Question

我正在尝试创建tutorial #5中提到的主题交换与tutorial #6中提到的RPC的组合，虽然它只运行一次，但除非重新启动使用者代码，否则它不会再次运行

在使用RabbitMQ服务器的机器上运行的客户端代码中，我有register_request（）接收消息（来自Flask的更高级别）并根据路由密钥将其添加到交换机，然后等待回应。回调reply_queue_callback（）将响应添加到字典，其中键是相关ID。

class QueueManager(object):
    def __init__(self):
        """
        Initializes an exchange and a reply queue.
        """
        self.responses = {}

        self.connection = pika.BlockingConnection(pika.ConnectionParameters(host="localhost"))
        atexit.register(self.close_connection)

        self.channel = self.connection.channel()
        self.channel.exchange_declare(exchange=EXCHANGE_NAME, type="topic")
        result = self.channel.queue_declare(exclusive=True)
        self.reply_queue = result.method.queue
        self.channel.basic_consume(self.reply_queue_callback, no_ack=True, queue=self.reply_queue)


    def close_connection(self):
        """
        Closes the connection to RabbitMQ. Runs upon destruction of the instance.
        """
        print "*** Closing queue connection..."
        self.connection.close()


    def reply_queue_callback(self, ch, method, props, body):
        """
        A callback that is executed when there's a new message in the reply queue.
        """
        self.responses[props.correlation_id] = literal_eval(body)


    def register_request(self, routing_key, message):
        """
        Adds a message to the exchange.
        """
        corr_id = str(uuid.uuid4())
        self.channel.basic_publish(exchange=EXCHANGE_NAME, routing_key=routing_key,
                                   properties=pika.BasicProperties(
                                       reply_to=self.reply_queue,
                                       correlation_id=corr_id),
                                   body=message)
        print "*** Sent request with correlation ID", corr_id
        return corr_id


    def fetch_response(self, corr_id):
        """
        A polling function that waits for a message in the reply queue.
        """
        print "Waiting for a response..."
        while not self.responses.get(corr_id):
            self.connection.process_data_events()

        return self.responses.pop(corr_id)

在另一台机器上运行的消费者代码中，receive_requests（）是主函数，request_callback（）是新消息的回调函数。

def request_callback(ch, method, props, message):
    """
    A callback that is executed when a relevant message is found in the exchange.
    """
    print "Pulled a request with correlation ID %s" % props.correlation_id
    response = produce_response(message)
    print "Produced a response, publishing..."
    ch.basic_publish(exchange="",
                     routing_key=props.reply_to,
                     properties=pika.BasicProperties(correlation_id=props.correlation_id),
                     body=response)
    ch.basic_ack(delivery_tag=method.delivery_tag)
    print " [*] Waiting for new messages\n"


def receive_requests():
    """
    The main loop. Opens a connection to the RabbitMQ server and consumes messages from the exchange.
    """
    connection = pika.BlockingConnection(pika.ConnectionParameters(host=RABBITMQ_IP))

    channel = connection.channel()
    channel.exchange_declare(exchange=EXCHANGE_NAME, type="topic")

    result = channel.queue_declare(exclusive=True)
    queue_name = result.method.queue

    for binding_key in BINDING_KEYS:
        channel.queue_bind(exchange=EXCHANGE_NAME, queue=queue_name, routing_key=binding_key)

    channel.basic_consume(request_callback, queue=queue_name, no_ack=True)

    try:
        print(" [*] Waiting for messages. To exit press CTRL+C\n")
        channel.start_consuming()
    except KeyboardInterrupt:
        print "Aborting..."

当我第一次生成消息时，消费者处理它并得到回复，但是第二条消息似乎没有任何消息到达消费者（客户端打印出它将新消息添加到交换机，但是消费者不打印任何东西）。我假设消费者出了问题，因为如果在第一条消息之后我重新启动消费者代码并保持客户端按原样运行，则第二条消息可以正常工作。

知道问题是什么吗？也许我在消费者的回调中缺少一些东西？

RabbitMQ主题交换和RPC的组合只能工作一次

0 个答案: