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 <jasonjwwilliams@gmail.com>
Reply: user@flume.apache.org <user@flume.apache.org>
Date: 7 June 2016 at 09:43:34
To: user@flume.apache.org <user@flume.apache.org>
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 <chris@hor.rocks> 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 (jasonjwwilliams@gmail.com) 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


Kafka topic config: kafka-topics --zookeeper localhost/kafka --create --topic activity.history --partitions 20 --replication-factor 1



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