目录
一、RocketMQ
1、延时消息
2、批量消息
批量切分发送
3、消息的过滤
Tag过滤
Sql过滤
延时消息:Producer 将消息发送到消息队列 RocketMQ 服务端,但并不期望这条消息立马投递(被消费者消费),而是延迟一定时间后才投递到 Consumer 进行消费,该消息即延时消息。
适用场景:消息生产和消费有时间窗口要求:比如在电商交易中超时未支付关闭订单的场景,在订单创建时向RocketMQ发送一条延时消息。这条消息将会在 30 分钟以后投递给消费者,消费者收到此消息后需要判断对应的订单是否已完成支付。 如支付未完成,则关闭订单。如已完成支付则忽略。
延迟消息的level,区分18个等级:level为1,表示延迟1秒后消费;level为2表示延迟5秒后消费;level为3表示延迟10秒后消费;以此类推;最大level为18表示延迟2个小时消费。具体标识如下:
level |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
延迟 |
1s |
5s |
10s |
30s |
1m |
2m |
3m |
4m |
5m |
level |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
延迟 |
6m |
7m |
8m |
9m |
10m |
20m |
30m |
1h |
2h |
生产消息跟普通的生产消息类似,只需要在消息上设置延迟队列的level即可。消费消息跟普通的消费消息一致。
生产者
package org.apache.rocketmq.example.schedule;
import java.nio.charset.StandardCharsets;
import org.apache.rocketmq.client.producer.DefaultMQProducer;
import org.apache.rocketmq.client.producer.SendResult;
import org.apache.rocketmq.common.message.Message;
public class ScheduledMessageProducer {
public static final String PRODUCER_GROUP = "ExampleProducerGroup";
public static final String DEFAULT_NAMESRVADDR = "127.0.0.1:9876";
public static final String TOPIC = "TestTopic";
public static void main(String[] args) throws Exception {
// Instantiate a producer to send scheduled messages
DefaultMQProducer producer = new DefaultMQProducer(PRODUCER_GROUP);
//设置NameServ的地址
producer.setNamesrvAddr(DEFAULT_NAMESRVADDR);
// Launch producer
producer.start();
int totalMessagesToSend = 10;
for (int i = 0; i < totalMessagesToSend; i++) {
Message message = new Message(TOPIC, ("Hello scheduled message " + i).getBytes(StandardCharsets.UTF_8));
// This message will be delivered to consumer 10 seconds later.
message.setDelayTimeLevel(3);
// Send the message
SendResult result = producer.send(message);
System.out.print(result);
}
// Shutdown producer after use.
producer.shutdown();
}
}
消费者
package org.apache.rocketmq.example.schedule;
import org.apache.rocketmq.client.consumer.DefaultMQPushConsumer;
import org.apache.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
import org.apache.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import org.apache.rocketmq.common.message.MessageExt;
public class ScheduledMessageConsumer {
public static final String CONSUMER_GROUP = "ExampleConsumer";
public static final String DEFAULT_NAMESRVADDR = "127.0.0.1:9876";
public static final String TOPIC = "TestTopic";
public static void main(String[] args) throws Exception {
// Instantiate message consumer
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer(CONSUMER_GROUP);
// Uncomment the following line while debugging, namesrvAddr should be set to your local address
consumer.setNamesrvAddr(DEFAULT_NAMESRVADDR);
// Subscribe topics
consumer.subscribe(TOPIC, "*");
// Register message listener
consumer.registerMessageListener((MessageListenerConcurrently) (messages, context) -> {
for (MessageExt message : messages) {
// Print approximate delay time period
//打印消息消费延迟
System.out.printf("Receive message[msgId=%s %d ms later]\n", message.getMsgId(),
System.currentTimeMillis() - message.getStoreTimestamp());
}
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
});
// Launch consumer
consumer.start();
//info:to see the time effect, run the consumer first , it will wait for the msg
//then start the producer
}
}
查看消费者消息信息
