Session does not work with Redis when the client has HTTP keep-alives disabled about session

[Tratcher]

There shouldn't be any relation between session and keep-alives. Can you share the application logs for before and after?

[tcuk]

To produce these logs I launched ASP.NET core behind my nginx reverse proxy, opened a new incognito browser window and requested the same URL three times via a URL pointing to nginx. I used a single session variable which was a counter being incremented. In the failure case the counter does not persist and remains at 1.

Working case (Connection = keep-alive):

Running aspnet
[?1h=Hosting environment: Production
Content root path: /dotnetapp
Now listening on: http://[::]:5000
Application started. Press Ctrl+C to shut down.
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 GET http://remove/  
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[1]
      Executing action method Woo.Web.Controllers.HomepageController.Index (Woo.Web) with arguments ((n
ull)) - ModelState is Valid
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ContentResultExecutor[1]
      Executing ContentResult with HTTP Response ContentType of text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[2]
      Executed action Woo.Web.Controllers.HomepageController.Index (Woo.Web) in 840.0717ms
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 1111.6613ms 200 text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 GET http://remove/  
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[1]
      Executing action method Woo.Web.Controllers.HomepageController.Index (Woo.Web) with arguments ((n
ull)) - ModelState is Valid
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ContentResultExecutor[1]
      Executing ContentResult with HTTP Response ContentType of text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[2]
      Executed action Woo.Web.Controllers.HomepageController.Index (Woo.Web) in 4.0174ms
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 7.6ms 200 text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 GET http://remove/  
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[1]
      Executing action method Woo.Web.Controllers.HomepageController.Index (Woo.Web) with arguments ((n
ull)) - ModelState is Valid
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ContentResultExecutor[1]
      Executing ContentResult with HTTP Response ContentType of text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[2]
      Executed action Woo.Web.Controllers.HomepageController.Index (Woo.Web) in 2.7991ms
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 5.4859ms 200 text/plain; charset=utf-8

Failure case (Connection = close):

Running aspnet
[?1h=Hosting environment: Production
Content root path: /dotnetapp
Now listening on: http://[::]:5000
Application started. Press Ctrl+C to shut down.
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 GET http://remove/  
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[1]
      Executing action method Woo.Web.Controllers.HomepageController.Index (Woo.Web) with arguments ((n
ull)) - ModelState is Valid
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ContentResultExecutor[1]
      Executing ContentResult with HTTP Response ContentType of text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[2]
      Executed action Woo.Web.Controllers.HomepageController.Index (Woo.Web) in 881.3667ms
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Session.SessionMiddleware[10]
      Committing the session was canceled.
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 1162.6012ms 200 text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 GET http://remove/  
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[1]
      Executing action method Woo.Web.Controllers.HomepageController.Index (Woo.Web) with arguments ((n
ull)) - ModelState is Valid
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ContentResultExecutor[1]
      Executing ContentResult with HTTP Response ContentType of text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[2]
      Executed action Woo.Web.Controllers.HomepageController.Index (Woo.Web) in 3.7355ms
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Session.SessionMiddleware[10]
      Committing the session was canceled.
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 6.014ms 200 text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]
      Request starting HTTP/1.1 GET http://remove/  
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[1]
      Executing action method Woo.Web.Controllers.HomepageController.Index (Woo.Web) with arguments ((n
ull)) - ModelState is Valid
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ContentResultExecutor[1]
      Executing ContentResult with HTTP Response ContentType of text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker[2]
      Executed action Woo.Web.Controllers.HomepageController.Index (Woo.Web) in 11.195ms
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Session.SessionMiddleware[10]
      Committing the session was canceled.
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[2]
      Request finished in 12.8115ms 200 text/plain; charset=utf-8
[40m[32minfo[39m[22m[49m: Microsoft.AspNetCore.Hosting.Internal.WebHost[1]

My test controller:

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Caching.Distributed;
using System;
using System.Collections.Generic;
using System.Text;

namespace Woo.Web.Controllers
{
	[Route("")]
	public class HomepageController : Controller
	{
		private const string CountKey = "Count";

		[Route("")]
		public IActionResult Index()
		{
			var counter = Counter++;
			
			return Content($"I have counted to {counter}. " + DateTime.Now + " / " + HttpContext.Session.Id + " / " + Request.Headers["Connection"]);
		}

		private int Counter
		{
			get
			{
				return HttpContext.Session.GetInt32(CountKey) ?? 1;
			}
			set
			{
				HttpContext.Session.SetInt32(CountKey, value);
			}
		}
	}
}

[Tratcher]

Ah. The response has a content-length so the client can disconnect as soon as it gets the last byte, which is before the session gets committed. Kestrel's client disconnect notice triggers, which triggers RequestAborted, which prevents the session from being committed.

This appears to be an order of operations bug in Kestrel. The complete request has been received and the complete response has been sent so if the client disconnects then it's out of scope of the request and it should't trigger RequestAborted. I'll move this issue to the Kestrel repo.

Workaround: call session.CommitAsync() when you're done modifying the session.

[Tratcher]

This issue was moved to aspnet/KestrelHttpServer#2195

[Tratcher]

After some discussion we've decided to change both Session and Kestrel. Session will no longer depend on RequestAborted for commits, only it's normal timeout.

Session/src/Microsoft.AspNetCore.Session/SessionMiddleware.cs

Line 117 in be6b099

await feature.Session.CommitAsync(context.RequestAborted);

[aspnet-hello]

This issue was moved to dotnet/aspnetcore#2395