ASP.NET HttpContext Cache removes right after insertion

Question

I have an ASP.NET 4 web-service.
It has an ImportModule action in a ModuleController controller.

That's how it works:

The user uploads a module as a CSV-file.
This file is being read using HttpPostedFileBase.InputStream and custom CSV-reading class.
This file is being transformed to a C# object according to some rules and validations. If a file is valid, then it transforms to C# object, stores in a Cache with unique GUID name and a user is redirected to CompleteImportModule action.
User checks if data is correct and he confirms uploading.

Long story short, there is a code which tells you more:
ImportModule action.

public ActionResult ImportModule(HttpPostedFileBase file)
{
    if (!ModelState.IsValid) 
    {
        return RedirectToAction("Index");
    }

    ModuleQuestion[] questions;
    ModuleInfo moduleInfo;
    string uploadId = Guid.NewGuid().ToString();

    // It is my custom CSV-reader and it works. Values are assigned
    FormDataCsvReader csvReader = new FormDataCsvReader(file.InputStream);
    if (!csvReader.Process(out questions, out moduleInfo))
    {
        // File is invalid
        return RedirectToAction("Index");
    }

    ViewBag.UploadId = uploadId;
    ViewBag.ModuleInfo = moduleInfo;
    ViewBag.Questions = questions;

    HttpContext.Cache.Add("UploadModule_" + uploadId,
        new Tuple<ModuleInfo, ModuleQuestion[]>(moduleInfo, questions),
        null,
        Cache.NoAbsoluteExpiration,
        TimeSpan.FromMinutes(30),
        CacheItemPriority.NotRemovable,
        (k, v, r) => 
        {
            LoggingFactory.GetLogger().Debug("Removed from cache: {0}. Reason: {1}", k, r);
        });     

    return View();   
}

In View ImportModule:

// Output data from ViewBag.ModuleInfo and ViewBag.Questions

<form method="POST" action="@Url.Action("CompleteImportModule")">
    <input type="hidden" name="uploadId" value="@ViewBag.UploadId"/>
    <input type="submit" value="Send">
</form>

CompleteImportModule action:

[HttpPost]
public ActionResult CompleteImportModule(string uploadId)
{
    var item = HttpContext.Cache["UploadModule_" + uploadId];
    if (item == null) RedirectToAction("Index");
    // upload module 
    HttpContext.Cache.Remove("UploadModule_" + uploadId);
    return RedirectToAction("Index");
}

However, I met some problems. I cannot upload the module because the value is removed from a Cache right after being inserted. It is stored only for a second:

DEBUG 2015-06-22 15:00:18,696 thread 85: Added to cache:
UploadModule_c843077d-21d0-4e9f-9e5e-3df82da4bac8

DEBUG 2015-06-22 15:00:19,935 thread 48: Removed from cache:
UploadModule_c843077d-21d0-4e9f-9e5e-3df82da4bac8. Reason: Removed

The reason is "Removed" meaning that it is not expired and IIS hasn't removed it due to optimization but it looks like I removed is myself. I am pretty sure that I am even not accessing this cache record before CompleteImportModule.

I have tried putting new StackTrace().ToString() in a CacheItemRemovedCallback. That's it, if it can help somehow:

at CPMAdministrator.Controllers.ModulesReferenceController.<ImportModule>b__9(String key, Object value, CacheItemRemovedReason reason)
   at System.Web.Caching.CacheEntry.CallCacheItemRemovedCallback(CacheItemRemovedCallback callback, CacheItemRemovedReason reason)
   at System.Web.Caching.CacheEntry.Close(CacheItemRemovedReason reason)
   at System.Web.Caching.CacheSingle.UpdateCache(CacheKey cacheKey, CacheEntry newEntry, Boolean replace, CacheItemRemovedReason removedReason, Object& valueOld)
   at System.Web.Caching.CacheSingle.Dispose(Boolean disposing)
   at System.Web.Caching.CacheMultiple.Dispose(Boolean disposing)
   at System.Web.HttpRuntime.Dispose()
   at System.Web.HttpRuntime.ReleaseResourcesAndUnloadAppDomain(Object state)
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()

Why is it happening? Is it sort of IIS pool recycling? How can I ensure that the file is not being removed? Or how can I effictively store this data another way?

Is this in a production environment or debugging through VS? — heymega, Jun 22 '15 at 09:53

score 3 · Accepted Answer · edited May 23 '17 at 12:29

I have spent several hours finding an answer and found it right after posting a question! Let me share my experience with you.

According to my StackTrace, I understood that the cache has been cleared because the application has been ended and disposed:

at System.Web.HttpRuntime.Dispose()
at System.Web.HttpRuntime.ReleaseResourcesAndUnloadAppDomain(Object state)

All I needed is to find a reason of it.

I have opened my Global.asax file and added a Application_End method.

public class MvcApplication : HttpApplication
{
    protected void Application_End()
    {
    }
}

It has been triggered right after view rendering success and right before cache clearing. Success! Now I needed to know the reason of application ending.

This post helped me:

There's System.Web.Hosting.HostingEnvironment.ShutdownReason property that indicates why the application is being terminated. Its value can be retrieved from inside Application_End().

I added a breakpoint in a beginning of Application_End and added System.Web.Hosting.HostingEnvironment.ShutdownReason to watch.

That's what it stored: BinDirChangeOrDirectoryRename.

After that, I have understood that the reason is that my log4net is writing logs right in BinDirectory. I just never knew that IIS is finishing web applications if bin directory has been changed.

I have moved my logs to a parent (application itself) folder and now it works.
It looks like I need to read more about ASP.NET.
I hope that it will help someone. Thanks to everybody who tried to help.

Yes indeed, stay away from your bin directory! :) – DavidG Jun 22 '15 at 10:12 — DavidG, Jun 22 '15 at 10:12

score 1 · Answer 2 · answered Jun 22 '15 at 10:02

1

The reason given for removal is Removed, from the documentation that means:

The item is removed from the cache by a Remove method call or by an Insert method call that specified the same key.

So you have either explicitly called Remove somewhere else or are overwriting it with an Insert.

answered Jun 22 '15 at 10:02

DavidG

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Thank you. I have found a solution! Read my own answer. – Yeldar Kurmangaliyev Jun 22 '15 at 10:09

ASP.NET HttpContext Cache removes right after insertion

2 Answers2

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