> ## Documentation Index
> Fetch the complete documentation index at: https://docs.litejoin.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Kafka Source

> Consume messages from Kafka topics using a consumer group.

# Kafka Source

The `kafka` source consumes messages from one or more Kafka topics using a consumer group.

## Configuration

```yaml theme={null}
sources:
  - type: kafka
    name: kafka-main
    topics:
      - orders
      - users
    config:
      brokers: "localhost:9092"
      group_id: "litejoin-consumer"
```

| Field      | Type      | Required | Description                                     |
| ---------- | --------- | -------- | ----------------------------------------------- |
| `brokers`  | string    | yes      | Comma-separated list of Kafka broker addresses. |
| `group_id` | string    | yes      | Consumer group ID.                              |
| `topics`   | string\[] | yes      | List of Kafka topics to consume from.           |

## Message Mapping

Kafka messages are mapped to LiteJoin messages as follows:

| Kafka Field | LiteJoin Field |
| ----------- | -------------- |
| Topic       | `topic`        |
| Key         | `key`          |
| Value       | `payload`      |
| Timestamp   | `timestamp`    |

## Example

Consume orders and users from Kafka, join them, and forward to a webhook:

```yaml theme={null}
sources:
  - type: kafka
    name: kafka-main
    topics:
      - orders
      - users
    config:
      brokers: "broker1:9092,broker2:9092"
      group_id: "litejoin-prod"

joins:
  - name: order-user-join
    query: |
      SELECT o.key, o.payload, u.payload
      FROM orders o
      INNER JOIN users u ON json_extract(o.payload, '$.user_id') = u.key
      WHERE o.timestamp > (strftime('%s', 'now') - 3600)
    sink: webhook-out

sinks:
  - type: http
    name: webhook-out
    config:
      url: "http://localhost:9000/webhook"
```

## When to Use

Use the Kafka source when:

* You already have a Kafka cluster producing events
* You want LiteJoin to enrich or join Kafka streams with other data sources
* You need consumer group semantics (offset management, partition assignment)

For systems without Kafka, use the [API Source](/sources/api-source) or [HTTP Source](/sources/http-source).