上一篇演示了通过redis实现ID生成器,本篇模拟缓存击穿，穿透，雪崩的场景。
package com.coderman.jedis.clusterdemo.hack;import com.coderman.jedis.clusterdemo.ClusterTest;import org.junit.Test;/*** @Author fanchunshuai* @Date /1/31 15* @Description:* * 缓存穿透：* 参考 https://mp./s?__biz=MzU0MDEwMjgwNA==&mid=2247486705&idx=2&sn=33f90d9606ad32384d351a2cc170ba2d&chksm=fb3f150acc489c1c967f2bb250d14c3e44d4f4f2dff6991f8315043ca247819b3bfd973650ef&mpshare=1&scene=1&srcid=&sharer_sharetime=1579147583247&sharer_shareid=9c9dad852994f99c77b36e07bf5e0634&key=e10552fbfdccf7e3c22c51843df41144e9c3289850973823df906830ec355cb3e209383648ee671a95a76047a8153bff8ebc315cdcb6a94cb28e546b334ff71bab7a01ea25dc2a703afcccd1ddd6d5fe&ascene=1&uin=MjYzNzcyMTYyNw%3D%3D&devicetype=Windows+10&version=6208006f&lang=zh_CN&exportkey=AQFkC39NhSkTnb6SD70SAfY%3D&pass_ticket=iG9ywRBijCrb47ifDs6%2B%2Fgz8gQXaPnoVEkBXC0Kvb1%2BAmKJ3ZR3f48KpJcp2%2BWKI** 参考 /kongtiao5/article/details/82771694*/public class RedisHackTest extends ClusterTest {private static final String STAFF_PREFIX = "sso:staff:";/*** 缓存穿透测试* 缓存穿透是指缓存和数据库中都没有的数据，而用户不断发起请求，* 如发起为id为“-1”的数据或id为特别大不存在的数据。这时的用户很可能是攻击者，攻击会导致数据库压力过大。*/@Testpublic void cacheThroughTest(){//假设缓存中就只有1000个keyfor (int i = 1 ;i<1000;i++){String staffId = STAFF_PREFIX + i;cluster.set(staffId,"樊春帅"+i,"NX","EX",30);}Thread [] threads = new Thread[1000];//使用1000个线程访问一个不存在的keyfor (int i = 0 ;i<1000;i++){Thread pop = new Thread(()->{for (int k = 0;k < 10000;k++){//访问一个不存在的keyString notExitKey = STAFF_PREFIX + 1001;String x = cluster.get(notExitKey);System.out.println("x = "+x);if(x == null || "".equals(x)){//db.get();}}},"pop-"+i);threads[i] = pop;}for (int i = 0 ;i<1000;i++){threads[i].start();try {threads[i].join();} catch (InterruptedException e) {e.printStackTrace();}}}/*** 缓存击穿测试* 缓存击穿是指缓存中没有但数据库中有的数据（一般是缓存时间到期），* 这时由于并发用户特别多，同时读缓存没读到数据，又同时去数据库去取数据，引起数据库压力瞬间增大，造成过大压力* 我这边理解的具体场景有两种* 1.在高并发下某个key被突然访问，但是缓存中数据还没有建立起来，而数据库中可能有，此时会有大量请求走到DB* 2.在高并发下某个key失效后被突然访问，但是缓存中数据还没有建立起来，而数据库可能有，此时会有大量请求走到DB** 突然成为热点key存在缓存击穿情况*/@Testpublic void cacheBreakDownTest(){for (int i = 1 ;i < 1000;i++){String staffId = STAFF_PREFIX + i;cluster.set(staffId,"樊春帅"+i,"NX","EX",30);}String key = STAFF_PREFIX + 1000;//设计1000个线程，突然在某一刻访问第1000个key，之前缓存中一直没有也没有建立起来，这里来演示这种情况Thread [] threads = new Thread[1000];for (int i = 0 ;i<1000;i++){Thread pop = new Thread(()->{for (int k = 0;k < 10000;k++){//访问一个缓存中不存在的keyString x = cluster.get(key);System.out.println("x = "+x);if(x == null || "".equals(x)){//很多请求查询db//db.get();//这里是数据库里有，所以会很快重建缓存cluster.set(key,"冲冲冲","NX","EX",30);//这里涉及到缓存失效后如何重建缓存，后面大家可以自行百度}}},"pop-"+i);threads[i] = pop;}for (int i = 0 ;i<1000;i++){threads[i].start();try {threads[i].join();} catch (InterruptedException e) {e.printStackTrace();}}}/*** 缓存雪崩* 参考 /p/b880570a1545*/@Testpublic void CacheAvalancheTest(){for (int i = 1 ;i < 1000;i++){String staffId = STAFF_PREFIX + i;cluster.set(staffId,"樊春帅"+i,"NX","EX",30);}try {//休息30秒，让缓存过期Thread.sleep(30 * 1000);} catch (InterruptedException e) {e.printStackTrace();}//所有缓存key都很快失效Thread [] threads = new Thread[1000];for (int i = 0 ;i<1000;i++){Thread pop = new Thread(()->{for (int k = 1;k < 1000;k++){String staffId = STAFF_PREFIX + k;String x = cluster.get(staffId);System.out.println("x = "+x);if(x == null || "".equals(x)){//很多请求查询db//db.get();}}},"pop-"+i);threads[i] = pop;}for (int i = 0 ;i<1000;i++){threads[i].start();try {threads[i].join();} catch (InterruptedException e) {e.printStackTrace();}}}}
