一、死信队列
描述：Q1队列绑定了x-dead-letter-exchange(死信交换机)为X2，x-dead-letter-routing-key（死信路由key)指向Q2(队列2)
P(生产者)发送消息经X1(交换机1)路由到Q1(队列1)，Q1的消息触发特定情况，自动把消息经X2(交换机2)路由到Q2(队列2)，C(消费者)直接消息Q2的消息。
特定情况有哪些呢：
- 1.消息被拒(basic.reject or basic.nack)并且没有重新入队(requeue=false)；
- 2.当前队列中的消息数量已经超过最大长度(创建队列时指定" x-max-length参数设置队列最大消息数量)。
- 3.消息在队列中过期，即当前消息在队列中的存活时间已经超过了预先设置的TTL(Time To Live)时间；
这里演示情况1：
假如场景：Q1中队列数据不完整，就算从新处理也会报错，那就可以不ack，把这个消息转到死信队列另外处理。
生产者：
public static void SendMessage()
{
//死信交换机
string dlxexChange = "dlx.exchange";
//死信队列
string dlxQueueName = "dlx.queue";
//消息交换机
string exchange = "direct-exchange";
//消息队列
string queueName = "queue_a";
using (var connection = RabbitMQHelper.GetConnection())
{
using (var channel = connection.CreateModel())
{
//创建死信交换机
channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建死信队列
channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
//死信队列绑定死信交换机
channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);
// 创建消息交换机
channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建消息队列,并指定死信队列
channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
new Dictionary<string, object> {
{ "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX(死信交换机)
{ "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
});
//消息队列绑定消息交换机
channel.QueueBind(queueName, exchange, routingKey: queueName);
string message = "hello rabbitmq message";
var properties = channel.CreateBasicProperties();
properties.Persistent = true;
//发布消息
channel.BasicPublish(exchange: exchange,
routingKey: queueName,
basicProperties: properties,
body: Encoding.UTF8.GetBytes(message));
Console.WriteLine($"向队列:{queueName}发送消息:{message}");
}
}
}
消费者：
public static void Consumer()
{
//死信交换机
string dlxexChange = "dlx.exchange";
//死信队列
string dlxQueueName = "dlx.queue";
//消息交换机
string exchange = "direct-exchange";
//消息队列
string queueName = "queue_a";
var connection = RabbitMQHelper.GetConnection();
{
//创建信道
var channel = connection.CreateModel();
{
//创建死信交换机
channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建死信队列
channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
//死信队列绑定死信交换机
channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);
// 创建消息交换机
channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建消息队列,并指定死信队列
channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
new Dictionary<string, object> {
{ "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX
{ "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
});
//消息队列绑定消息交换机
channel.QueueBind(queueName, exchange, routingKey: queueName);
var consumer = new EventingBasicConsumer(channel);
channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: true);
consumer.Received += (model, ea) =>
{
//处理业务
var message = Encoding.UTF8.GetString(ea.Body.ToArray());
Console.WriteLine($"队列{queueName}消费消息:{message},不做ack确认");
//channel.BasicAck(ea.DeliveryTag, false);
//不ack(BasicNack),且不把消息放回队列(requeue:false)
channel.BasicNack(ea.DeliveryTag, false, requeue: false);
};
channel.BasicConsume(queueName, autoAck: false, consumer);
}
}
}
消费者加上channel.BasickNack()模拟消息处理不了，不ack确认。
执行结果：
RabbitMQ管理界面：
看到消息队列为queue_a，特性有DLX(死信交换机)，DLK（死信路由）。因为消费端不nack，触发了死信，被转发到了死信队列dlx.queue。
二、延时队列
延时队列其实也是配合死信队列一起用，其实就是上面死信队列的第二中情况。给队列添加消息过时时间（TTL），变成延时队列。
