Marc, As Erik said, the behavior I was referring to is for the standard Kafka producer, which the REST proxy uses for sending data to Kafka. Batches are not of a predetermined fixed size or anything like that. Internally, the producer maintains a queue of messages, keeping track of both outstanding requests (we've sent the request to the broker, but not seen the ack yet) and requests that we can't yet send (we already have max.in.flight.requests.per.connection requests to the broker). If you have nothing in the queue, you'll always be able to send immediately. The linger.ms setting is one of the settings that controls batching. By default it is set to 0, meaning that if it is able to send a new request (has at least one more request allowed for the connection), it will not wait at all for any more messages. So if the rate of messages is low enough, messages will always be sent out immediately. If it is higher, batching will automatically occur on messages that have to wait to be sent -- as soon as an ack from another message is received, the producer will look at what messages need to be sent, collect *up to* a full batch (batch.size setting) of them, and send out a request with that data.
If you turn linger.ms up, it delays messages for the specified number of milliseconds, providing some time for other messages to collect before sending out a message. You might want to do this if you are willing to risk losing that data as it sits in the in-memory queue in order to avoid making a bunch of smaller produce requests to the server. Note that there is *always* a risk of losing some messages if they have to sit in the buffer on the producer. The way to minimize this is to adjust the settings to match your workload such that messages *never* wait to be sent. However, beware that this can result in a *lot* of very small messages to Kafka, and each message has overhead. Sending requests that aggressively can impact performance and throughput. -Ewen On Thu, Aug 27, 2015 at 6:58 AM, Helleren, Erik <erik.helle...@cmegroup.com> wrote: > Hi Marc, > That describes the behavior of the kafka producer library that batches > writes to kafka. This post on confluent.io explains it pretty well: > http://kafka.apache.org/082/javadoc/index.html?org/apache/kafka/clients/pro > ducer/KafkaProducer.html > > But the general idea is that the producer will group together a bunch of > writes to kafka for a specific topic and partition, and then send them as > a single request. > > Durability guarantees in kafka depend on your configuration, and can be > very week, or very strong. Reading the kafka documentation page¹s sections > about producers should make it clear which setting improve Durability at > the cost of latency and throughput. But there would be a risk of loosing > the messages that are inside the proxy application during a failure, > unless there is a replay ability from the source. > -Erik > > > > > On 8/27/15, 12:34 AM, "Marc Bollinger" <m...@lumoslabs.com> wrote: > > >Apologies if this is somewhat redundant, I'm quite new to both Kafka and > >the Confluent Platform. Ewen, when you say "Under the hood, the new > >producer will automatically batch requests." > > > >Do you mean that this is a current or planned behavior of the REST proxy? > >Are there any durability guarantees, or are batches just held in memory > >before being sent to Kafka (or some other option)? > > > >Thanks! > > > >> On Aug 26, 2015, at 9:50 PM, Ewen Cheslack-Postava <e...@confluent.io> > >>wrote: > >> > >> Hemanth, > >> > >> The Confluent Platform 1.0 version of have JSON embedded format support > >> (i.e. direct embedding of JSON messages), but you can serialize, base64 > >> encode, and use the binary mode, paying a bit of overhead. However, > >>since > >> then we merged a patch to add JSON support: > >> https://github.com/confluentinc/kafka-rest/pull/89 The JSON support > does > >> not interact with the schema registry at all. If you're ok building your > >> own version from trunk you could use that, or this will be released with > >> our next platform version. > >> > >> In the REST proxy, each HTTP requests will result in one call to > >> producer.send(). Under the hood, the new producer will automatically > >>batch > >> requests. The default settings will only batch when it's necessary > >>(because > >> there are already too many outstanding requests, so messages pile up in > >>the > >> local buffer), so you get the advantages of batching, but with a lower > >> request rate the messages will still be sent to the broker immediately. > >> > >> -Ewen > >> > >> On Wed, Aug 26, 2015 at 9:31 PM, Hemanth Abbina > >><heman...@eiqnetworks.com> > >> wrote: > >> > >>> Ewen, > >>> > >>> Thanks for the explanation. > >>> > >>> We have control over the logs format coming to HAProxy. Right now, > >>>these > >>> are plain JSON logs (just like syslog messages with few additional meta > >>> information) sent to HAProxy from remote clients using HTTPs. No > >>> serialization is used. > >>> > >>> Currently, we have one log each of the HTTP request. I understood that > >>> every request is produced individually without batching. > >>> > >>> Will this work with REST proxy, without using schema registry ? > >>> > >>> --regards > >>> Hemanth > >>> > >>> -----Original Message----- > >>> From: Ewen Cheslack-Postava [mailto:e...