在初始阶段，ASP.NET WebAPI的响应速度很慢

时间：2018-08-01 07:58:45

标签： iis asp.net-web-api async-await task

我制作了一个仅引用Web API的空项目，并调整了这些简单的API，以查看是否存在性能差异，并且其中一个异步作业可能挂起。

public class TestController : ApiController
{
    [HttpGet]
    [Route("Welcome")]
    public async Task<string> Welcome()
    {
        string r = await SlowMethod();
        return r;
    }

    public async Task<string> SlowMethod()
    {
        Thread.Sleep(3000);
        return await Task.FromResult("data");
    }

    [HttpGet]
    [Route("WelcomeSync")]
    public string WelcomeSync()
    {
        string r = SlowSyncMethod();
        return r;
    }

    public string SlowSyncMethod()
    {
        Thread.Sleep(3000);
        return "data";
    }
}

然后我使用带有this test plan的jMeter运行了API测试。就吞吐量而言，结果几乎是相同的，但是与jMeter相比，此结果表中的“ Max”项存在明显的差异。

Label   Samples Average Min     Max     Std.Dev             Error%    Throughput    Received KB/sec     Sent KB/sec         Avg.Bytes

Async   100000  3193    3000    [32046] 1343.6219321793749  0.0 62.534550339062335  21.557320575868168  7.69468099875181    353.0    
Sync    100000  3003    3000    [3050]  3.523236520886259   0.0 66.54055014396047   23.458143165986066  8.447530779994983   361.0
顺便说一下，

Max 是毫秒单位。由于Thread.Sleep(3000);，每个API每个请求至少要花费3秒的时间，但是其中一个请求（或其中一些请求）需要32秒才能完成。

这是否意味着至少有一项异步工作挂起？如果有，死刑的罪魁祸首是什么？

已更新

我曾经怀疑异步工作挂起行为，但事实并非如此。只需更改测试顺序即可得出相同的结果。 第一次测试在测试开始时总是很慢。这与异步与同步作业完全无关。

无论如何，我尝试使用SlowMethod();在Stopwatch之间保留日志，以查看async方法是否真正挂起，并且很快我发现在async和sync API上肯定没有挂起。日志总是打印“花了3秒钟”。 

2018-08-12 13:40:11 "Welcome async 'Welcome'. It took 3 seconds"
2018-08-12 13:40:14 "Welcome async 'Welcome'. It took 3 seconds"
2018-08-12 13:40:17 "Welcome async 'Welcome'. It took 3 seconds"
.
.
.

最近才是HTTP响应本身。并且在速度上有一个明显的特征。

  • 演出很快就失去了节奏。
  • 它会一直减速直到达到30〜40秒的处理时间
  • 此后，它开始从拖动性能中恢复。
  • 最终它会在3秒钟内保持响应，直到结束。

