Behaviour definition for partitioners that assign partitions for produce requests.

A partitioner is responsible for determining which partition a message should be sent to when no explicit partition is provided.

Implementing a Custom Partitioner

To implement a custom partitioner, create a module that implements the assign_partition/4 callback:

defmodule MyApp.RoundRobinPartitioner do
  @behaviour KafkaEx.Producer.Partitioner

  def assign_partition(_topic, _key, _value, partition_count) do
    # Simple round-robin - in practice you'd want state for this
    :rand.uniform(partition_count) - 1
  end
end

Then configure it in your application:

config :kafka_ex, partitioner: MyApp.RoundRobinPartitioner

Built-in Partitioners

• KafkaEx.Producer.Partitioner.Default - Uses murmur2 hash of key for consistent partitioning, or random selection when no key is provided.