Prevent view caching in Nancy when using the Spark template engine

Question

I'm using a self-hosted Nancy with Spark templates. I've disabled the cache specifically (though in DEBUG is should be disabled by default).

    protected override void ApplicationStartup(Nancy.TinyIoc.TinyIoCContainer container, IPipelines pipelines)
    {
        base.ApplicationStartup(container, pipelines);

        ...

        StaticConfiguration.Caching.EnableRuntimeViewDiscovery = true;
        StaticConfiguration.Caching.EnableRuntimeViewUpdates = true;
    }

However, making changes to the templates while the app is running doesn't seem to work, as the template changes are not picked up.

Is there anything else required to disable views caching?

Answer 1

Ok, managed to get this to work by adding a custom ViewCache in the bootstrapper:

public class MyBootstrapper : DefaultNancyBootstrapper
{
#if DEBUG
    protected override IRootPathProvider RootPathProvider
    {
        get
        {
            // this sets the root folder to the VS project directory
            // so that any template updates in VS will be picked up
            return new MyPathProvider();
        }
    }

    protected override NancyInternalConfiguration InternalConfiguration
    {
        get
        {
            return NancyInternalConfiguration.WithOverrides(
                x =>
                    { x.ViewCache = typeof(MyViewCache); });
        }
    }
#endif

The new ViewCache just reloads the template on every request:

public class MyViewCache : IViewCache
{
...
    public TCompiledView GetOrAdd<TCompiledView>(
        ViewLocationResult viewLocationResult, Func<ViewLocationResult, TCompiledView> valueFactory)
    {
        //if (viewLocationResult.IsStale())
        //    {
                object old;
                this.cache.TryRemove(viewLocationResult, out old);
        //    }

        return (TCompiledView)this.cache.GetOrAdd(viewLocationResult, x => valueFactory(x));
    }
}

Somehow the viewLocationResult.IsStale() was always returning false.

By default, this is an instance of FileSystemViewLocationResult which just compares the last update time of the view, but the timestamp this.lastUpdated was being updated before calling IsStale() from the DefaultViewCache, so the template was never removed from the cache

public override bool IsStale()
{
    return this.lastUpdated != this.fileSystem.GetLastModified(this.fileName);
}

Answer 2

Since you're application is self hosted, I'm guessing you've either overriden the view location convention to find views as embedded resources in your assembly or have configured your Visual Studio project to copy views into the output directory at compile time. In both cases your application is not running off the view files you have in the Visial Studio project, but rather off copies of them. In that case caching is not the issue.