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
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