umbraco mediaservice on sperate thread generates an exception

Terry Clancy 204 posts 944 karma points

Mar 17, 2017 @ 07:51

Umbraco MediaService on sperate thread generates an Exception

Note this has also been posted at http://eureka.ucommerce.net/#!/question/2157/Problem-adding-thousands-of-uCommerce-products-Umbraco-MediaService-on-sperate-thread-generates-an-Exception#top

Dear Umbraco Folk,

I have a log running service that creates several thousands of uCommerce products and for most of them it adds a related photo.

I kick off this process using a web service and because the process runs for over one hour the web API call times out after one hour.

To address this I call the long running class using Task.Run so it runs on a separate new thread. This works fine except for if I need to add photos.

Adding Photos as Umbraco Media requires the media service defined as follows

var mediaService = ApplicationContext.Current.Services.MediaService;

BUT then some lines that then use this mediaService cause an exception. Some do not . For example the first line below does not and the second line does.

                        IMedia ProductImage_StndrdSize = mediaService.CreateMedia(productImage_StndrdSize_FileName, tTImagesFolderID, "Image");    <<<<< This line works
                        mediaService.Save(ProductImage_StndrdSize);   <<<<< This line causes exception

This only happens when running the method on a separate thread.

The exception is

System.ArgumentNullException was unhandled by user code HResult=-2147467261 Message=Value cannot be null. Parameter name: httpContext ParamName=httpContext Source=System.Web StackTrace: at System.Web.HttpContextWrapper..ctor(HttpContext httpContext) at Umbraco.Web.SingletonHttpContextAccessor.getValue() at Umbraco.Web.RequestLifespanMessagesFactory.Get() at Umbraco.Core.Services.MediaService.Umbraco.Core.Services.IMediaServiceOperations.Save(IMedia media, Int32 userId, Boolean raiseEvents) at Umbraco.Core.Services.MediaService.Save(IMedia media, Int32 userId, Boolean raiseEvents) at TeraTastic.TTClasses.TTUCommerceAdmin.TTImportData(RequestTTImportData requestTTImportData, String webSiteRootPhysicalPath) in D:\Clancy\ATeraTastic\Dev\TeraTastic14\TeraTastic\TTClasses\TTUCommerceAdmin.cs:line 3474 at TeraTastic.Controllers.TTUCAdminController.<>cDisplayClass120.0() in D:\Clancy\ATeraTastic\Dev\TeraTastic14\TeraTastic\Controllers\TT_UCAdminController.cs:line 441 at System.Threading.Tasks.Task.InnerInvoke() at System.Threading.Tasks.Task.Execute() InnerException:

I think the problem is that because I am running the code on a new thread I lose the httpContext I had on the calling thread.

Assuming this to be the problem (let me know if otherwise) my question becomes:

Can I, and how can I, run this code on a hew thread when I don't have httpContext ?

Terry Clancy

ClanceZ

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Dan Diplo 1554 posts 6205 karma points MVP 6x c-trib

Mar 17, 2017 @ 11:59

You are right, it's the lack of the underlying HttpContext that causes the issue. I have heard of people faking the context, but not sure if this will work in every instance.

Here's an example of faking it you might be able to try:

https://gist.github.com/sniffdk/7600822

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Terry Clancy 204 posts 944 karma points

Mar 18, 2017 @ 06:41

Thank you Dan,

The solution you suggested did not fix the problem, probably because it fakes UmbracoContext rather than httpContext.

I did however solve my problem by Faking httpContext based on code from http://stackoverflow.com/questions/28085439/parameter-cannot-be-null-parameter-name-http-context

Here is my (very similar) code:

The Helper Class

    public class TT_ContextHelpers
{
        public static HttpContext CreateHttpContext(HttpRequest httpRequest, HttpResponse httpResponse)
        {
            var httpContext = new HttpContext(httpRequest, httpResponse);

            var sessionContainer = new HttpSessionStateContainer("id", new SessionStateItemCollection(),
                                                    new HttpStaticObjectsCollection(), 10, true,
                                                    HttpCookieMode.AutoDetect,
                                                    SessionStateMode.InProc, false);

            httpContext.Items["AspSession"] = typeof(HttpSessionState).GetConstructor(
                                        BindingFlags.NonPublic | BindingFlags.Instance,
                                        null, CallingConventions.Standard,
                                        new[] { typeof(HttpSessionStateContainer) },
                                        null)
                                .Invoke(new object[] { sessionContainer });

            return httpContext;
        }
}

and here is how you use it. In my case I put this are the beginning of the Method I call as a new thread:

            HttpContext.Current = TT_ContextHelpers.CreateHttpContext(
            new HttpRequest("", "http://localhost/", ""),
            new HttpResponse(new StringWriter())
            );

I actually think this is a kind of ugly solution. If anyone has a better approach let me know !!

Otherwise, I hope this helps folk :-)

Terry Clancy

ClanceZ

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Umbraco MediaService on sperate thread generates an Exception