C# 操作rabbitmq（二）

接着上一篇继续分析rabbitmq的使用，此篇介绍rabbitmq的publish/Subcribe

一、Exchange
rabbitmq建议消息的producer不要直接的把消息发送给queue，而是把消息发送给Exchange。
Exchange一边接收来自producer的消息，一边将消息push给queue。

rabbitmq提供了四种exchange type：

• direct ：第三篇
• topic ：第四篇

• headers ：很少使用，rabbitmq官网没有给出例子
  此类型的exchange和以上三个都不一样，其路由的规则是根据header来判断，其中的header就是以下方法的arguments参数：

  Dictionary aHeader = new Dictionary();
  aHeader.Add("format", "pdf");
  aHeader.Add("type", "report");
  aHeader.Add("x-match", "all");
  channel.QueueBind(queue: "queue.A",
              exchange: "agreements",
              routingKey: string.Empty,
              arguments: aHeader);
  

  其中的x-match为特殊的header，可以为all则表示要匹配所有的header，如果为any则表示只要匹配其中的一个header即可。

  var factory = new ConnectionFactory() { HostName = "localhost" };
  using (var connection = factory.CreateConnection())
  using (var channel = connection.CreateModel())
  {
      // Headers类型的exchange, 名称 agreements
      channel.ExchangeDeclare(exchange: "agreements",
                      type: ExchangeType.Headers,
                      durable: true,
                      autoDelete: false,
                      arguments: null);
  
      // 创建queue.A队列
      channel.QueueDeclare(queue: "queue.A", durable: true, exclusive: false, autoDelete: false, arguments: null);
  
      /*发布者*/
      string message1 = "hello world";
      var body = Encoding.UTF8.GetBytes(message1);
      var properties = channel.CreateBasicProperties();
      properties.Persistent = true;
      Dictionary mHeader1 = new Dictionary();
      mHeader1.Add("format", "pdf");
      mHeader1.Add("type", "report");
      properties.Headers = mHeader1;
  
      //queue.A 的binding (format=pdf, type=report, x-match=all)
      channel.BasicPublish(exchange: "agreements",
                      routingKey: string.Empty,
                      basicProperties: properties,
                      body: body);
  
      //接收者
      Dictionary aHeader = new Dictionary();
      aHeader.Add("format", "pdf");
      aHeader.Add("type", "report");
      aHeader.Add("x-match", "all");
      channel.QueueBind(queue: "queue.A",
                  exchange: "agreements",
                  routingKey: string.Empty,
                  arguments: aHeader);
  }
  

• fanout ： 将接收到消息广播给它所知道的queue

  channel.ExchangeDeclare("logs", "fanout"); //声明一个fanout类型的exchange ，名称为logs
  
  var message = GetMessage(args);
  var body = Encoding.UTF8.GetBytes(message);
  channel.BasicPublish(exchange: "logs",
               routingKey: "",
               basicProperties: null,
               body: body);
  

我们知道，无论什么时候连接rabbitmq需要一个全新的空的queue，因此可以用获取一个随机的queue名称,更多关于queue属性请参考 guide on queue

//create a non-durable, exclusive, autodelete queue with a generated name:
var queueName = channel.QueueDeclare().QueueName;

//将queue与exchange绑定
channel.QueueBind(queue: queueName,
              exchange: "logs",
              routingKey: "");

publish

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

class EmitLog
{
    public static void Main(string[] args)
    {
        var factory = new ConnectionFactory() { HostName = "localhost" };
        using(var connection = factory.CreateConnection())
        using(var channel = connection.CreateModel())
        {
            channel.ExchangeDeclare(exchange: "logs", type: "fanout");

            var message = GetMessage(args);
            var body = Encoding.UTF8.GetBytes(message);
            channel.BasicPublish(exchange: "logs",
                                 routingKey: "",
                                 basicProperties: null,
                                 body: body);
            Console.WriteLine(" [x] Sent {0}", message);
        }

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

    private static string GetMessage(string[] args)
    {
        return ((args.Length > 0)
               ? string.Join(" ", args)
               : "info: Hello World!");
    }
}

Subcribe

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

class ReceiveLogs
{
    public static void Main()
    {
        var factory = new ConnectionFactory() { HostName = "localhost" };
        using(var connection = factory.CreateConnection())
        using(var channel = connection.CreateModel())
        {
            channel.ExchangeDeclare(exchange: "logs", type: "fanout");

            var queueName = channel.QueueDeclare().QueueName;
            channel.QueueBind(queue: queueName,
                              exchange: "logs",
                              routingKey: "");

            Console.WriteLine(" [*] Waiting for logs.");

            var consumer = new EventingBasicConsumer(channel);
            consumer.Received += (model, ea) =>
            {
                var body = ea.Body;
                var 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();
        }
    }
}