OWIN Ninject middleware unavailable after app pool restart

Question

I have an OWIN app with the following startup:

    public virtual void Configuration(IAppBuilder app) {
        var config = new HttpConfiguration();            
        config.Filters.Add(new UserNotifyExceptionFilter());
        ConfigureAuth(app);
        app.UseNinjectMiddleware(CreateKernel);
        app.UseNinjectWebApi(config);
        WebApiConfig.Register(config);
        ConfigureLogging(app);
        config.EnableCors();
        ConfigErrorHandling(config);
        HelpPages(app, config);
    }

It appears to load ninject, correctly, and the app runs fine for hours or days under IIS 8. Then, mysteriously, it stops working, and all [Inject]ed dependencies become null on all controllers. Nothing in my code meddles with ninject's configuration after the initial load in the startup class.

I am stumped on this one, and no one else seems to be asking about it on SO.

Where is your configuration class built in your application? Is it being called by the `Application_Start` method? — NightOwl888, Feb 08 '17 at 20:39
@NightOwl888 This is a pure OWIN app, so there is no global Application_Start, only the Startup.cs with the `[assembly: OwinStartup(typeof(Startup))]` at the top. The Ninject configuration is built inside a method on Startup, `public virtual IKernel CreateKernel()`. It's pretty straightforward, at the moment, and just returns `new StandardKernel(new ApiModule(whoAmI))`. — Chris D, Feb 08 '17 at 21:02

score 0 · Accepted Answer · answered Jun 15 '17 at 16:25

I was looking back through my old questions, and thought I should post the answer I eventually found for this. For starters, the Ninject middleware has been broken for some time. We ended up swapping that for the following

config.Services.Replace(typeof(IHttpControllerActivator), new ServiceActivator(config, diKernel));

With ServiceActivator defined as:

    public class ServiceActivator : IHttpControllerActivator
    {
        private IKernel kernel;

        public ServiceActivator(HttpConfiguration configuration, IKernel kernel)
        {
            this.kernel = kernel;
        }

        public IHttpController Create(
            HttpRequestMessage request,
            HttpControllerDescriptor controllerDescriptor,
            Type controllerType)
        {
            var controller = kernel.Get(controllerType) as IHttpController;
            return controller;
        }
    }

Side note: in the longer run, we've switched to AutoFac, for now. Ninject gets you coding faster, but AutoFac claims looser coupling. Is tea better than coffee? We shall see.

OWIN Ninject middleware unavailable after app pool restart

1 Answers1