rabbitmq(3)消息队列(轮询分发)

1、模型

一个生产者绑定一个队列,对应多个消费者:

这里写图片描述

2、代码

2.1、生产者

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
private final static String QUEUE_NAME = "hello";

public static void main(String[] args) throws Exception {

ConnectionFactory factory = new ConnectionFactory();
factory.setHost("192.168.1.7");
factory.setUsername("root");
factory.setPassword("123456");

Connection connection = factory.newConnection();
Channel channel = connection.createChannel();

channel.queueDeclare(QUEUE_NAME, true, false, false, null);
for(int i=0;i<20;i++) {
String message = "Hello "+i;
channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
System.out.println(" [1] Sent '" + message + "'");
}

channel.close();
connection.close();
}

2.2、消费者1

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
private final static String QUEUE_NAME = "hello";

public static void main(String[] args) throws Exception {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("192.168.1.7");
factory.setUsername("root");
factory.setPassword("123456");

Connection connection = factory.newConnection();
Channel channel = connection.createChannel();

channel.queueDeclare(QUEUE_NAME, true, false, false, null);
System.out.println(" [1] Waiting for messages.");
Consumer consumer = new DefaultConsumer(channel) {
@Override
public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties,
byte[] body) throws IOException {
String message = new String(body, "UTF-8");
System.out.println(" [1] Received '" + message + "'");
}
};
/*
* 自动确认,一旦rabbitmq将消息发送到消费者,则rabbitmq将删除该消息
* 若消费者未处理完消息前中断,会导致消息丢失的问题
*/
boolean autoAck = true;
channel.basicConsume(QUEUE_NAME, autoAck, consumer);
}

2.3、消费者2

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
private final static String QUEUE_NAME = "hello";

public static void main(String[] args) throws Exception {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("192.168.1.7");
factory.setUsername("root");
factory.setPassword("123456");

Connection connection = factory.newConnection();
Channel channel = connection.createChannel();

channel.queueDeclare(QUEUE_NAME, true, false, false, null);
System.out.println(" [2] Waiting for messages.");
Consumer consumer = new DefaultConsumer(channel) {
@Override
public void handleDelivery(String consumerTag, Envelope envelope, AMQP.BasicProperties properties,
byte[] body) throws IOException {
String message = new String(body, "UTF-8");
System.out.println(" [2] Received '" + message + "'");
// 让消费者2处理速度远低于消费者1
try {
Thread.sleep(500);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
boolean autoAck = true;
channel.basicConsume(QUEUE_NAME, autoAck, consumer);
}

3、效果

即使消费者2的处理速度远低于消费者1,两者接收到的任务数量几乎相同,即rabbitmq将消息均匀分发给所有消费者,即使其中有的消费者闲置有的消费者高负荷。