System.Web.HttpException - Session state has created a session id, but cannot save it because the response was already flushed by the application.
어느 순간부터 Visual Studio F5 디버깅 시 다음과 같은 예외가 발생합니다.
System.Web.HttpException occurred
HResult=0x80004005
Message=Session state has created a session id, but cannot save it because the response was already flushed by the application.
Source=<Cannot evaluate the exception source>
이때의 콜 스택은 다음과 같습니다.
> System.Web.dll!System.Web.SessionState.SessionIDManager.SaveSessionID(System.Web.HttpContext context, string id = "eve4iweszqlbotwmqseaava5", out bool redirected, out bool cookieAdded) Unknown Symbols loaded.
System.Web.dll!System.Web.SessionState.SessionStateModule.CreateSessionId() Unknown Symbols loaded.
System.Web.dll!System.Web.SessionState.SessionStateModule.DelayedGetSessionId() Unknown Symbols loaded.
System.Web.dll!System.Web.SessionState.SessionStateModule.ReleaseStateGetSessionID() Unknown Symbols loaded.
System.Web.dll!System.Web.SessionState.SessionStateModule.OnReleaseState(object source, System.EventArgs eventArgs) Unknown Symbols loaded.
System.Web.dll!System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() Unknown Symbols loaded.
System.Web.dll!System.Web.HttpApplication.ExecuteStepImpl(System.Web.HttpApplication.IExecutionStep step) Unknown Symbols loaded.
System.Web.dll!System.Web.HttpApplication.ExecuteStep(System.Web.HttpApplication.IExecutionStep step = {System.Web.HttpApplication.SyncEventExecutionStep}, ref bool completedSynchronously = false) Unknown Symbols loaded.
System.Web.dll!System.Web.HttpApplication.PipelineStepManager.ResumeSteps(System.Exception error) Unknown Symbols loaded.
System.Web.dll!System.Web.HttpApplication.BeginProcessRequestNotification(System.Web.HttpContext context, System.AsyncCallback cb) Unknown Symbols loaded.
System.Web.dll!System.Web.HttpRuntime.ProcessRequestNotificationPrivate(System.Web.Hosting.IIS7WorkerRequest wr = {System.Web.Hosting.IIS7WorkerRequest}, System.Web.HttpContext context = {System.Web.HttpContext}) Unknown Symbols loaded.
System.Web.dll!System.Web.Hosting.PipelineRuntime.ProcessRequestNotificationHelper(System.IntPtr rootedObjectsPointer, System.IntPtr nativeRequestContext = 0x000001b031b6e6d8, System.IntPtr moduleData, int flags) Unknown Symbols loaded.
System.Web.dll!System.Web.Hosting.PipelineRuntime.ProcessRequestNotification(System.IntPtr rootedObjectsPointer, System.IntPtr nativeRequestContext, System.IntPtr moduleData, int flags) Unknown Symbols loaded.
[Native to Managed Transition] Annotated Frame
[Managed to Native Transition] Annotated Frame
System.Web.dll!System.Web.Hosting.PipelineRuntime.ProcessRequestNotificationHelper(System.IntPtr rootedObjectsPointer, System.IntPtr nativeRequestContext, System.IntPtr moduleData, int flags) Unknown Symbols loaded.
System.Web.dll!System.Web.Hosting.PipelineRuntime.ProcessRequestNotification(System.IntPtr rootedObjectsPointer, System.IntPtr nativeRequestContext, System.IntPtr moduleData, int flags) Unknown Symbols loaded.
[AppDomain Transition] Annotated Frame
문제는, 이것이 어떤 URL을 호출해서 발생한 것인지 예외 정보만으로는 알 수 없다는 점입니다. 이럴 때 유용한 것이 바로 "HttpContext.Current" 입니다. Visual Studio의 Watch 창에 HttpContext.Current를 치면 Request 정보가 나오고 그 안에서 URL을 알아낼 수 있습니다.
그것을 통해 보니, 다음과 같은 예제 코드를 담은 empty3.aspx 페이지가 그 원인이었습니다.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
namespace WebSiteTest
{
public partial class empty3 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
HttpContext.Current.Response.Flush();
}
}
}
아래의 글에 보면,
What's causing “Session state has created a session id, but cannot save it because the response was already flushed by the application.”
; https://stackoverflow.com/questions/904952/whats-causing-session-state-has-created-a-session-id-but-cannot-save-it-becau
다음과 같은 해법이 나옵니다.
Solutions/tricks :
Avoid flushing in Page_Load as already said
Desactivate session state on the page (EnableSessionState)
Use the SessionID trick before the flush
Use Response.End() in place of .Flush() if you don't care about errors which can occur after your flush
실제로 제 테스트 조건이 저것과 일치합니다. Sesseion State가 설정되어 있고, Page_Load에서 Flush 하고 있으며 Flush 전에 SessionID를 전혀 접근하지 않고 있는 것입니다.
Flush 사용을 위한 테스트 코드이기 때문에 Response.End로 바꿔주지는 않고 다음과 같이 SessionID를 Flush 전에 건드려 주는 것으로 해결했습니다.
protected void Page_Load(object sender, EventArgs e)
{
string sessionId = HttpContext.Current.Session.SessionID;
HttpContext.Current.Response.Flush();
}
[이 글에 대해서 여러분들과 의견을 공유하고 싶습니다. 틀리거나 미흡한 부분 또는 의문 사항이 있으시면 언제든 댓글 남겨주십시오.]