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限流尽可能在满足需求的情况下越简单越好！

1、基于Redsi的increment方法实现固定窗口限流

• Redis的increment方法保证并发线程安全
• 窗口尽可能越小越好(太大可能某一小段时间就打满请求剩下的都拿不到令牌了)
• 这个原理其实就是用当前时间戳然后除窗口大小 在这个窗口大小的时间内 key都一样

public class RedisRateLimiter {private final StringRedisTemplate redisTemplate;// 命令前缀private final String key;private final int rate;private final int window;public RedisRateLimiter(StringRedisTemplate redisTemplate, String key, int rate,int window) {this.redisTemplate = redisTemplate;this.key = key;this.rate = rate;Assert.isTrue(window > 0 && window <= 60,"窗口只支持分钟内");this.window = window;}// 检查并获取令牌public boolean acquire() {String currentKey = key + "_" + (DateUtil.currentSeconds() / window);Long currentCount = redisTemplate.opsForValue().increment(currentKey);redisTemplate.expire(currentKey, window, TimeUnit.SECONDS);if (currentCount > rate){return false;}return true;}public void acquireSleep() {int count = 0;while (!acquire()){ThreadUtil.sleep(1,TimeUnit.SECONDS);count++;log.info("RedisRateLimiter[{}] try acquire sleep {}",key,count);}}public boolean acquireSleep(int waitSecond) {int count = 0;while (!acquire()){if (count >= waitSecond){return false;}ThreadUtil.sleep(1,TimeUnit.SECONDS);count++;log.info("RedisRateLimiter[{}] try acquire sleep {}",key,count);}return true;}}

使用案例：

下面这个任务是实时请求评论和子评论接口，但是两个接口每分钟不能超过100，所以我们使用限流限制10秒不超过18即可也能满足需求。

public class ScCommentRealTimeSyncTask  {private RedisRateLimiter rateLimiter;@PostConstructpublic void init(){rateLimiter = newRedisRateLimiter(stringRedisTemplate,KAOLA_COMMENT_RATE_KEY,16,10);}@Scheduled(fixedDelay = 3000)public void task(){// 请求接口1rateLimiter.acquireSleep();request1();//请求接口2rateLimiter.acquireSleep();request2();}}