令牌桶限流算法

令牌桶限流算法

令牌桶算法是一个桶，匀速向桶里放令牌，控制桶最大容量（令牌最大数）和放入令牌速率（生成令牌/秒）。所有的请求在处理之前都需要拿到一个可用的令牌才会被处理，如果桶里面没有令牌的话，则拒绝服务；

 

• 接口限制 t 秒内最大访问次数为 n，则每隔 t/n 秒会放一个 token 到桶中；
• 桶中最多可以存放 b 个 token，如果 token 到达时令牌桶已经满了，那么这个 token 会被丢弃；
• 接口请求会先从令牌桶中取 token，拿到 token 则处理接口请求，拿不到 token 则执行限流；
• 当一个n个字节的数据包到达时，就从令牌桶中删除n个令牌（不同大小的数据包，消耗的令牌数量不一样），并且数据包被发送到网络；

Rate limiting Spring Boot with bucket4j

 每分钟10个限流，每分钟10个速度放入令牌token

?

1 2 3 4 5 6 7 8 9 10

Refill refill = Refill.intervally(10, Duration.ofMinutes(1)); Bandwidth limit = Bandwidth.classic(10, refill); Bucket bucket = Bucket4j.builder()     .addLimit(limit)     .build();    for (int i = 1; i <= 10; i++) {     assertTrue(bucket.tryConsume(1)); } assertFalse(bucket.tryConsume(1));

 

Use Spring MVC Interceptor

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

public class RateLimitInterceptor implements HandlerInterceptor {       @Autowired     private PricingPlanService pricingPlanService;       @Override     public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)             throws Exception {         String apiKey = request.getHeader("X-api-key");         if (apiKey == null || apiKey.isEmpty()) {             response.sendError(HttpStatus.BAD_REQUEST.value(), "Missing Header: X-api-key");             return false;         }           String url = request.getRequestURI();           Bucket tokenBucket = pricingPlanService.resolveBucket(apiKey+"-"+url);         ConsumptionProbe probe = tokenBucket.tryConsumeAndReturnRemaining(1);         if (probe.isConsumed()) {             response.addHeader("X-Rate-Limit-Remaining", String.valueOf(probe.getRemainingTokens()));             return true;         } else {             long waitForRefill = probe.getNanosToWaitForRefill() / 1_000_000_000;             response.addHeader("X-Rate-Limit-Retry-After-Seconds", String.valueOf(waitForRefill));             response.sendError(HttpStatus.TOO_MANY_REQUESTS.value(),                     "You have exhausted your API Request Quota");             return false;         }     } }

　　

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

public class PricingPlanService {       private final Map<String, Bucket> cache = new ConcurrentHashMap<>();       public Bucket resolveBucket(String apiKey) {         return cache.computeIfAbsent(apiKey, this::newBucket);     }       private Bucket newBucket(String apiKey) {         PricingPlan pricingPlan = PricingPlan.resolvePlanFromApiKey(apiKey);         return Bucket4j.builder()                 .addLimit(pricingPlan.getLimit())                 .build();     } }

 

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

public enum PricingPlan implements BandwidthFactory {       FREE(){         @Override         public Bandwidth getLimit() {             return Bandwidth.classic(20, Refill.intervally(20, Duration.ofHours(1)));         }     },     BASIC(){         @Override         public Bandwidth getLimit() {             return Bandwidth.classic(40, Refill.intervally(40, Duration.ofHours(1)));         }     },     PROFESSIONAL(){         @Override         public Bandwidth getLimit() {             return Bandwidth.classic(100, Refill.intervally(100, Duration.ofHours(1)));         }     }; }

　　

?

1 2 3 4 5 6 7 8 9 10 11 12

@SpringBootConfiguration public class AppConfig implements WebMvcConfigurer {       @Autowired     private RateLimitInterceptor interceptor;       @Override     public void addInterceptors(InterceptorRegistry registry) {         registry.addInterceptor(interceptor)                 .addPathPatterns("/api/v1/area/**");     } }

 

?

1 2 3 4 5 6

@PostMapping("/api/v1/area/rectangle3") public ResponseEntity<AreaV1> rectangle3(@RequestHeader(value = "X-api-key") String apiKey,                                         @RequestBody RectangleDimensionsV1 dimensions) {         return ResponseEntity.ok()                 .body(new AreaV1("rectangle", dimensions.getLength() * dimensions.getWidth())); }

　　

发起测试请求

?

1 2 3

curl -v -X POST http://localhost:8071/api/v1/area/rectangle3 \     -H "Content-Type: application/json" -H "X-api-key:FX001-99999" \     -d '{ "length": 10, "width": 12 }'

　　

每小时20个token，剩余19个token可用