简单的描述就是：P(生产者)发送消息到Q1(延时队列)，Q1的消息有过期时间，比如10s，那10s后消息过期就会触发死信，从而把消息转发到Q2（死信队列）。
解决问题场景：像商城下单，未支付时取消订单场景。下单时写一条记录入Q1,延时30分钟后转到Q2，消费Q2，检查订单，支付则不做操作，没支付则取消订单，恢复库存。
生产者代码：
public static void SendMessage()
{
//死信交换机
string dlxexChange = "dlx.exchange";
//死信队列
string dlxQueueName = "dlx.queue";
//消息交换机
string exchange = "direct-exchange";
//消息队列
string queueName = "delay_queue";
using (var connection = RabbitMQHelper.GetConnection())
{
using (var channel = connection.CreateModel())
{
//创建死信交换机
channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建死信队列
channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
//死信队列绑定死信交换机
channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);
// 创建消息交换机
channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建消息队列,并指定死信队列，和设置这个队列的消息过期时间为10s
channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
new Dictionary<string, object> {
{ "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX(死信交换机)
{ "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
{ "x-message-ttl",10000} //设置队列的消息过期时间
});
//消息队列绑定消息交换机
channel.QueueBind(queueName, exchange, routingKey: queueName);
string message = "hello rabbitmq message";
var properties = channel.CreateBasicProperties();
properties.Persistent = true;
//发布消息
channel.BasicPublish(exchange: exchange,
routingKey: queueName,
basicProperties: properties,
body: Encoding.UTF8.GetBytes(message));
Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message}");
}
}
}
消费者代码：
public static void Consumer()
{
//死信交换机
string dlxexChange = "dlx.exchange";
//死信队列
string dlxQueueName = "dlx.queue";
var connection = RabbitMQHelper.GetConnection();
{
//创建信道
var channel = connection.CreateModel();
{
//创建死信交换机
channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建死信队列
channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
//死信队列绑定死信交换机
channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);
var consumer = new EventingBasicConsumer(channel);
channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: true);
consumer.Received += (model, ea) =>
{
//处理业务
var message = Encoding.UTF8.GetString(ea.Body.ToArray());
Console.WriteLine($"{DateTime.Now}，队列{dlxQueueName}消费消息:{message}");
channel.BasicAck(ea.DeliveryTag, false);
};
channel.BasicConsume(dlxQueueName, autoAck: false, consumer);
}
}
}
执行代码：
向延时队列发送消息，监听死信队列，发送和收到消息时间刚好是设置的10s。
RabbitMQ管理界面：
三、延时消息设置不同过期时间
上面的延时队列能解决消息过期时间都是相同的场景，能不能解决消息的过期时间是不一样的呢？
例如场景：机器人客服，为了更像人为操作，收到消息后要随机3-10秒回复客户。
- 1）队列不设置TTL（消息过期时间），把过期时间设置在消息上。
生产者代码：
public static void SendMessage()
{
//死信交换机
string dlxexChange = "dlx.exchange";
//死信队列
string dlxQueueName = "dlx.queue";
//消息交换机
string exchange = "direct-exchange";
//消息队列
string queueName = "delay_queue";
using (var connection = RabbitMQHelper.GetConnection())
{
using (var channel = connection.CreateModel())
{
//创建死信交换机
channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建死信队列
channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
//死信队列绑定死信交换机
channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);
// 创建消息交换机
channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建消息队列,并指定死信队列，和设置这个队列的消息过期时间为10s
channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
