In kafka, you can configure your payload with a message, message headers and message key. All these configurations are available within ProducerBuilder class.

#Configuring message headers

To configure the message headers, use the withHeaders method:

use Junges\Kafka\Facades\Kafka;

Kafka::publishOn('topic')
    ->withHeaders([
        'header-key' => 'header-value'
    ])

#Configure the message body

You can configure the message with the withMessage or withBodyKey methods.

The withMessage sets the entire message, and it accepts a Junges\Kafka\Message\Message::class instance as argument.

This is how you should use it:

use Junges\Kafka\Facades\Kafka;
use Junges\Kafka\Message\Message;

$message = new Message(
    headers: ['header-key' => 'header-value'],
    body: ['key' => 'value'],
    key: 'kafka key here'  
)

Kafka::publishOn('topic')->withMessage($message);

The withBodyKey method sets only a key in your message.

use Junges\Kafka\Facades\Kafka;

Kafka::publishOn('topic')->withBodyKey('key', 'value');

#Using Kafka Keys

In Kafka, keys are used to determine the partition within a log to which a message get's appended to. If you want to use a key in your message, you should use the withKafkaKey method:

use Junges\Kafka\Facades\Kafka;

Kafka::publishOn('topic')->withKafkaKey('your-kafka-key');