Rabbit MQ

ActiveMQ vs RabbitMQ vs Kafka

When to Use:

• ActiveMQ: Best suited for traditional enterprise systems, legacy JMS-based applications, and use cases requiring multiple protocol support.
• RabbitMQ: Ideal for modern cloud-native applications, microservices, real-time messaging, and scenarios requiring high throughput.
• Kafka: Designed for event-driven architectures, big data pipelines, real-time analytics, and scenarios requiring extremely high throughput and durability.

RabbitMQ is not popular anymore, we usually choose Kafka for large systems or choose a queue within cloud we use like Google pub/sub if you're using GCP (Google Cloud Platform) or Amazon Simple Queue Service (SQS).

Today we will learn about rabbitMQ to know basis about how a queue works

1. Producer (Provider Service)
   • Sends messages to an exchange in RabbitMQ.
   • Uses direct, topic, fanout, or headers exchanges depending on routing needs.
2. Broker (RabbitMQ Server)
   • Routes messages to queues based on exchange type.
3. Consumer (Public Subscriber)
   • Listens to queues and processes messages.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-amqp</artifactId>
</dependency>

docker-compose.yml

services:
  rabbitmq:
    image: rabbitmq:3.12-management  # Includes the web management UI
    container_name: rabbitmq
    restart: always
    environment:
      RABBITMQ_DEFAULT_USER: admin
      RABBITMQ_DEFAULT_PASS: admin
    ports:
      - "5672:5672"   # AMQP protocol port
      - "15672:15672" # Management UI port
    volumes:
      - rabbitmq_data:/var/lib/rabbitmq  # Persist RabbitMQ data

volumes:
  rabbitmq_data:
    driver: local

docker-compose up -d

In order to access web, using port 15672, http://localhost:15672

RabbitMQ Exchange types

RabbitMQ supports four main types of exchanges: Direct, Fanout, Topic, and Headers.

Exchange Type && When to Use

• Direct: Specific routing based on exact keys.
• Fanout: Broadcast to multiple consumers.
• Topic: Pattern-based routing (e.g., logs, multi-level keys).
• Headers: Advanced routing with custom attributes.

1. Direct Exchange (direct)

Routes messages to queues with an exact matching routing key

• Create a new queue: error_queue
• Create a new direct exchange: direct_exchange
• In direct_exchange, add binding to error_queue with routing key: error
• Write code to send message to direct_exchange
• Write code to receive message from error_queue queue

import org.springframework.amqp.core.Binding;
import org.springframework.amqp.core.BindingBuilder;
import org.springframework.amqp.core.DirectExchange;
import org.springframework.amqp.core.Queue;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class RabbitMQConfig {

    public static final String QUEUE_NAME = "error_queue";
    public static final String EXCHANGE_NAME = "direct_exchange";
    public static final String ROUTING_KEY = "error";
}

import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class MessageProducer {

    @Autowired
    private RabbitTemplate rabbitTemplate;

    public void sendMessage(String message) {
        rabbitTemplate.convertAndSend(RabbitMQConfig.EXCHANGE_NAME, RabbitMQConfig.ROUTING_KEY, message);        
    }
}

2. Fanout Exchange (fanout)

Broadcasts messages to all bound queues, ignoring routing keys.

• Create 2 new queues: log_queue_1, log_queue_2
• Create a new fanout exchange: log_exchange
• In log_exchange, add binding to log_queue_1, log_queue_2
• Write code to send message to log_exchange
• Write code to receive message from log_queue_1 and log_queue_2 queues

rabbitTemplate.convertAndSend("log_exchange", "", message);

3. Topic Exchange (topic)

Routes messages based on pattern matching in routing keys using:

• * → Matches one word.
• # → Matches multiple words.

Create 2 queues: app1_logs, app2_log

Create topic exchange: logs_topic

In logs_topic, create 2 binding to 2 queues

1. binding 1:
   • to queue: app1_log
   • routing key: logs.error.app1
2. binding 2:
   • to queue: app2_log
   • routing key: logs.info.app2

Send message to logs_topic with routing key: logs.*.app1

Only app1_log queue receive message.

4. Headers Exchange (headers)

Uses message headers (instead of routing keys) for routing.

• Create a queue: pdf_logs
• Create header exchange: logs_headers
  • format = pdf
• Send message to logs_headers with headers: {format: "pdf", type: "report" }

public void sendHeadersMessage() {
    MessageProperties messageProperties = new MessageProperties();
    messageProperties.setHeader("format", "pdf");
    messageProperties.setHeader("type", "report");

    Message msg = new Message("Here is a headers message".getBytes(StandardCharsets.UTF_8), messageProperties);
    rabbitTemplate.send("logs_headers", "", msg); // Headers exchange ignores routing keys        
}