Redis 延时任务
Java项目开发
共 5346字,需浏览 11分钟
·
2022-01-11 16:42
引言
生成订单30分钟未支付,则自动取消 生成订单60秒后,给用户发短信
定时任务有明确的触发时间,延时任务没有 定时任务有执行周期,而延时任务在某事件触发后一段时间内执行,没有执行周期 定时任务一般执行的是批处理操作是多个任务,而延时任务一般是单个任务
方案分析
(1) 数据库轮询
<dependency>
<groupId>org.quartz-schedulergroupId>
<artifactId>quartzartifactId>
<version>2.2.2version>
dependency>
public class MyJob implements Job {
public void execute(JobExecutionContext context)
throws JobExecutionException {
System.out.println("要去数据库扫描啦。。。");
}
public static void main(String[] args) throws Exception {
// 创建任务
JobDetail jobDetail = JobBuilder.newJob(MyJob.class)
.withIdentity("job1", "group1").build();
// 创建触发器 每3秒钟执行一次
Trigger trigger = TriggerBuilder.newTrigger()
.withIdentity("trigger1", "group3")
.withSchedule(SimpleScheduleBuilder.simpleSchedule()
.withIntervalInSeconds(3)
.repeatForever())
.build();
Scheduler scheduler = new StdSchedulerFactory().getScheduler();
// 将任务及其触发器放入调度器
scheduler.scheduleJob(jobDetail, trigger);
// 调度器开始调度任务
scheduler.start();
}
}
要去数据库扫描啦。。。
优缺点
简单易行,支持集群操作
对服务器内存消耗大 存在延迟,比如你每隔3分钟扫描一次,那最坏的延迟时间就是3分钟 假设你的订单有几千万条,每隔几分钟这样扫描一次,数据库损耗极大
(2) JDK的延迟队列
Poll()
:获取并移除队列的超时元素,没有则返回空take()
:获取并移除队列的超时元素,如果没有则wait当前线程,直到有元素满足超时条件,返回结果。
public class OrderDelay implements Delayed {
private String orderId;
private long timeout;
OrderDelay(String orderId, long timeout) {
this.orderId = orderId;
this.timeout = timeout + System.nanoTime();
}
public int compareTo(Delayed other) {
if (other == this) {
return 0;
}
OrderDelay t = (OrderDelay) other;
long d = (getDelay(TimeUnit.NANOSECONDS) -
t.getDelay(TimeUnit.NANOSECONDS));
return (d == 0) ? 0 : ((d < 0) ? (-1) : 1);
}
// 返回距离你自定义的超时时间还有多少
public long getDelay(TimeUnit unit) {
return unit.convert(timeout - System.nanoTime(), TimeUnit.NANOSECONDS);
}
void print() {
System.out.println(orderId + "编号的订单要删除啦。。。。");
}
}
public class DelayQueueDemo
{
public static void main(String[] args)
{
// TODO Auto-generated method stub
List < String > list = new ArrayList < String > ();
list.add("00000001");
list.add("00000002");
list.add("00000003");
list.add("00000004");
list.add("00000005");
DelayQueue < OrderDelay > queue = newDelayQueue < OrderDelay > ();
long start = System.currentTimeMillis();
for(int i = 0; i < 5; i++)
{
//延迟三秒取出
queue.put(new OrderDelay(list.get(i), TimeUnit.NANOSECONDS.convert(3, TimeUnit.SECONDS)));
try
{
queue.take().print();
System.out.println("After " + (System.currentTimeMillis() - start) + " MilliSeconds");
}
catch(InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
00000001编号的订单要删除啦。。。。
After 3003 MilliSeconds
00000002编号的订单要删除啦。。。。
After 6006 MilliSeconds
00000003编号的订单要删除啦。。。。
After 9006 MilliSeconds
00000004编号的订单要删除啦。。。。
After 12008 MilliSeconds
00000005编号的订单要删除啦。。。。
After 15009 MilliSeconds
优缺点
效率高,任务触发时间延迟低。
服务器重启后,数据全部消失,怕宕机 集群扩展相当麻烦 因为内存条件限制的原因,比如下单未付款的订单数太多,那么很容易就出现OOM异常 代码复杂度较高
(3)时间轮算法
<dependency>
