Does Kafka use Consistent Hashing?

Yes, Kafka uses consistent hashing to distribute partitions across brokers in a Kafka cluster. This approach ensures that each message is assigned to a specific partition based on a consistent hashing algorithm, which helps in achieving load balancing and fault tolerance in the Kafka cluster.

1. Partitioning

Kafka topics are divided into partitions, each of which is replicated across multiple brokers for fault tolerance. When a producer sends a message to a topic, Kafka needs to determine which partition of the topic the message should be sent to.

2. Consistent Hashing

Kafka uses a consistent hashing algorithm to map each message key to a specific partition. The consistent hashing algorithm ensures that messages with the same key are always assigned to the same partition, which helps in maintaining the order of messages with the same key.

3. Partition Assignment

Kafka brokers maintain metadata about the topic partitions and their respective leaders (the leader is the broker responsible for handling reads and writes for a partition). When a message is produced for a topic, the producer uses the consistent hashing algorithm to determine the partition for the message based on its key.

4. Load Balancing

Consistent hashing helps in distributing messages evenly across partitions and brokers, which helps in achieving load balancing. It also ensures that if a new broker is added to the cluster or an existing broker goes down, only a subset of partitions need to be reassigned, minimizing the impact on the system.

Overall, consistent hashing in Kafka helps in achieving scalability, fault tolerance, and efficient message routing in distributed systems.