangg...@gmail.com
> > > > > >wrote:
> > > > > >
> > > > > >> Hello Kane,
> > > > > >>
> > > > > >> As discussed in the other thread, even if a timeout response is
> > sent
> > > > > back
> > > > > >> to the producer, the message may still be committed.
> > > > > >>
> > > > > >> Did you shut down the leader broker of the partition or a
> follower
> > > > > broker?
> > > > > >>
> > > > > >> Guozhang
> > > > > >>
> > > > > >> On Fri, Oct 25, 2013 at 8:45 AM, Kane Kane <
> kane.ist...@gmail.com
> > >
> > > > > wrote:
> > > > > >>
> > > > > >> > I have cluster of 3 kafka brokers. With the following script I
> > > send
> > > > > some
> > > > > >> > data to kafka and in the middle do the controlled shutdown of
> 1
> > > > > broker.
> > > > > >> All
> > > > > >> > 3 brokers are ISR before I start sending. When i shutdown the
> > > > broker i
> > > > > >> get
> > > > > >> > a couple of exceptions and I expect data shouldn't be written.
> > > Say,
> > > > I
> > > > > >> send
> > > > > >> > 1500 lines and get 50 exceptions. I expect to consume 1450
> > lines,
> > > > but
> > > > > >> > instead i always consume more, i.e. 1480 or 1490. I want to
> > decide
> > > > if
> > > > > I
> > > > > >> > want to retry sending myself, not using
> > message.send.max.retries.
> > > > But
> > > > > >> looks
> > > > > >> > like if I retry sending if there is an exception - I will end
> up
> > > > with
> > > > > >> > duplicates. Is there anything I'm doing wrong or having wrong
> > > > > >> assumptions
> > > > > >> > about kafka?
> > > > > >> >
> > > > > >> > Thanks.
> > > > > >> >
> > > > > >> > val prod = new MyProducer("10.80.42.147:9092,
> 10.80.42.154:9092,
> > > > > >> > 10.80.42.156:9092")
> > > > > >> > var count = 0
> > > > > >> > for(line <- Source.fromFile(file).getLines()){
> > > > > >> > try {
> > > > > >> > prod.send("benchmark", buffer.toList)
> > > > > >> > count += 1
> > > > > >> > println("sent %s", count)
> > > > > >> > } catch {
> > > > > >> > case _ => println("Exception!")
> > > > > >> > }
> > > > > >> > }
> > > > > >> >
> > > > > >> > class MyProducer(brokerList: String) {
> > > > > >> > val sync = true
> > > > > >> > val requestRequiredAcks = "-1"
> > > > > >> >
> > > > > >> > val props = new Properties()
> > > > > >> > props.put("metadata.broker.list", brokerList)
> > > > > >> > props.put("producer.type", if(sync) "sync" else "async")
> > > > > >> > props.put("request.required.acks", requestRequiredAcks)
> > > > > >> > props.put("key.serializer.class",
> > > classOf[StringEncoder].getName)
> > > > > >> > props.put("serializer.class",
> classOf[StringEncoder].getName)
> > > > > >> > props.put("message.send.max.retries", "0")
> > > > > >> > props.put("request.timeout.ms", "2000")
> > > > > >> >
> > > > > >> > val producer = new Producer[AnyRef, AnyRef](new
> > > > > ProducerConfig(props))
> > > > > >> >
> > > > > >> > def send(topic: String, messages: List[String]) = {
> > > > > >> > val requests = new ArrayBuffer[KeyedMessage[AnyRef,
> AnyRef]]
> > > > > >> > for (message <- messages) {
> > > > > >> > requests += new KeyedMessage(topic, null, message,
> > message)
> > > > > >> > }
> > > > > >> > producer.send(requests)
> > > > > >> > }
> > > > > >> > }
> > > > > >> >
> > > > > >>
> > > > > >>
> > > > > >>
> > > > > >> --
> > > > > >> -- Guozhang
> > > > > >>
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
> > >
> > >
> > > --
> > > -- Guozhang
> > >
> >
>
--
-- Guozhang