这是可以帮助您更好地描绘图片的日志。

2018-08-04 04:48:50.030 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 3. The result was "data"
2018-08-04 04:48:50.030 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 3. The result was "data"
2018-08-04 04:48:50.030 +09:00 [INF] CurrentThread 9, Context LeaseLifeTimeServiceProperty, Time passed 3. The result was "data"
2018-08-04 04:48:50.030 +09:00 [INF] CurrentThread 10, Context LeaseLifeTimeServiceProperty, Time passed 3. The result was "data"
2018-08-04 04:48:50.632 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 4. The result was "data"
2018-08-04 04:48:51.637 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 5. The result was "data"
2018-08-04 04:48:52.631 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 6. The result was "data"
2018-08-04 04:48:52.968 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 6. The result was "data"
2018-08-04 04:48:52.969 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 6. The result was "data"
2018-08-04 04:48:52.969 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 6. The result was "data"
2018-08-04 04:48:52.973 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 6. The result was "data"
2018-08-04 04:48:53.631 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 7. The result was "data"
2018-08-04 04:48:53.637 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 7. The result was "data"
2018-08-04 04:48:54.631 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 8. The result was "data"
2018-08-04 04:48:54.640 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 8. The result was "data"
2018-08-04 04:48:55.633 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 9. The result was "data"
2018-08-04 04:48:55.635 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 9. The result was "data"
2018-08-04 04:48:55.975 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 9. The result was "data"
2018-08-04 04:48:55.976 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 9. The result was "data"
2018-08-04 04:48:55.976 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 9. The result was "data"
2018-08-04 04:48:55.979 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 9. The result was "data"
2018-08-04 04:48:56.633 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 10. The result was "data"
2018-08-04 04:48:56.636 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 10. The result was "data"
2018-08-04 04:48:56.642 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 10. The result was "data"
.
.
.
2018-08-04 04:49:04.647 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 18. The result was "data"
2018-08-04 04:49:04.650 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 18. The result was "data"
2018-08-04 04:49:04.994 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 18. The result was "data"
2018-08-04 04:49:04.994 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 18. The result was "data"
2018-08-04 04:49:04.998 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 18. The result was "data"
2018-08-04 04:49:04.999 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 18. The result was "data"
2018-08-04 04:49:05.633 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 19. The result was "data"
2018-08-04 04:49:05.636 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 19. The result was "data"
2018-08-04 04:49:05.640 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 19. The result was "data"
2018-08-04 04:49:05.643 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 19. The result was "data"
2018-08-04 04:49:05.646 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 19. The result was "data"
2018-08-04 04:49:05.652 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 19. The result was "data"
2018-08-04 04:49:06.633 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 20. The result was "data"
2018-08-04 04:49:06.638 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 20. The result was "data"
2018-08-04 04:49:06.641 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 20. The result was "data"
2018-08-04 04:49:06.643 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 20. The result was "data"
2018-08-04 04:49:06.647 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 20. The result was "data"
2018-08-04 04:49:06.655 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 20. The result was "data"
.
.
.
2018-08-04 04:49:15.634 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 28. The result was "data"
2018-08-04 04:49:15.639 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 28. The result was "data"
2018-08-04 04:49:15.644 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 28. The result was "data"
2018-08-04 04:49:15.648 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 28. The result was "data"
2018-08-04 04:49:15.652 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:15.653 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:15.655 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:15.665 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:16.635 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:16.638 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:16.647 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 30. The result was "data"
2018-08-04 04:49:16.650 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:16.669 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 30. The result was "data"
2018-08-04 04:49:16.669 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 30. The result was "data"
2018-08-04 04:49:16.669 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 30. The result was "data"
2018-08-04 04:49:16.670 +09:00 [INF] CurrentThread 10, Context LeaseLifeTimeServiceProperty, Time passed 30. The result was "data"
2018-08-04 04:49:16.673 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 30. The result was "data"
2018-08-04 04:49:17.014 +09:00 [INF] CurrentThread 16, Context LeaseLifeTimeServiceProperty, Time passed 30. The result was 
2018-08-04 04:49:17.662 +09:00 [INF] CurrentThread 16, Context LeaseLifeTimeServiceProperty, Time passed 30. The result was "data"
2018-08-04 04:49:17.668 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:17.675 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:17.676 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:18.634 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:18.644 +09:00 [INF] CurrentThread 10, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:18.647 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:18.648 +09:00 [INF] CurrentThread 15, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:18.651 +09:00 [INF] CurrentThread 15, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:18.654 +09:00 [INF] CurrentThread 15, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:18.661 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 31. The result was "data"
2018-08-04 04:49:18.668 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 32. The result was "data"
2018-08-04 04:49:18.671 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 32. The result was "data"
2018-08-04 04:49:18.675 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 32. The result was "data"
2018-08-04 04:49:19.640 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 32. The result was "data"
2018-08-04 04:49:19.646 +09:00 [INF] CurrentThread 11, Context LeaseLifeTimeServiceProperty, Time passed 32. The result was "data"
2018-08-04 04:49:19.646 +09:00 [INF] CurrentThread 16, Context LeaseLifeTimeServiceProperty, Time passed 32. The result was "data"
2018-08-04 04:49:19.656 +09:00 [INF] CurrentThread 16, Context LeaseLifeTimeServiceProperty, Time passed 32. The result was "data"
2018-08-04 04:49:19.659 +09:00 [INF] CurrentThread 16, Context LeaseLifeTimeServiceProperty, Time passed 32. The result was "data"
2018-08-04 04:49:19.667 +09:00 [INF] CurrentThread 16, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:19.669 +09:00 [INF] CurrentThread 16, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:19.673 +09:00 [INF] CurrentThread 16, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:19.677 +09:00 [INF] CurrentThread 15, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:19.679 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 29. The result was "data"
2018-08-04 04:49:20.016 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 28. The result was "data"
2018-08-04 04:49:20.017 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 27. The result was "data"
2018-08-04 04:49:20.023 +09:00 [INF] CurrentThread 12, Context LeaseLifeTimeServiceProperty, Time passed 27. The result was "data"
.
.
.
2018-08-04 05:03:11.422 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 3. The result was "data"
2018-08-04 05:03:14.492 +09:00 [INF] CurrentThread 14, Context LeaseLifeTimeServiceProperty, Time passed 3. The result was "data"

