I seems to me that performance wide, acks=1 and acks=0 will be pretty much the same if max.in.flight.request.per.connection is set to very high and does not cause a request sending to block.
In new producer, if there are send failure from time to time, I would guess asks=1 would even have better performance than acks=0. Because in acks=0, when error occurred, broker will disconnect the connection. In that case, subsequent send from the producer needs to reconnect to the broker, that means it has to go through 3-way handshake, TCP slow-start, etc, etc. On the other hand, acks=1 will not have this issue. Maybe the major difference is still the delivery guarantee? acks=0 means send and forget while acks=1 means user still want to know if the messages were sent successfully or not. On Mon, Jul 27, 2015 at 10:57 AM, Ewen Cheslack-Postava <e...@confluent.io> wrote: > If only we had some sort of system test framework with a producer > performance test that we could parameterize with the different acks > settings to validate these performance differences... > > wrt out of order: yes, with > 1 in flight requests with retries, messages > can get out of order. Becket had a great presentation addressing that and a > bunch of other issues with no data loss pipelines: > > http://www.slideshare.net/JiangjieQin/no-data-loss-pipeline-with-apache-kafka-49753844 > Short version: as things are today, you have to *really* understand the > producer settings, and some producer internals, to get the exact behavior > you want. > > > On Mon, Jul 27, 2015 at 9:44 AM, Gwen Shapira <gshap...@cloudera.com> > wrote: > > > Yeah, using acks=0 should result in higher throughput since we are not > > limited by the roundtrip time to the broker. > > > > Btw. regarding in-flight requests: With acks = 1 (or -1), can we send > > a message batch to a partition before the brokers "acked" a previous > > request? Doesn't it risk getting messages out of order? > > > > On Mon, Jul 27, 2015 at 9:41 AM, Guozhang Wang <wangg...@gmail.com> > wrote: > > > I think there is still a subtle difference between "async with acks = > 0" > > > and "async with callback", that when the #.max-inflight-requests has > > > reached the subsequent requests cannot be sent until previous responses > > are > > > returned (which could happen, for example, when the broker is slow / > > > network issue happens) in the second case but not in the first. > > > > > > Given this difference, I feel there are still scenarios, though > probably > > > rare, that users would like to use "acks = 0" even with new producer's > > > callbacks. > > > > > > Guozhang > > > > > > On Mon, Jul 27, 2015 at 9:25 AM, Mayuresh Gharat < > > gharatmayures...@gmail.com > > >> wrote: > > > > > >> So basically this means that with acks = 0, their is no guarantee that > > the > > >> message has been received by Kafka broker. I am just wondering, why > > would > > >> anyone be using acks = 0, since anyone using kafka and doing > > >> producer.send() would want that, their message got to kafka brokers. > > Also > > >> as Jay said, with new producer with async mode, clients will not have > to > > >> wait for the response since it will be handled in callbacks. So the > use > > of > > >> acks = 0 sounds very rare to me and I am not able to think of an > usecase > > >> around it. > > >> > > >> Thanks, > > >> > > >> Mayuresh > > >> > > >> On Sun, Jul 26, 2015 at 2:40 PM, Gwen Shapira <gshap...@cloudera.com> > > >> wrote: > > >> > > >> > Aha! Yes, I was missing the part with the dummy response. > > >> > Thank you! > > >> > > > >> > Gwen > > >> > > > >> > > > >> > On Sun, Jul 26, 2015 at 2:17 PM, Ewen Cheslack-Postava > > >> > <e...