High Availability

# Join nodes to a cluster (on node 2 and 3)
rabbitmqctl stop_app
rabbitmqctl join_cluster rabbit@node1
rabbitmqctl start_app

# Verify cluster status
rabbitmqctl cluster_status

# Declare a quorum queue (AMQP 0-9-1 args)
@Bean
public Queue orderQueue() {
    return QueueBuilder.durable("orders.processing")
        .quorum()                                // x-queue-type=quorum
        .withArgument("x-quorum-initial-group-size", 3)  // 3 replicas
        .build();
}

// Quorum queue policy via rabbitmqctl
rabbitmqctl set_policy quorum-all ".*" \
  '{"x-queue-type":"quorum","x-quorum-initial-group-size":3}' \
  --apply-to queues

# HAProxy configuration for RabbitMQ AMQP (port 5672)
frontend rabbitmq_front
    bind *:5672
    default_backend rabbitmq_back

backend rabbitmq_back
    balance roundrobin
    option tcp-check
    server rabbit1 10.0.0.1:5672 check inter 5s
    server rabbit2 10.0.0.2:5672 check inter 5s
    server rabbit3 10.0.0.3:5672 check inter 5s

# Spring Boot application.properties — multiple broker addresses
spring.rabbitmq.addresses=10.0.0.1:5672,10.0.0.2:5672,10.0.0.3:5672
spring.rabbitmq.connection-timeout=5000

# Or use address-shuffle-mode=random for client-side load spreading
spring.rabbitmq.address-shuffle-mode=random

@Configuration
public class RabbitConfig {

    @Bean
    public CachingConnectionFactory connectionFactory() {
        CachingConnectionFactory factory = new CachingConnectionFactory();
        factory.setAddresses("rabbit1:5672,rabbit2:5672,rabbit3:5672");
        // Automatic recovery is ON by default in the underlying amqp-client
        factory.getRabbitConnectionFactory()
               .setAutomaticRecoveryEnabled(true);
        factory.getRabbitConnectionFactory()
               .setNetworkRecoveryInterval(5_000);

        // Enable publisher confirms for durability guarantee
        factory.setPublisherConfirmType(
            CachingConnectionFactory.ConfirmType.CORRELATED);
        return factory;
    }

    @Bean
    public RabbitTemplate rabbitTemplate(CachingConnectionFactory cf) {
        RabbitTemplate template = new RabbitTemplate(cf);
        template.setConfirmCallback((correlationData, ack, cause) -> {
            if (!ack) {
                log.error("Message NOT confirmed — cause: {}", cause);
                // re-queue or dead-letter the message
            }
        });
        return template;
    }
}