rabbitmq(3)消息队列(轮询分发)

rabbitmq

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

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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

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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

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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。

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