Guava RateLimiter 實(shí)現(xiàn) API 限流，這才是正確的姿勢(shì)！
Guava提供的RateLimiter可以限制物理或邏輯資源的被訪(fǎng)問(wèn)速率，咋一聽(tīng)有點(diǎn)像java并發(fā)包下的Samephore，但是又不相同，RateLimiter控制的是速率，Samephore控制的是并發(fā)量。
???com.google.guava
???guava
???23.0
public?static?void?main(String[]?args)?{
????String?start?=?new?SimpleDateFormat("yyyy-MM-dd?HH:mm:ss").format(new?Date());
????RateLimiter?limiter?=?RateLimiter.create(1.0);?//?這里的1表示每秒允許處理的量為1個(gè)
????for?(int?i?=?1;?i?<=?10;?i++)?{?
????????limiter.acquire();//?請(qǐng)求RateLimiter,?超過(guò)permits會(huì)被阻塞
????????System.out.println("call?execute.."?+?i);
????}
????String?end?=?new?SimpleDateFormat("yyyy-MM-dd?HH:mm:ss").format(new?Date());
????System.out.println("start?time:"?+?start);
????System.out.println("end?time:"?+?end);
}
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實(shí)際項(xiàng)目中使用
@Service
public?class?GuavaRateLimiterService?{
????/*每秒控制5個(gè)許可*/
????RateLimiter?rateLimiter?=?RateLimiter.create(5.0);
?
????/**
?????*?獲取令牌
?????*
?????*?@return
?????*/
????public?boolean?tryAcquire()?{
????????return?rateLimiter.tryAcquire();
????}
????
}
??@Autowired
????private?GuavaRateLimiterService?rateLimiterService;
????
????@ResponseBody
????@RequestMapping("/ratelimiter")
????public?Result?testRateLimiter(){
????????if(rateLimiterService.tryAcquire()){
????????????return?ResultUtil.success1(1001,"成功獲取許可");
????????}
????????return?ResultUtil.success1(1002,"未獲取到許可");
????}
jmeter起10個(gè)線(xiàn)程并發(fā)訪(fǎng)問(wèn)接口，測(cè)試結(jié)果如下：
可以發(fā)現(xiàn)，10個(gè)并發(fā)訪(fǎng)問(wèn)總是只有6個(gè)能獲取到許可，結(jié)論就是能獲取到RateLimiter.create(n)中n+1個(gè)許可，總體來(lái)看Guava的RateLimiter是比較優(yōu)雅的。本文就是簡(jiǎn)單的提了下RateLimiter的使用。
翻閱發(fā)現(xiàn)使用上述方式使用RateLimiter的方式不夠優(yōu)雅，盡管我們可以把RateLimiter的邏輯包在service里面，controller直接調(diào)用即可，但是如果我們換成：自定義注解+切面 的方式實(shí)現(xiàn)的話(huà)，會(huì)優(yōu)雅的多，詳細(xì)見(jiàn)下面代碼：
import?java.lang.annotation.*;
?
/**
?*?自定義注解可以不包含屬性，成為一個(gè)標(biāo)識(shí)注解
?*/
@Inherited
@Documented
@Target({ElementType.METHOD,?ElementType.FIELD,?ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public?@interface?RateLimitAspect?{
???
}
import?com.google.common.util.concurrent.RateLimiter;
import?com.simons.cn.springbootdemo.util.ResultUtil;
import?net.sf.json.JSONObject;
import?org.aspectj.lang.ProceedingJoinPoint;
import?org.aspectj.lang.annotation.Around;
import?org.aspectj.lang.annotation.Aspect;
import?org.aspectj.lang.annotation.Pointcut;
import?org.springframework.beans.factory.annotation.Autowired;
import?org.springframework.context.annotation.Scope;
import?org.springframework.stereotype.Component;
?
import?javax.servlet.ServletOutputStream;
import?javax.servlet.http.HttpServletResponse;
import?java.io.IOException;
?
@Component
@Scope
@Aspect
public?class?RateLimitAop?{
?
????@Autowired
????private?HttpServletResponse?response;
?
????private?RateLimiter?rateLimiter?=?RateLimiter.create(5.0);?//比如說(shuō)，我這里設(shè)置"并發(fā)數(shù)"為5
?
????@Pointcut("@annotation(com.simons.cn.springbootdemo.aspect.RateLimitAspect)")
????public?void?serviceLimit()?{
?
????}
?
????@Around("serviceLimit()")
????public?Object?around(ProceedingJoinPoint?joinPoint)?{
????????Boolean?flag?=?rateLimiter.tryAcquire();
????????Object?obj?=?null;
????????try?{
????????????if?(flag)?{
????????????????obj?=?joinPoint.proceed();
????????????}else{
????????????????String?result?=?JSONObject.fromObject(ResultUtil.success1(100,?"failure")).toString();
????????????????output(response,?result);
????????????}
????????}?catch?(Throwable?e)?{
????????????e.printStackTrace();
????????}
????????System.out.println("flag="?+?flag?+?",obj="?+?obj);
????????return?obj;
????}
????
????public?void?output(HttpServletResponse?response,?String?msg)?throws?IOException?{
????????response.setContentType("application/json;charset=UTF-8");
????????ServletOutputStream?outputStream?=?null;
????????try?{
????????????outputStream?=?response.getOutputStream();
????????????outputStream.write(msg.getBytes("UTF-8"));
????????}?catch?(IOException?e)?{
????????????e.printStackTrace();
????????}?finally?{
????????????outputStream.flush();
????????????outputStream.close();
????????}
????}
}
import?com.simons.cn.springbootdemo.aspect.RateLimitAspect;
import?com.simons.cn.springbootdemo.util.ResultUtil;
import?org.springframework.stereotype.Controller;
import?org.springframework.web.bind.annotation.RequestMapping;
import?org.springframework.web.bind.annotation.ResponseBody;
?
/**
?*?類(lèi)描述：RateLimit限流測(cè)試（基于?注解+切面?方式）
?*?創(chuàng)建人：simonsfan
?*/
@Controller
public?class?TestController?{
?
????@ResponseBody
????@RateLimitAspect?????????//可以非常方便的通過(guò)這個(gè)注解來(lái)實(shí)現(xiàn)限流
????@RequestMapping("/test")
????public?String?test(){
????????return?ResultUtil.success1(1001,?"success").toString();
????}
這樣通過(guò)自定義注解@RateLimiterAspect來(lái)動(dòng)態(tài)的加到需要限流的接口上，個(gè)人認(rèn)為是比較優(yōu)雅的實(shí)現(xiàn)吧。推薦一個(gè) Spring Boot 基礎(chǔ)教程及實(shí)戰(zhàn)示例：https://www.javastack.cn/categories/Spring-Boot/
壓測(cè)結(jié)果：
可以看到，10個(gè)線(xiàn)程中無(wú)論壓測(cè)多少次，并發(fā)數(shù)總是限制在6，也就實(shí)現(xiàn)了限流。另外，關(guān)注公眾號(hào)Java技術(shù)棧，在后臺(tái)回復(fù)：面試，可以獲取我整理的 Java 多線(xiàn)程系列面試題和答案，非常齊全。
作者：飯一碗
來(lái)源：https://blog.csdn.net/fanrenxiang/article/details/80949079
關(guān)注Java技術(shù)?？锤喔韶?/strong>
