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:
[OutputCache(Duration = 360, VaryByParam = "none")]
public ActionResult Index() => this.View();
- web.Config 添加对静态文件的缓存
<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
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
}
<modules>
<remove name="FormsAuthentication" />
<!--<add type="WhitespaceModule" name="WhitespaceModule" />-->
<add type="WebApp.ETagHttpModule" name="ETagHttpModule" />
</modules>
- Action页面级
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");
}
} }
//[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