Spring Cloud限流详解

爱被打了一巴掌 2022-06-04 01:59 180阅读 0赞

# Spring Cloud限流详解 #

Spring Cloud   Spring Cloud   2017/12/01

在高并发的应用中，限流往往是一个绕不开的话题。本文详细探讨在Spring Cloud中如何实现限流。

在`Zuul` 上实现限流是个不错的选择，只需要编写一个过滤器就可以了，关键在于如何实现限流的算法。常见的限流算法有漏桶算法以及令牌桶算法。这个可参考 [https://www.cnblogs.com/LBSer/p/4083131.html][https_www.cnblogs.com_LBSer_p_4083131.html] ，写得通俗易懂，你值得拥有，我就不拽文了。

`Google Guava` 为我们提供了限流工具类`RateLimiter` ，于是乎，我们可以撸代码了。

## 代码示例 ##

<table style="border-spacing:0px; border-collapse:collapse; background-color:transparent; width:710px"> 
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   <td style="padding:0px"> <pre style="overflow:auto; font-family:Menlo,Monaco,Consolas,&quot;Courier New&quot;,monospace; font-size:13px; padding:0px; margin-top:0px; margin-bottom:0px; line-height:1.42857; color:rgb(51,51,51); word-break:break-all; word-wrap:break-word; background:none; border:none">
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Component</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
       
        
      <span style="">public</span> 
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">class</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(255,198,109)">RateLimitZuulFilter</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(194,98,48)">extends</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(255,198,109)">ZuulFilter</span></span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style="color:rgb(194,98,48)">private</span></span> 
       
        
      <span style=""><span style="color:rgb(194,98,48)">final</span></span> RateLimiter rateLimiter = RateLimiter.create(
       
        
      <span style=""><span style="color:rgb(165,194,97)">1000.0</span></span>);
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Override</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">public</span></span></span><span style=""> String </span><span style=""><span style=""><span style="color:rgb(255,198,109)">filterType</span></span></span><span style=""><span style="">(<span style="color:rgb(208,208,255)"></span>)</span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">return</span></span> FilterConstants.PRE_TYPE;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
           }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Override</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">public</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(194,98,48)">int</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(255,198,109)">filterOrder</span></span></span><span style=""><span style="">(<span style="color:rgb(208,208,255)"></span>)</span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">return</span></span> Ordered.HIGHEST_PRECEDENCE;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
           }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Override</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">public</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(194,98,48)">boolean</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(255,198,109)">shouldFilter</span></span></span><span style=""><span style=""><span style="color:rgb(208,208,255)">()</span></span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style="">// 这里可以考虑弄个限流开启的开关，开启限流返回<span style="">true</span>，关闭限流返回<span style="">false</span>，你懂的。</span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">return</span></span> 
       
        
      <span style="">true</span>;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
           }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Override</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">public</span></span></span><span style=""> Object </span><span style=""><span style=""><span style="color:rgb(255,198,109)">run</span></span></span><span style=""><span style="">(<span style="color:rgb(208,208,255)"></span>)</span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">try</span></span> {
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                   RequestContext currentContext = RequestContext.getCurrentContext();
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                   HttpServletResponse response = currentContext.getResponse();
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style=""><span style="color:rgb(194,98,48)">if</span></span> (!rateLimiter.
       
        
      <span style="color:rgb(194,98,48)">try</span>Acquire()) {
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                       HttpStatus httpStatus = HttpStatus.TOO_MANY_REQUESTS;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style="color:rgb(194,98,48)">response</span>
       
        
      <span style="color:rgb(155,112,63)">.setContentType</span>(
       
        
      <span style="color:rgb(194,98,48)">MediaType</span>
       
        
      <span style="color:rgb(155,112,63)">.TEXT_PLAIN_VALUE</span>);
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style="color:rgb(194,98,48)">response</span>
       
        
      <span style="color:rgb(155,112,63)">.setStatus</span>(
       
        
      <span style="color:rgb(194,98,48)">httpStatus</span>
       
        
      <span style="color:rgb(155,112,63)">.value</span>());
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style="color:rgb(194,98,48)">response</span>
       
        
      <span style="color:rgb(155,112,63)">.getWriter</span>()
       
        
      <span style="color:rgb(155,112,63)">.append</span>(
       
        
      <span style="color:rgb(194,98,48)">httpStatus</span>
       
        
      <span style="color:rgb(155,112,63)">.getReasonPhrase</span>());
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                       currentContext.setSendZuulResponse(
       
        
      <span style="">false</span>);
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style=""><span style="color:rgb(194,98,48)">throw</span></span> 
       
        
      <span style=""><span style="color:rgb(194,98,48)">new</span></span> ZuulException(
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                        
       
        
      <span style="color:rgb(194,98,48)">httpStatus</span>
       
        
      <span style="color:rgb(155,112,63)">.getReasonPhrase</span>(),
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                               httpStatus.
       
