rabbitmq 消费者成为生产者

Question

我在消费者内部接收来自 RabbitMQ 的消息。我必须处理该消息并将处理后的消息发布到不同的队列中。我将如何做到这一点？

我的代码是

using (IConnection connection = factory.CreateConnection())
{
    using (IModel channel = connection.CreateModel())
    {
        if (!String.IsNullOrEmpty(EXCHANGE_NAME))
            channel.ExchangeDeclare(EXCHANGE_NAME, ExchangeType.Direct, durable);

        if (!String.IsNullOrEmpty(QUEUE_NAME))
            channel.QueueDeclare(QUEUE_NAME, false, false, false, null);

        string data = "";
        EventingBasicConsumer consumer = new EventingBasicConsumer();
        consumer.Received += (o, e) =>
        {
            //This is the received message
            data = data + Encoding.ASCII.GetString(e.Body) + Environment.NewLine;
            string processed_data = "processed data = " + data; 
            //I want to write some code here to post the processed message to a different queue.
            //or other idea is "can I use duplex services? 

        };
        string consumerTag = channel.BasicConsume(QUEUE_NAME, true, consumer);

        channel.QueueBind(QUEUE_NAME, EXCHANGE_NAME, ROUTING_KEY, null);
        channel.QueueUnbind(QUEUE_NAME, EXCHANGE_NAME, ROUTING_KEY, null);
    }
}

Answer 1

底线是您可以共享线程之间的连接，但不能共享通道。因此，在您的示例中，您可以使用相同的连接，但是当您想要发布时需要创建一个新通道（因为 consumer.Received 事件将在不同的线程上引发）：

using (IConnection connection = factory.CreateConnection())
{
    using (IModel channel = connection.CreateModel())
    {
        if (!String.IsNullOrEmpty(EXCHANGE_NAME))
            channel.ExchangeDeclare(EXCHANGE_NAME, ExchangeType.Direct, durable);

        if (!String.IsNullOrEmpty(QUEUE_NAME))
            channel.QueueDeclare(QUEUE_NAME, false, false, false, null);

        string data = "";
        EventingBasicConsumer consumer = new EventingBasicConsumer();
        consumer.Received += (o, e) =>
        {
            //This is the received message
            data = data + Encoding.ASCII.GetString(e.Body) + Environment.NewLine;
            string processed_data = "processed data = " + data; 
            //I want to write some code here to post the processed message to a different queue.
            //or other idea is "can I use duplex services? 

            using (IModel channel = connection.CreateModel())
            {
                channel.Publish( ... );
            }

        };
        string consumerTag = channel.BasicConsume(QUEUE_NAME, true, consumer);

        channel.QueueBind(QUEUE_NAME, EXCHANGE_NAME, ROUTING_KEY, null);
        channel.QueueUnbind(QUEUE_NAME, EXCHANGE_NAME, ROUTING_KEY, null);

        // don't dispose of your channel until you've finished consuming
    }

    // don't dispose of your connection until you've finished consuming
}

确保在您想停止消费之前不要处置您的消费渠道。连接也是如此。这是一个常见的错误。