Choreography-Based Saga

Choreography-Based Saga Overview

At its core, choreography-based saga is about doing one thing well inside your Apache Kafka project. Once you understand the pattern, you can apply it consistently across features and teams.

Good choreography-based saga pays off across the whole codebase: fewer surprises, easier testing, and smoother onboarding. The snippet below is a solid starting point.

// each service reacts to events and emits new ones
await consumer.subscribe({ topic: 'payment-completed' });
await consumer.run({
  eachMessage: async ({ message }) => {
    const payment = JSON.parse(message.value.toString());
    await producer.send({
      topic: 'order-confirmed',
      messages: [{ key: payment.orderId, value: JSON.stringify(payment) }],
    });
  },
});

Event-driven services stay decoupled by reacting to and emitting Kafka events.

Choreography-Based Saga Example

import { Kafka } from 'kafkajs';

const kafka = new Kafka({ clientId: 'app', brokers: ['localhost:9092'] });
const producer = kafka.producer();
const consumer = kafka.consumer({ groupId: 'group' });

• Start from a minimal Choreography-Based Saga example and grow it only as needed.
• Keep configuration explicit so Choreography-Based Saga behaves the same in every environment.
• Name things clearly so teammates understand your Choreography-Based Saga at a glance.
• Add tests around Choreography-Based Saga early to lock in expected behaviour.

Apache Kafka Cheatsheet

Handy KafkaJS reference related to choreography-based saga.

How Choreography-Based Saga Works in Apache Kafka

Choreography-Based Saga builds on Kafka's log-based design, where producers append events to partitioned topics and consumer groups read them independently, tracking their own offsets.

Event-driven services stay decoupled by reacting to and emitting Kafka events.

• Topics are split into partitions for parallelism and ordering per key.
• Producers choose a partition, usually by message key.
• Consumer groups share partitions so work scales horizontally.
• Offsets record how far each group has read.

Practical Guidance for Choreography-Based Saga

In production, choreography-based saga needs attention to delivery guarantees, retries, and observability. Make handlers idempotent and monitor consumer lag closely.

Common Mistakes

• Copying choreography-based saga snippets without understanding what each line does.
• Skipping error handling and edge cases when wiring up choreography-based saga.
• Leaving choreography-based saga untested, so regressions slip into production.
• Over-engineering choreography-based saga before you actually need the extra flexibility.

Key Takeaways

• Choreography-Based Saga is a core part of working effectively with Apache Kafka.
• Start small and keep choreography-based saga focused on a single responsibility.
• Apply consistent patterns so choreography-based saga scales across your project.
• Test and document choreography-based saga to keep it maintainable over time.