一、书接上文

Redis之缓存雪崩问题解决方案

二、介绍

缓存击穿就是大量并发访问同一个热点数据，一旦这个热点数据缓存失效，则请求压力都来到数据库。

三、解决方案

1. 单例双检锁

	@Overridepublic CoursePublish getCoursePublishCache(Long courseId) {String key = "content:course:publish:" + courseId;//布隆过滤器boolean contains = bloomFilter.contains(key);if (!contains){return null;}//先查询redisObject object = redisTemplate.opsForValue().get(key);if (object != null){String string = object.toString();CoursePublish coursePublish = JSON.parseObject(string, CoursePublish.class);return coursePublish;}else {//后查询数据库//加锁，防止缓存击穿synchronized (this){//单例双检锁object = redisTemplate.opsForValue().get(key);if (object != null){String string = object.toString();CoursePublish coursePublish = JSON.parseObject(string, CoursePublish.class);return coursePublish;}CoursePublish coursePublish = getCoursePublish(courseId);if (coursePublish != null) {bloomFilter.add(key);redisTemplate.opsForValue().set(key, JSON.toJSONString(coursePublish));} else {int timeout = 10 + new Random().nextInt(20);redisTemplate.opsForValue().set(key, JSON.toJSONString(coursePublish), timeout, TimeUnit.SECONDS);}return coursePublish;}}}

2. 缓存预热和定时任务

使用缓存预热，把数据提前放入缓存，然后根据过期时间，发布合理的定时任务，主动去更新缓存，让热点数据永不过期。