Source Connectors

Source Connectors Overview

Source Connectors is a building block you will reach for often in Apache Kafka. It keeps related logic together and makes your intent obvious to reviewers and future maintainers.

When you learn source connectors properly, you avoid the guesswork that leads to bugs and rework. The example below shows the shape you will use in most real Apache Kafka projects.

// consume, transform, and re-produce (a simple stream stage)
await consumer.run({
  eachMessage: async ({ message }) => {
    const event = JSON.parse(message.value.toString());
    const enriched = { ...event, receivedAt: Date.now() };
    await producer.send({
      topic: 'orders-enriched',
      messages: [{ key: event.id, value: JSON.stringify(enriched) }],
    });
  },
});

Stream processing consumes from one topic, transforms events, and produces to another.

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

Apache Kafka Cheatsheet

Handy KafkaJS reference related to source connectors.

How Source Connectors Works in Apache Kafka

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

Stream processing consumes from one topic, transforms events, and produces to another.

• 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 Source Connectors

In production, source connectors needs attention to delivery guarantees, retries, and observability. Make handlers idempotent and monitor consumer lag closely.

Common Mistakes

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

Key Takeaways

• Source Connectors is a core part of working effectively with Apache Kafka.
• Start small and keep source connectors focused on a single responsibility.
• Apply consistent patterns so source connectors scales across your project.
• Test and document source connectors to keep it maintainable over time.