kafka-streams-cogroup

Kafka Streams Cogroup

This module demonstrates the following:

• The usage of the Kafka Streams DSL, including cogroup(), groupBy(), aggregate(), toStream() and peek().
• Unit testing using Topology Test Driver.

In this module, records of type <String, KafkaPerson> are streamed from two topics named PERSON_TOPIC and PERSON_TOPIC_TWO. The streams are processed using the Kafka Streams DSL to perform cogrouping based on the last name of each KafkaPerson record. The following tasks are performed:

1. Group the streams by last name using the groupBy() operation.
2. Apply a cogroup operation to combine the records from both streams with the same last name.
3. Apply an aggregator that combines each KafkaPerson record with the same last name into a KafkaPersonGroup object and aggregates the first names by last name.
4. Write the resulting records to a new topic named PERSON_COGROUP_TOPIC.

The output records will be in the following format:

{"firstNameByLastName":{"Last name 1":{"First name 1", "First name 2", "First name 3"}}}
{"firstNameByLastName":{"Last name 2":{"First name 4", "First name 5", "First name 6"}}}
{"firstNameByLastName":{"Last name 3":{"First name 7", "First name 8", "First name 9"}}}

Requirements

To compile and run this demo, you will need the following:

• Java 21
• Maven
• Docker

Running the Application

To run the application manually, please follow the steps below:

• Start a Confluent Platform in a Docker environment.
• Produce records of type <String, KafkaPerson> to topics named PERSON_TOPIC and PERSON_TOPIC_TWO. You can use the producer person to do this.
• Start the Kafka Streams.

To run the application in Docker, please use the following command:

docker-compose up -d

This command will start the following services in Docker:

• 1 Kafka broker KRaft
• 1 Schema registry
• 1 Control Center
• 1 producer Person
• 1 Kafka Streams Cogroup