It's by design of Kafka (and by extension flume). The producers are designed to be many-to-one (producers to partitions) and as such picking a random partition every 10 minutes prevents separate producer instances from all randomly picking the same partition.
-- Chris Horrocks From: Jason Williams <[email protected]> Reply: [email protected] <[email protected]> Date: 7 June 2016 at 09:43:34 To: [email protected] <[email protected]> Subject: Re: Kafka Sink random partition assignment Hey Chris, Thanks for help! Is that a limitation of the Flume Kafka sink or Kafka itself? Because when I use another Kafka producer and publish without a key, it randomly moves among the partitions on every publish. -J Sent via iPhone On Jun 7, 2016, at 00:08, Chris Horrocks <[email protected]> wrote: The producers bind to random partitions and move every 10 minutes. If you leave it long enough you should see it in the producer flume agent logs, although there's nothing to stop it from "randomly" choosing the same partition twice. Annoyingly there's no concept of producer groups (yet) to ensure that producers apportion the available partitions between them as this would create a synchronisation issue between what should be entirely independent processes. -- Chris Horrocks On 7 June 2016 at 00:32:29, Jason J. W. Williams ([email protected]) wrote: Hi, New to flume and I'm trying to relay log messages received over netcat source to Kafka sink. Everything seems to be fine, except that Flume is acting like it IS assigning a partition key to the produced messages though none is assigned. I'd like the messages to be assigned to a random partition, so that consumers are load balanced. * Flume 1.6.0 * Kafka 0.9.0.1 Flume config: https://gist.github.com/williamsjj/8ae025906955fbc4b5f990e162b75d7c Kafka topic config: kafka-topics --zookeeper localhost/kafka --create --topic activity.history --partitions 20 --replication-factor 1 Python consumer program: https://gist.github.com/williamsjj/9e67287f0154816c3a733a39ad008437 Test program (publishes to Flume): https://gist.github.com/williamsjj/1eb097a187a3edb17ec1a3913e47e58b Flume agent listens on 3132tcp for connections, and publishes messages received to the Kafka activity.history topic. I'm running two instances of the Python consumer. What happens however, is all logs messages get sent to a single Kafka consumer...if I restart Flume (leave consumers running) and re-run the test, all messages get published to the other consumer. So it feels like Flume is assigning a permanent partition key even though one is not defined (and should therefore be random). Any advice is greatly appreciated. -J
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