RocketMQ批量消费、消息重试、消费模式、刷盘方式

一、Consumer

批量消费

可以通过

consumer.setConsumeMessageBatchMaxSize(10);//每次拉取10条

这里需要分为2种情况1、Consumer端先启动 2、Consumer端后启动. 正常情况下：应该是Consumer需要先启动

1、Consumer端先启动

Consumer代码如下

package quickstart;

import java.util.List;

import com.alibaba.rocketmq.client.consumer.DefaultMQPushConsumer;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
import com.alibaba.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.common.consumer.ConsumeFromWhere;
import com.alibaba.rocketmq.common.message.MessageExt;

/**
 * Consumer，订阅消息
 */
public class Consumer {

	public static void main(String[] args) throws InterruptedException, MQClientException {
		DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("please_rename_unique_group_name_4");
		consumer.setNamesrvAddr("192.168.100.145:9876;192.168.100.146:9876");
		consumer.setConsumeMessageBatchMaxSize(10);
		/**
		 * 设置Consumer第一次启动是从队列头部开始消费还是队列尾部开始消费<br>
		 * 如果非第一次启动，那么按照上次消费的位置继续消费
		 */
		consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);

		consumer.subscribe("TopicTest", "*");

		consumer.registerMessageListener(new MessageListenerConcurrently() {

			public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {
				
				try {
					System.out.println("msgs的长度" + msgs.size());
					System.out.println(Thread.currentThread().getName() + " Receive New Messages: " + msgs);
				} catch (Exception e) {
					e.printStackTrace();
					return ConsumeConcurrentlyStatus.RECONSUME_LATER;
				}
				
				
				
				return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
			}
		});

		consumer.start();

		System.out.println("Consumer Started.");
	}
}

由于这里是Consumer先启动，所以他会去轮询MQ上是否有订阅队列的消息，由于每次producer插入一条，Consumer就拿一条所以测试结果如下（每次size都是1）：

2、Consumer端后启动，也就是Producer先启动

由于这里是Consumer后启动，所以MQ上也就堆积了一堆数据，Consumer的

consumer.setConsumeMessageBatchMaxSize(10);//每次拉取10条

所以这段代码就生效了测试结果如下（每次size最多是10）：

二、消息重试机制：消息重试分为2种1、Producer端重试 2、Consumer端重试

1、Producer端重试

也就是Producer往MQ上发消息没有发送成功，我们可以设置发送失败重试的次数

package quickstart;

import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.client.producer.DefaultMQProducer;
import com.alibaba.rocketmq.client.producer.SendResult;
import com.alibaba.rocketmq.common.message.Message;

/**
 * Producer，发送消息
 * 
 */
public class Producer {
	public static void main(String[] args) throws MQClientException, InterruptedException {
		DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");
		producer.setNamesrvAddr("192.168.100.145:9876;192.168.100.146:9876");
		producer.setRetryTimesWhenSendFailed(10);//失败的 情况发送10次
		producer.start();

		for (int i = 0; i < 1000; i++) {
			try {
				Message msg = new Message("TopicTest",// topic
						"TagA",// tag
						("Hello RocketMQ " + i).getBytes()// body
				);
				SendResult sendResult = producer.send(msg);
				System.out.println(sendResult);
			} catch (Exception e) {
				e.printStackTrace();
				Thread.sleep(1000);
			}
		}

		producer.shutdown();
	}
}

2、Consumer端重试

2.1、exception的情况，一般重复16次 10s、30s、1分钟、2分钟、3分钟等等

上面的代码中消费异常的情况返回

return ConsumeConcurrentlyStatus.RECONSUME_LATER;//重试

正常则返回：

return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;//成功

package quickstart;


import java.util.List;

import com.alibaba.rocketmq.client.consumer.DefaultMQPushConsumer;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
import com.alibaba.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.common.consumer.ConsumeFromWhere;
import com.alibaba.rocketmq.common.message.MessageExt;

/**
 * Consumer，订阅消息
 */
public class Consumer {

	public static void main(String[] args) throws InterruptedException, MQClientException {
		DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("please_rename_unique_group_name_4");
		consumer.setNamesrvAddr("192.168.100.145:9876;192.168.100.146:9876");
		consumer.setConsumeMessageBatchMaxSize(10);
		/**
		 * 设置Consumer第一次启动是从队列头部开始消费还是队列尾部开始消费<br>
		 * 如果非第一次启动，那么按照上次消费的位置继续消费
		 */
		consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);

		consumer.subscribe("TopicTest", "*");

		consumer.registerMessageListener(new MessageListenerConcurrently() {

			public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {

				try {
					// System.out.println("msgs的长度" + msgs.size());
					System.out.println(Thread.currentThread().getName() + " Receive New Messages: " + msgs);
					for (MessageExt msg : msgs) {
						String msgbody = new String(msg.getBody(), "utf-8");
						if (msgbody.equals("Hello RocketMQ 4")) {
							System.out.println("======错误=======");
							int a = 1 / 0;
						}
					}

				} catch (Exception e) {
					e.printStackTrace();
					if(msgs.get(0).getReconsumeTimes()==3){
						//记录日志
						
						return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;// 成功
					}else{
						
					return ConsumeConcurrentlyStatus.RECONSUME_LATER;// 重试
					}
				}

				return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;// 成功
			}
		});

		consumer.start();