        
      <span style="color:rgb(194,98,48)">value</span>(),
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                        
       
        
      <span style="color:rgb(194,98,48)">httpStatus</span>
       
        
      <span style="color:rgb(155,112,63)">.getReasonPhrase</span>()
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                       );
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                   }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
               } 
       
        
      <span style=""><span style="color:rgb(194,98,48)">catch</span></span> (
       
        
      <span style="color:rgb(194,98,48)">Exception</span> e) {
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style="color:rgb(194,98,48)">ReflectionUtils</span>
       
        
      <span style="color:rgb(155,112,63)">.rethrowRuntimeException</span>(e);
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
               }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">return</span></span> 
       
        
      <span style="">null</span>;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
           }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
       }
      
       
     </div></pre> </td> 
  </tr> 
 </tbody> 
</table>

如上，我们编写了一个`pre` 类型的过滤器。对Zuul过滤器有疑问的可参考我的博客：

*  Spring Cloud内置的Zuul过滤器详解：[http://www.itmuch.com/spring-cloud/zuul/zuul-filter-in-spring-cloud][http_www.itmuch.com_spring-cloud_zuul_zuul-filter-in-spring-cloud]
 *  Spring Cloud Zuul过滤器详解：[http://www.itmuch.com/spring-cloud/zuul/spring-cloud-zuul-filter][http_www.itmuch.com_spring-cloud_zuul_spring-cloud-zuul-filter]

在过滤器中，我们使用`Guava RateLimiter` 实现限流，如果已经达到最大流量，就抛异常。

## 分布式场景下的限流 ##

以上单节点Zuul下的限流，但在生产中，我们往往会有多个Zuul实例。对于这种场景如何限流呢？我们可以借助Redis实现限流。

使用redis实现，存储两个key，一个用于计时，一个用于计数。请求每调用一次，计数器增加1，若在计时器时间内计数器未超过阈值，则可以处理任务

## 实现微服务级别的限流 ##

一些场景下，我们可能还需要实现微服务粒度的限流。此时可以有两种方案：

方式一：在微服务本身实现限流。

和在Zuul上实现限流类似，只需编写一个过滤器或者拦截器即可，比较简单，不作赘述。个人不太喜欢这种方式，因为每个微服务都得编码，感觉成本很高啊。

加班那么多，作为程序猿的我们，应该学会偷懒，这样才可能有时间孝顺父母、抱老婆、逗儿子、遛狗养鸟、聊天打屁、追求人生信仰。好了不扯淡了，看方法二吧。

方法二：在Zuul上实现微服务粒度的限流。

在讲解之前，我们不妨模拟两个路由规则，两种路由规则分别代表Zuul的两种路由方式。

如配置所示，在这里，我们定义了两个路由规则，`microservice-provider-user` 以及`user2` ，其中`microservice-provider-user` 这个路由规则使用到Ribbon + Hystrix，走的是`RibbonRoutingFilter` ；而`user2` 这个路由用不上Ribbon也用不上Hystrix，走的是`SipleRoutingFilter` 。如果你搞不清楚这点，请参阅我的博客：

搞清楚这点之后，我们就可以撸代码了：

<table style="border-spacing:0px; border-collapse:collapse; background-color:transparent; width:843px"> 
 <tbody style=""> 
  <tr style=""> 
   <td style="padding:0px"> <pre style="overflow:auto; font-family:Menlo,Monaco,Consolas,&quot;Courier New&quot;,monospace; font-size:13px; padding:0px; margin-top:0px; margin-bottom:0px; line-height:1.42857; color:rgb(51,51,51); word-break:break-all; word-wrap:break-word; background:none; border:none">
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Component</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
       
        
      <span style="">public</span> 
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">class</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(255,198,109)">RateLimitZuulFilter</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(194,98,48)">extends</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(255,198,109)">ZuulFilter</span></span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style="">private</span> 
       
        
      <span style="color:rgb(109,156,190)">Map</span>&lt;
       
