Can you explain what the term 'Consumer' means in the context of message exchange systems or data processing?

In the context of messaging or data processing systems, the term "Consumer" refers to a component or service that receives and processes messages or data coming from a queue, topic, or other source.

For example, in a message broker system (like Kafka, RabbitMQ), the Producer is the one who sends messages, and the Consumer is the one who reads and processes them. A Consumer can perform various actions: saving data to a database, executing business logic, sending notifications.

Example in Java using Kafka Consumer:

KafkaConsumer<String, String> consumer = new KafkaConsumer<>(props);
consumer.subscribe(Arrays.asList("my-topic"));
while (true) {
    ConsumerRecords<String, String> records = consumer.poll(Duration.ofMillis(100));
    for (ConsumerRecord<String, String> record : records) {
        System.out.printf("Received message: key = %s, value = %s%n", record.key(), record.value());
        // message processing
    }
}

Thus, a Consumer is an active receiver and processor of data in a messaging architecture.