簡介
延遲隊列存儲的消息是不希望被消費者立刻拿到的，而是等待特定時間後，消費者才能拿到這個消息進行消費。使用場景比較多，例如訂單限時30分鐘內支付，否則取消，再如分佈式環境中每隔一段時間重複執行某操作。
下面舉一個簡單的例子，例子大概意思是分別在首次發送消息後的10秒、40秒、100秒後重新讀取到消息。爲了直觀，不使用RabbitMQ其他多餘的特性。
準備工作
在Centos7下安裝RabbitMQ，版本爲3.6.12單機版本（非集羣），IP是127.0.0.1，端口是15672，使用web管理頁面或者rabbitmqctl提前準備好相關的用戶、exchange和queue。
用戶有producer（密碼同用戶名）、consumer（密碼同用戶名）。
Default exchange是RabbitMQ預定義的，名稱爲空字符串，自動綁定到每個queue，類型爲direct，routingKey等於queue的名稱。
三個死信交換器（隊列中的消息過期後會被髮送到該隊列的死信交換器）10sDeadLetterExchange、30sDeadLetterExchange、60sDeadLetterExchange。
三個死信隊列，10sDeadLetterQueue、30sDeadLetterQueue、60sDeadLetterQueue分別與三個死信交換器綁定。
三個隊列，10sDelayQueue、30sDelayQueue、60sDelayQueue，分別設置過期時間爲10秒、30秒、60秒，並設置對應的死信交換器。
示例
使用java代碼創建一個生產者和三個消費者。生產者往Default exchange發送消息，routingKey爲10sDelayQueue。三個消費者分別訂閱三個死信隊列。先啓動三個消費者，再啓動生產者。消費者會持續訂閱死信隊列，需要手動關閉連接。
Rabbitmq10sDeadLetterQueueConsumer消費者代碼如下：
import com.rabbitmq.client.*;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.UUID;
import java.util.concurrent.TimeoutException;
public class Rabbitmq10sDeadLetterQueueConsumer {
public static void main(String[] args) throws IOException, TimeoutException {
ConnectionFactory connectionFactory = new ConnectionFactory();
connectionFactory.setVirtualHost("/");
connectionFactory.setUsername("consumer");
connectionFactory.setPassword("consumer");
connectionFactory.setHost("127.0.0.1");
connectionFactory.setPort(15672);
Connection connection = connectionFactory.newConnection();
Channel channel = connection.createChannel();
channel.basicQos(64);
channel.basicConsume("10sDeadLetterQueue", false, UUID.randomUUID().toString(),
new DefaultConsumer(channel) {
@Override
public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
System.out.println("第一次重試時間：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()));
System.out.println("consumerTag:" + consumerTag);
System.out.println("envelope:" + envelope.toString());
System.out.println("basicProperties:" + properties.toString());
System.out.println("message:" + new String(body, "utf-8"));
channel.basicAck(envelope.getDeliveryTag(), false);
channel.basicPublish("", "30sDelayQueue",
new AMQP.BasicProperties().builder().deliveryMode(2).build(),
body);
}
});
}
}
Rabbitmq30sDeadLetterQueueConsumer消費者代碼如下：
import com.rabbitmq.client.*;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.UUID;
import java.util.concurrent.TimeoutException;
public class Rabbitmq30sDeadLetterQueueConsumer {
public static void main(String[] args) throws IOException, TimeoutException {
ConnectionFactory connectionFactory = new ConnectionFactory();
connectionFactory.setVirtualHost("/");
connectionFactory.setUsername("consumer");
connectionFactory.setPassword("consumer");
connectionFactory.setHost("127.0.0.1");
connectionFactory.setPort(15672);
Connection connection = connectionFactory.newConnection();
Channel channel = connection.createChannel();
channel.basicQos(64);
channel.basicConsume("30sDeadLetterQueue", false, UUID.randomUUID().toString(),
new DefaultConsumer(channel) {
@Override
public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
System.out.println("第二次重試時間：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()));
System.out.println("consumerTag:" + consumerTag);
System.out.println("envelope:" + envelope.toString());
System.out.println("basicProperties:" + properties.toString());
System.out.println("message:" + new String(body, "utf-8"));
channel.basicAck(envelope.getDeliveryTag(), false);
channel.basicPublish("", "60sDelayQueue",
new AMQP.BasicProperties().builder().deliveryMode(2).build(),
body);
}
});
}
}
Rabbitmq60sDeadLetterQueueConsumer消費者代碼如下：
import com.rabbitmq.client.*;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.UUID;
import java.util.concurrent.TimeoutException;
public class Rabbitmq60sDeadLetterQueueConsumer {
public static void main(String[] args) throws IOException, TimeoutException {
ConnectionFactory connectionFactory = new ConnectionFactory();
connectionFactory.setVirtualHost("/");
connectionFactory.setUsername("consumer");
