Kafka Intermediate: Kafka Streams Joins

Kafka Streams provides powerful capabilities for joining streams and tables, enabling complex data processing tasks such as aggregations and lookups. This guide covers the key concepts and methods for performing joins in Kafka Streams applications.

1. Types of Joins in Kafka Streams

Kafka Streams supports different types of joins, each suited for various use cases:

• Stream-Stream Join: Joins two streams based on a common key, combining their values.
• Stream-Table Join: Joins a stream with a table (or state store), where the stream’s records are enriched with data from the table.
• Table-Table Join: Joins two tables, which is less common but useful for certain use cases.

2. Stream-Stream Joins

Stream-stream joins are used to combine two streams of data based on a common key. This type of join is useful for scenarios where you have two streams of related data and need to combine their values.

import org.apache.kafka.streams.KafkaStreams;
import org.apache.kafka.streams.StreamsBuilder;
import org.apache.kafka.streams.StreamsConfig;
import org.apache.kafka.streams.kstream.KStream;
import org.apache.kafka.streams.kstream.Joined;
import org.apache.kafka.streams.kstream.Materialized;
import org.apache.kafka.streams.kstream.Produced;
import org.apache.kafka.streams.state.Stores;
import java.util.Properties;

public class StreamStreamJoinExample {
    public static void main(String[] args) {
        // Step 1: Set up properties for the Kafka Streams application