ASP.NET MVC 请求在 RAM 相对较低时挂起

Question

I stuck with the following mysterious problem when using ASP.NET MVC and IIS. I have a very simple controller:

public class SimpleController : Controller
{
    public ActionResult Huge()
    {
        return Content(new string('a', 3000000));
    }

    public ActionResult Small()
    {
        return Content(new string('a', 1000000));
    }
}

If I run this example with IIS Express or more complicated examples with ordinary IIS, than I sometimes facing a problem, that request to the /Huge method handler just hangs: in browser, it looks like infinite page loading, in Wireshark I saw that TCP connection opened but after this, there is no activity from server (I also try to make raw requests with python via requests lib and in this case it also hangs for /Huge method handler). On the other hand, requests to the /Small method handler works fine.

I discovered, that this behavior stably reproduced with a relatively small amount of free RAM. But it's very strange for me: Process Explorer shows that at least 8GB of RAM is available (problem reproduced when only less than 8GB of free space available, but with more space both of these controllers works fine)

I also try to reproduce this behavior with ASP NET Core and Kestrel server and with this setup everything works fine and no hangs occurred.

Can anybody shed the light on this mysterious problem? What is the cause of the problem and are there any workarounds for it?

My configurations are the following:

• .NET Framework 4.8
• Windows 10 Pro (version 1909)
• RAM: 32 GB (with an enabled swap of the fixed size - 24 GB)
• Server: Microsoft-IIS/10.0

Answer 1

I dig a little bit deeper and found errors in HTTP.sys log files ( C:\\Windows\\System32\\LogFiles\\HTTPERR\\httperr1.log ). There is an error for request with the following tag: Connection_Abandoned_By_ReqQueue . This information helps me to find a blog post about a similar problem: https://mvolo.com/low-pagefile-can-cause-503-service-unavailable-on-azure-web-roles/

The suggested workaround is to increase swap size. I do it (increase swap by 64GB to ensure that IIS will be happy with it) - and problem resolved

Anyway, I don't understand what's wrong with IIS and why it can't use available memory in my initial setup (Kestrel in ASP NET Core can handle requests and I write a dummy app that simply allocates some memory - 5-8GB - and it works fine)