RabbitMQ介绍4 - 编程（C#客户端示例）
C#终端的说明文档： http://www.rabbitmq.com/dotnet-api-guide.html
这里介绍使用RabbitMQ的几种典型场景。
1. 简单direct模式（ http://www.rabbitmq.com/tutorials/tutorial-one-dotnet.html）。生产者发送消息到一个队列，消费者从队列读取消息。这是最简单的使用场景，下面的代码使用默认exchange，消息自动确认。注意后台接收消息的线程完成前不要关闭连接，这里消费者是通过Console.ReadLine();保证连接不会Dispose。
生产者：
public static void test1()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
using (var channel = connection.CreateModel())
{
channel.QueueDeclare(queue: "hello",
durable: false,
exclusive: false,
autoDelete: false,
arguments: null);string message = "Hello World!";
var body = Encoding.UTF8.GetBytes(message);channel.BasicPublish(exchange: "",
routingKey: "hello",
basicProperties: null,
body: body);
Console.WriteLine(" [x] Sent {0}", message);
}Console.WriteLine(" Press [enter] to exit.");
Console.ReadLine();
}消费者
public static void test1()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
using (var channel = connection.CreateModel())
{
channel.QueueDeclare(queue: "hello",
durable: false,
exclusive: false,
autoDelete: false,
arguments: null);var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) =>
{
var body = ea.Body;
var message = Encoding.UTF8.GetString(body);
Console.WriteLine(" [x] Received {0}", message);
};
channel.BasicConsume(queue: "hello",
noAck: true,
consumer: consumer);Console.WriteLine(" Press [enter] to exit.");
Console.ReadLine();
}
}
![(P) -> [|||] -> (C)](http://www.rabbitmq.com/img/tutorials/python-one.png)
2. 多个消费者连接队列（http://www.rabbitmq.com/tutorials/tutorial-two-dotnet.html）。使用场景：生产者发送比较耗时的任务，多个消费者从队列获取任务，完成计算。优点：方便系统扩展，添加消费者即可增加系统的负载能力，通过显式消息确认、prefetch消息量的控制，可以实现多个消费者之间的负载均衡。prefetch N的意思是在消费者确认前，只发送N个消息，也就是等待确认的消息最多N个（默认不设，队列的消息会全部发给消费者，然后等待确认），只要客户端的连接保持，便不会重发，如果连接中断，消息还是没有确认，则会重新发送。
生产者代码和前一个例子类似，这里只给出消费者代码
public static void test2()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
using (var channel = connection.CreateModel())
{
channel.QueueDeclare(queue: "task_queue",
durable: true,
exclusive: false,
autoDelete: false,
arguments: null);
channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: false);Console.WriteLine(" [*] Waiting for messages.");
var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) =>
{
var body = ea.Body;
var message = Encoding.UTF8.GetString(body);
Console.WriteLine(" [x] Received {0}", message);int dots = message.Split('.').Length - 1;
Thread.Sleep(dots * 10000);Console.WriteLine(" [x] Done");
channel.BasicAck(deliveryTag: ea.DeliveryTag, multiple: false);
};
channel.BasicConsume(queue: "task_queue",
noAck: false,
consumer: consumer);Console.WriteLine(" Press [enter] to exit.");
Console.ReadLine();
}
}
3. 订阅发布模式（http://www.rabbitmq.com/tutorials/tutorial-three-dotnet.html）。exchange使用fanout模式。注意下面代码创建了命名队列（通过队列名可以方便标识消费者），如果队列不需要持久化，也可以使用临时队列（queueName = channel.QueueDeclare().QueueName;），RabbitMQ为队列分配一个唯一标识，消费者断开后会自动删除队列。
生产者：
public static void test3(string[] args)
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
using (var channel = connection.CreateModel())
{
channel.ExchangeDeclare("logs", "fanout");for (int i = 0; i < args.Length; i++)
{
var message = "task_queue_t3";
var body = Encoding.UTF8.GetBytes(message);var properties = channel.CreateBasicProperties();
properties.SetPersistent(true);channel.BasicPublish(exchange: "logs", routingKey: "", basicProperties: properties, body: body);
Console.WriteLine(" [x] Sent {0}", message);
}}
}消费者：
public static void test3()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
using (var channel = connection.CreateModel())
{
channel.ExchangeDeclare("logs", ExchangeType.Fanout);string queueName = "task_queue_t3";
Console.WriteLine(Encoding.UTF8.GetBytes(queueName).Length);
channel.QueueDeclare(queue: queueName,
durable: true,
exclusive: true,
autoDelete: true,
arguments: null);
//queueName = channel.QueueDeclare().QueueName;channel.QueueBind(queue: queueName, exchange: "logs", routingKey: "");
Console.WriteLine(" [*] Waiting for messages.");
var consumer = new EventingBasicConsumer(channel);
consumer.Received += (model, ea) =>
{
var body = ea.Body;
var message = Encoding.UTF8.GetString(body);
Console.WriteLine(" [x] Received {0}", message);int dots = message.Split('.').Length - 1;
Thread.Sleep(dots * 1000);Console.WriteLine(" [x] Done");
