多 Broker（或集群）支持

Doubao 中英对照 Multiple Broker (or Cluster) Support

2.3 版本为单个应用程序与多个 broker 或 broker 集群之间的通信增加了更多便利。在消费者一侧，主要好处是基础设施可以自动将自动声明的队列关联到相应的 broker。

下面用一个例子最能说明这一点：

@SpringBootApplication(exclude = RabbitAutoConfiguration.class)
public class Application {

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

    @Bean
    CachingConnectionFactory cf1() {
        return new CachingConnectionFactory("localhost");
    }

    @Bean
    CachingConnectionFactory cf2() {
        return new CachingConnectionFactory("otherHost");
    }

    @Bean
    CachingConnectionFactory cf3() {
        return new CachingConnectionFactory("thirdHost");
    }

    @Bean
    SimpleRoutingConnectionFactory rcf(CachingConnectionFactory cf1,
            CachingConnectionFactory cf2, CachingConnectionFactory cf3) {

        SimpleRoutingConnectionFactory rcf = new SimpleRoutingConnectionFactory();
        rcf.setDefaultTargetConnectionFactory(cf1);
        rcf.setTargetConnectionFactories(Map.of("one", cf1, "two", cf2, "three", cf3));
        return rcf;
    }

    @Bean("factory1-admin")
    RabbitAdmin admin1(CachingConnectionFactory cf1) {
        return new RabbitAdmin(cf1);
    }

    @Bean("factory2-admin")
    RabbitAdmin admin2(CachingConnectionFactory cf2) {
        return new RabbitAdmin(cf2);
    }

    @Bean("factory3-admin")
    RabbitAdmin admin3(CachingConnectionFactory cf3) {
        return new RabbitAdmin(cf3);
    }

    @Bean
    public RabbitListenerEndpointRegistry rabbitListenerEndpointRegistry() {
        return new RabbitListenerEndpointRegistry();
    }

    @Bean
    public RabbitListenerAnnotationBeanPostProcessor postProcessor(RabbitListenerEndpointRegistry registry) {
        MultiRabbitListenerAnnotationBeanPostProcessor postProcessor
                = new MultiRabbitListenerAnnotationBeanPostProcessor();
        postProcessor.setEndpointRegistry(registry);
        postProcessor.setContainerFactoryBeanName("defaultContainerFactory");
        return postProcessor;
    }

    @Bean
    public SimpleRabbitListenerContainerFactory factory1(CachingConnectionFactory cf1) {
        SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
        factory.setConnectionFactory(cf1);
        return factory;
    }

    @Bean
    public SimpleRabbitListenerContainerFactory factory2(CachingConnectionFactory cf2) {
        SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
        factory.setConnectionFactory(cf2);
        return factory;
    }

    @Bean
    public SimpleRabbitListenerContainerFactory factory3(CachingConnectionFactory cf3) {
        SimpleRabbitListenerContainerFactory factory = new SimpleRabbitListenerContainerFactory();
        factory.setConnectionFactory(cf3);
        return factory;
    }

    @Bean
    RabbitTemplate template(SimpleRoutingConnectionFactory rcf) {
        return new RabbitTemplate(rcf);
    }

    @Bean
    ConnectionFactoryContextWrapper wrapper(SimpleRoutingConnectionFactory rcf) {
        return new ConnectionFactoryContextWrapper(rcf);
    }

}

@Component
class Listeners {

    @RabbitListener(queuesToDeclare = @Queue("q1"), containerFactory = "factory1")
    public void listen1(String in) {

    }

    @RabbitListener(queuesToDeclare = @Queue("q2"), containerFactory = "factory2")
    public void listen2(String in) {

    }

    @RabbitListener(queuesToDeclare = @Queue("q3"), containerFactory = "factory3")
    public void listen3(String in) {

    }

}

如你所见，我们声明了 3 套基础设施（连接工厂、admin、容器工厂）。如前所述，@RabbitListener 可以指定使用哪个容器工厂；本例中它们还使用了 queuesToDeclare，如果队列不存在，就会在 broker 上声明该队列。通过按 <容器工厂名>-admin 的约定命名 RabbitAdmin bean，基础设施就能确定应由哪个 admin 来声明队列。这对于 bindings = @QueueBinding(…​) 同样有效，届时交换机和绑定也会被声明。它不适用于 queues，因为 queues 要求队列已经存在。

在生产者一侧，提供了一个便捷的 ConnectionFactoryContextWrapper 类，使 RoutingConnectionFactory（参见路由连接工厂）的使用更加简单。

如你在上面所见，已经添加了一个 SimpleRoutingConnectionFactory bean，其路由键为 one、two 和 three。还有一个使用该工厂的 RabbitTemplate。下例展示了如何使用该模板配合包装器路由到其中一个 broker 集群。

@Bean
public ApplicationRunner runner(RabbitTemplate template, ConnectionFactoryContextWrapper wrapper) {
    return args -> {
        wrapper.run("one", () -> template.convertAndSend("q1", "toCluster1"));
        wrapper.run("two", () -> template.convertAndSend("q2", "toCluster2"));
        wrapper.run("three", () -> template.convertAndSend("q3", "toCluster3"));
    };
}