一种接口限速方案

心已赠人 2022-06-14 02:17 267阅读 0赞

如果一个接口的频繁调用会严重影响到系统稳定性的话，那就要考虑限速了。

谷歌有个现有的开源实现：Guava的RateLimiter类，RateLimiter使用的是一种叫令牌桶的流控算法，RateLimiter会按照一定的频率往桶里扔令牌，线程拿到令牌才能执行，比如你希望自己的应用程序QPS不要超过1000，那么RateLimiter设置1000的速率后，就会每秒往桶里扔1000个令牌。  
详情请戳：[Guava官方文档-RateLimiter类][Guava_-RateLimiter]

用法简单说一下吧，首先声明一个限速策略：

final RateLimiter rateLimiter = RateLimiter.create(10.0);

然后在需要限流的地方贴上：

rateLimiter.acquire();

这样就可以保证每秒钟只能有两次请求成功了。

但是，我需要更多的功能来实现，比如超过限速阈值后也要返回一个东西，这时候就不太好办了，RateLimiter只是在内部采用令牌桶隐式地对接口进行了限速，下面是我的实现：

package com.lovnx.test;
    
    import java.util.Timer;
    import java.util.TimerTask;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    import java.util.concurrent.atomic.AtomicInteger;
    
    public class mytst { 
        //单位时间内的调用次数
        private int flag = 10;
        //线程数量
        private int threadNum = 10;
        //单位时间1000ms * 60 = 1min
        private int timeRound = 1000*60;
        //用来标记调用次数
        private AtomicInteger num = new AtomicInteger(0);
    
        public static void main(String[] args) {
    
            new mytst().call();
        }
    
        private void call() {
            ExecutorService executor = Executors.newFixedThreadPool(threadNum);
    
            Timer timer = new Timer();
            timer.schedule(new TimerTask(){
              @Override
              public void run() {
                  num.set(0);;
              }
            }, 0, timeRound);
    
            for (int i = 0; i < 1000; i++) {
                executor.execute(new Runnable() {
    
                    @Override
                    public void run() {
                        try {
                            Thread.sleep(10000);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println(Thread.currentThread().getName()+" 进来了!");
                        num.incrementAndGet();
                        if (num.get() <= flag) {
                            System.out.println(Thread.currentThread().getName()+" 执行任务!");
                        } else {
                            System.out.println(Thread.currentThread().getName()+" 执行任务失败!调用超限！");
                        }
                    }
                });
            }
    
            executor.shutdown();
        }
    }

我比较粗暴，直接用一个原子类AtomicInteger来标记。

在接口层面就是这样的：

package com.lovnx.web;
    
    import java.util.Timer;
    import java.util.TimerTask;
    import java.util.concurrent.atomic.AtomicInteger;
    
    import org.apache.log4j.Logger;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.cloud.client.ServiceInstance;
    import org.springframework.cloud.client.discovery.DiscoveryClient;
    import org.springframework.web.bind.annotation.RequestMapping;
    import org.springframework.web.bind.annotation.RequestMethod;
    import org.springframework.web.bind.annotation.RequestParam;
    import org.springframework.web.bind.annotation.RestController;
    
    @RestController
    public class ComputeController {
    
        private final Logger logger = Logger.getLogger(getClass());
    
        //单位时间内的调用次数
        private int flag = 10;
        //单位时间1000ms * 60 = 1min
        private static int timeRound = 1000*60;
        //用来标记调用次数
        private static AtomicInteger num = new AtomicInteger(0);
    
        @Autowired
        private DiscoveryClient client;
    
        static{
            Timer timer = new Timer();
            timer.schedule(new TimerTask(){
              @Override
              public void run() {
                  num.set(0);;
              }
            }, 0, timeRound);
        }
    
        @RequestMapping(value = "/add" ,method = RequestMethod.GET)
        public String add(@RequestParam Integer a, @RequestParam Integer b) {
    
            num.incrementAndGet();
    
            if (num.get() <= flag) {
                ServiceInstance instance = client.getLocalServiceInstance();
                Integer r = a + b;
                logger.info("/add, host:" + instance.getHost() + ", service_id:" + instance.getServiceId() + ", result:" + r);
                return "From Service-B, Result is " + r+"\nPort:"+instance.getPort();
            }
            return "调用次数超限，一分钟内最多只能调用10次！";
        }
    
    }

更多内容请戳：[代码托管][Link 1]

[Guava_-RateLimiter]: http://ifeve.com/guava-ratelimiter/
[Link 1]: https://github.com/Lovnx/micro-service