ChildContainer disposing of TenantContext

This bug can be seen with the sample if you make a few tweaks.

Problem

Take the structure map sample, then add a service or controller which has the AppTenant injected into it’s constructor.

What seems to happen is this:

1. The middleware sets HttpContext.RequestServices to a nested container.
2. After downstream middleware has been awaited (i.e and your service / controller has been resolved) the TenantContext appears to now be registered in the nested container.
3. The middleware disposes of the nested container, which now triggers a dispose on the TenantContext.
4. The TenantContext disposes of it’s properties, including the TenantContainer but it’s left in the memory cache
5. Subsequent requests, the middleware resolves the TenantContext from the cache (the disposed instance) and get;s the disposed TenantContainer which it attempts to use, resulting in an exception.

The reason you don’t see this problem in the current sample, is because AppTenant is not injected anywhere. You also only see it from the second request onwards.

[dazinator]

I believe Ben Foster was working on a new version with a fix. If you need something more urgent in the meantime you are welcome to try my saaskit- inspired library: https://github.com/dazinator/Dotnettency.Samples and https://github.com/dazinator/Dotnettency

[benfoster]

@dazinator unfortunately this only fixes the problem resolving the tenant instance, not the TenantContext.

When not using the StructureMap package, registering the TenantContext per “scope” works since the scope is the request.

For tenant containers the scope is the tenant context instance. However, since the TenantContext is resolved using the nested request container, and it implements IDisposable it will be disposed at the end of the request.

One solution is to have the tenant container register the tenant context to itself. Nested containers will bubble up to the parent container if they can’t resolve a type and will only dispose transient dependencies. The code below effectively registers the TenantContext as a singleton in the tenant container:

        public virtual Task<IContainer> BuildAsync(TenantContext<TTenant> tenant)
        {
            Ensure.Argument.NotNull(tenant, nameof(tenant));

            var tenantContainer = Container.CreateChildContainer();
            tenantContainer.Configure(config => 
            {
                config.For<TenantContext<TTenant>>().Use(tenant);
                Configure(tenant.Tenant, config);
            });

            return Task.FromResult(tenantContainer);
        }

Unfortunately updating SaasKit with the above requires breaking changes to the ITenantContainerBuilder interface.

An alternative solution is to drop TenantContext entirely. I’m going to complete the upgrade to csprojand clean things up a bit then will spike this out. I may do an interim release with the above fix if that’s what people would prefer.