死信处理和优先级

何为Dead letter
max_length:
1）queue长度限制 【mongodg oplog】就是一个固定集合
2）queue中的message过期时间
3）basicreject basicnack等等
一、Dead letter exchange
有时候我们不希望message被drop掉，而是走到另外一个队列中，又或者是保存起来

二、Dead letter routing key
打到exchange中去的时候，确定routingkey的值

代码演示如下：
1、生产者

			//基础配置
            ConnectionFactory factory = new ConnectionFactory()
            {
                HostName = "10.123.44.12",
                UserName = "datamip",
                Password = "datamip"
            };

            //第一步：创建connection
            using (var connection = factory.CreateConnection())
            {
                //第二步：创建channel
                using (var channel = connection.CreateModel())
                {
                    channel.QueueDeclare("mytest", false, false, false, new Dictionary<string, object>()
                    {
                        {"x-max-length",10 },
                        { "x-dead-letter-exchange","mydead_exchange"},
                        {"x-dead-letter-routing-key","mydead_queue" }
                    });
                    for (int i = 0; i < 15; i++)
                    {
                        channel.BasicPublish(string.Empty, "mytest", null, Encoding.UTF8.GetBytes(string.Format("你好{0}", i)));
                    }
                }
            }
            Console.WriteLine("生产成功!");
            Console.ReadKey();

　　

2、消费者

			//创建连接工厂
            ConnectionFactory factory = new ConnectionFactory
            {
                UserName = "datamip",//用户名
                Password = "datamip",//密码
                HostName = "10.123.44.12"//rabbitmq ip
            };
            //第一步：创建connection
            using (var connection = factory.CreateConnection())
            {
                //第二步：创建channel
                using (var channel = connection.CreateModel())
                {
				
                    channel.ExchangeDeclare("mydead_exchange", ExchangeType.Direct, false, false, null);
                    channel.QueueDeclare("mydead_queue",true,false,false,null);
                    channel.QueueBind("mydead_queue", "mydead_exchange", "mydead_queue", null);
                    EventingBasicConsumer consumer = new EventingBasicConsumer(channel);
                    consumer.Received +=(sender,e)=> {
                        var msg = Encoding.UTF8.GetString(e.Body.ToArray());
                        Console.WriteLine(msg);
                    };
                    channel.BasicConsume("mydead_queue",true, consumer);
                    Console.ReadKey();
                }
            }

　　

三、Maximum priority
优先级加载队列上，就是一个优先级队列 【堆，大根堆，小根堆】
1、给队列贴上一个优先级的标签 x-max-priority=10
2、给message打上具体的优先级的value value<=10
代码演示：
1、生产者

			//基础配置
            ConnectionFactory factory = new ConnectionFactory()
            {
                HostName = "10.123.44.12",
                UserName = "datamip",
                Password = "datamip"
            };

            //第一步：创建connection
            using (var connection = factory.CreateConnection())
            {
                //第二步：创建channel
                using (var channel = connection.CreateModel())
                {
                    channel.QueueDeclare("mytest", false, false, false, new Dictionary<string, object>()
                    {
                        {"x-max-priority",10 }
                    });
                    var properties = channel.CreateBasicProperties();
                    for (int i = 0; i < 10; i++)
                    {
                        properties.Priority = (byte)i;
                        channel.BasicPublish(string.Empty, "mytest", properties, Encoding.UTF8.GetBytes(string.Format("你好{0}", i)));
                    }
                }
            }
            Console.WriteLine("生产成功!");
            Console.ReadKey();

　　

2、消费者

			//创建连接工厂
            ConnectionFactory factory = new ConnectionFactory
            {
                UserName = "datamip",//用户名
                Password = "datamip",//密码
                HostName = "10.123.44.12"//rabbitmq ip
            };
            //第一步：创建connection
            using (var connection = factory.CreateConnection())
            {
                //第二步：创建channel
                using (var channel = connection.CreateModel())
                {
                    EventingBasicConsumer consumer = new EventingBasicConsumer(channel);
                    consumer.Received +=(sender,e)=> {
                        var msg = Encoding.UTF8.GetString(e.Body.ToArray());
                        Console.WriteLine(msg);
                    };
                    channel.BasicConsume("mytest", true, consumer);
                    Console.ReadKey();
                }
            }