IIS recompilation，IIS application pool recycling和IIS idle timeout设置是主要的可疑对象，但事实证明它们与此问题无关。严重是什么原因？

2 个答案:

答案 0 :(得分：2)

虽然可以在同步测试中使用Thread.Sleep(3000);，但是在伪造长时间运行的异步调用时，使用Task.Delay可以得到更好的表示。

public async Task<string> SlowMethod() {
    await Task.Delay(3000);
    return "data";
}

答案 1 :(得分：0)

罪魁祸首

我终于打开了引擎盖，尝试检查可能导致此性能问题的每一个小细节。问题出在ThreadPool。从现在起，将其称为问题似乎不再存在。

ThreadPool的本质是，它不喜欢创建新线程并增加其池中的线程数，并且倾向于在适用时回落到最小线程数。这种现象的背后。

在我的环境中，ThreadPool以4个线程开头。我能够通过打电话来实现这一点。

ThreadPool.GetMinThreads(out int threadCount, out int portThread);

在初始阶段只有4个线程根本不足以处理jMeter测试期间传入的HTTP请求。因此，让ThreadPool维持至少200个线程，以便它可以从200个线程开始，就解决了这个问题。

ThreadPool.SetMinThreads(200, 4);

现在，每个请求将在测试结束前的3秒内得到处理。但是不建议以无意义的方式操作ThreadPool中的最小线程数，因为这可能会影响应用程序的性能。

这是MSDN的警告

  

默认情况下，最小线程数设置为系统上的处理器数。您可以使用SetMinThreads方法来增加最小线程数。但是，不必要地增加这些值可能会导致性能问题。如果太多任务同时开始，则它们似乎都变慢了。在大多数情况下，线程池使用自己的分配线程算法会更好地执行。将最小值降低到少于处理器数量也会损害性能。

无需使用SetMinThreads

的简便解决方案

使用Task.Delay(3000);而不是Thread.Sleep(3000)也消除了这个问题。由于Thread.Sleep(3000)仅阻塞当前线程，因此可能导致ThreadPool创建更多线程。实际上，您可以在资源监视器中看到这种情况。

这是Task.Delay(3000);版本，我在测试开始1分钟后拍摄了此屏幕截图。在测试过程中，仅创建了59个线程，并且数量保持不变或低于。

enter image description here

这是Thread.Sleep(3000);版本，我是同时使用的。但是iisexpress已产生116个线程，并且在测试过程中 keeps不断增加。

enter image description here

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