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RocketMq入门
RocketMq是一种消息中间件，作用是业务相互调用时解耦。可以想象有一个消息的大池子，消息的生产者只要将消息丢到池子里即可。消息的消费者可以被动收到消息或者主动定时去池子里找消息，分别对应了消息系统设计上的推和拉模型。
这么多消息在一起肯定要做区分，所以设计了topic和tag做分组的标识。
这个大池子就是Broker。
为了方便生产者和消费者找到这个池子（路由），设计了一个叫Name Server的角色。
RocketMq的角色还是比较清晰的：
发送消息
Rocket发送消息三种方式：同步、异步、单向传播。
同步的例子：
package com.yunsheng.simpleOrder;
import com.alibaba.rocketmq.client.producer.DefaultMQProducer;
import com.alibaba.rocketmq.client.producer.SendResult;
import com.alibaba.rocketmq.common.message.Message;
import com.alibaba.rocketmq.remoting.common.RemotingHelper;
public class SyncProducer {
public static void main(String[] args) throws Exception {
//Instantiate with a producer group name.
DefaultMQProducer producer = new
DefaultMQProducer("produce1");
producer.setNamesrvAddr("10.135.17.26:9876;10.135.17.27:9876");
producer.setVipChannelEnabled(false);
//Launch the instance.
producer.start();
for (int i = 0; i < 10; i++) {
//Create a message instance, specifying topic, tag and message body.
Message msg = new Message("TopicTest", "TagA",
("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET)
);
//Call send message to deliver message to one of brokers.
SendResult sendResult = producer.send(msg);
System.out.printf("%s%n", sendResult);
}
//Shut down once the producer instance is not longer in use.
producer.shutdown();
}
}
我使用的client版本是3.6.2,从3.4.*开始，默认开启了VIP通道，VIP通道端口为10911-2=10909。若Rocket服务器未启动端口10909，则报connect to <：10909> failed。
这里要加producer.setVipChannelEnabled(false);
同理，consumer也要加这一句。
package com.yunsheng.simpleOrder;
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 java.util.List;
public class SyncConsumer {
public static void main(String[] args) throws InterruptedException, MQClientException {
//声明并初始化一个consumer
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("consumer1");
consumer.setNamesrvAddr("10.135.17.26:9876;10.135.17.27:9876");
consumer.setVipChannelEnabled(false);
//这里设置的是一个consumer的消费策略
//CONSUME_FROM_LAST_OFFSET 默认策略，从该队列最尾开始消费，即跳过历史消息
//CONSUME_FROM_FIRST_OFFSET 从队列最开始开始消费，即历史消息（还储存在broker的）全部消费一遍
//CONSUME_FROM_TIMESTAMP 从某个时间点开始消费，和setConsumeTimestamp()配合使用，默认是半个小时以前
consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);
//设置consumer所订阅的Topic和Tag，*代表全部的Tag
consumer.subscribe("TopicTest", "TagA");
//设置一个Listener，主要进行消息的逻辑处理
consumer.registerMessageListener(new MessageListenerConcurrently() {
public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs,
ConsumeConcurrentlyContext context) {
// System.out.println(new String(msgs.get(0).getBody()));
System.out.println(Thread.currentThread().getName() + " Receive New Messages: " + msgs);
//返回消费状态
//CONSUME_SUCCESS 消费成功
//RECONSUME_LATER 消费失败，需要稍后重新消费
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
}
});
//调用start()方法启动consumer
consumer.start();
System.out.println("Consumer Started.");
}
}
异步的例子：
package com.yunsheng.simpleOrder;
import com.alibaba.rocketmq.client.producer.DefaultMQProducer;
import com.alibaba.rocketmq.client.producer.SendCallback;
import com.alibaba.rocketmq.client.producer.SendResult;
import com.alibaba.rocketmq.common.message.Message;
import com.alibaba.rocketmq.remoting.common.RemotingHelper;
public class AsyncProducer {
public static void main(String[] args) throws Exception {
//Instantiate with a producer group name.
DefaultMQProducer producer = new DefaultMQProducer("ExampleProducerGroup");
producer.setNamesrvAddr("10.135.17.26:9876;10.135.17.27:9876");
producer.setVipChannelEnabled(false);
//Launch the instance.
producer.start();
producer.setRetryTimesWhenSendAsyncFailed(0);
for (int i = 0; i < 5; i++) {
final int index = i;
//Create a message instance, specifying topic, tag and message body.
Message msg = new Message("TopicTest",
"TagA",
"OrderID188",
"Hello world".getBytes(RemotingHelper.DEFAULT_CHARSET));
producer.send(msg, new SendCallback() {
public void onSuccess(SendResult sendResult) {
System.out.printf("%-10d OK %s %n", index,
sendResult.getMsgId());
}
public void onException(Throwable e) {
System.out.printf("%-10d Exception %s %n", index, e);
e.printStackTrace();
}
});
}
//Shut down once the producer instance is not longer in use.
producer.shutdown();
}
}
producer.setRetryTimesWhenSendFailed(0);//发送失败后，重试0次
单向
单向传播适用于对可靠性要求不高的场景，如日志收集。
package com.yunsheng.simpleOrder;
import com.alibaba.rocketmq.client.producer.DefaultMQProducer;
import com.alibaba.rocketmq.common.message.Message;
import com.alibaba.rocketmq.remoting.common.RemotingHelper;
public class OnewayProducer {
public static void main(String[] args) throws Exception {
//Instantiate with a producer group name.
DefaultMQProducer producer = new DefaultMQProducer("ExampleProducerGroup");
producer.setNamesrvAddr("10.135.17.26:9876;10.135.17.27:9876");
producer.setVipChannelEnabled(false);
//Launch the instance.
producer.start();
for (int i = 0; i < 5; i++) {
//Create a message instance, specifying topic, tag and message body.
Message msg = new Message("TopicTest" /* Topic */,
"TagA" /* Tag */,
("Hello RocketMQ " +
i).getBytes(RemotingHelper.DEFAULT_CHARSET) /* Message body */
);
//Call send message to deliver message to one of brokers.
producer.sendOneway(msg);
}
//Shut down once the producer instance is not longer in use.
producer.shutdown();
}
}
这个send是没有返回值的，就是说把消息丢出去就完事，不再管消息是否投递成功。
