Question

我不明白，为什么async / await不能解决IIS线程的问题。

我发现当我使用IIS并且IIS表达没有限制时，我们对IIS线程的限制等于10。

我在HomeController中添加了2个方法来重复此问题。其中一个（方法）使用Thread.Sleep和其他使用async / await。

当然我使用logger（NLog）来更详细地描述这个问题。

我使用apache-jmeter-3.0对100个并行请求进行压力测试。

当IIS的测试执行时间大致相同且IIS Express的测试执行时间大致相同时，我感到非常惊讶。

来自HomeController的一些代码

[SessionState(SessionStateBehavior.Disabled)]
public class HomeController : Controller
{
    private const int _waitTimeout = 30000;
    private const string _beginFmt = "Begin method; Count = {0}; OperId = {1};";
    private const string _endFmt =   "End method  ; Count = {0}; OperId = {1};";

    private static volatile int _counter = 0;
    private static Logger _logger = LogManager.GetCurrentClassLogger();

    public JsonResult GetWithThreadSleep()
    {
        Guid operId = Guid.NewGuid();

        _logger.Info(_beginFmt, Interlocked.Increment(ref _counter), operId);

        Thread.Sleep(_waitTimeout);

        _logger.Info(_endFmt, Interlocked.Decrement(ref _counter), operId);

        return Json(null, JsonRequestBehavior.AllowGet);
    }

    public async Task<JsonResult> GetWithTaskAwait()
    {
        Guid operId = Guid.NewGuid();

        _logger.Info(_beginFmt, Interlocked.Increment(ref _counter), operId);

        await Task.Delay(_waitTimeout);

        _logger.Info(_endFmt, Interlocked.Decrement(ref _counter), operId);

        return Json(null, JsonRequestBehavior.AllowGet);
    }
}

日志格式

    <target xsi:type="File" 
            name="f" fileName="${basedir}/logs/${shortdate}.log"
            layout="${threadid} @ ${date:format=HH\:mm\:ss} @ ${level} @${aspnet-sessionid} @ ${message} @ ${callsite:className=False}" 
    />

测试场景一：我向方法 GetWithTaskAwait 发送100个并行GET请求，并期望处理的速度超过 5分钟，因为线程应该重用。

但事实并非如此。测试持续时间等于5分钟

1 @ 23:43:54 @ Info @ @ MVC Count = 1; @ .ctor 1 @ 23:43:54 @ Info @ @ APP Count = 1; @ Application_Start 11 @ 23:44:06 @ Info @ @ MVC Count = 2; @ .ctor ... 13 @ 23:45:36 @ Info @ @ End method ; Count = 8; OperId = 28818fba-5535-4c01-9d6d-5efa3943cf37; @ MoveNext 19 @ 23:45:36 @ Info @ @ Begin method; Count = 9; OperId = c3cd3339-ec29-4625-adb9-62d5c72831b0; @ GetWithTaskAwait 12 @ 23:45:36 @ Info @ @ End method ; Count = 9; OperId = d1686c05-ca7a-400c-8c17-43dfb7b9218a; @ MoveNext 16 @ 23:45:36 @ Info @ @ Begin method; Count = 10; OperId = c1ec5517-649c-4733-9db3-e666e648abae; @ GetWithTaskAwait 13 @ 23:45:36 @ Info @ @ End method ; Count = 9; OperId = fbcfc9d9-fb84-456b-82a1-a0d593ef0815; @ MoveNext ... 26 @ 23:49:06 @ Info @ @ End method ; Count = 8; OperId = 766d4bc5-3739-4e20-a242-1f114dd44442; @ MoveNext 22 @ 23:49:06 @ Info @ @ End method ; Count = 7; OperId = 0ba18b30-11c9-49fe-8c94-40bbfa817e88; @ MoveNext 16 @ 23:49:06 @ Info @ @ End method ; Count = 9; OperId = 6d7afd57-6128-4bee-bf32-92de7cfc6a34; @ MoveNext 26 @ 23:49:06 @ Info @ @ End method ; Count = 6; OperId = 4c022744-9932-4f94-be1d-b982e36460f2; @ MoveNext 22 @ 23:49:06 @ Info @ @ End method ; Count = 5; OperId = 05476e6a-106f-4da5-b99b-098b90dbab89; @ MoveNext 16 @ 23:49:07 @ Info @ @ End method ; Count = 4; OperId = 3aba1ad2-56b0-4cf5-8aee-7e918eca9fba; @ MoveNext 27 @ 23:49:07 @ Info @ @ End method ; Count = 3; OperId = ef972cdd-7992-4816-9452-ecabaf189767; @ MoveNext 15 @ 23:49:07 @ Info @ @ End method ; Count = 2; OperId = 9a0f735e-bf6b-4217-b2ef-8abd9ce01d27; @ MoveNext 30 @ 23:49:07 @ Info @ @ End method ; Count = 0; OperId = cc75b44a-4e8d-4534-9906-40bddc027267; @ MoveNext 33 @ 23:49:07 @ Info @ @ End method ; Count = 1; OperId = bbef36b3-051b-444d-858a-2766bcfcd12b; @ MoveNext ... 26 @ 23:49:49 @ Info @ @ MVC Count = 10; @ Dispose 30 @ 23:50:19 @ Info @ @ MVC Count = 9; @ Dispose 16 @ 23:50:49 @ Info @ @ MVC Count = 8; @ Dispose

