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：

2、代码

2.1、生产者

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

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

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。