Spring AMQP空队列名问题：如何获取RabbitMQ生成的队列名？

场景与问题 #

我希望创建空名称队列，让RabbitMQ自动生成队列名称，代码如下：

var queue = QueueBuilder
    .durable("")
    .exclusive()
    .autoDelete().build();

var binding = BindingBuilder.bind(queue).to(exchange).with(bindingKey).noargs();
Declarables d = new Declarables(queue, binding);

但调用getActualName()返回的是：spring.gen-vuiRwjOmRkihAE8C72rbmw_awaiting_declaration

d.getDeclarablesByType(Queue.class).get(0).getActualName();

而RabbitMQ中的实际队列名称是：amq.gen-wpaYnybu9vOdD5v2ej66IQ

原因分析 #

查看Spring AMQP核心的Queue构造方法，可知当队列名称为空时，Spring会先生成一个临时名称：

public Queue(String name, boolean durable, boolean exclusive, boolean autoDelete,
        @Nullable Map<String, Object> arguments) {

    super(arguments);
    Assert.notNull(name, "'name' cannot be null");
    this.name = name;
    this.actualName = StringUtils.hasText(name) ? name
            : (Base64UrlNamingStrategy.DEFAULT.generateName() 
+ "_awaiting_declaration");
    this.durable = durable;
    this.exclusive = exclusive;
    this.autoDelete = autoDelete;
}

这个带_awaiting_declaration后缀的临时名称，是队列尚未被RabbitMQ实际声明时的标识。只有当队列被成功声明到RabbitMQ后，才能获取到RabbitMQ自动生成的真实名称。

使用自动命名队列的原因是为了避免竞争条件：

When auto-delete or exclusive queues use well-known (static) names, in case of client disconnection and immediate reconnection there will be a natural race condition between RabbitMQ nodes that will delete such queues and recovering clients that will try to re-declare them. This can result in client-side connection recovery failure or exceptions, and create unnecessary confusion or affect application availability.

补充场景与报错 #

我们通过RabbitAdmin bean初始化连接，调用d.setAdminsThatShouldDeclare(admin)，代码如下：

public Declarables someEventsDeclarables(
@Qualifier("rabbitAdmin") RabbitAdmin admin,
@Qualifier("AmqpExchange") Exchange exchange
) {
    final var bindingKey = somePrefix +".*." +someSuffix;
    final var cfg = new OurEventsDeclarables(
        exchange,
        "", // no queue name - RabbitMq generates it
        bindingKey,
        true
    );

    final var declarables = cfg.declarables();
    for (Declarable d : declarables.getDeclarables()) {
        d.setAdminsThatShouldDeclare(admin);
        admin.declareQueue();
    }
    return declarables;
}

运行集成测试时出现报错：

org.springframework.amqp.rabbit.listener.BlockingQueueConsumer$DeclarationException: Failed to declare queue(s):[spring.gen-QUh8ffN0TimELGG_kF1wFw_awaiting_declaration]

可行解决方案 #

通过手动声明队列并获取真实名称，再设置到队列对象中，最后声明绑定。在其他测试场景中可能需要将Declarables和AutoAckConsumer标记为@MockBean：

public class AmqpConfig{
...
@Bean("someEventsDeclarables")
public Declarables someEventsDeclarables(
@Qualifier("rabbitAdmin") RabbitAdmin admin,
@Qualifier("AmqpExchange") Exchange exchange
) {
final var bindingKey = somePrefix +".*." +someSuffix;
final var cfg = new OurEventsDeclarables(
    exchange,
    "", // no queue name - RabbitMq generates it
    bindingKey,
    true
);

final var declarables = cfg.declarables();

/** declare queue and bindings */
final List<Queue> queues = declarables.getDeclarablesByType(Queue.class);
final List<Binding> bindings = declarables.getDeclarablesByType(Binding.class);
if (queues.size() == 0) {
    throw new BeanCreationException("Queue for empty-queue-name is not found");
}
if (bindings.size() == 0) {
    throw new BeanCreationException("Binding for {} is not found of empty-queue-name", bindingKey);
}
Queue queue = queues.get(0);
Binding binding = bindings.get(0);
// 声明队列并获取RabbitMQ生成的真实名称
String declareQueue = admin.declareQueue(queue);
// 将真实名称设置到队列对象
queue.setActualName(declareQueue);
// 声明绑定
admin.declareBinding(binding);
return declarables;
}

内容的提问来源于stack exchange，提问作者Endre Moen