new Dictionary<string, object> {
{ "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX(死信交换机)
{ "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
//{ "x-message-ttl",10000} //设置队列的消息过期时间
});
//消息队列绑定消息交换机
channel.QueueBind(queueName, exchange, routingKey: queueName);
string message = "hello rabbitmq message 10s后处理";
var properties = channel.CreateBasicProperties();
properties.Persistent = true;
properties.Expiration = "10000";//消息的有效期10s
//发布消息,延时10s
channel.BasicPublish(exchange: exchange,
routingKey: queueName,
basicProperties: properties,
body: Encoding.UTF8.GetBytes(message));
Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message},延时:10s");
string message2 = "hello rabbitmq message 5s后处理";
var properties2 = channel.CreateBasicProperties();
properties2.Persistent = true;
properties2.Expiration = "5000";//消息有效期5s
//发布消息,延时5s
channel.BasicPublish(exchange: exchange,
routingKey: queueName,
basicProperties: properties2,
body: Encoding.UTF8.GetBytes(message2));
Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message2},延时:5s");
}
}
}
消费者代码还是上面延时队列的不变，先试下效果。
生产者向队列中发送一条延时10s的消息再发一条延时5秒的消息，但消费者却先拿到延时10s的，再拿到延时5秒的，我想要的结果是先拿到延时5s的再拿到延时10s的，是什么原因呢。
原因是：队列是先进先出的，而RabbitMQ只会对首位第一条消息做检测，第一条没过期，那么后面的消息就会阻塞住等待前面的过期。
解决办法：增加一个消费者对延时队列消费，不ack，把第一条消息放到队列尾部。一直让消息在流动，这样就能检测到了。
- 2）新增消费者代码：
public static void SendMessage()
{
//死信交换机
string dlxexChange = "dlx.exchange";
//死信队列
string dlxQueueName = "dlx.queue";
//消息交换机
string exchange = "direct-exchange";
//消息队列
string queueName = "delay_queue";
using (var connection = RabbitMQHelper.GetConnection())
{
using (var channel = connection.CreateModel())
{
//创建死信交换机
channel.ExchangeDeclare(dlxexChange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建死信队列
channel.QueueDeclare(dlxQueueName, durable: true, exclusive: false, autoDelete: false);
//死信队列绑定死信交换机
channel.QueueBind(dlxQueueName, dlxexChange, routingKey: dlxQueueName);
// 创建消息交换机
channel.ExchangeDeclare(exchange, type: ExchangeType.Direct, durable: true, autoDelete: false);
//创建消息队列,并指定死信队列，和设置这个队列的消息过期时间为10s
channel.QueueDeclare(queueName, durable: true, exclusive: false, autoDelete: false, arguments:
new Dictionary<string, object> {
{ "x-dead-letter-exchange",dlxexChange}, //设置当前队列的DLX(死信交换机)
{ "x-dead-letter-routing-key",dlxQueueName}, //设置DLX的路由key，DLX会根据该值去找到死信消息存放的队列
//{ "x-message-ttl",10000} //设置队列的消息过期时间
});
//消息队列绑定消息交换机
channel.QueueBind(queueName, exchange, routingKey: queueName);
string message = "hello rabbitmq message 10s后处理";
var properties = channel.CreateBasicProperties();
properties.Persistent = true;
properties.Expiration = "10000";//消息的有效期10s
//发布消息,延时10s
channel.BasicPublish(exchange: exchange,
routingKey: queueName,
basicProperties: properties,
body: Encoding.UTF8.GetBytes(message));
Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message},延时:10s");
string message2 = "hello rabbitmq message 5s后处理";
var properties2 = channel.CreateBasicProperties();
properties2.Persistent = true;
properties2.Expiration = "5000";//消息有效期5s
//发布消息,延时5s
channel.BasicPublish(exchange: exchange,
routingKey: queueName,
basicProperties: properties2,
body: Encoding.UTF8.GetBytes(message2));
Console.WriteLine($"{DateTime.Now},向队列:{queueName}发送消息:{message2},延时:5s");
