RabbitMQ消息队列（七）-通过fanout模式将消息推送到多个Queue中（.Net Core版）

前面第六章我们使用的是direct直连模式来进行消息投递和分发。本章将介绍如何使用fanout模式将消息推送到多个队列。 
有时我们会遇到这样的情况，多个功能模块都希望得到完整的消息数据。例如一个log的消息，一个我们希望输出在屏幕上实时监控，另外一个用户持久化日志。这时就可以使用fanout模式。fanout模式模式不像direct模式通过routingkey来进行匹配，而是会把消息发送到所以的已经绑定的队列中。

新建FanoutProduct用来发布消息。FanoutCustomerA和FanoutCustomerB用来订阅不同队列消费消息。

FanoutProduct代码：

using System;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;

namespace FanoutProduct
{
    class Program
    {
        static void Main(string[] args)
        {
            String exchangeName = "wytExchange";
            String message = "Hello World!";

            ConnectionFactory factory = new ConnectionFactory();
            factory.HostName = "192.168.63.129";
            factory.Port = ;
            factory.VirtualHost = "/wyt";
            factory.UserName = "wyt";
            factory.Password = "wyt";

            using (IConnection connection=factory.CreateConnection())
            {
                using (IModel channel=connection.CreateModel())
                {
                    channel.ExchangeDeclare(exchange: exchangeName, type: "fanout", durable: true, autoDelete: false, arguments: null);

                    IBasicProperties properties = channel.CreateBasicProperties();
                    properties.Persistent = true;

                    Task.Run(() =>
                    {
                        while (true)
                        {
                            for (int i = ; i < ; i++)
                            {
                                Byte[] body = Encoding.UTF8.GetBytes(message + i);
                                channel.BasicPublish(exchange: exchangeName, routingKey: "", basicProperties: properties, body: body);
                            }
                            Thread.Sleep();
                        }
                    }).Wait();

                    Console.WriteLine(" [x] Sent {0}", message);
                }
            }

            Console.WriteLine(" Press [enter] to exit.");
            Console.ReadLine();

        }
    }
}

FanoutCustomerA与FanoutCustomerB（代码相同）：

using System;
using System.Text;
using RabbitMQ.Client;
using RabbitMQ.Client.Events;

namespace FanoutCustomerA
{
    class Program
    {
        static void Main(string[] args)
        {
            String exchangeName = "wytExchange";

            ConnectionFactory factory = new ConnectionFactory();
            factory.HostName = "192.168.63.129";
            factory.Port = ;
            factory.VirtualHost = "/wyt";
            factory.UserName = "wyt";
            factory.Password = "wyt";

            using (IConnection connection=factory.CreateConnection())
            {
                using (IModel channel=connection.CreateModel())
                {
                    channel.ExchangeDeclare(exchange: exchangeName, type: "fanout", durable: true, autoDelete: false, arguments: null);

                    String queueName = channel.QueueDeclare().QueueName;

                    channel.QueueBind(queue: queueName, exchange: exchangeName, routingKey: "", arguments: null);

                    EventingBasicConsumer consumer = new EventingBasicConsumer(channel);
                    consumer.Received += (model, ea) =>
                    {
                        Byte[] body = ea.Body;
                        String message = Encoding.UTF8.GetString(body);
                        Console.WriteLine(" [x] {0}", message);
                    };

                    channel.BasicConsume(queue: queueName, autoAck: true, consumer: consumer);

                    Console.WriteLine(" Press [enter] to exit.");
                    Console.ReadLine();

                }
            }
        }
    }
}

可以看到FanoutCustomerA和FanoutCustomerB收到的消息完全一致。注意以上代码FanoutProduct中并没有新建队列，所以先运行FanoutCustomerA和FanoutCustomerB，如果先运行FanoutProduct因为找不到绑定的队列数据就会丢失。 
还有一种情况我们有可能随时增加一项处理机制，如果在声明queue时不指定名字，那么RabbitMQ会随机为我们生成一个名字，如果不指定queue为持久化队列那在消息为空并且订阅者为0时自动删除该队列。这样Queue挥之即来呼之即去。

String queueName = channel.QueueDeclare().QueueName;