@confluent.io> wrote: > > >> > > It's different because it changes whether the client waits for the > > >> > response > > >> > > from the broker at all. Take a look at > > >> > NetworkClient.handleCompletedSends, > > >> > > which fills in dummy responses when a response is not expected > (and > > >> that > > >> > > flag gets set via Sender.produceRequest using acks != 0 as a flag > to > > >> > > ClientRequest). This means that the producer will invoke the > > callback & > > >> > > resolve the future as soon as the request hits the TCP buffer on > the > > >> > > client. At that point, the behavior of the broker wrt generating a > > >> > response > > >> > > doesn't matter -- the client isn't waiting on that response > anyway. > > >> > > > > >> > > This definitely is faster since you aren't waiting for the round > > trip, > > >> > but > > >> > > it seems like it is of questionable value with the new producer as > > Jay > > >> > > explained. It is slightly better than just assuming records have > > been > > >> > sent > > >> > > as soon as you call Producer.send() in this shouldn't trigger a > > >> callback > > >> > > until the records have made it through the internal KafkaProducer > > >> > > buffering. But since it still has to make it through the TCP > > buffers it > > >> > > doesn't really guarantee anything that useful. > > >> > > > > >> > > -Ewen > > >> > > > > >> > > > > >> > > On Sun, Jul 26, 2015 at 1:40 PM, Gwen Shapira < > > gshap...@cloudera.com> > > >> > wrote: > > >> > > > > >> > >> What bugs me is that even with acks = 0, the broker will append > to > > >> > >> local log before responding (unless I'm misreading the code), so > I > > >> > >> don't see why a client with acks = 0 will be any faster. Unless > the > > >> > >> client chooses to not wait for response, which is orthogonal to > > acks > > >> > >> parameter. > > >> > >> > > >> > >> On Mon, Jul 20, 2015 at 8:52 AM, Jay Kreps <j...@confluent.io> > > wrote: > > >> > >> > acks=0 is a one-way send, the client doesn't need to wait on > the > > >> > >> response. > > >> > >> > Whether this is useful sort of depends on the client > > implementation. > > >> > The > > >> > >> > new java producer does all sends async so "waiting" on a > response > > >> > isn't > > >> > >> > really a thing. For a client that lacks this, though, as some > of > > >> them > > >> > do, > > >> > >> > acks=0 will be a lot faster. > > >> > >> > > > >> > >> > It also makes some sense in terms of what is completed when the > > >> > request > > >> > >> is > > >> > >> > considered satisfied > > >> > >> > acks = 0 - message is written to the network (buffer) > > >> > >> > acks = 1 - message is written to the leader log > > >> > >> > acks = -1 - message is committed > > >> > >> > > > >> > >> > -Jay > > >> > >> > > > >> > >> > On Sat, Jul 18, 2015 at 10:50 PM, Gwen Shapira < > > >> gshap...@cloudera.com > > >> > > > > >> > >> > wrote: > > >> > >> > > > >> > >> >> Hi, > > >> > >> >> > > >> > >> >> I was looking into the different between acks = 0 and acks = 1 > > in > > >> the > > >> > >> >> new producer, and was a bit surprised at what I found. > > >> > >> >> > > >> > >> >> Basically, if I understand correctly, the only difference is > > that > > >> > with > > >> > >> >> acks = 0, if the leader fails to append locally, it closes the > > >> > network > > >> > >> >> connection silently and with acks = 1, it sends an actual > error > > >> > >> >> message. > > >> > >> >> > > >> > >> >> Which seems to mean that with acks = 0, any failed produce > will > > >> lead > > >> > >> >> to metadata refresh and a retry (because network error), while > > >> acks = > > >> > >> >> 1 will lead to either retries or abort, depending on the > error. > > >> > >> >> > > >> > >> >> Not only this doesn't match the documentation, it doesn't even > > make > > >> > >> >> much sense... > > >> > >> >> "acks = 0" was supposed to somehow makes things "less safe but > > >> > >> >> faster", and it doesn't seem to be doing that any more. I'm > not > > >> even > > >> > >> >> sure there's any case where the "acks = 0" behavior is > > desirable. > > >> > >> >> > > >> > >> >> Is it my misunderstanding, or did we somehow screw up the > logic > > >> here? > > >> > >> >> > > >> > >> >> Gwen > > >> > >> >> > > >> > >> > > >> > > > > >> > > > > >> > > > > >> > > -- > > >> > > Thanks, > > >> > > Ewen > > >> > > > >> > > >> > > >> > > >> -- > > >> -Regards, > > >> Mayuresh R. Gharat > > >> (862) 250-7125 > > >> > > > > > > > > > > > > -- > > > -- Guozhang > > > > > > -- > Thanks, > Ewen >
