最大并发HttpWebRequests数

Question

我正在对一个web应用程序进行压力测试，并且已经设置了一个windows测试程序，该程序会启动一些线程，并在每个线程上发送一个web请求。

问题是我得到了以下输出：

01/09/09 11:34:04 Starting new HTTP request on 10
01/09/09 11:34:04 Starting new HTTP request on 11
01/09/09 11:34:04 Starting new HTTP request on 13
01/09/09 11:34:05 Starting new HTTP request on 14
01/09/09 11:34:05 Starting new HTTP request on 11
01/09/09 11:34:05 11 has finished!
01/09/09 11:34:05 Starting new HTTP request on 13
01/09/09 11:34:05 13 has finished!
01/09/09 11:34:05 Starting new HTTP request on 14
01/09/09 11:34:05 14 has finished!
01/09/09 11:34:05 Starting new HTTP request on 11
01/09/09 11:34:05 11 has finished!
01/09/09 11:34:05 Starting new HTTP request on 14
01/09/09 11:34:05 14 has finished!
01/09/09 11:34:05 Starting new HTTP request on 13
01/09/09 11:34:05 13 has finished!
01/09/09 11:34:05 Starting new HTTP request on 15
01/09/09 11:34:06 Starting new HTTP request on 11
01/09/09 11:34:06 11 has finished!
01/09/09 11:34:06 Starting new HTTP request on 14
01/09/09 11:34:06 14 has finished!

这看起来最多有5个线程，即使我这样创建了100个线程：

int numberOfThreads = Convert.ToInt32(txtConcurrentThreads.Text);

    List<BackgroundWorker> workers = new List<BackgroundWorker>();

    for (int N = 0; N < numberOfThreads; N++)
    {

        BackgroundWorker worker = new BackgroundWorker();
        worker.DoWork += new DoWorkEventHandler(worker_DoWork);
        worker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(worker_RunWorkerCompleted);
        workers.Add(worker);
    }


    foreach(BackgroundWorker worker in workers)
    {
        worker.RunWorkerAsync();
    }

有谁能告诉我到底是怎么回事？

谢谢

编辑:如果我像建议的那样休眠5秒，而不是httpwebrequest，那么我确实会得到更多的线程触发，但没有我预期的那么多：

01/09/09 11:56:14 Starting new HTTP request on 7
01/09/09 11:56:14 Starting new HTTP request on 11
01/09/09 11:56:15 Starting new HTTP request on 12
01/09/09 11:56:15 Starting new HTTP request on 13
01/09/09 11:56:16 Starting new HTTP request on 14
01/09/09 11:56:16 Starting new HTTP request on 15
01/09/09 11:56:17 Starting new HTTP request on 16
01/09/09 11:56:17 Starting new HTTP request on 17
01/09/09 11:56:18 Starting new HTTP request on 18
01/09/09 11:56:19 Starting new HTTP request on 7
01/09/09 11:56:19 7 has finished!
01/09/09 11:56:19 Starting new HTTP request on 11
01/09/09 11:56:19 11 has finished!
01/09/09 11:56:19 Starting new HTTP request on 19
01/09/09 11:56:20 Starting new HTTP request on 20
01/09/09 11:56:20 Starting new HTTP request on 12
01/09/09 11:56:20 12 has finished!

看起来我每秒只能启动2个线程，这对我来说似乎非常慢。我想Console.WriteLine可能是个问题吧？

编辑:我设置

ThreadPool.SetMinThreads(100, 4); 

和

System.Net.ServicePointManager.DefaultConnectionLimit = 100;

并得到以下结果：

01/09/09 14:00:07 Starting new HTTP request on 11
01/09/09 14:00:07 Starting new HTTP request on 81
01/09/09 14:00:07 Starting new HTTP request on 82
01/09/09 14:00:07 Starting new HTTP request on 79
01/09/09 14:00:07 Starting new HTTP request on 83
01/09/09 14:00:07 Starting new HTTP request on 84
01/09/09 14:00:07 Starting new HTTP request on 85
01/09/09 14:00:07 Starting new HTTP request on 87
01/09/09 14:00:07 Starting new HTTP request on 88
...
01/09/09 14:00:07 84 has finished! Took 323.0323 milliseconds
01/09/09 14:00:08 88 has finished! Took 808.0808 milliseconds
01/09/09 14:00:08 96 has finished! Took 806.0806 milliseconds
01/09/09 14:00:08 94 has finished! Took 806.0806 milliseconds
01/09/09 14:00:08 98 has finished! Took 801.0801 milliseconds
01/09/09 14:00:08 80 has finished! Took 799.0799 milliseconds
01/09/09 14:00:08 86 has finished! Took 799.0799 milliseconds
01/09/09 14:00:08 92 has finished! Took 799.0799 milliseconds
01/09/09 14:00:08 100 has finished! Took 812.0812 milliseconds
01/09/09 14:00:08 82 has finished! Took 1010.101 milliseconds

因此能够同时推送出大量的web请求。它似乎在排队(呼叫STA COM+服务器)，所以这就是我所期望的。

谢谢你的帮忙

Answer 1

您的所有(或大部分)请求是否碰巧都发往同一主机？每台主机都有一个内置的限制。您可以在system.Net connectionManagement元素的app.config中对其进行更改。

另一件事是线程池只会逐渐增加它的线程数量-它每半秒启动一个新线程，IIRC。这就是你所看到的吗？试着把HttpWebRequest从等式中去掉--只需要睡几秒钟……

我怀疑后一个问题是您最初遇到的问题，但第一个问题也会给您带来问题。

Answer 2

同时传出HTTP连接的数量有限制。我认为您可以在创建HttpWebRequest对象之前使用System.Net.ServicePointManager.DefaultConnectionLimit静态属性来控制这一点。

Answer 3

我没有听说过太多关于.NET核心的事情。ServicePointManager没有包含在.NET核心1中，但在版本2中似乎又回来了。但是，对于HttpClient，您也可以像这样设置最大连接数：

new HttpClient(new HttpClientHandler
                {
                    MaxConnectionsPerServer = 100
                })