测试场景二：我向方法 GetWithThreadSleep 发送100个并行GET请求，并期望处理相等 5分钟，因为线程不应该重用。

1 @ 00:15:41 @ Info @ @ MVC Count = 1; @ .ctor 1 @ 00:15:41 @ Info @ @ APP Count = 1; @ Application_Start 11 @ 00:16:14 @ Info @ @ MVC Count = 2; @ .ctor ... 15 @ 00:16:15 @ Info @ @ Begin method; Count = 8; OperId = cedb5075-405c-4c23-93cb-388dc34537ba; @ GetWithThreadSleep 17 @ 00:16:15 @ Info @ @ MVC Count = 10; @ .ctor 17 @ 00:16:15 @ Info @ @ Begin method; Count = 9; OperId = 777d7464-f900-48c1-991f-ef8c8f7e6e86; @ GetWithThreadSleep 18 @ 00:16:16 @ Info @ @ MVC Count = 11; @ .ctor 18 @ 00:16:16 @ Info @ @ Begin method; Count = 10; OperId = f9b4b717-94a5-4196-958f-c1234d19514c; @ GetWithThreadSleep 12 @ 00:16:45 @ Info @ @ End method ; Count = 8; OperId = 9e40acd4-888f-4656-a5a3-c5a1d210cc88; @ GetWithThreadSleep 5 @ 00:16:45 @ Info @ @ End method ; Count = 9; OperId = b068e03e-37e9-446e-ad42-c9ab4c30da93; @ GetWithThreadSleep 11 @ 00:16:45 @ Info @ @ End method ; Count = 7; OperId = 22e510e5-62f7-4bc8-8ab0-fdeb3080e250; @ GetWithThreadSleep ... 18 @ 00:21:15 @ Info @ @ End method ; Count = 2; OperId = 169ef436-6b27-4f4c-a3ca-0b18a5a796cf; @ GetWithThreadSleep 13 @ 00:21:16 @ Info @cubgm2zsojblkhrwwpixaaej @ End method ; Count = 1; OperId = ee346be8-17c5-45ac-88b5-67e724250bbf; @ GetWithThreadSleep 12 @ 00:21:16 @ Info @ @ End method ; Count = 0; OperId = 68d5deaa-95d6-4627-a129-144ffafcc2ef; @ GetWithThreadSleep 13 @ 00:22:11 @ Info @ @ MVC Count = 10; @ Dispose 9 @ 00:22:41 @ Info @ @ MVC Count = 9; @ Dispose

重要信息：

IIS版本10.0.14393.0

.NET Framework 4.5.1

Windows 10 Pro

您可以从GitHub
下载完整的解决方案

Answer 1

桌面操作系统上的IIS（Win 7/8/10）会将您的请求限制为10个并发。

在服务器操作系统（2008/2012/2016）上，该限制不存在。

在IIS Express上，该限制也不存在。

此限制的原因是您无法在桌面操作系统上使用IIS进行生产。

https://weblogs.asp.net/owscott/windows-8-iis-8-concurrent-requests-limit

Answer 2

IIS不限制线程，而是并发请求（或连接，不确定）。异步等待无法绕过这个限制。

为什么异步等待无法在IIS上运行，但它正在使用IIS Express

2 个答案: