MVC Authentication Timeout Prior to ticket expiration - asp.net-mvc

Question

I have an asp.net MVC application that was exhibiting some strange authentication timeout behavior. We had the timeout on the forms authentication tag in the web.config set to two days.
<forms loginUrl="~/Login/Index" timeout="2880" />
What we noticed though was the application was timing out around the 20 min mark. So, after researching the issue and trying various settings we decided to add code to the global.asax in the Applicatoni_AuthenticateRequest method that reads the ticket from the cookie, and updates the expiration .
Sub Application_AuthenticateRequest(sender As Object, e As EventArgs)
Dim authCookie As HttpCookie = Context.Request.Cookies(FormsAuthentication.FormsCookieName)
If (IsNothing(authCookie) OrElse authCookie.Value = "") Then
Return
End If
Dim authTicket As FormsAuthenticationTicket
Try
authTicket = RefreshLoginCookie()
Catch
Return
End Try
'string[] roles = authTicket.UserData.Split(';');
'if (Context.User != null) Context.User = new GenericPrincipal(Context.User.Identity, roles);
End Sub
Function RefreshLoginCookie() As FormsAuthenticationTicket
Dim authCookie As HttpCookie = HttpContext.Current.Request.Cookies(FormsAuthentication.FormsCookieName)
If (IsNothing(authCookie) OrElse authCookie.Value = "") Then
Return Nothing
End If
Dim oldTicket As FormsAuthenticationTicket = FormsAuthentication.Decrypt(authCookie.Value)
Dim expiryDate As Date = DateTime.Now.Add(FormsAuthentication.Timeout)
HttpContext.Current.Response.Cookies.Remove(FormsAuthentication.FormsCookieName)
Dim newTicket As FormsAuthenticationTicket = New FormsAuthenticationTicket(oldTicket.Version, oldTicket.Name, oldTicket.IssueDate, expiryDate, oldTicket.IsPersistent, oldTicket.UserData, oldTicket.CookiePath)
authCookie.Value = FormsAuthentication.Encrypt(newTicket)
authCookie.Expires = expiryDate
HttpContext.Current.Response.Cookies.Add(authCookie)
Return newTicket
End Function
Testing this in visual studio 2012 debugger everything worked beautifully, but once we deployed it to our IIS 7 environment the timeout issue returned.
To aid in my debugging I set the cookie expiration to be the same as the ticket's expiration so that I could easily tell what the ticket was being set to.
When the timeout occurs I see that the expiration should have occurred on 11/16, but that's not what's happening :
Here is the cookie information (at least the relevant information)
Name Expiration
.ASPXAUTH 11/16/2014, 9:00:47
putting logging in I see that the expiration update succeeds on the next request, but I still am getting sent to the login.
I'm stumped. I know it must be some setting in IIS 7 that is causing this because as I stated, it works fine in the debugger in visual studio (which is IIS 8 Express) so there must be something somewhere overriding this functionality.
I think it may be something specific to MVC though, because I'm using this same functionality on another site and am not seeing the same problem.
UPDATE
Forgot to mention, I'm also NOT seeing an authentication ticket timeout record in the event viewer.

Answer 1

Ok, so I finally figured out the answer to this problem. The Application Pool was hitting its Idle Timeout setting of 20 minutes. So, after 20 minutes of inactivity in the application, the app pool was recycled. Thus, when the user would eventually continue, the pool would reinitialize, and the current authentication cookie was no longer valid.
To modify this setting, go into the advanced settings on your application pool in IIS. Setting it to 0 will disable the idle timeout, or you can set it to whatever value in minutes that you determine appropriate.