NancyFX + .NET Core + NHibernate - nhibernate

Question

I have created a small API based on NancyFx on .NET Core 2. It uses AutoFac as the IOC container and NHibernate 5.3 to access the database.
I have run into a problem with threading and the CurrentSessionContext. Basically when I enter the AfterRequest pipeline, I am usually on another thread, and then the CurrentSessionContext doesn't know about the binding I did at the beginning of the request.
I have tried to use the WebSessionContext instead, but since I am using the stack I am, there is no HttpContext.Current. To get access to the HttpContext you have to inject the Microsoft.AspNetCore.Http.IHttpContextAccessor where you need it.
How can I tell NHibernate to bind to my own context somehow, so I my session isn't lost between BeforeRequest and AfterRequest?
To make it easy to wrap my data accecss in a transaction I have added the following to my Nancy Bootstrapper:
protected override void ApplicationStartup(ILifetimeScope container, IPipelines pipelines)
{
base.ApplicationStartup(container, pipelines);
ConfigureNHibernateSessionPerRequest(container, pipelines);
}
private void ConfigureNHibernateSessionPerRequest(ILifetimeScope container, IPipelines pipelines)
{
pipelines.BeforeRequest += ctx => CreateSession(container);
pipelines.AfterRequest += ctx => CommitSession(container);
pipelines.OnError += (ctx, ex) => RollbackSession(container);
}
private Response CreateSession(ILifetimeScope container)
{
var provider = container.Resolve<INHibernaterSessionFactoryProvider>();
var sessionFactory = provider.Factory;
var requestSession = sessionFactory.OpenSession();
CurrentSessionContext.Bind(requestSession);
requestSession.BeginTransaction();
return null;
}
private AfterPipeline CommitSession(ILifetimeScope container)
{
var provider = container.Resolve<INHibernaterSessionFactoryProvider>();
var sessionFactory = provider.Factory;
if (CurrentSessionContext.HasBind(sessionFactory))
{
var requestSession = sessionFactory.GetCurrentSession();
requestSession.Transaction.Commit();
CurrentSessionContext.Unbind(sessionFactory);
requestSession.Dispose();
}
return null;
}
private Response RollbackSession(ILifetimeScope container)
{
var provider = container.Resolve<INHibernaterSessionFactoryProvider>();
var sessionFactory = provider.Factory;
if (CurrentSessionContext.HasBind(sessionFactory))
{
var requestSession = sessionFactory.GetCurrentSession();
requestSession.Transaction.Rollback();
CurrentSessionContext.Unbind(sessionFactory);
requestSession.Dispose();
}
return null;
}
My hibernate.cfg.xml looks like this:
<?xml version="1.0" encoding="utf-8" ?>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
<session-factory>
<property name="connection.provider">NHibernate.Connection.DriverConnectionProvider</property>
<property name="dialect">NHibernate.Dialect.MsSql2012Dialect</property>
<property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property>
<property name="connection.connection_string">...</property>
<property name="show_sql">true</property>
<property name ="current_session_context_class">thread_static</property>
</session-factory>
</hibernate-configuration>
And I wire up the Sessionfactory like this:
var configuration = new Configuration();
configuration.Configure();
configuration.AddAssembly(Assembly.GetExecutingAssembly());
_factory = configuration.BuildSessionFactory();

Answer 1

You can try using AspNetCore middleware since that will give you access to HttpContext.

Answer 2

I found a solution that works, but isn't really as nice as I would have liked it to be.
In my Nancy Bootstrapper I have added a public static property that I populate from the ApplicationStartup hook:
public class Bootstrapper : AutofacNancyBootstrapper
{
public static IHttpContextAccessor HttpContextAccessor { get; private set; }
protected override void ApplicationStartup(ILifetimeScope container, IPipelines pipelines)
{
HttpContextAccessor = container.Resolve<IHttpContextAccessor>();
}
}
Then I have created a new custom CurrentSessionContext that I just called CoreSessionContext. It extends the abstract MapBasedSessionContext just like the WebSessionContext does, and then I inject the HttpContextAccessor in the constructor by accessing the static property on the Bootstrapper.
public class CoreSessionContext : MapBasedSessionContext
{
private IHttpContextAccessor _httpContextAccessor;
private const string SessionFactoryMapKey = "NHibernate.Context.WebSessionContext.SessionFactoryMapKey";
public CoreSessionContext(ISessionFactoryImplementor factory) : base(factory)
{
_httpContextAccessor = Bootstrapper.HttpContextAccessor;
}
protected override IDictionary GetMap()
{
return _httpContextAccessor.HttpContext.Items[SessionFactoryMapKey] as IDictionary;
}
protected override void SetMap(IDictionary value)
{
_httpContextAccessor.HttpContext.Items[SessionFactoryMapKey] = value;
}
}
The last thing I did was to remove the current_session_context_class element from the hibernate.cfg.xml file and then wire up the SessionFactory with my custom session context like this in line three:
var configuration = new Configuration();
configuration.Configure();
configuration.CurrentSessionContext<CoreSessionContext>();
configuration.AddAssembly(Assembly.GetExecutingAssembly());
_factory = configuration.BuildSessionFactory();
Then I am able to use the HttpContext provided by AspNetCore.
Not as pretty as I would like it to be, but it works.