        
      <span style="color:rgb(109,156,190)">String</span>, RateLimiter&gt; map = Maps.newConcurrentMap();
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Override</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">public</span></span></span><span style=""> String </span><span style=""><span style=""><span style="color:rgb(255,198,109)">filterType</span></span></span><span style=""><span style="">(<span style="color:rgb(208,208,255)"></span>)</span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">return</span></span> FilterConstants.PRE_TYPE;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
           }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Override</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">public</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(194,98,48)">int</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(255,198,109)">filterOrder</span></span></span><span style=""><span style="">(<span style="color:rgb(208,208,255)"></span>)</span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(188,148,88); font-style:italic">// 这边的order一定要大于org.springframework.cloud.netflix.zuul.filters.pre.PreDecorationFilter的order</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(188,148,88); font-style:italic">// 也就是要大于5</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(188,148,88); font-style:italic">// 否则，RequestContext.getCurrentContext()里拿不到serviceId等数据。</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">return</span></span> Ordered.LOWEST_PRECEDENCE;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
           }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Override</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">public</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(194,98,48)">boolean</span></span></span><span style=""> </span><span style=""><span style=""><span style="color:rgb(255,198,109)">shouldFilter</span></span></span><span style=""><span style=""><span style="color:rgb(208,208,255)">()</span></span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style="">// 这里可以考虑弄个限流开启的开关，开启限流返回<span style="">true</span>，关闭限流返回<span style="">false</span>，你懂的。</span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">return</span></span> 
       
        
      <span style="">true</span>;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
           }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style="color:rgb(155,133,157)">@Override</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">    
       
        
      <span style=""><span style=""><span style=""><span style="color:rgb(194,98,48)">public</span></span></span><span style=""> Object </span><span style=""><span style=""><span style="color:rgb(255,198,109)">run</span></span></span><span style=""><span style="">(<span style="color:rgb(208,208,255)"></span>)</span></span><span style=""> </span></span>{
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">try</span></span> {
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                   RequestContext context = RequestContext.getCurrentContext();
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                   HttpServletResponse response = context.getResponse();
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style="color:rgb(109,156,190)">String</span> key = 
       
        
      <span style=""><span style="color:rgb(194,98,48)">null</span></span>;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style=""><span style="color:rgb(188,148,88); font-style:italic">// 对于service格式的路由，走RibbonRoutingFilter</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style="color:rgb(109,156,190)">String</span> serviceId = (
       
        
      <span style="color:rgb(109,156,190)">String</span>) context.
       
        
      <span style="color:rgb(194,98,48)">get</span>(SERVICE_ID_KEY);
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style=""><span style="color:rgb(194,98,48)">if</span></span> (serviceId != 
       
        
      <span style="">null</span>) {
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                       key = serviceId;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style="color:rgb(194,98,48)">map</span>
       
        
      <span style="color:rgb(155,112,63)">.putIfAbsent</span>(
       
        
      <span style="color:rgb(194,98,48)">serviceId</span>, 
       
        
      <span style="color:rgb(194,98,48)">RateLimiter</span>
       
        
      <span style="color:rgb(155,112,63)">.create</span>(
       
        
      <span style="">1000<span style="color:rgb(155,112,63)">.0</span></span>));
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                   }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style=""><span style="color:rgb(188,148,88); font-style:italic">// 如果压根不走RibbonRoutingFilter，则认为是URL格式的路由</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style=""><span style="color:rgb(194,98,48)">else</span></span> {
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style=""><span style="color:rgb(188,148,88); font-style:italic">// 对于URL格式的路由，走SimpleHostRoutingFilter</span></span>
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                       URL routeHost = context.getRouteHost();
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style=""><span style="color:rgb(194,98,48)">if</span></span> (routeHost != 
       
        
      <span style="">null</span>) {
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                    
       
        
      <span style="color:rgb(109,156,190)">String</span> url = routeHost.toString();
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                           key = url;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                    
       
        
      <span style="color:rgb(194,98,48)">map</span>
       
        
      <span style="color:rgb(155,112,63)">.putIfAbsent</span>(
       
        
      <span style="color:rgb(194,98,48)">url</span>, 
       
        
      <span style="color:rgb(194,98,48)">RateLimiter</span>
       
        
      <span style="color:rgb(155,112,63)">.create</span>(
       
        
      <span style="">2000<span style="color:rgb(155,112,63)">.0</span></span>));
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                       }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                   }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style="color:rgb(218,73,57)">RateLimiter</span> rateLimiter = 
       
        
      <span style="color:rgb(109,156,190)">map</span>.
       
        
      <span style="color:rgb(194,98,48)">get</span>(key);
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style=""><span style="color:rgb(194,98,48)">if</span></span> (!rateLimiter.
       
