IIS上的请求处理之前，HttpClient POST延迟较长，多线程

Question

I have a simple console application which sends HTTP POST from multiple threads:

List<Task> tasks = new List<Task>();
for (int i = 0; i < 100; i++)
{
    tasks.Add(Task.Factory.StartNew(() => SendQuery(url1, query1)));
    tasks.Add(Task.Factory.StartNew(() => SendQuery(url2, query2)));
}

Task.WaitAll(tasks.ToArray());

SendQuery(string uri, string requestString) looks like this:

Uri url = new Uri(uri);

try
{
   using (HttpClient client = new HttpClient { Timeout = new TimeSpan(0, 0, 10, 0) })
   {
      StringContent content = new StringContent(requestString);
      content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
      HttpResponseMessage response = client.PostAsync(url, content).Result;
      response.EnsureSuccessStatusCode();
   }
}
catch (Exception ex)
{
   Console.WriteLine(ex);
}

The program works without any errors, all the queries are processed finally, but after filling tasks list each thread hangs on client.PostAsync(url, content).Result , after several minutes IIS starts to process queries. Why does this delay occur? What's happening during this time? I am using IIS 7.5 running on Windows Server 2008 R2 to host web-services which provide url1 and url2 .

Answer 1

Set this value to 500 or 1000 at the start of your program and let us know the effects. Your requests maybe getting throttled at the default value of 2. (depending on the .net version)

ServicePointManager.DefaultConnectionLimit = 500;