Receive message[msgId=C0A800AB351018B4AAC2293131720003 500 ms later]
Receive message[msgId=C0A800AB351018B4AAC22931315C0000 501 ms later]
Receive message[msgId=C0A800AB351018B4AAC22931316F0002 500 ms later]
Receive message[msgId=C0A800AB351018B4AAC2293131680001 500 ms later]
Receive message[msgId=C0A800AB351018B4AAC22931317B0007 500 ms later]
Receive message[msgId=C0A800AB351018B4AAC2293131790006 500 ms later]
Receive message[msgId=C0A800AB351018B4AAC2293131770005 500 ms later]
Receive message[msgId=C0A800AB351018B4AAC22931317F0009 500 ms later]
Receive message[msgId=C0A800AB351018B4AAC2293131740004 500 ms later]
Receive message[msgId=C0A800AB351018B4AAC22931317D0008 500 ms later]
在高并发场景中,批量发送消息能显著提高传递消息发送时的性能(减少网络连接及IO的开销)。使用批量消息时的限制是这些批量消息应该有相同的topic,相同的waitStoreMsgOK(集群时会细讲),且不能是延时消息。
在发送批量消息时先构建一个消息对象集合,然后调用send(Collection msg)系列的方法即可。由于批量消息的4MB限制,所以一般情况下在集合中添加消息需要先计算当前集合中消息对象的大小是否超过限制,如果超过限制也可以使用分割消息的方式进行多次批量发送。
因为批量消息是一个Collection,所以送入消息可以是List,也可以使Set,这里为方便起见,使用List进行批量组装发送。
package org.apache.rocketmq.example.batch;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;
import org.apache.rocketmq.client.producer.DefaultMQProducer;
import org.apache.rocketmq.client.producer.SendResult;
import org.apache.rocketmq.common.message.Message;
public class SimpleBatchProducer {
public static final String PRODUCER_GROUP = "BatchProducerGroupName";
public static final String DEFAULT_NAMESRVADDR = "127.0.0.1:9876";
public static final String TOPIC = "BatchTest";
public static final String TAG = "Tag";
public static void main(String[] args) throws Exception {
DefaultMQProducer producer = new DefaultMQProducer(PRODUCER_GROUP);
// Uncomment the following line while debugging, namesrvAddr should be set to your local address
producer.setNamesrvAddr(DEFAULT_NAMESRVADDR);
producer.start();
//If you just send messages of no more than 1MiB at a time, it is easy to use batch
//Messages of the same batch should have: same topic, same waitStoreMsgOK and no schedule support
List messages = new ArrayList<>();
messages.add(new Message(TOPIC, TAG, "OrderID001", "Hello world 0".getBytes(StandardCharsets.UTF_8)));
messages.add(new Message(TOPIC, TAG, "OrderID002", "Hello world 1".getBytes(StandardCharsets.UTF_8)));
messages.add(new Message(TOPIC, TAG, "OrderID003", "Hello world 2".getBytes(StandardCharsets.UTF_8)));
SendResult sendResult = producer.send(messages);
System.out.printf("%s", sendResult);
}
}
如果消息的总长度可能大于4MB时,这时候最好把消息进行分割,案例中以1M大小进行消息分割。
我们需要发送10万元素的数组,这个量很大,怎么快速发送完。使用批量发送,同时每一批控制在1M左右确保不超过消息大小限制。
package org.apache.rocketmq.example.batch;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.apache.rocketmq.client.producer.DefaultMQProducer;
import org.apache.rocketmq.client.producer.SendResult;
import org.apache.rocketmq.common.message.Message;
public class SplitBatchProducer {
public static final String PRODUCER_GROUP = "BatchProducerGroupName";
public static final String DEFAULT_NAMESRVADDR = "127.0.0.1:9876";
public static final int MESSAGE_COUNT = 100 * 1000;
public static final String TOPIC = "BatchTest";
public static final String TAG = "Tag";
public static void main(String[] args) throws Exception {
DefaultMQProducer producer = new DefaultMQProducer(PRODUCER_GROUP);
// Uncomment the following line while debugging, namesrvAddr should be set to your local address
producer.setNamesrvAddr(DEFAULT_NAMESRVADDR);
producer.start();