<groupId>io.nettygroupId>
<artifactId>netty-allartifactId>
<version>4.1.24.Finalversion>
dependency>
public class HashedWheelTimerTest
{
static class MyTimerTask implements TimerTask
{
boolean flag;
public MyTimerTask(boolean flag)
{
this.flag = flag;
}
public void run(Timeout timeout) throws Exception
{
// TODO Auto-generated method stub
System.out.println("要去数据库删除订单了。。。。");
this.flag = false;
}
}
public static void main(String[] argv)
{
MyTimerTask timerTask = new MyTimerTask(true);
Timer timer = new HashedWheelTimer();
timer.newTimeout(timerTask, 5, TimeUnit.SECONDS);
int i = 1;
while(timerTask.flag)
{
try
{
Thread.sleep(1000);
}
catch(InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(i + "秒过去了");
i++;
}
}
}
1秒过去了
2秒过去了
3秒过去了
4秒过去了
5秒过去了
要去数据库删除订单了。。。。
6秒过去了
优缺点
效率高,任务触发时间延迟时间比delayQueue低,代码复杂度比delayQueue低。
服务器重启后,数据全部消失,怕宕机 集群扩展相当麻烦 因为内存条件限制的原因,比如下单未付款的订单数太多,那么很容易就出现OOM异常
(4) redis缓存
添加元素: ZADD key score member [[score member] [score member] …]
按顺序查询元素: ZRANGE key start stop [WITHSCORES]
查询元素: score:ZSCORE key member
移除元素: ZREM key member [member …]
# 添加单个元素
redis> ZADD page_rank 10 google.com
(integer) 1
# 添加多个元素
redis> ZADD page_rank 9 baidu.com 8 bing.com
(integer) 2
redis> ZRANGE page_rank 0 -1 WITHSCORES
1) "bing.com"
2) "8"
3) "baidu.com"
4) "9"
5) "google.com"
6) "10"
# 查询元素的score值
redis> ZSCORE page_rank bing.com
"8"
# 移除单个元素
redis> ZREM page_rank google.com
(integer) 1
redis> ZRANGE page_rank 0 -1 WITHSCORES
1) "bing.com"
2) "8"
3) "baidu.com"
4) "9"
public class AppTest
{
private static final String ADDR = "127.0.0.1";
private static final int PORT = 6379;
private static JedisPool jedisPool = new JedisPool(ADDR, PORT);
public static Jedis getJedis()
{
return jedisPool.getResource();
}
//生产者,生成5个订单放进去
public void productionDelayMessage()
{
for(int i = 0; i < 5; i++)
{
//延迟3秒
Calendar cal1 = Calendar.getInstance();
cal1.add(Calendar.SECOND, 3);
int second3later = (int)(cal1.getTimeInMillis() / 1000);
AppTest.getJedis().zadd("OrderId", second3later, "OID0000001" + i);
System.out.println(System.currentTimeMillis() + "ms:redis生成了一个订单任务:订单ID为" + "OID0000001" + i);
}
}
//消费者,取订单
public void consumerDelayMessage()
{
Jedis jedis = AppTest.getJedis();
while(true)
{
Set < Tuple > items = jedis.zrangeWithScores("OrderId", 0, 1);
if(items == null || items.isEmpty())
{
System.out.println("当前没有等待的任务");
try
{
Thread.sleep(500);
}
catch(InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
continue;
}
int score = (int)((Tuple) items.toArray()[0]).getScore();
Calendar cal = Calendar.getInstance();
int nowSecond = (int)(cal.getTimeInMillis() / 1000);
if(nowSecond >= score)
{
String orderId = ((Tuple) items.toArray()[0]).getElement();
jedis.zrem("OrderId", orderId);
System.out.println(System.currentTimeMillis() + "ms:redis消费了一个任务:消费的订单OrderId为" + orderId);
}
}
}
public static void main(String[] args)
{
AppTest appTest = new AppTest();
