Spring MultiRabbit is a library to enable multiple RabbitMQ brokers in SpringBoot applications. The modules are:

• spring-multirabbit - the main module, that provides the auto-configuration feature;
• spring-multirabbit-example-java - an example project in Java;
• spring-multirabbit-example-kotlin - an example project in Kotlin;
• spring-multirabbit-extension-example - an example project of how to extend spring-multirabbit;

To use the library, the project must:

1. Be a SpringBoot project annotated with @EnableRabbit, as usual;
2. Import the library spring-multirabbit;
3. Enable MultiRabbit by setting spring.multirabbitmq.enabled=true. By default, MultiRabbit is disabled.
4. Provide configuration for additional brokers under spring.multirabbitmq.connections. All attributes available for spring.rabbitmq can be used under spring.multirabbitmq.connections.
5. Change the container factory context when using non-default connections:
   1. For RabbitTemplate, use SimpleResourceHolder.bind() and SimpleResourceHolder.unbind();
   2. For @RabbitListener, define the containerFactory or leave it blank for the default connection.

@EnableRabbit
@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

Add the reference to the repository, and the necessary libs:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-amqp</artifactId>
    </dependency>
    <dependency>
        <groupId>com.free-now.multirabbit</groupId>
        <artifactId>spring-multirabbit</artifactId>
        <version>${multirabbit.version}</version>
    </dependency>
</dependencies>

spring:
    rabbitmq:
        host: 10.0.0.10
        port: 5672
    multirabbitmq:
        enabled: true
        connections:
            connectionNameA:
                host: 200.10.10.10
                port: 5672
            connectionNameB:
                host: 173.49.20.18
                port: 5672

@Autowired
private RabbitTemplate rabbitTemplate;

void someMethod() {
    SimpleResourceHolder.bind(rabbitTemplate.getConnectionFactory(), "connectionNameA");
    try {
        rabbitTemplate.convertAndSend("someExchange", "someRoutingKey", "someMessage"); // Use RabbitTemplate
    } finally {
        SimpleResourceHolder.unbind(rabbitTemplate.getConnectionFactory());
    }
}

/**
 * Listener for the default connection. 
 */
@RabbitListener(queues = "someQueue")
void someListener(String message) {
    // Consume message
}

/**
 * Listener for the broker tagged as `connectionNameA`. 
 */
@RabbitListener(queues = "anotherQueue", containerFactory = "connectionNameA") 
void anotherListener(String message) {
    // Consume message
}

This library enables the possibility of having multiple RabbitMQ brokers, configured from the property spring.multirabbitmq. However, for maximum compatibility, it does not change the default capacity of configuring a connection with the existent spring.rabbitmq property.

Thus, it's important to understand how the application will behave when multiple configurations are provided:

• Unlimited number of connections can be set, but the user must be aware of the implications of maintaining them;
• The default server spring.rabbitmq will always exist, even if not explicitly defined.
  • EXCEPT when one server under spring.multirabbit is set with defaultConnection: true. In this case, any configuration provided with the default spring.rabbitmq will be ignored.
• It's not possible to have more than one connection under spring.multirabbit being set with defaultConnection: true.

This is the most simple scenario where only one Rabbit server is needed. In this case, the application does not even need the spring-multirabbit library. No different behavior is expected and no need for Rabbit context change.

spring:
    rabbitmq:
        host: localhost
        port: 5672

This scenario is tricky and must be well understood, since the behavior of Spring will enforce the creation of the default connection using spring.rabbitmq even when it's not provided. The same will happen here. The following example will instantiate 3 connections, which one of them is the default, configured with default parameters. To use any of the connections under spring.multirabbitmq.connections, the connection factory context must be provided.

spring:
    multirabbitmq:
        enabled: true
        connections:
            connectionNameA:
                host: localhost
                port: 5673
            connectionNameB:
                host: localhost
                port: 5674

This scenario is pretty straightforward, since there will be no implicit connection. In this case, there will exist 2 connections, and the connection connectionNameA can be accessed with or without definition of context, since it's the default connection.

spring:
    multirabbitmq:
        enabled: true
        defaultConnection: connectionNameA
        connections:
            connectionNameA:
                host: localhost
                port: 5673
            connectionNameB:
                host: localhost
                port: 5674

In this scenario, 3 connections will be available, the ones under spring.multirabbit will require context.

spring:
    rabbitmq:
        host: localhost
        port: 5672
    multirabbitmq:
        enabled: true
        connections:
            connectionNameA:
                host: localhost
                port: 5673
            connectionNameB:
                host: localhost
                port: 5674

In this scenario, only 2 connections will be available. Since there is one set explicitly as default, the one provided at spring.rabbitmq will be ignored. The connection connectionNameA can be accessed with or without Rabbit context.

spring:
    rabbitmq:
        host: localhost
        port: 5672
    multirabbitmq:
        enabled: true
        connections:
            connectionNameA:
                defaultConnection: true
                host: localhost
                port: 5672
            connectionNameB:
                host: localhost
                port: 5672

For the table of compatibility, please visit the Wiki page.

More examples can be found at the modules spring-multirabbit-example-java and spring-multirabbit-example-kotlin. As listeners are defined, they will try to connect in 3 different addresses:

• localhost:5672;
• localhost:5673;
• localhost:5674.

To easily provide RabbitMQ connections for the applications, you can create 3 Docker containers:

docker run -d -p 5672:5672 -p 15672:15672 rabbitmq:3-management; \
docker run -d -p 5673:5672 -p 15673:15672 rabbitmq:3-management; \
docker run -d -p 5674:5672 -p 15674:15672 rabbitmq:3-management

You need to create the Exchange, Queue and Bind them with a Routing Key:

• Exchange: sampleExchange
• Queue: sampleQueue
• Routing Key: sampleRoutingKey

To send messages to the different servers, run:

curl -X POST http://localhost:8080 -H 'Content-Type: application/json' -d "someMessage"
curl -X POST http://localhost:8080?connection=connectionNameA -H 'Content-Type: application/json' -d "someMessage"
curl -X POST http://localhost:8080?connection=connectionNameB -H 'Content-Type: application/json' -d "someMessage"