高级----RateLimiter
注意事项
RateLimiter rateLimiter = RateLimiter.create(2);表示:1秒钟只有两个线程跑,也就是,第二个线程等待第一个现场0.5秒,不是一次性两个线程同时跑,然后1秒之后又来两个线程跑。
Demo
RateLimiter堵塞使用
public class RateLimiterDemo { public static void main(String[] args) { //1秒钟只有两个线程跑,也就是,第二个线程等待第一个现场0.5秒 RateLimiter rateLimiter = RateLimiter.create(2); List<Runnable> tasks = new ArrayList<Runnable>(); for(int i = 0;i < 100; i++){ tasks.add(new UserRequest(i)); } ExecutorService threadPool = Executors.newCachedThreadPool(); for (Runnable runnable : tasks){ //每个线程需要等待1/4秒,rateLimiter.acquire()会造成线程堵塞 System.out.println("等待时间:" + rateLimiter.acquire()); threadPool.execute(runnable); } } private static class UserRequest implements Runnable { private int id; public UserRequest(int id) { this.id = id; } public void run() { try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(id+"执行run"); } } }
RateLimiter非堵塞使用
public class RateLimiterDemo { public static void main(String[] args) { //1秒钟只有两个线程跑,也就是,第二个线程等待第一个线程500毫秒 RateLimiter rateLimiter = RateLimiter.create(2); List<Runnable> tasks = new ArrayList<Runnable>(); for(int i = 0;i < 100; i++){ tasks.add(new UserRequest(i)); } ExecutorService threadPool = Executors.newCachedThreadPool(); for (Runnable runnable : tasks){ //因为设置的是第二个线程需要等待第一个线程500毫秒,如果线程值等待400毫秒,就会失败 if(rateLimiter.tryAcquire(400, TimeUnit.MILLISECONDS)) { //未请求到limiter则立即返回false //doSomething(); System.out.println("成功"); }else{ //doSomethingElse(); System.out.println("失败"); } threadPool.execute(runnable); } } private static class UserRequest implements Runnable { private int id; public UserRequest(int id) { this.id = id; } public void run() { try { Thread.sleep(5000); } catch (InterruptedException e) { e.printStackTrace(); } System.out.println(id+"执行run"); } } }
简单案例
@Controller @RequestMapping("/seckill") public class SeckillController implements InitializingBean { //基于令牌桶算法的限流实现类 RateLimiter rateLimiter = RateLimiter.create(10); @RequestMapping(value = "/do_seckill", method = RequestMethod.POST) @ResponseBody public Result<Integer> list() { if (!rateLimiter.tryAcquire(1000, TimeUnit.MILLISECONDS)) { return Result.error(CodeMsg.ACCESS_LIMIT_REACHED); } }
RateLimiter+AOP
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