Question

I am trying to enable RavenDB Aggressive Caching in a WebApi application, for a single action method within a larger application.

In order to achieve this, I went the route of creating an action filter attribute, which gets the IDocumentSession, and in OnActionExecuting invokes the method to enable Aggressive Caching for 15 minutes. Then, in OnActionexecuted, I call DisableAggressiveCaching() on the same session.

In short, this has resulted in some fairly weird behaviour. After the action method that uses Aggressive Caching has been called, subsequent requests to other action methods, that do not in anyway rely on the cache (they are making completely different requests), end up getting an IDocumentSession where the AggressiveCacheDuration is 15mins. The frequency with which this happens seems proportional to the number of times that the cached action method has been called previously. I should add, I am using StructureMap for DI, using an IDocumentStore singleton, and injecting a HttpContextScoped IDocumentSession. I’ve confirmed that a new IDocumentSession is being injected each and every request, yet some of them have caching enabled.

Some code to try and elaborate further…

IoC – RavenRegistry

var documentStore = new DocumentStore {ConnectionStringName = "RavenDB"};

documentStore.Initialize();

For<IDocumentStore>().Singleton().Use(documentStore);
For<IDocumentSession>().HttpContextScoped().Use(x =>
{
    var store = x.GetInstance<IDocumentStore>();
    var session =  store.OpenSession();
    return session;
});

AggressivelyCacheAttribute

public class AggressivelyCacheAttribute : ActionFilterAttribute
{
    private IDocumentSession _documentSession;

    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        base.OnActionExecuting(actionContext);

        _documentSession = actionContext.Request.GetDependencyScope()
            .GetService(typeof(IDocumentSession)) as IDocumentSession;

        _documentSession.Advanced.DocumentStore
            .AggressivelyCacheFor(TimeSpan.FromMinutes(15));
    }

    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
        base.OnActionExecuted(actionExecutedContext);
        _documentSession.Advanced.DocumentStore.DisableAggressiveCaching();
    }
}

The same IDocumentSession is then used later in the pipeline to query the database, the results of which are cached.

In subsequent request, on methods where the attribute is not present, the injected IDocumentSession has caching set to 15mins. Why is this so?

The only examples I have seen online are where the session is created, with caching, inside a using statement. Is that the only ‘safe’ way to use Aggressive Caching, or is it possible to do what I’m trying? If so, how?

Answer 1

Based on Ayende’s blogging platform code, you need to have a reference in your filter class:

private IDisposable _cachingHandle;

Then when you make the caching declaration, assign the result to that:

_cachingHandle  = _documentSession.Advanced.DocumentStore
    .AggressivelyCacheFor(TimeSpan.FromMinutes(15));

Then in your Executed,

if(_cachingHandle != null)
    _cachingHandle.Dispose();

That should stop the unwanted caching.