kafka-streams-left-join-stream-table

Kafka Streams Left Join Stream Table

This module demonstrates the following:

• The usage of the Kafka Streams DSL, including leftJoin() between KStream and KTable, selectKey() and peek().
• Unit testing using Topology Test Driver.

In this module, records of type <String, KafkaPerson> are streamed from a topic named PERSON_TOPIC, and records of type <String, KafkaCountry> are streamed from a topic named COUNTRY_TOPIC. The following tasks are performed:

1. Join the two streams on the country code and create a new object KafkaJoinPersonCountry that contains the person and country information. If no country is matched for a person, a value holding the person is still emitted as a result of the leftJoin() operation.
2. Write the resulting KafkaJoinPersonCountry objects to a new topic named PERSON_COUNTRY_LEFT_JOIN_STREAM_TABLE_TOPIC.

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, KafkaCountry> to a topic named COUNTRY_TOPIC. You can use the producer country to do this.
• Produce records of type <String, KafkaPerson> to a topic named PERSON_TOPIC. 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 Country
• 1 producer Person
• 1 Kafka Streams Left Loin Stream Table