Redisson之RRateLimiterHTTP限流

基于Redis的分布式限流器（RateLimiter）可以用来在分布式环境下现在请求方的调用频率。既适用于不同Redisson实例下的多线程限流，也适用于相同Redisson实例下的多线程限流。该算法不保证公平性。除了同步接口外，还提供了异步（Async）、反射式（Reactive）和RxJava2标准的接口。

如何限制HTTP请求次数（分布式）

本地缓存显然不能满足，只能考虑redis当然redis中采用lua脚本也是可以实现的。今天文中的redisson中RateLimiter也是可以的

官方例子看一下 https://github.com/redisson/redisson/wiki/6.-%E5%88%86%E5%B8%83%E5%BC%8F%E5%AF%B9%E8%B1%A1

RRateLimiter rateLimiter = redisson.getRateLimiter("myRateLimiter");
// 初始化
// 最大流速 = 每1秒钟产生10个令牌
rateLimiter.trySetRate(RateType.OVERALL, 10, 1, RateIntervalUnit.SECONDS);

CountDownLatch latch = new CountDownLatch(2);
limiter.acquire(3);
// ...

Thread t = new Thread(() -> {
    limiter.acquire(2);
    // ...        
});

1、创建AOP切面

@Component
@Scope
@Aspect
public class RateLimitAop {

    @Autowired
    private RedissonClient redissonClient;

    @Pointcut("@annotation(com.data.estimated.limiter.RateLimitAspect)")
    public void serviceLimit() {

    }

    @Around("serviceLimit()")
    public Object around(ProceedingJoinPoint joinPoint) {
        ServletRequestAttributes servletRequestAttributes = ((ServletRequestAttributes) RequestContextHolder.getRequestAttributes());
        HttpServletRequest request = servletRequestAttributes.getRequest();//获取请求
        HttpServletResponse response = servletRequestAttributes.getResponse();//获取响应
        StringBuffer buffer = new StringBuffer();
        String url = request.getRequestURI();
        buffer.append(StrUtil.replace(url,"/","_"));
        buffer.append("_");
        buffer.append(IPUtil.getIpAddr(request));//获取请求IP信息
        RRateLimiter rRateLimiter = getRRateLimiter(joinPoint,buffer.toString());//获取配置RRateLimiter信息
        boolean flag = rRateLimiter.tryAcquire();
        Object obj = null;
        try {
            if (flag) {
                obj = joinPoint.proceed();
            }else{
                outRateLimiterMsg(response,new JSONObject(BaseResult.LIMIT_FAIL()).toString());//响应浏览器,超频请求
            }
        } catch (Throwable e) {
            e.printStackTrace();
            outRateLimiterMsg(response,new JSONObject(BaseResult.FAIL()).toString());//响应浏览器,错误
        }
        return obj;
    }

    /**
     *
     * @param joinPoint
     * @param limitKey
     * @return
     */
    private RRateLimiter getRRateLimiter(ProceedingJoinPoint joinPoint,String limitKey){
        RateLimitAspect rateLimit = getRateLimitAspect(joinPoint);
        long count = rateLimit.count();//限流次数
        long time = rateLimit.time();//限流时间
        RRateLimiter rRateLimiter = redissonClient.getRateLimiter(StrUtil.isBlank(rateLimit.key()) ? limitKey : rateLimit.key());
        if(rRateLimiter.isExists()){
            RateLimiterConfig rateLimiterConfig = rRateLimiter.getConfig();//读取已经存在配置
            long rateInterval = rateLimiterConfig.getRateInterval();//限时时间
            long rate = rateLimiterConfig.getRate();//次数
            if(time != rateInterval || rate != count){
                rRateLimiter.delete();//移除配置，重新加载配置
                rRateLimiter.trySetRate(RateType.OVERALL, count ,time , RateIntervalUnit.SECONDS);
            }
        }
        rRateLimiter.trySetRate(RateType.OVERALL, count ,time , RateIntervalUnit.SECONDS);
        return rRateLimiter;
    }

    /**
     * 获取脚注配置信息
     * @param joinPoint
     * @return
     */
    private RateLimitAspect getRateLimitAspect(ProceedingJoinPoint joinPoint){
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        Method method = signature.getMethod();
        RateLimitAspect rateLimit = method.getAnnotation(RateLimitAspect.class);
        return rateLimit;
    }

    /**
     * 客户端返回数据
     */
    private void outRateLimiterMsg(HttpServletResponse response,String message){
        PrintWriter writer = null;
        try {
            response.reset();
            response.setCharacterEncoding("utf-8");
            response.setHeader("content-type", "application/json;charset=utf-8");
            response.addHeader("Access-Control-Allow-Origin", "*");
            response.addHeader("Access-Control-Allow-Headers", "X-Requested-With");
            response.addHeader("Access-Control-Allow-Methods", "GET,POST,OPTIONS");
            writer = response.getWriter();
            writer.write(message);
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            IoUtil.close(writer);
        }
    }
}

2、创建脚注

/**
 * 自定义注解可以不包含属性，成为一个标识注解
 */
@Inherited
@Documented
@Target({ElementType.METHOD, ElementType.FIELD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface RateLimitAspect {
    /**
     * 限流唯一标示
     *
     * @return
     */
    String key() default "";

    /**
     * 限流时间
     * @return
     */
    long time() default 5;

    /**
     * 限流次数
     * @return
     */
    long count() default 1;
}

最后一步实战操作

//默认无参数方法
@RateLimitAspect

//有参数
@RateLimitAspect(key = "RateLimitAspect",count = 2,time = 10)

//如果可以多个方法key均为RateLimitAspect这采用同一个限制。