Kafka producer and partitions

There are only a few possible ways to specify partitions while using the Kafka Producer API

• Just specify it in the ProducerRecord itself
• If key is not null, (by default) Kafka will hash your key and calculate the partition
• If key is null, (by default) Kafka will round-robin b/w all the partitions (to load balance the data)
• If not, just use a custom Partitioner

If interested, you can also check out the Kafka Partitioning blog

Cheers!