Competition Webservices ASMX with Ajax

Question

I realized that when called by XHR, the ASMX webservices can handle few simultaneous requests. Consider the following scenario:

Page ASPX:

 <asp:ScriptManager ID="scrManager" runat="server">
     <Services>
         <asp:ServiceReference Path="~/WebService.asmx" />
     </Services>
 </asp:ScriptManager>

Webservice method:

[WebMethod]
public string HelloWorld()
{
   Thread.Sleep(1000);
   return "Hello World";
}

And the Javascript code that calls it:

$(document).ready(function () {
    var ws = new WebApplication1.WebService();

    for (var i = 0; i < 100; i++) {
        var start = new Date().getTime();
        function sucesso() {
            var end = new Date().getTime();
            var time = end - start;
            console.log('Duração: ' + time);
        }

        ws.HelloWorld(sucesso, function () { alert("erro"); });
    }
});

And the result is more or less this:

I expected each request to take approximately 1s, but with each more or less 5 requests, the waiting time increases. That is, the request was on hold, because there were other connections open. My question is: how to increase the number of simultaneous requests, so that more calls take the same time. I know it would not be good if the 100 requests were opened at once, but I find very little the number I currently have.

Searching around, I found the following configuration (web.config) but it didn’t work:

<system.net>
  <connectionManagement>
    <add address="*" maxconnection="40"/>
  </connectionManagement>
 </system.net>

_{Note: I know that web services made with asmx are a legacy technology, but I have a whole large system that uses them on the front end, in a similar way to the one exposed here. It is not an option now to change the technology.}

Answer 1

One possible way to address the problem is to declare the [WebMethod] in two parts - one of type IAsyncResult initiating the call and a string that concludes it. I am without access to an IIS server to test, but I based on that post: http://chroniclesofnojo.blogspot.com.br/2011/06/asynchronous-asmx-web-services.html

Also, if you are using ASP 2.0 integrated into IIS7, you need to set the configuration of MaxConcurrentRequestsPerCPU to deal with threading. Source: http://www.iis.net/learn/application-frameworks/building-and-running-aspnet-applications/aspnet-20-breaking-changes-on-iis