channel.BasicAck(deliveryTag: ea.DeliveryTag, multiple: false);
};
channel.BasicConsume(queue: queueName,
noAck: false,
consumer: consumer);Console.WriteLine(" Press [enter] to exit.");
Console.ReadLine();
}
}
4. 路由（http://www.rabbitmq.com/tutorials/tutorial-four-dotnet.html）。exchange使用Direct模式，通过binding key 精确匹配routing key选择消息路由。可以有多个binding key。
生产者：
channel.ExchangeDeclare("direct_logs", "direct");
channel.BasicPublish(exchange: "direct_logs", routingKey: "info", basicProperties: properties, body: body);
消费者：
channel.ExchangeDeclare("direct_logs", "direct");
string queueName = channel.QueueDeclare().QueueName;
channel.QueueBind(queueName, "direct_logs", "info");
channel.QueueBind(queueName, "direct_logs", "error");
5. Topic模式（http://www.rabbitmq.com/tutorials/tutorial-five-dotnet.html）。exchange使用Topic模式，可以实现模糊匹配。
生产者：
channel.ExchangeDeclare("topic_logs", ExchangeType.Topic);
channel.BasicPublish(exchange: "topic_logs", routingKey: "lazy.green.cat", basicProperties: properties, body: body);
消费者：
channel.ExchangeDeclare("topic_logs", "topic");
string queueName = "Q2";
channel.QueueDeclare(queue: queueName,
durable: true,
exclusive: true,
autoDelete: true,
arguments: null);channel.QueueBind(queueName, "topic_logs", "*.*.rabbit");
channel.QueueBind(queueName, "topic_logs", "lazy.#");
6. 远程过程调用RPC（http://www.rabbitmq.com/tutorials/tutorial-six-dotnet.html）。实现客户和服务之间的通信。一次通信过程如下：
- 客户端发送请求消息。客户端发送请求时通过reply_to指定回复的地址（回复的queue，由于RPC的特殊性，我们使用默认的exchange来做路由，这时候queue名字便是路由键）和correlation_id（标记发送的消息，回复的时候通过这个ID来确认回复的是哪个请求）。在reply_to的queue上等待回复。
- 服务器收到请求，处理后发送回复到默认exchange，用请求消息的reply_to做路由键，这样回复便发到了reply_to指定的queue。设置的回复消息的correlation_id=请求消息的correction_id。
- 客户端在reply_to的队列上收到回复。
- 通过ack和prefetch N控制同步。
RPCServer端代码：
public static void RPCServer()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
using (var connection = factory.CreateConnection())
using (var channel = connection.CreateModel())
{
channel.QueueDeclare(queue: "rpc_queue",
durable: false,
exclusive: false,
autoDelete: false,
arguments: null);
channel.BasicQos(0, 1, false);
var consumer = new QueueingBasicConsumer(channel);
channel.BasicConsume(queue: "rpc_queue",
noAck: false,
consumer: consumer);
Console.WriteLine(" [x] Awaiting RPC requests");while (true)
{
string response = null;
var ea = (BasicDeliverEventArgs)consumer.Queue.Dequeue();var body = ea.Body;
var props = ea.BasicProperties;
var replyProps = channel.CreateBasicProperties();
replyProps.CorrelationId = props.CorrelationId;try
{
var message = Encoding.UTF8.GetString(body);
int n = int.Parse(message);
Console.WriteLine(" [.] fib({0})", message);
response = "abc"; //do time consuming work here
}
catch (Exception e)
{
Console.WriteLine(" [.] " + e.Message);
response = "";
}
finally
{
var responseBytes = Encoding.UTF8.GetBytes(response);
channel.BasicPublish(exchange: "",
routingKey: props.ReplyTo,
basicProperties: replyProps,
body: responseBytes);
channel.BasicAck(deliveryTag: ea.DeliveryTag,
multiple: false);
}
}
}
}
客户端代码：
class RPCClient
{
private IConnection connection;
private IModel channel;
private string replyQueueName;
private QueueingBasicConsumer consumer;public RPCClient()
{
var factory = new ConnectionFactory() { HostName = "localhost" };
connection = factory.CreateConnection();
channel = connection.CreateModel();
replyQueueName = channel.QueueDeclare().QueueName;
consumer = new QueueingBasicConsumer(channel);
channel.BasicConsume(queue: replyQueueName,
noAck: true,
consumer: consumer);
}public string Call(string message)
{
var corrId = Guid.NewGuid().ToString();
var props = channel.CreateBasicProperties();
props.ReplyTo = replyQueueName;
props.CorrelationId = corrId;var messageBytes = Encoding.UTF8.GetBytes(message);
channel.BasicPublish(exchange: "",
routingKey: "rpc_queue",
basicProperties: props,
body: messageBytes);while (true)
{
var ea = (BasicDeliverEventArgs)consumer.Queue.Dequeue();
if (ea.BasicProperties.CorrelationId == corrId)
{
return Encoding.UTF8.GetString(ea.Body);
}
}
}public void Close()
{
connection.Close();
}
}
//测试
public static void RPCTest()
{
var rpcClient = new RPCClient();Console.WriteLine(" [x] Requesting fib(30)");
var response = rpcClient.Call("30");
Console.WriteLine(" [.] Got '{0}'", response);rpcClient.Close();
}