appTest.productionDelayMessage();
appTest.consumerDelayMessage();
}
}
package com.rjzheng.delay4;
import java.util.concurrent.CountDownLatch;
public class ThreadTest
{
private static final int threadNum = 10;
private static CountDownLatch cdl = newCountDownLatch(threadNum);
static class DelayMessage implements Runnable
{
public void run()
{
try
{
cdl.await();
}
catch(InterruptedException e)
{
// TODO Auto-generated catch block
e.printStackTrace();
}
AppTest appTest = new AppTest();
appTest.consumerDelayMessage();
}
}
public static void main(String[] args)
{
AppTest appTest = new AppTest();
appTest.productionDelayMessage();
for(int i = 0; i < threadNum; i++)
{
new Thread(new DelayMessage()).start();
cdl.countDown();
}
}
}
if(nowSecond >= score)
{
String orderId = ((Tuple) items.toArray()[0]).getElement();
jedis.zrem("OrderId", orderId);
System.out.println(System.currentTimeMillis() + "ms:redis消费了一个任务:消费的订单OrderId为" + orderId);
}
if(nowSecond >= score)
{
String orderId = ((Tuple) items.toArray()[0]).getElement();
Long num = jedis.zrem("OrderId", orderId);
if(num != null && num > 0)
{
System.out.println(System.currentTimeMillis() + "ms:redis消费了一个任务:消费的订单OrderId为" + orderId);
}
}
notify-keyspace-events Ex
public class RedisTest
{
private static final String ADDR = "127.0.0.1";
private static final int PORT = 6379;
private static JedisPool jedis = new JedisPool(ADDR, PORT);
private static RedisSub sub = new RedisSub();
public static void init()
{
new Thread(new Runnable()
{
public void run()
{
jedis.getResource().subscribe(sub, "__keyevent@0__:expired");
}
}).start();
}
public static void main(String[] args) throws InterruptedException
{
init();
for(int i = 0; i < 10; i++)
{
String orderId = "OID000000" + i;
jedis.getResource().setex(orderId, 3, orderId);
System.out.println(System.currentTimeMillis() + "ms:" + orderId + "订单生成");
}
}
static class RedisSub extends JedisPubSub
{ < ahref = 'http://www.jobbole.com/members/wx610506454' > @Override < /a>
public void onMessage(String channel, String message)
{
System.out.println(System.currentTimeMillis() + "ms:" + message + "订单取消");
}
}
}
Because Redis Pub/Sub is fire and forget currently there is no way to use this feature if your application demands reliable notification of events, that is, if your Pub/Sub client disconnects, and reconnects later, all the events delivered during the time the client was disconnected are lost.
Redis的发布/订阅目前是即发即弃(fire and forget)模式的,因此无法实现事件的可靠通知。也就是说,如果发布/订阅的客户端断链之后又重连,则在客户端断链期间的所有事件都丢失了。
优缺点
由于使用Redis作为消息通道,消息都存储在Redis中。如果发送程序或者任务处理程序挂了,重启之后,还有重新处理数据的可能性。 做集群扩展相当方便 时间准确度高
需要额外进行redis维护
(5)使用消息队列
x-message-tt
,来控制消息的生存时间,如果超时,则消息变为dead letter
x-dead-letter-exchange
和x-dead-letter-routing-key
(可选)两个参数,用来控制队列内出现了deadletter,则按照这两个参数重新路由。优缺点
高效,可以利用rabbitmq的分布式特性轻易的进行横向扩展,消息支持持久化增加了可靠性。
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