Problem (because of clean-up?) when running in IIS

[chucker]

I'm trying to use IsolatedRazor to build HTML e-mails based on Razor templates. This is inside an ASP.NET Web API project; IsolatedRazor lives inside an ApiController and gets called on a schedule using FluentScheduler.

Intermittently, but frequently enough that it's not practical to use right now, I get one of two errors:

• a FileNotFoundException trying to load ImpromptuInterface or one of its dependencies. Here's an example stacktrace:

2018-05-04 06:00:02.6015|3|ERROR|TAG.Accounts.WebApi.Controllers.Statistics.NightlyUserAccountStatisticsController|System.AggregateException: Mindestens ein Fehler ist aufgetreten. ---> System.Reflection.TargetInvocationException: Ein Aufrufziel hat einen Ausnahmefehler verursacht. ---> System.IO.FileNotFoundException: Die Datei oder Assembly "ImpromptuInterface, Version=6.2.2.0, Culture=neutral, PublicKeyToken=0b1781c923b2975b" oder eine Abh�ngigkeit davon wurde nicht gefunden. Das System kann die angegebene Datei nicht finden.
   bei IsolatedRazor.DynamicViewBag..ctor(Object parentViewBag)
   bei IsolatedRazor.TemplateBase..ctor()
   bei IsolatedRazor.RazorTemplate.C_GetTemplate_SummaryTableAsync..ctor()
   --- Ende der internen Ausnahmestapel�berwachung ---
   bei System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   bei System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   bei System.Activator.CreateInstance(Type type, Boolean nonPublic)
   bei System.Activator.CreateInstance(Type type)
   bei IsolatedRazor.RazorTemplater.PrepareTemplate(String assemblyPath, String typeName, DynamicViewBag viewBag, TemplateCache templateCache, TemplateEncoding encoding)
   bei IsolatedRazor.RazorTemplater.RenderTemplateInternal[T](String assemblyPath, String typeName, T model, DynamicViewBag viewBag, TemplateCache templateCache, TemplateEncoding encoding)
   bei IsolatedRazor.RazorTemplater.RenderTemplateInternal[T](String assemblyPath, String typeName, T model, DynamicViewBag viewBag, TemplateCache templateCache, TemplateEncoding encoding)
   bei IsolatedRazor.RazorTemplater.<>c__DisplayClass4c`1.<Render>b__4b()
   bei System.Threading.Tasks.Task`1.InnerInvoke()
   bei System.Threading.Tasks.Task.Execute()

• or an UnauthorizedAccessException trying to delete a generated template DLL:

2018-04-25 23:03:51.5419|2|ERROR|TAG.Accounts.WebApi.WebApiApplication|System.UnauthorizedAccessException: Der Zugriff auf den Pfad "C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\15a0a301\13ba4d00\_GetTemplate_SummaryTableAsync.dll" wurde verweigert.
   bei System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   bei System.IO.File.InternalDelete(String path, Boolean checkHost)
   bei IsolatedRazor.RazorTemplater.Dispose()
   bei IsolatedRazor.RazorTemplater.Finalize() 

This happens regardless of whether I set persistTemplates to true. Other than that, IsolatedRazor gets called like so:

                using (var templateEngine = new IsolatedRazor.RazorTemplater(templateAssemblyPath, renderTimeout: 5000))
                {
[..various calls to merge portions of the templates..]

// …the final piece:

                    return await _GetTemplate_StatisticsAsync(summaryTable, newAccountsTable, unusedAccountsTable, templateEngine);
                }

And on the inside:

        private async Task<string> _GetTemplate_StatisticsAsync(string summaryTable, string newAccountsTable, string unusedAccountsTable, IsolatedRazor.RazorTemplater templateEngine)
        {
            var result = new Models.Statistics
            {
                SummaryTable = summaryTable,
                NewAccountsTable = newAccountsTable,
                UnusedAccountsTable = unusedAccountsTable,
            };

            var template = System.IO.File.ReadAllText(System.Web.Hosting.HostingEnvironment.MapPath("~/Mails/TemplateHTML/NightlyUserAccountStatistics.cshtml"));

            return await _ParseTemplate(templateEngine, template, result);
        }

        private async Task<string> _ParseTemplate<T>(IsolatedRazor.RazorTemplater templateEngine,
                                                     string template,
                                                     T model,
                                                     [System.Runtime.CompilerServices.CallerMemberName] string caller = "")
        {
            var templateName = caller;

            return await templateEngine.ParseAsync(templateName, template, DateTime.Now, model);
        }

I'm guessing the two exceptions are related: when the clean-up fails in IsolatedRazor.RazorTemplater.Dispose(), IsolatedRazor can't subsequently load its references in IsolatedRazor.TemplateBase..ctor(). However, I'm not sure about that.

I also believe I observed that when this does happen, IsolatedRazor no longer tries to run in its own app domain.

This is unfortunately not 100% reproducible (as far as I can see).

[chucker]

(This is with NuGet package version 1.1.1.0 on .NET Framework 4.7.)

[chrfin]

Hi,

my system is also running in IIS and is used to render HTML e-mails, but I do not get such errors. Is it possible you "re-use" the same template name? In my case that does not happen and at least could cause the UnauthorizedAccessException.
Aside from that I do not know why this is happening. Especially as ImpromptuInterface is only used at one place and there is a "try/catch-all" around it, so you should not get such an exception.

If you can send me a reproducable case I can look into it, but I on my side am in the process of replacing the razor-based templates in my project in favor of fluid (see https://github.com/sebastienros/fluid).

regards
Christoph

[chucker]

Hi,

thanks for the speedy response!

I do reuse the template name. I can append a GUID to make it unique on each call, but won't I eventually end up with a lot of temporary files that way that never get cleaned up? Presumably, the problem is that some file lock never gets cleared.

Anyway, I'll do that for now.

[ I've also recently looked into Fluid/Liquid and might ultimately move to that. Among the reasons Razor is attractive is that some web developers here are already familiar with its syntax, it ships with VS, I can extend (in theory, anyway) it with additional functions in C#, etc. I haven't looked into how well Fluid integrates (e.g., getting IntelliSense for your model properties). ]

Thanks again

[chrfin]

The template-files should get cleanup up either by the templater on dispose (if persistTemplates is false) or by IIS when it recreates the shadow copy directory.

I had exactly the same reasons to choose Razor, but for several other reasons I'm moving to Fluid, as it has most of the benefits (e.g. can be extended via "code") without some of the drawbacks.

[abhishekbhalani]

Hi Christoph,
Have you used Caching template for long time instead of in Memory as I am using Razor engine for template.
It taking too much time on our MVC C# application.

If you can share any example with file caching to hold more time than memory caching. would be Appreciate it.
Thank you.

[chrfin]

@abhishekbhalani Sorry, but I do not understand what exactly is your problem?

Aside from that as already noted above I do not use this project anymore as I switched completely to Fluid.

[abhishekbhalani]

OK @chrfin
Fluid is templating framework?
I have not heard about Fluid.

My question was about the C# templating framework.
We are using the Razor Engine but it takes more time to compile while first time load. then it loaded in memory.
so second time it get quick load..
I am looking some solution for the Quick load .. so Is it possible to compile all Razor template into file system or other way ?

Thank you.
Abhi

[chrfin]

@abhishekbhalani  Yes, Fluid is a C# template framework: https://github.com/sebastienros/fluid

The performance you describe sounds like you re-generate the templates after each restart. You need to persist the generated template Dlls to be re-usable and get a faster execution after restart.

[abhishekbhalani]

@chrfin Thank you for update. for now am using the razor template. will look on fluid template.