Session does not seem to be persisted across Http Requests

[Etchelon]

Hello.
I've enabled Session in my aspnet core 2.1 app. To do this I followed the documentation, and have added

services.AddDistributedMemoryCache();
services.AddSession(options =>
{
	options.IdleTimeout = TimeSpan.FromHours(1);
	options.Cookie.HttpOnly = true;
	options.Cookie.Name = ".Nuvyta.Session";
});

and

app.UseSession();

Problem: at every REQUEST, .HttpContext.Session.Id is different and the session storage is reset.
What is wrong? The documentation isn't that complex and doesn't say much more...

p.s.: my colleague just found out that the Session is persisted from the moment that something is actually set into it. Otherwise if it's empty it's reset every time... ok you should at least say this in the docs...

[SIkebe]

I followed the documentation

Which documentation?

[Etchelon]

https://docs.microsoft.com/en-US/aspnet/core/fundamentals/app-state?view=aspnetcore-2.1&tabs=aspnetcore2x

[Tratcher]

Anything in the logs?

You only have one server instance, correct?

[Etchelon]

I searched the MessageTemplate property of the logs via this regex: /session/gi and couldn't find anything.
Anyway yeah, simple ASP.NET Core app from the VS2017 template. Add those 3 lines of code to enable the session and you'll see that in HomeController.Index, at every refresh of the webpage, HttpContext.Session.Id is different.
Unless in that method (or just once, somewhere else in your app), you do:
HttpContext.Session.Set("anything", new byte[0]);
In that case, the Session will persist.

[Tratcher]

Ah, that's expected. Empty sessions are not persisted.

[Tratcher]

@guardrex another note for dotnet/AspNetCore.Docs#7029

[Etchelon]

Ok I expected exactly that.
If it's in the docs sorry, otherwise it should be added imo. Took us a while to figure out the problem.
Regards.

[guardrex]

Thanks @Etchelon ... I've updated the PR overhaul for the app state topic (dotnet/AspNetCore.Docs#7029), so this will appear in the next version. It should go live after one more review and round of updates.