ASP.NET MVC ETag & Cache等优化方法

背景

最近有一个项目是用SmartAdmin + Jquery + EasyUI 一个ASP.NET MVC5的项目,一直存在一个性能问题,加载速度比较慢,第一次加载需要(在没有cache的情况下)需要4-5秒完成全部的加载.

如下图就是用Chrome PageSpeed 测试的结果 

有几个非常重要的指标

Fist Contentfu Paint:第一次绘出页面,需要4秒,前4秒都是白屏,确实有点长

Fist Meaningfull Paint:第一次绘出有意义的内容,需要8.6秒,才出现可见的操作页面.

Eliminate render-blocking resources:阻塞加载资源文件,因为的项目在head中加载了jquery和css,因为有些代码必须先执行导致的

Remove unused css:存在大量的没用的css样式定义,这也很难避免.

分析一下原因

出现上述问题的主要原因,页面本身的大小,所有资源加起来超过3.2M,Jquery EasyUI的JS+css 就接近3M,另外页面里有嵌入了好几个PartialView,还有就是执行js的时间,EasyUI DataGrid需要从后台抓起数据并生成复杂的Dom结构这都需要时间.

一般的优化手段

Cache

第一想到的就是使用cache,单只能解决第二次访问的速度问题,对少有点用,我一般会这样做,设置的方法有

• 添加outputcache 例如:

 

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1 2	[OutputCache(Duration = 360, VaryByParam = "none")] public ActionResult Index() => this.View();

 

• web.Config 添加对静态文件的缓存

 

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<system.webServer>         <staticContent>             <remove fileExtension=".js" />             <mimeMap fileExtension=".js" mimeType="text/javascript" />             <remove fileExtension=".ico" />             <mimeMap fileExtension=".ico" mimeType="image/x-icon" />             <remove fileExtension=".eot" />             <mimeMap fileExtension=".eot" mimeType="application/vnd.ms-fontobject" />             <remove fileExtension=".woff" />             <mimeMap fileExtension=".woff" mimeType="application/x-font-woff" />             <remove fileExtension=".woff2" />             <mimeMap fileExtension=".woff2" mimeType="application/x-font-woff2" />             <remove fileExtension=".svg" />             <mimeMap fileExtension=".svg" mimeType="image/svg+xml" />             <remove fileExtension=".ttf" />             <mimeMap fileExtension=".ttf" mimeType="application/x-font-ttf" />             <clientCache cacheControlMode="UseMaxAge" httpExpires="365.00:00:00" cacheControlMaxAge="365.00:00:00" />         </staticContent> </system.webServer>

压缩和合并资源文件

尽量减少资源文件的大小和请求次数,通常的做法就是使用BundleConfig.cs合并和压缩js,css文件.我现在使用bundleconfig.json配置代替System.Web.Optimization.配置灵活一点,如果使用bundleconfig.json 编译压缩还需要解决客户端更新的缓存的问题,我使用一下代码添加一个指纹标志

public class Fingerprint
    {
        public static string Tag(string rootRelativePath)
        {
            if (HttpRuntime.Cache[rootRelativePath] == null)
            {
                string absolute = HostingEnvironment.MapPath("~" + rootRelativePath);

                DateTime date = File.GetLastWriteTime(absolute);
                int index = rootRelativePath.LastIndexOf('/');

                string result = rootRelativePath.Insert(index, "/v-" + date.Ticks);
                HttpRuntime.Cache.Insert(rootRelativePath, result, new CacheDependency(absolute));
            }

            return HttpRuntime.Cache[rootRelativePath] as string;
        }
    }

<system.webServer>
   <urlCompression doStaticCompression="true" doDynamicCompression="true" dynamicCompressionBeforeCache="false" />
   <rewrite>
      <rules>
        <rule name="fingerprint">
          <match url="([\S]+)(/v-[0-9]+/)([\S]+)" />
          <action type="Rewrite" url="{R:1}/{R:3}" />
        </rule>
      </rules>
    </rewrite>
 </system.webServer>

<link rel="stylesheet" href="@Fingerprint.Tag("/content/site.css")" />

ETag

ETags 是用于 Web 缓存验证的工具，允许有条件的客户端请求。通过 ETags，浏览器可以判断某项资源是否被需要。如果不需要，浏览器就不会向 Web 服务器发送请求，从而最小化请求数量。配置方法

