Asp MVC session lost after RedirectToAction

Question

I have a MVC4 web application which works perfect on my local machine when I run it in Visual Studio.

So I publish the website to a server to go live with my application. But when I try to login my application goes to the following code:

[HttpPost]
public ActionResult CheckLogin(LoginViewModel vm)
{
     if (!String.IsNullOrWhiteSpace(vm.UserName) && !String.IsNullOrWhiteSpace(vm.Password))
     {
           User u = ... 
           // Get user from database with credentials

           System.Web.HttpContext.Current.Session.Add("UserIdSession", u.Id);
           return RedirectToAction("Validate", "Overview");
     }
     else
     {
         // process the error that the login failed
     }
}

The redirect goes to the following Action:

    [HttpGet]
    public ActionResult Validate()
    {
        if (HttpContext.Current.Session["UserIdSession"] != null)
        {
            return View();
        }
        else
        {
             return RedirectToAction("Index", "Login");
        }
    }

But the problem is that the session variable does not exists and it always send me back to the loginscreen

I've found that doing a redirect after setting a session is causing this behaviour, but I couldn't find an answer to solve this issue...

So I have some questions about it:

1. Why does it work on my local machine and not on a server?
2. Can I modify server settings to work this way that i'm intented to do? Does it recycle stuff after a redirect?
3. Can I reproduce this behaviour on my local machine like it would on the server with some settings?
4. There must be an easy way to solve this or am i wrong? Do i really need to store session variables in a database or something like that?

Answer 1

Do you have clustered servers with load balancing, if yes, then you may want to enable sticky session on it, so that all requests from one session goes to the same server.

if you have Server Clustering Answers :

1) When you store the session in memeory, you want to make sure all requests goes to the same server otherwise you would get this error on server, but not local.

2) If you just enable sticky session on server this error might go away.

3) If the error is because of clustering then you cannot reproduce it on local.

4) If you cannot enable sticky session on loadbalancer, then you may either have to store the session to a file accessible to all clustered servers or store it in the db.