connectionFactory.setPassword("consumer");
connectionFactory.setHost("127.0.0.1");
connectionFactory.setPort(15672);
Connection connection = connectionFactory.newConnection();
Channel channel = connection.createChannel();
channel.basicQos(64);
channel.basicConsume("60sDeadLetterQueue", false, UUID.randomUUID().toString(),
new DefaultConsumer(channel) {
@Override
public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties, byte[] body) throws IOException {
System.out.println("第三次重試時間：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()));
System.out.println("consumerTag:" + consumerTag);
System.out.println("envelope:" + envelope.toString());
System.out.println("basicProperties:" + properties.toString());
System.out.println("message:" + new String(body, "utf-8"));
channel.basicAck(envelope.getDeliveryTag(), false);
System.out.println("執行完成");
}
});
}
}
生產者代碼如下：
import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.UUID;
import java.util.concurrent.TimeoutException;
public class RabbitmqDelayQueueProducer {
public static void main(String[] args) throws IOException, TimeoutException {
Connection connection = null;
Channel channel = null;
try {
ConnectionFactory connectionFactory = new ConnectionFactory();
connectionFactory.setVirtualHost("/");
connectionFactory.setUsername("producer");
connectionFactory.setPassword("producer");
connectionFactory.setHost("127.0.0.1");
connectionFactory.setPort(15672);
connection = connectionFactory.newConnection();
channel = connection.createChannel();
channel.basicPublish("", "10sDelayQueue",
new AMQP.BasicProperties().builder().deliveryMode(2).build(),
("測試延遲隊列" + UUID.randomUUID().toString()).getBytes("utf-8"));
System.out.println("發送時間：" + new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date()));
} finally {
if (channel != null) {
channel.close();
}
if (connection != null) {
connection.close();
}
}
}
}
生產者打印：
發送時間：2019-08-25 10:08:29
Rabbitmq10sDeadLetterQueueConsumer消費者打印：
第一次重試時間：2019-08-25 10:08:39
consumerTag:83787685-28a9-4ae8-b2bc-b89b90f14b68
envelope:Envelope(deliveryTag=1, redeliver=false, exchange=10sDeadLetterExchange, routingKey=10sDelayQueue)
basicProperties:#contentHeader<basic>(content-type=null, content-encoding=null, headers={x-death=[{reason=expired, count=1, exchange=, time=Sun Aug 25 10:08:37 CST 2019, routing-keys=[10sDelayQueue], queue=10sDelayQueue}]}, delivery-mode=2, priority=null, correlation-id=null, reply-to=null, expiration=null, message-id=null, timestamp=null, type=null, user-id=null, app-id=null, cluster-id=null)
message:測試延遲隊列f862c616-a99a-4b65-9482-d74d5aee0814
Rabbitmq30sDeadLetterQueueConsumer消費者打印：
第二次重試時間：2019-08-25 10:09:09
consumerTag:27bb0e0e-07fe-49b6-8c0f-06fbc32cd784
envelope:Envelope(deliveryTag=1, redeliver=false, exchange=30sDeadLetterExchange, routingKey=30sDelayQueue)
basicProperties:#contentHeader<basic>(content-type=null, content-encoding=null, headers={x-death=[{reason=expired, count=1, exchange=, time=Sun Aug 25 10:09:07 CST 2019, routing-keys=[30sDelayQueue], queue=30sDelayQueue}]}, delivery-mode=2, priority=null, correlation-id=null, reply-to=null, expiration=null, message-id=null, timestamp=null, type=null, user-id=null, app-id=null, cluster-id=null)
message:測試延遲隊列f862c616-a99a-4b65-9482-d74d5aee0814
Rabbitmq60sDeadLetterQueueConsumer消費者打印：
第三次重試時間：2019-08-25 10:10:09
consumerTag:8bfdc795-443d-4940-bf88-1e6f14e7b530
envelope:Envelope(deliveryTag=1, redeliver=false, exchange=60sDeadLetterExchange, routingKey=60sDelayQueue)
basicProperties:#contentHeader<basic>(content-type=null, content-encoding=null, headers={x-death=[{reason=expired, count=1, exchange=, time=Sun Aug 25 10:10:07 CST 2019, routing-keys=[60sDelayQueue], queue=60sDelayQueue}]}, delivery-mode=2, priority=null, correlation-id=null, reply-to=null, expiration=null, message-id=null, timestamp=null, type=null, user-id=null, app-id=null, cluster-id=null)
message:測試延遲隊列f862c616-a99a-4b65-9482-d74d5aee0814
執行完成