高级----RateLimiter

Posted 2020-12-21 yanxiaoge

RateLimiter

RateLimiter是guava提供的基于令牌桶算法的实现类，可以非常简单的完成限流特技，并且根据系统的实际情况来调整生成token的速率。

导入相关依赖包

<dependency>
    <groupId>com.google.guava</groupId>
    <artifactId>guava</artifactId>
    <version>20.0</version>
</dependency>

定义注解

@Inherited
    @Documented
    @Target(ElementType.METHOD)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface RateLimit {
        double limitNum() default 20;  //默认每秒放入桶中的token
}

封装定义返回结果

public class MyResult {
        private Integer status;
        private String msg;
        private List<Object> data;
 
        public MyResult(Integer status, String msg, List<Object> data) {
            this.status = status;
            this.msg = msg;
            this.data = data;
        }
 
        public static MyResult OK(String msg, List<Object> data) {
            return new MyResult(200, msg, data);
        }
 
        public static MyResult Error(Integer status, String msg) {
            return new MyResult(status, msg, null);
        }
}

aop实现

@Component
@Scope
@Aspect
public class RateLimitAspect {
    private Logger log = LoggerFactory.getLogger(this.getClass());
    //用来存放不同接口的RateLimiter(key为接口名称，value为RateLimiter)
    private ConcurrentHashMap<String, RateLimiter> map = new ConcurrentHashMap<>();
 
    private static ObjectMapper objectMapper = new ObjectMapper();
 
    private RateLimiter rateLimiter;
 
    @Autowired
    private HttpServletResponse response;
 
    @Pointcut("@annotation(com.icat.retalimitaop.annotation.RateLimit)")
    public void serviceLimit() {
    }
 
    @Around("serviceLimit()")
    public Object around(ProceedingJoinPoint joinPoint) throws NoSuchMethodException {
        Object obj = null;
        //获取拦截的方法名
        Signature sig = joinPoint.getSignature();
        //获取拦截的方法名
        MethodSignature msig = (MethodSignature) sig;
        //返回被织入增加处理目标对象
        Object target = joinPoint.getTarget();
        //为了获取注解信息
        Method currentMethod = target.getClass().getMethod(msig.getName(), msig.getParameterTypes());
        //获取注解信息
        RateLimit annotation = currentMethod.getAnnotation(RateLimit.class);
        double limitNum = annotation.limitNum(); //获取注解每秒加入桶中的token
        String functionName = msig.getName(); // 注解所在方法名区分不同的限流策略
 
        //获取rateLimiter,functionName作为key在真实项目中是不允许的，不同的类中functionName可能一样。全限定类+方法名可以
         if(map.containsKey(functionName)){
             rateLimiter = map.get(functionName);
         }else {
             map.put(functionName, RateLimiter.create(limitNum));
             rateLimiter = map.get(functionName);
         }
 
        try {
            if (rateLimiter.tryAcquire()) {
                //执行方法
                obj = joinPoint.proceed();
            } else {
                //拒绝了请求（服务降级）
                String result = objectMapper.writeValueAsString(MyResult.Error(500, "系统繁忙！"));
                log.info("拒绝了请求：" + result);
                outErrorResult(result);
            }
        } catch (Throwable throwable) {
            throwable.printStackTrace();
        }
        return obj;
    }
    //将结果返回
    public void outErrorResult(String result) {
        response.setContentType("application/json;charset=UTF-8");
        try (ServletOutputStream outputStream = response.getOutputStream()) {
            outputStream.write(result.getBytes("utf-8"));
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
 
    static {
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    }
 
}

给aciton接口添加注解

2个接口设定没秒限流5个和美妙限流10个 
    @RateLimit(limitNum = 5.0)
    public MyResult getResults() {
        log.info("调用了方法getResults");
        return MyResult.OK("调用了方法", null);
    }
 
    @RateLimit(limitNum = 10.0)
    public MyResult getResultTwo() {
        log.info("调用了方法getResultTwo");
        return MyResult.OK("调用了方法getResultTwo", null);
}

测试限流

Jmeter测试getResults接口

参考：https://blog.csdn.net/qq_39816039/article/details/83988517?utm_medium=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-3.add_param_isCf&depth_1-utm_source=distribute.pc_relevant.none-task-blog-BlogCommendFromMachineLearnPai2-3.add_param_isCf