        
      <span style="color:rgb(194,98,48)">try</span>Acquire()) {
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                       HttpStatus httpStatus = HttpStatus.TOO_MANY_REQUESTS;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style="color:rgb(194,98,48)">response</span>
       
        
      <span style="color:rgb(155,112,63)">.setContentType</span>(
       
        
      <span style="color:rgb(194,98,48)">MediaType</span>
       
        
      <span style="color:rgb(155,112,63)">.TEXT_PLAIN_VALUE</span>);
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style="color:rgb(194,98,48)">response</span>
       
        
      <span style="color:rgb(155,112,63)">.setStatus</span>(
       
        
      <span style="color:rgb(194,98,48)">httpStatus</span>
       
        
      <span style="color:rgb(155,112,63)">.value</span>());
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style="color:rgb(194,98,48)">response</span>
       
        
      <span style="color:rgb(155,112,63)">.getWriter</span>()
       
        
      <span style="color:rgb(155,112,63)">.append</span>(
       
        
      <span style="color:rgb(194,98,48)">httpStatus</span>
       
        
      <span style="color:rgb(155,112,63)">.getReasonPhrase</span>());
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                       context.setSendZuulResponse(
       
        
      <span style="">false</span>);
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)"></div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                
       
        
      <span style=""><span style="color:rgb(194,98,48)">throw</span></span> 
       
        
      <span style=""><span style="color:rgb(194,98,48)">new</span></span> ZuulException(
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                        
       
        
      <span style="color:rgb(194,98,48)">httpStatus</span>
       
        
      <span style="color:rgb(155,112,63)">.getReasonPhrase</span>(),
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                               httpStatus.
       
        
      <span style="color:rgb(194,98,48)">value</span>(),
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">                        
       
        
      <span style="color:rgb(194,98,48)">httpStatus</span>
       
        
      <span style="color:rgb(155,112,63)">.getReasonPhrase</span>()
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                       );
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
                   }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
               } 
       
        
      <span style=""><span style="color:rgb(194,98,48)">catch</span></span> (
       
        
      <span style="color:rgb(194,98,48)">Exception</span> e) {
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">            
       
        
      <span style="color:rgb(194,98,48)">ReflectionUtils</span>
       
        
      <span style="color:rgb(155,112,63)">.rethrowRuntimeException</span>(e);
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
               }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">        
       
        
      <span style=""><span style="color:rgb(194,98,48)">return</span></span> 
       
        
      <span style="">null</span>;
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
           }
      
       
     </div>
      
       
     <div style="overflow-x:auto; padding:0.5em; background:rgb(35,35,35); color:rgb(230,225,220)">
      
        
       }
      
       
     </div></pre> </td> 
  </tr> 
 </tbody> 
</table>

简单讲解一下这段代码：

对于`microservice-provider-user` 这个路由，我们可以用`context.get(SERVICE_ID_KEY);` 获取到serviceId，获取出来就是`microservice-provider-user` ；

而对于`user2` 这个路由，我们使用`context.get(SERVICE_ID_KEY);` 获得是null，但是呢，可以用`context.getRouteHost()` 获得路由到的地址，获取出来就是`http://localhost:8000/` 。接下来的事情，你们懂的。

## 改进与提升 ##

实际项目中，除以上实现的限流方式，还可能会：

一、在上文的基础上，增加配置项，控制每个路由的限流指标，并实现动态刷新，从而实现更加灵活的管理

二、基于CPU、内存、数据库等压力限流（感谢平安常浩智）提出。。

下面，笔者借助Spring Boot Actuator提供的`Metrics` 能力进行实现基于内存压力的限流——当可用内存低于某个阈值就开启限流，否则不开启限流。

三、实现不同维度的限流，例如：

*  对请求的目标URL进行限流（例如：某个URL每分钟只允许调用多少次）
 *  对客户端的访问IP进行限流（例如：某个IP每分钟只允许请求多少次）
 *  对某些特定用户或者用户组进行限流（例如：非VIP用户限制每分钟只允许调用100次某个API等）
 *  多维度混合的限流。此时，就需要实现一些限流规则的编排机制。与、或、非等关系。

## 参考文档 ##

*  分布式环境下限流方案的实现：[http://blog.csdn.net/Justnow\_/article/details/53055299][http_blog.csdn.net_Justnow_article_details_53055299]

[https_www.cnblogs.com_LBSer_p_4083131.html]: https://www.cnblogs.com/LBSer/p/4083131.html
[http_www.itmuch.com_spring-cloud_zuul_zuul-filter-in-spring-cloud]: http://www.itmuch.com/spring-cloud/zuul/zuul-filter-in-spring-cloud
[http_www.itmuch.com_spring-cloud_zuul_spring-cloud-zuul-filter]: http://www.itmuch.com/spring-cloud/zuul/spring-cloud-zuul-filter
[http_blog.csdn.net_Justnow_article_details_53055299]: http://blog.csdn.net/Justnow_/article/details/53055299