}
}
}
执行效果：
这会得到了想要的效果。
RabbitMQ管理界面：
四、延时消息用延时插件的方式实现
相比上面第三的延时消息，这里的插件方式会显的更加简单，也推荐用这种。
因为这里只需要一个交换机和一个对队列，生产者向队列发送消息，会直接是延时才会到队列。
安装插件：
地址：https://www.rabbitmq.com/community-plugins.html
找到和自己RabbitMQ一样的版本，下载下来上传到Linux，或F12查看这个文件的地址，直接Linux上下载(这里用这种)
Linux下载插件：
#下载插件
wget https://github.com/rabbitmq/rabbitmq-delayed-message-exchange/releases/download/3.9.0/rabbitmq_delayed_message_exchange-3.9.0.ez
已经下载到Linux上
#把文件复制到rabbitmq docker容器下的plugins文件夹
docker cp rabbitmq_delayed_message_exchange-3.9.0.ez rabbitmq:/plugins
#进入rabbitmq docker容器
docker exec -it rabbitmq bash
#开启插件：
rabbitmq-plugins enable rabbitmq_delayed_message_exchange
做完上面这些在RabbitMQ管理界面可以看到多了一个延时消息的交换机。
插件装好了，生产者代码：
public static void SendMessage()
{
//延时消息交换机
string delayExchange = "delay.exchange";
//延时消息队列
string delayQueueName = "delay_queue";
using (var connection = RabbitMQHelper.GetConnection())
{
using (var channel = connection.CreateModel())
{
Dictionary<string, object> args = new Dictionary<string, object>();
args.Add("x-delayed-type", "direct"); //x-delayed-type必须加
//创建延时交换机,type类型为x-delayed-message
channel.ExchangeDeclare(delayExchange, type: "x-delayed-message", durable: true, autoDelete: false,arguments: args);
//创建延时消息队列
channel.QueueDeclare(delayQueueName, durable: true, exclusive: false, autoDelete: false);
//交换机绑定队列
channel.QueueBind(delayQueueName, delayExchange, routingKey: delayQueueName);
string message = "hello rabbitmq message 10s后处理";
var properties = channel.CreateBasicProperties();
properties.Persistent = true;
//延时时间从header赋值
Dictionary<string, object> headers = new Dictionary<string, object>();
headers.Add("x-delay", 10000);
properties.Headers = headers;
//发布消息,按时10s
channel.BasicPublish(exchange: delayExchange,
routingKey: delayQueueName,
basicProperties: properties,
body: Encoding.UTF8.GetBytes(message));
Console.WriteLine($"{DateTime.Now},向队列:{delayQueueName}发送消息:{message},延时:10s");
string message2 = "hello rabbitmq message 5s后处理";
var properties2 = channel.CreateBasicProperties();
properties2.Persistent = true;
//延时时间从header赋值
Dictionary<string, object> headers2 = new Dictionary<string, object>();
headers2.Add("x-delay", 5000);
properties2.Headers = headers2;
//发布消息,延时5s
channel.BasicPublish(exchange: delayExchange,
routingKey: delayQueueName,
basicProperties: properties2,
body: Encoding.UTF8.GetBytes(message2));
Console.WriteLine($"{DateTime.Now},向队列:{delayQueueName}发送消息:{message2},延时:5s");
}
}
}
消费者代码：
public static void DelayMessageConsumer()
{
//延时队列
string queueName = "delay_queue";
var connection = RabbitMQHelper.GetConnection();
{
//创建信道
var channel = connection.CreateModel();
{
var consumer = new EventingBasicConsumer(channel);
channel.BasicQos(prefetchSize: 0, prefetchCount: 1, global: true);
consumer.Received += (model, ea) =>
{
//处理业务
var message = Encoding.UTF8.GetString(ea.Body.ToArray());
Console.WriteLine($"{DateTime.Now},接收到消息:{message}");
channel.BasicAck(ea.DeliveryTag, false);
};
channel.BasicConsume(queueName, autoAck: false, consumer);
}
}
}
执行代码：
RabbitMQ管理界面，只有一个队列：
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原文链接：https://www.cnblogs.com/wei325/p/15204179.html#4930350
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