RocketMQ学习：Pull和Push

摘要： 源代码版本是3.2.6。在rocketmq里，consumer被分为2类：MQPullConsumer和MQPushConsumer，其实本质都是拉模式（pull），即consumer轮询从broker拉取消息。

源代码版本是3.2.6。在rocketmq里，consumer被分为2类：MQPullConsumer和MQPushConsumer，其实本质都是拉模式（pull），即consumer轮询从broker拉取消息。

区别是：

push方式里，consumer把轮询过程封装了，并注册MessageListener监听器，取到消息后，唤醒MessageListener的consumeMessage()来消费，对用户而言，感觉消息是被推送过来的。

pull方式里，取消息的过程需要用户自己写，首先通过打算消费的Topic拿到MessageQueue的集合，遍历MessageQueue集合，然后针对每个MessageQueue批量取消息，一次取完后，记录该队列下一次要取的开始offset，直到取完了，再换另一个MessageQueue。

文字描述可能不是很清楚，前面的文章都是push方式的，所以这里只上pull方式的，贴代码：

<properties> <project.build.sourceEncoding>UTF-8project.build.sourceEncoding> <logback.version>1.0.13logback.version> <rocketmq.version>3.2.6rocketmq.version> properties> <dependencies> <dependency> <groupId>ch.qos.logbackgroupId> <artifactId>logback-classicartifactId> <version>1.0.13version> dependency> <dependency> <groupId>ch.qos.logbackgroupId> <artifactId>logback-coreartifactId> <version>1.0.13version> dependency> <dependency> <groupId>com.alibaba.rocketmqgroupId> <artifactId>rocketmq-clientartifactId> <version>${rocketmq.version}version> dependency> <dependency> <groupId>junitgroupId> <artifactId>junitartifactId> <version>4.10version> <scope>testscope> dependency> dependencies>

Producer：

package com.zoo.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("192.168.0.104:9876"); producer.start(); for (int i = 0; i < 5; i++) { try { Message msg = new Message("TopicTest",// topic "TagA",// tag ("Hello RocketMQ " + i).getBytes()// body ); SendResult sendResult = producer.send(msg); System.out.println(sendResult); Thread.sleep(6000); } catch (Exception e) { e.printStackTrace(); Thread.sleep(3000); } } producer.shutdown(); } }

Consumer:

package com.zoo.quickstart.pull; import java.util.HashMap; import java.util.Map; import java.util.Set; import com.alibaba.rocketmq.client.consumer.DefaultMQPullConsumer; import com.alibaba.rocketmq.client.consumer.PullResult; import com.alibaba.rocketmq.client.exception.MQClientException; import com.alibaba.rocketmq.common.message.MessageQueue; /** * PullConsumer，订阅消息 */ public class PullConsumer { private static final Map offseTable = new HashMap(); public static void main(String[] args) throws MQClientException { DefaultMQPullConsumer consumer = new DefaultMQPullConsumer("please_rename_unique_group_name_5"); consumer.setNamesrvAddr("192.168.0.104:9876"); consumer.start(); Set mqs = consumer.fetchSubscribeMessageQueues("TopicTest"); for (MessageQueue mq : mqs) { System.out.println("Consume from the queue: " + mq); SINGLE_MQ: while (true) { try { PullResult pullResult = consumer.pullBlockIfNotFound(mq, null, getMessageQueueOffset(mq), 32); System.out.println(pullResult); putMessageQueueOffset(mq, pullResult.getNextBeginOffset()); switch (pullResult.getPullStatus()) { case FOUND: // TODO break; case NO_MATCHED_MSG: break; case NO_NEW_MSG: break SINGLE_MQ; case OFFSET_ILLEGAL: break; default: break; } } catch (Exception e) { e.printStackTrace(); } } } consumer.shutdown(); } private static void putMessageQueueOffset(MessageQueue mq, long offset) { offseTable.put(mq, offset); } private static long getMessageQueueOffset(MessageQueue mq) { Long offset = offseTable.get(mq); if (offset != null) return offset; return 0; } }

还有一种定时的Consumer：

package com.zoo.quickstart.pull; import com.alibaba.rocketmq.client.consumer.MQPullConsumer; import com.alibaba.rocketmq.client.consumer.MQPullConsumerScheduleService; import com.alibaba.rocketmq.client.consumer.PullResult; import com.alibaba.rocketmq.client.consumer.PullTaskCallback; import com.alibaba.rocketmq.client.consumer.PullTaskContext; import com.alibaba.rocketmq.client.exception.MQClientException; import com.alibaba.rocketmq.common.message.MessageQueue; import com.alibaba.rocketmq.common.protocol.heartbeat.MessageModel; public class PullScheduleService { public static void main(String[] args) throws MQClientException { final MQPullConsumerScheduleService scheduleService = new MQPullConsumerScheduleService("GroupName1"); scheduleService.getDefaultMQPullConsumer().setNamesrvAddr("192.168.0.104:9876"); scheduleService.setMessageModel(MessageModel.CLUSTERING); scheduleService.registerPullTaskCallback("TopicTest", new PullTaskCallback() { @Override public void doPullTask(MessageQueue mq, PullTaskContext context) { MQPullConsumer consumer = context.getPullConsumer(); try { // 获取从哪里拉取 long offset = consumer.fetchConsumeOffset(mq, false); if (offset < 0) offset = 0; PullResult pullResult = consumer.pull(mq, "*", offset, 32); System.out.println(offset + "\t" + mq + "\t" + pullResult); switch (pullResult.getPullStatus()) { case FOUND: break; case NO_MATCHED_MSG: break; case NO_NEW_MSG: case OFFSET_ILLEGAL: break; default: break; } // 存储Offset，客户端每隔5s会定时刷新到Broker consumer.updateConsumeOffset(mq, pullResult.getNextBeginOffset()); // 设置再过100ms后重新拉取 context.setPullNextDelayTimeMillis(100); } catch (Exception e) { e.printStackTrace(); } } }); scheduleService.start(); } }