		System.out.println("Consumer Started.");
	}
}

打印结果：

假如超过了多少次之后我们可以让他不再重试记录日志。

if(msgs.get(0).getReconsumeTimes()==3){

//记录日志

return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;// 成功

}

2.2超时的情况，这种情况MQ会无限制的发送给消费端。

就是由于网络的情况，MQ发送数据之后，Consumer端并没有收到导致超时。也就是消费端没有给我返回return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;这样的就认为没有到达Consumer端。

这里模拟Producer只发送一条数据。consumer端暂停1分钟并且不发送接收状态给MQ

package model;

import java.util.List;

import com.alibaba.rocketmq.client.consumer.DefaultMQPushConsumer;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
import com.alibaba.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.common.consumer.ConsumeFromWhere;
import com.alibaba.rocketmq.common.message.MessageExt;

/**
 * Consumer，订阅消息
 */
public class Consumer {

	public static void main(String[] args) throws InterruptedException, MQClientException {
		DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("message_consumer");
		consumer.setNamesrvAddr("192.168.100.145:9876;192.168.100.146:9876");
		consumer.setConsumeMessageBatchMaxSize(10);
		/**
		 * 设置Consumer第一次启动是从队列头部开始消费还是队列尾部开始消费<br>
		 * 如果非第一次启动，那么按照上次消费的位置继续消费
		 */
		consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);

		consumer.subscribe("TopicTest", "*");

		consumer.registerMessageListener(new MessageListenerConcurrently() {

			public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {

				try {

					// 表示业务处理时间
					System.out.println("=========开始暂停===============");
					Thread.sleep(60000);

					for (MessageExt msg : msgs) {
						System.out.println(" Receive New Messages: " + msg);
					}

				} catch (Exception e) {
					e.printStackTrace();
					return ConsumeConcurrentlyStatus.RECONSUME_LATER;// 重试
				}

				return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;// 成功
			}
		});

		consumer.start();

		System.out.println("Consumer Started.");
	}
}

三、消费模式

广播消费：rocketMQ默认是集群消费,我们可以通过在Consumer来支持广播消费

consumer.setMessageModel(MessageModel.BROADCASTING);// 广播消费

package model;

import java.util.List;

import com.alibaba.rocketmq.client.consumer.DefaultMQPushConsumer;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;
import com.alibaba.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
import com.alibaba.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import com.alibaba.rocketmq.client.exception.MQClientException;
import com.alibaba.rocketmq.common.consumer.ConsumeFromWhere;
import com.alibaba.rocketmq.common.message.MessageExt;
import com.alibaba.rocketmq.common.protocol.heartbeat.MessageModel;

/**
 * Consumer，订阅消息
 */
public class Consumer2 {

	public static void main(String[] args) throws InterruptedException, MQClientException {
		DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("message_consumer");
		consumer.setNamesrvAddr("192.168.100.145:9876;192.168.100.146:9876");
		consumer.setConsumeMessageBatchMaxSize(10);
		consumer.setMessageModel(MessageModel.BROADCASTING);// 广播消费
	
		consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);

		consumer.subscribe("TopicTest", "*");

		consumer.registerMessageListener(new MessageListenerConcurrently() {

			public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs, ConsumeConcurrentlyContext context) {

				try {

					for (MessageExt msg : msgs) {
						System.out.println(" Receive New Messages: " + msg);
					}

				} catch (Exception e) {
					e.printStackTrace();
					return ConsumeConcurrentlyStatus.RECONSUME_LATER;// 重试
				}

				return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;// 成功
			}
		});

		consumer.start();

		System.out.println("Consumer Started.");
	}
}

如果我们有2台节点(非主关系),2个节点物理上是分开的，Producer往MQ上写入20条数据其中broker1中拉取了12条。broker2中拉取了8 条，这种情况下，假如broker1宕机，那么我们消费数据的时候，只能消费到broker2中的8条，broker1中的12条已经持久化到中。需要broker1回复之后这12条数据才能继续被消费。

异步复制和同步双写主要是主和从的关系。消息需要实时消费的，就需要采用主从模式部署

异步复制:比如这里有一主一从，我们发送一条消息到主节点之后，这样消息就算从producer端发送成功了，然后通过异步复制的方法将数据复制到从节点

同步双写:比如这里有一主一从，我们发送一条消息到主节点之后，这样消息就并不算从producer端发送成功了，需要通过同步双写的方法将数据同步到从节点后，才算数据发送成功。

四、刷盘方式

同步刷盘：在消息到达MQ后，RocketMQ需要将数据持久化，同步刷盘是指数据到达内存之后，必须刷到commitlog日志之后才算成功，然后返回producer数据已经发送成功。

异步刷盘：，同步刷盘是指数据到达内存之后,返回producer说数据已经发送成功。，然后再写入commitlog日志。

commitlog：

commitlog就是来存储所有的元信息，包含消息体，类似于Mysql、Oracle的redolog,所以主要有CommitLog在，Consume Queue即使数据丢失，仍然可以恢复出来。

consumequeue：记录数据的位置,以便Consume快速通过consumequeue找到commitlog中的数据

原文链接：https://blog.csdn.net/u010634288/article/details/56049305

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