Microservices with Clojure

Using Kafka as a messaging system

Kafka provides both queuing (http://en.wikipedia.org/wiki/Message_queue) and publish-subscribe (http://en.wikipedia.org/wiki/Publish-subscribe_pattern) constructs of a messaging system by the concept of a Consumer Group. The messages published on a topic partition are broadcasted to a consumer within each Consumer Group and within the Consumer Group, each consumer receives the messages from a different partition of a topic. Therefore, the number of consumers present in the Consumer Group must not be more than the number of partitions present in a topic. If they are more than the number of partitions, then they will be just sitting idle and will only get the message if one of the consumers fails within the ...