RabbitMQ怎样实现保持监听并且每次只消费一条消息

Question

建立连接时，使用using 每次连接完毕即释放，这样导致了一个问题，除非是进程正在监听中，否则生产出来的消息，消费者接收不到
如果不使用using，保持channel活跃，这样可以将消息队列里面的消息挨个取出来，但是无法使用消息的手动确认
如果在连接服务器处也不使用using，保持连接活跃，这样会保持监听，但是会将所有的消息都取出来

以下代码为片段
//using (var connection = factory.CreateConnection())//连接服务器，即正在创建终结点。
//using (var channel = connection.CreateModel())
var connection = factory.CreateConnection();
                var channel = connection.CreateModel();

                channel.QueueDeclare(queue: config.QUEENNAME, durable: true, exclusive: false, autoDelete: false, arguments: null);
                        channel.ExchangeDeclare(exchange: config.EXCHANGENAME, type: "topic", durable: true);

                        channel.QueueBind(queue: config.QUEENNAME, exchange: config.EXCHANGENAME, routingKey: config.ROUNTINGKEY);

                        var consumer = new EventingBasicConsumer(channel);//消费者

                        Utility.WriteLog("连接至消费者");
                        //确认消息，noAck: false,手动确认
                        //channel.BasicConsume(queue: config.QUEENNAME, noAck: false, consumer: consumer);
                        Utility.WriteLog("next1");
                        //while (true)
                        //{
                        consumer.Received += (model, ea) =>
                        {
                            var body = ea.Body.ToArray();
                            var message = Encoding.UTF8.GetString(body);
                            
                            var routingKey = ea.RoutingKey;
                            Utility.WriteLog("W-messagr" + message);
                            //消息确认
                            try
                            {
                                Utility.WriteLog("W-BasicAck" + System.DateTime.Now.ToString());
                                channel.BasicAck(deliveryTag: ea.DeliveryTag, multiple: false);
                                Utility.WriteLog("W-BasicAck-end" + System.DateTime.Now.ToString());
                            }
                            catch(Exception ex)
                            {
                                Utility.WriteLog("确认失败" + ex);
                            }
                            //channel.BasicAck(deliveryTag: ea.DeliveryTag, multiple: false);
                            Utility.WriteLog("返回ACK");
                        };

                        //}

                        //}
                        Utility.WriteLog("next2");
                        channel.BasicConsume(queue: config.QUEENNAME, noAck: false, consumer: consumer);

Answer 1

不需要using释放掉连接，消费端本来就是需要保持长久连接的。消息是可以手动确认的，每处理一条就手动确认一条，确认后队列就会移除该条消息。
看我的代码示例

//队列消费者
public class ReceiveMq
    {
        private ConnectionFactory factory;
        public ReceiveMq() {
            factory = new ConnectionFactory() { HostName = "localhost" };
        }

        public void receive(Action<string> action) {
            var connection = factory.CreateConnection();
            var channel = connection.CreateModel();

            channel.QueueDeclare(queue: "helloaa",
                                         durable: false,
                                         exclusive: false,
                                         autoDelete: false,
                                         arguments: null);

            var consumer = new EventingBasicConsumer(channel);
            consumer.Received += (sender, e) => {
                var body = e.Body.ToArray();
                var message = Encoding.UTF8.GetString(body);             
                action(message);
                channel.BasicAck(e.DeliveryTag, false); //确认消息
            };
         //channel.BasicConsume(queue: "helloaa", autoAck: true, consumer: consumer); //自动确认消息
        } 
    }

//调用
ReceiveMq receiveMq = new ReceiveMq();
receiveMq.receive(msg => {
      Console.WriteLine(" [x] Received {0}", msg);
});

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