@confluent.io] > >>> Sent: Thursday, August 27, 2015 9:14 AM > >>> To: users@kafka.apache.org > >>> Subject: Re: Http Kafka producer > >>> > >>> Hemanth, > >>> > >>> Can you be a bit more specific about your setup? Do you have control > >>>over > >>> the format of the request bodies that reach HAProxy or not? If you do, > >>> Confluent's REST proxy should work fine and does not require the Schema > >>> Registry. It supports both binary (encoded as base64 so it can be > >>>passed > >>> via the JSON request body) and Avro. With Avro it uses the schema > >>>registry, > >>> but the binary mode doesn't require it. > >>> > >>> If you don't have control over the format, then the REST proxy is not > >>> currently designed to support that use case. I don't think HAProxy can > >>> rewrite request bodies (beyond per-line regexes, which would be hard to > >>> make work), so that's not an option either. It would certainly be > >>>possible > >>> to make a small addition to the REST proxy to allow binary request > >>>bodies > >>> to be produced directly to a topic specified in the URL, though you'd > >>>be > >>> paying pretty high overhead per message -- without the ability to > >>>batch, > >>> you're doing one HTTP request per messages. This might not be bad if > >>>your > >>> messages are large enough? (Then again, the same issue applies > >>>regardless > >>> of what solution you end up with if each of the requests to HAProxy > >>>only > >>> contains one message). > >>> > >>> -Ewen > >>> > >>> > >>> > >>> On Wed, Aug 26, 2015 at 5:05 PM, Hemanth Abbina > >>><heman...@eiqnetworks.com> > >>> wrote: > >>> > >>>> Marc, > >>>> > >>>> Thanks for your response. Let's have more details on the problem. > >>>> > >>>> As I already mentioned in the previous post, here is our expected data > >>>> flow: logs -> HAProxy -> {new layer } -> Kafka Cluster > >>>> > >>>> The 'new layer' should receive logs as HTTP requests from HAproxy and > >>>> produce the same logs to Kafka without loss. > >>>> > >>>> Options that seems to be available, are 1. Flume: It has a HTTP source > >>>> & Kafka sink, but the documentation says HTTP source is not for > >>>> production use. > >>>> 2. Kafka Rest Proxy: Though this seems to be fine, adding another > >>>> dependency of Schema Registry servers to validate the schema, which > >>>> should be again used by the consumers. > >>>> 3. Custom plugin to handle this functionality: Though the > >>>> functionality seems to be simple - scalability, reliability aspects > >>>> and maintenance would be more. > >>>> > >>>> Thanks > >>>> Hemanth > >>>> > >>>> -----Original Message----- > >>>> From: Marc Bollinger [mailto:m...@lumoslabs.com] > >>>> Sent: Thursday, August 27, 2015 4:39 AM > >>>> To: users@kafka.apache.org > >>>> Cc: dev-subscr...@kafka.apache.org > >>>> Subject: Re: Http Kafka producer > >>>> > >>>> I'm actually also really interested in this...I had a chat about this > >>>> on the distributed systems slack's <http://dist-sys.slack.com> Kafka > >>>> channel a few days ago, but we're not much further than griping about > >>> the problem. > >>>> We're basically migrating an existing event system, one which packed > >>>> messages into files, waited for a time-or-space threshold to be > >>>> crossed, then dealt with distribution in terms of files. Basically, > >>>> we'd like to keep a lot of those semantics: we can acknowledge success > >>>> on the app server as soon as we've flushed to disk, and rely on the > >>>> filesystem for durability, and total order across the system doesn't > >>>> matter, as the HTTP PUTs sending the messages are load balanced across > >>>> many app servers. We also can tolerate [very] long downstream event > >>>> system outages, because...we're ultimately just writing sequentially > >>>> to disk, per process (I should mention that this part is in Rails, > >>>> which means we're dealing largely in terms of processes, not threads). > >>>> > >>>> RocksDB was mentioned in the discussion, but spending exactly 5 > >>>> minutes researching that solution, it seems like the dead simplest > >>>> solution on an app server in terms of moving parts (multiple processes > >>>> writing, one process reading/forwarding to Kafka) wouldn't work well > >>> with RocksDB. > >>>> Although now that I'm looking at it more, it looks like they're > >>>> working on a MySQL storage engine? > >>>> > >>>> Anyway yeah, I'd love some discussion on this, or war stories of > >>>> migration to Kafka from other event systems (F/OSS or...bespoke). > >>>> > >>>> On Wed, Aug 26, 2015 at 3:45 PM, Hemanth Abbina > >>>> <heman...@eiqnetworks.com> > >>>> wrote: > >>>> > >>>>> Hi, > >>>>> > >>>>> Our application receives events through a HAProxy server on HTTPs, > >>>>> which should be forwarded and stored to Kafka cluster. > >>>>> > >>>>> What should be the best option for this ? > >>>>> This layer should receive events from HAProxy & produce them to > >>>>> Kafka cluster, in a reliable and efficient way (and should scale > >>> horizontally). > >>>>> > >>>>> Please suggest. > >>>>> > >>>>> --regards > >>>>> Hemanth > >>> > >>> > >>> > >>> -- > >>> Thanks, > >>> Ewen > >> > >> > >> > >> -- > >> Thanks, > >> Ewen > > -- Thanks, Ewen
