RocketMQ 定时消息和批量消息

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RocketMQ 定时消息和批量消息

 

RocketMQ 定时消息

定时消息是指消息发到 Broker 后，不能立刻被 Consumer 消费，要到特定的时间点或者等待特定的时间后才能被消费。

RocketMQ 目前只支持固定精度的定时消息。官方说法如下：

如果要支持任意的时间精度，在 Broker 层面，必须要做消息排序，如果再涉及到持久化，那么消息排序要不可避免的产生巨大性能开销。

延迟级别：

延迟级别	时间
1	1s
2	5s
3	10s
4	30s
5	1m
6	2m
7	3m
8	4m
9	5m
10	6m
11	7m
12	8m
13	9m
14	10m
15	20m
16	30m
17	1h
18	2h

发送消息时，设置延迟级别，如下Producer，

import org.apache.rocketmq.client.producer.DefaultMQProducer;
import org.apache.rocketmq.common.message.Message;

public class ScheduledMessageProducer {

    public static void main(String[] args) throws Exception {
        // Instantiate a producer to send scheduled messages
        DefaultMQProducer producer = new DefaultMQProducer("ExampleProducerGroup");
        producer.setNamesrvAddr("127.0.0.1:9876");
        // Launch producer
        producer.start();
        int totalMessagesToSend = 100;
        for (int i = 0; i < totalMessagesToSend; i++) {
            Message message = new Message("schedule_message_test_topic", ("Hello scheduled message " + i).getBytes());
            // This message will be delivered to consumer 10 seconds later.
            message.setDelayTimeLevel(3);
            // Send the message
            producer.send(message);
        }

        // Shutdown producer after use.
        producer.shutdown();
    }

}

Consumer，

import org.apache.rocketmq.client.consumer.DefaultMQPushConsumer;
import org.apache.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;
import org.apache.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
import org.apache.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import org.apache.rocketmq.common.consumer.ConsumeFromWhere;
import org.apache.rocketmq.common.message.MessageExt;

import java.util.List;

public class ScheduledMessageConsumer {

    public static void main(String[] args) throws Exception {
        // Instantiate message consumer
        DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("ExampleConsumer");

        consumer.setNamesrvAddr("127.0.0.1:9876");
        consumer.setInstanceName("ScheduledMessageConsumer");
        consumer.setConsumeFromWhere(ConsumeFromWhere.CONSUME_FROM_FIRST_OFFSET);

        // Subscribe topics
        consumer.subscribe("schedule_message_test_topic", "*");
        // Register message listener
        consumer.registerMessageListener(new MessageListenerConcurrently() {
            @Override
            public ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> messages, ConsumeConcurrentlyContext context) {
                for (MessageExt message : messages) {
                    // Print approximate delay time period
                    System.out.println("Receive message[msgId=" + message.getMsgId() + "] "
                            + (System.currentTimeMillis() - message.getStoreTimestamp()) + "ms later");
                }
                return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
            }
        });
        // Launch consumer
        consumer.start();
    }
}

来自：https://github.com/YunaiV/Blog/blob/master/RocketMQ/1010-RocketMQ%E6%BA%90%E7%A0%81%E8%A7%A3%E6%9E%90%EF%BC%9A%E5%AE%9A%E6%97%B6%E6%B6%88%E6%81%AF%E4%B8%8E%E6%B6%88%E6%81%AF%E9%87%8D%E8%AF%95.md

 

RocketMQ 批量消息

当有大量相同topic，相同发送状态且非定时发送的消息时，可以批量发送消息。但是一次发送的消息不能超过1MiB。如果大于1MiB，可以使用如下方法分割，然后批量发送。

import org.apache.rocketmq.common.message.Message;

import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class ListSplitter implements Iterator<List<Message>> {

    private final int SIZE_LIMIT = 1000 * 1000;
    private final List<Message> messages;
    private int currIndex;

    public ListSplitter(List<Message> messages) {
        this.messages = messages;
    }

    @Override
    public boolean hasNext() {
        return currIndex < messages.size();
    }

    @Override
    public List<Message> next() {
        int nextIndex = currIndex;
        int totalSize = 0;
        for (; nextIndex < messages.size(); nextIndex++) {
            Message message = messages.get(nextIndex);
            int tmpSize = message.getTopic().length() + message.getBody().length;
            Map<String, String> properties = message.getProperties();
            for (Map.Entry<String, String> entry : properties.entrySet()) {
                tmpSize += entry.getKey().length() + entry.getValue().length();
            }
            tmpSize = tmpSize + 20; //for log overhead
            if (tmpSize > SIZE_LIMIT) {
                //it is unexpected that single message exceeds the SIZE_LIMIT
                //here just let it go, otherwise it will block the splitting process
                if (nextIndex - currIndex == 0) {
                    //if the next sublist has no element, add this one and then break, otherwise just break
                    nextIndex++;
                }
                break;
            }
            if (tmpSize + totalSize > SIZE_LIMIT) {
                break;
            } else {
                totalSize += tmpSize;
            }

        }
        List<Message> subList = messages.subList(currIndex, nextIndex);
        currIndex = nextIndex;
        return subList;
    }
}

批量发送消息的Producer，

import org.apache.rocketmq.client.exception.MQClientException;
import org.apache.rocketmq.client.producer.DefaultMQProducer;
import org.apache.rocketmq.common.message.Message;
import org.apache.rocketmq.remoting.common.RemotingHelper;

import java.util.ArrayList;
import java.util.List;

public class BatchProducer {

    public static void main(String[] args) throws MQClientException, InterruptedException {
        DefaultMQProducer producer = new DefaultMQProducer("BatchProducerGroup");

        producer.setNamesrvAddr("127.0.0.1:9876");
        producer.start();

        List<Message> msgs = new ArrayList<Message>();
        for (int i = 0; i < 1000; i++) {
            try {
                // Create a message instance, specifying topic, tag and message body.
                Message msg = new Message(
                        "batch_send_message_topic" /* Topic */,
                        "TagA" /* Tag */,
                        ("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET) /* Message body */
                );
                msgs.add(msg);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        //then you could split the large list into small ones:
        ListSplitter splitter = new ListSplitter(msgs);
        while (splitter.hasNext()) {
            try {
                List<Message> listItem = splitter.next();
                producer.send(listItem);
            } catch (Exception e) {
                e.printStackTrace();
                //handle the error
            }
        }

        // Shut down once the producer instance is not longer in use.
        producer.shutdown();
    }

}

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转载于:https://my.oschina.net/xinxingegeya/blog/1577977