Message consumers

The consumer is any one who subscribes for topics in Kafka. Each consumer belongs to a consumer group and some consumer groups contains multiple consumers. Consumers are an interesting part of Kafka and we will cover them in detail.

So, it's clear that groups play an important role; in Kafka's initial version, Zookeeper was used for group management, but in the latest version, Kafka has its own group protocol built in. One of the brokers will act as a group coordinator and will be responsible for assigning and managing partitions for groups. We will talk about Zookeeper and its own protocol in later chapters specific to the consumer.

Remember that we talked about assigning an offset to a message in a partition; each consumer reads the offset and commits the offset to the group coordinator or Zookeeper. So if consumers fail for any reason, it will start from the next message of the committed offset.