• 全局方案,自定义一个HttpModule

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public class ETagHttpModule : IHttpModule {   #region IHttpModule Members   void IHttpModule.Dispose()   {     // Nothing to dispose;   }   void IHttpModule.Init(HttpApplication context)   {     context.BeginRequest += new EventHandler(context_BeginRequest);     WebPageHttpHandler.DisableWebPagesResponseHeader = true;   }   #endregion   void context_BeginRequest(object sender, EventArgs e)   {     HttpApplication app = sender as HttpApplication;       //if (app.Request.CurrentExecutionFilePath.EndsWith("/") || app.Request.CurrentExecutionFilePath.EndsWith(".cshtml"))     //{       app.Response.Filter = new ETagStream(app.Response, app.Request);     //}   }   #region Stream filter   public class ETagStream : MemoryStream   {     private HttpResponse _response = null;     private HttpRequest _request;     private Stream _filter = null;     public ETagStream(HttpResponse response, HttpRequest request)     {       _response = response;       _request = request;       _filter = response.Filter;     }     private string GetToken(Stream stream)     {       var checksum = new byte[0];       checksum = MD5.Create().ComputeHash(stream);       return Convert.ToBase64String(checksum, 0, checksum.Length);     }     public override void Write(byte[] buffer, int offset, int count)     {       var data = new byte[count];       Buffer.BlockCopy(buffer, offset, data, 0, count);       var token = GetToken(new MemoryStream(data));       var clientToken = _request.Headers["If-None-Match"];       if (token != clientToken)       {         _response.AddHeader("ETag", token);         _filter.Write(data, 0, count);       }       else       {         _response.SuppressContent = true;         _response.StatusCode = 304;         _response.StatusDescription = "Not Modified";         _response.AddHeader("Content-Length", "0");       }     }   }   #endregion }

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<modules>             <remove name="FormsAuthentication" />             <!--<add type="WhitespaceModule" name="WhitespaceModule" />-->            <add type="WebApp.ETagHttpModule" name="ETagHttpModule" /> </modules>

• Action页面级

　　

+ View Code?

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public class ETagAttribute : ActionFilterAttribute   {     public override void OnActionExecuting(ActionExecutingContext filterContext) => filterContext.HttpContext.Response.Filter = new ETagFilter(filterContext.HttpContext.Response, filterContext.RequestContext.HttpContext.Request);   }     public class ETagFilter : MemoryStream   {     private HttpResponseBase _response = null;     private HttpRequestBase _request;     private Stream _filter = null;       public ETagFilter(HttpResponseBase response, HttpRequestBase request)     {       _response = response;       _request = request;       _filter = response.Filter;     }       private string GetToken(Stream stream)     {       var checksum = new byte[0];       checksum = MD5.Create().ComputeHash(stream);       return Convert.ToBase64String(checksum, 0, checksum.Length);     }       public override void Write(byte[] buffer, int offset, int count)     {       var data = new byte[count];         Buffer.BlockCopy(buffer, offset, data, 0, count);         var token = GetToken(new MemoryStream(data));       var clientToken = _request.Headers["If-None-Match"];         if (token != clientToken)       {         _response.AddHeader("ETag", token);         _filter.Write(data, 0, count);       }       else       {         _response.SuppressContent = true;         _response.StatusCode = 304;         _response.StatusDescription = "Not Modified";         _response.AddHeader("Content-Length", "0");       }     }          }

　　

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//[OutputCache(Duration = 360, VaryByParam = "none")] [ETag] public ActionResult Index() => this.View();

效果图,回发的字节数确实减少了很多,单响应时间差不多,不是很明显.

总结

优化方案有很多,但是感觉效果都不是很理想,要做到极致的用户体验,可能真的要抛弃Jquery,EasyUI,这类肥大又复杂的类库.

问题

另外大家有没有非常好用又简单的方法解决初始加载白屏的问题,我试过用js preloading图层动画,但是效果还是不理想.但看过一些网址和APP做的效果非常好,不知道具体是如何实现的,在Asp.net mvc环境下能不能用

参考文章

(ASP.NET MVC 应用提速的十种方法)http://blog.oneapm.com/apm-tech/679.html