关于AysncController的一次测试（url重写后静态页文件内容的读取是否需要使用异步？）

因为做网站的静态页缓存，所以做了这个测试

MVC项目

准备了4个Action,分两组，一组是读取本地磁盘的一个html页面文件，一组是延时2秒

public class TestController : Controller
{
    public ActionResult Article(string name)
    {
        string path = @"I:\c#\nn.html";
        using (StreamReader reader = new StreamReader(path))
        {
            return Content(reader.ReadToEnd());
        }
    }

    public async Task<ActionResult> Article2(string name)
    {
        string path = @"I:\c#\nn.html";
        using (StreamReader reader = new StreamReader(path))
        {
            return Content(await reader.ReadToEndAsync());
        }
    }

    public ActionResult Index1()
    {
        Thread.Sleep(2000);

        return Content("synchronized");
    }

    public async Task<ActionResult> Index2()
    {
        await Task.Delay(2000);

        return Content("asynchronized");
    }
}

控制台程序，测试代码

class Program
{
    static void Main(string[] args)
    {
        var syncUrl = "http://localhost:61771/Test/Article";
        var asyncUrl = "http://localhost:61771/Test/Article2";

        var syncUrl2 = "http://localhost:61771/Test/Index1";
        var asyncUrl2 = "http://localhost:61771/Test/Index2";
        var count = 20;

        int i = 0;
        while (true)
        {
            Console.WriteLine();

            Benchmark(asyncUrl, count);
            Benchmark(syncUrl, count);
            Benchmark(asyncUrl2, count);
            Benchmark(syncUrl2, count);

            i++;
            if (Console.ReadKey().Key == ConsoleKey.C)
            {
                break;
            }
        }

        Console.ReadKey();
    }
    static void Benchmark(string url, int count)
    {
        var stopwatch = new Stopwatch();
        stopwatch.Start();

        var threads = new List<Thread>();
        var countdown = new CountdownEvent(count);
        for (int i = 0; i < count; i++)
        {
            threads.Add(new Thread(() =>
            {
                using (var client = new WebClient())
                {
                    client.DownloadData(url);
                    countdown.Signal();
                }
            }));
        }

        for (int i = 0; i < count; i++)
        {
            threads[i].Start();
        }

        while (!countdown.IsSet) ;

        stopwatch.Stop();

        Console.WriteLine(string.Format("{0} costs {1} ms", url, stopwatch.ElapsedMilliseconds.ToString()));
    }
}

测试结果

运行环境：笔记本电脑本地测试。
执行结果：

count = 20
count = 100
count = 200

count = 500
测试时WebClient抛出了请求超时的警告，
代码调整如下：

 public class NewWebClient : WebClient
 {
 	private int _timeout;
 	public NewWebClient()
 	{
 		this._timeout = 60000;
 	}
 
 	public NewWebClient(int timeout)
 	{
 		this._timeout = timeout;
 	}
 
 	protected override WebRequest GetWebRequest(Uri address)
 	{
 		var result = base.GetWebRequest(address);
 		result.Timeout = this._timeout;
 		return result;
 	}
 }
 
 static void Benchmark(string url, int count)
 {
 	var stopwatch = new Stopwatch();
 	stopwatch.Start();
 
 	var threads = new List<Thread>();
 	var countdown = new CountdownEvent(count);
 	for (int i = 0; i < count; i++)
 	{
 		threads.Add(new Thread(() =>
 		{
 			using (var client = new NewWebClient(30 * 60 * 1000))
 			{
 				client.DownloadData(url);
 				countdown.Signal();
 			}
 		}));
 	}
 
 	for (int i = 0; i < count; i++)
 	{
 		threads[i].Start();
 	}
 
 	while (!countdown.IsSet) ;
 
 	stopwatch.Stop();
 
 	Console.WriteLine(string.Format("{0} costs {1} ms", url, stopwatch.ElapsedMilliseconds.ToString()));
 }

count = 1000
count = 1500

总结

按照过去看过的资料描述，应该是 AsyncController虽然会因为线程切换而使单个请求增加额外的处理时间，但使耗时的操作不再占用工作线程，从而可以让IIS在相同时间内可以响应更多的请求，提高吞吐率。

第二组Action(延时2秒)的测试结果数据确实反映了这一效果。

但第一组读取本地文件的测试结果则是单个请求的处理时间，异步Action明显高于同步不说，处理相同请求数所消耗的时间也是异步高于同步……，磁盘文件的并发读取是不是有什么限制呢？，待确认。

UrlRewrite

在已经完成MapHandler后就不能重写了，所以一般在BeginRequest的时候，执行重写
IIS的url不区分大小写
///////home//////index//////////////////,request.Url.PathAndQuery依然是/home/index/
/index.html/ 末尾带斜杠访问一个动态页可以正常访问（样式可能会乱掉），但访问一个静态页会报404

补充测试

    protected void Application_BeginRequest()
    {
        var context = HttpContext.Current;
        var request = context.Request;
        if (request.RequestType == "GET")//过滤所有API
        {
            string regularUrl = request.Url.PathAndQuery;
            if (regularUrl.StartsWith("/Test/Article3"))
            {
                context.RewritePath("/Project_Readme.html");
            }
            else if (regularUrl.StartsWith("/Test/Article4"))
            {
                string path = context.Server.MapPath("~/Project_Readme.html");
                if (File.Exists(path))
                {
                    using (StreamReader reader = new StreamReader(path))
                    {
                        context.Response.Write( reader.ReadToEnd());
                        context.Response.End();
                    }
                }
            }
        }
    }