Producing Messages

This guide shows how to produce messages to Korvet using Kafka clients.

Using kafka-console-producer

The simplest way to produce messages:

kafka-console-producer --bootstrap-server localhost:9092 --topic my-topic

Type messages and press Enter to send each one.

Java Producer

Properties props = new Properties();
props.put("bootstrap.servers", "localhost:9092");
props.put("key.serializer", "org.apache.kafka.common.serialization.StringSerializer");
props.put("value.serializer", "org.apache.kafka.common.serialization.StringSerializer");

KafkaProducer<String, String> producer = new KafkaProducer<>(props);

ProducerRecord<String, String> record =
    new ProducerRecord<>("my-topic", "key", "value");

producer.send(record, (metadata, exception) -> {
    if (exception == null) {
        System.out.println("Sent to partition " + metadata.partition() +
                         " at offset " + metadata.offset());
    } else {
        exception.printStackTrace();
    }
});

producer.close();

Python Producer

from kafka import KafkaProducer

producer = KafkaProducer(bootstrap_servers='localhost:9092')

producer.send('my-topic', b'Hello, Korvet!')
producer.flush()

Message Format

Messages consist of:

Key (optional): Used for partitioning
Value: The message payload
Headers (optional): Key-value metadata
Timestamp: Automatically set if not provided

Partitioning

Messages are distributed across partitions based on:

Key hash: If a key is provided, messages with the same key go to the same partition
Round-robin: If no key is provided, messages are distributed evenly

Next Steps