//large batch
List messages = new ArrayList<>(MESSAGE_COUNT);
for (int i = 0; i < MESSAGE_COUNT; i++) {
messages.add(new Message(TOPIC, TAG, "OrderID" + i, ("Hello world " + i).getBytes(StandardCharsets.UTF_8)));
}
//split the large batch into small ones:
ListSplitter splitter = new ListSplitter(messages);
while (splitter.hasNext()) {
List listItem = splitter.next();
SendResult sendResult = producer.send(listItem);
System.out.printf("%s", sendResult);
}
}
}
class ListSplitter implements Iterator> {
private static final int SIZE_LIMIT = 1000 * 1000;
private final List messages;
private int currIndex;
public ListSplitter(List messages) {
this.messages = messages;
}
@Override
public boolean hasNext() {
return currIndex < messages.size();
}
@Override
public List 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 properties = message.getProperties();
for (Map.Entry entry : properties.entrySet()) {
tmpSize += entry.getKey().length() + entry.getValue().length();
}
//for log overhead
tmpSize = tmpSize + 20;
if (tmpSize > SIZE_LIMIT) {
//it is unexpected that single message exceeds the sizeLimit
//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 subList = messages.subList(currIndex, nextIndex);
currIndex = nextIndex;
return subList;
}
@Override
public void remove() {
throw new UnsupportedOperationException("Not allowed to remove");
}
}
在实际的开发应用中,对于一类消息尽可能使用一个Topic进行存储,但在消费时需要选择您想要的消息,这时可以使用RocketMQ的消息过滤功能,具体实现是利用消息的Tag和Key。
Key一般用于消息在业务层面的唯一标识。对发送的消息设置好 Key,以后可以根据这个 Key 来查找消息。比如消息异常,消息丢失,进行查找会很方便。RocketMQ 会创建专门的索引文件,用来存储 Key与消息的映射,由于底层实现是 Hash 索引,应尽量使 Key唯一,避免潜在的哈希冲突。
Tag可以理解为是二级分类。以淘宝交易平台为例,订单消息和支付消息属于不同业务类型的消息,分别创建OrderTopic 和PayTopic,其中订单消息根据不同的商品品类以不同的 Tag 再进行细分,如手机类、家电类、男装类、女装类、化妆品类,最后它们都被各个不同的系统所接收。通过合理的使用 Topic 和 Tag,可以让业务结构清晰,更可以提高效率。
Key和Tag的主要差别是使用场景不同,Key主要用于通过命令行命令查询消息,而Tag用于在消息端的代码中,用来进行服务端消息过滤。
使用Tag过滤的方式是在消息生产时传入感兴趣的Tag标签,然后在消费端就可以根据Tag来选择您想要的消息。具体的操作是在创建Message的时候添加,一个Message只能有一个Tag。
package org.apache.rocketmq.example.filter;
import org.apache.rocketmq.client.producer.DefaultMQProducer;
import org.apache.rocketmq.client.producer.SendResult;
import org.apache.rocketmq.common.message.Message;
import org.apache.rocketmq.remoting.common.RemotingHelper;
public class TagFilterProducer {
public static void main(String[] args) throws Exception {
DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");
producer.setNamesrvAddr("127.0.0.1:9876");
producer.start();
String[] tags = new String[] {"TagA", "TagB", "TagC"};
for (int i = 0; i < 60; i++) {
Message msg = new Message("TagFilterTest",
tags[i % tags.length],
"Hello world".getBytes(RemotingHelper.DEFAULT_CHARSET));
SendResult sendResult = producer.send(msg);
System.out.printf("%s%n", sendResult);
}
producer.shutdown();
}
}
消费者消费时,只选择TagA和TagC的消息。
package org.apache.rocketmq.example.filter;
import java.util.List;
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.client.exception.MQClientException;
import org.apache.rocketmq.common.message.MessageExt;
public class TagFilterConsumer {
public static void main(String[] args) throws MQClientException {
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("please_rename_unique_group_name");
consumer.setNamesrvAddr("127.0.0.1:9876");
consumer.subscribe("TagFilterTest", "TagA || TagC");
consumer.registerMessageListener(new MessageListenerConcurrently() {
@Override
public ConsumeConcurrentlyStatus consumeMessage(List msgs,
ConsumeConcurrentlyContext context) {
System.out.printf("%s Receive New Messages: %s %n", Thread.currentThread().getName(), msgs);
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
}
});
consumer.start();
System.out.printf("Consumer Started.%n");
}
}
注意事项
Tag过滤的形式非常简单,||代表或、*代表所有,所以使用Tag过滤这对于复杂的场景可能不起作用。在这种情况下,可以使用SQL表达式筛选消息。
SQL特性可以通过发送消息时的属性来进行消息的过滤计算。具体的操作是使用SQL92标准的sql语句,前提是只有使用push模式的消费者才能用(消费的模式就是push)
SQL基本语法
数值比较:比如:>,>=,<,<=,BETWEEN,=;
字符比较:比如:=,<>,IN;
IS NULL 或者 IS NOT NULL;
逻辑符号:AND,OR,NOT;
常量支持类型为:
数值,比如:123,3.1415;
字符,比如:'abc',必须用单引号包裹起来;
NULL,特殊的常量
布尔值,TRUE 或 FALSE
注意事项
Sql过滤需要Broker开启这项功能(如果消费时使用SQL过滤抛出异常错误,说明Sql92功能没有开启),需要修改Broker.conf配置文件。加入enablePropertyFilter=true 然后重启Broker服务。
package org.apache.rocketmq.example.filter;
import org.apache.rocketmq.client.producer.DefaultMQProducer;
import org.apache.rocketmq.client.producer.SendResult;
import org.apache.rocketmq.common.message.Message;
import org.apache.rocketmq.remoting.common.RemotingHelper;
public class SqlFilterProducer {
public static void main(String[] args) throws Exception {
DefaultMQProducer producer = new DefaultMQProducer("please_rename_unique_group_name");
producer.setNamesrvAddr("127.0.0.1:9876");
producer.start();
String[] tags = new String[] {"TagA", "TagB", "TagC"};
for (int i = 0; i < 10; i++) {
Message msg = new Message("SqlFilterTest",
tags[i % tags.length],
("Hello RocketMQ " + i).getBytes(RemotingHelper.DEFAULT_CHARSET)
);
//设置sql过滤的属性
msg.putUserProperty("a", String.valueOf(i));
SendResult sendResult = producer.send(msg);
System.out.printf("%s%n", sendResult);
}
producer.shutdown();
}
}
用MessageSelector.bySql来使用sql筛选消息
package org.apache.rocketmq.example.filter;
import java.util.List;
import org.apache.rocketmq.client.consumer.DefaultMQPushConsumer;
import org.apache.rocketmq.client.consumer.MessageSelector;
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.message.MessageExt;
public class SqlFilterConsumer {
public static void main(String[] args) throws Exception {
DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("please_rename_unique_group_name");
consumer.setNamesrvAddr("127.0.0.1:9876");
// Don't forget to set enablePropertyFilter=true in broker
consumer.subscribe("SqlFilterTest",
MessageSelector.bySql("(TAGS is not null and TAGS in ('TagA', 'TagB'))" +
"and (a is not null and a between 0 and 3)"));
consumer.registerMessageListener(new MessageListenerConcurrently() {
@Override
public ConsumeConcurrentlyStatus consumeMessage(List msgs,
ConsumeConcurrentlyContext context) {
System.out.printf("%s Receive New Messages: %s %n", Thread.currentThread().getName(), msgs);
return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;
}
});
consumer.start();
System.out.printf("Consumer Started.%n");
}
}
当一条消息初次消费失败,消息队列 RocketMQ 会自动进行消息重试;达到最大重试次数后,若消费依然失败,则表明消费者在正常情况下无法正确地消费该消息,此时,消息队列 RocketMQ 不会立刻将消息丢弃,而是将其发送到该消费者对应的特殊队列中。
在消息队列 RocketMQ 中,这种正常情况下无法被消费的消息称为死信消息(Dead-Letter Message),存储死信消息的特殊队列称为死信队列(Dead-Letter Queue)。
死信特性
死信消息具有以下特性:
不会再被消费者正常消费。
有效期与正常消息相同,均为 3 天,3 天后会被自动删除。因此,请在死信消息产生后的 3 天内及时处理。
死信队列具有以下特性:
不会再被消费者正常消费。
一个死信队列对应一个 Group ID, 而不是对应单个消费者实例。
如果一个 Group ID 未产生死信消息,消息队列 RocketMQ 不会为其创建相应的死信队列。
一个死信队列包含了对应 Group ID 产生的所有死信消息,不论该消息属于哪个 Topic。
RocketMQ Learning(一)
不是你觉的悟到的东西给了你,你也接不住!
干我们这行,啥时候懈怠,就意味着长进的停止,长进的停止就意味着被淘汰,只能往前冲,直到凤凰涅槃的一天!