how can I maintain IDocumentSession scope across more than one database in RavenDB?

Question

My first thought is to consider some unit of work pattern, but what I'm doing is pretty small and lightweight and I want to avoid overengineering my solution..

I would like to have a single transaction scope across more than one RavenDB database.. something like

class WidgetFacade
{
    void SaveData (Widget widget, User user)
    {
          IDocumentStore documentStore = new DocumentStore { Url = "http://server:8080/" };

          IDocumentSession session  = documentStore.OpenSession("database1");
          session.Store(user);

          session = documentStore.OpenSession("database2");
          session.Store(widget);
          session.Savechanges();
          session.Dispose();
    }    
}

Answer 1

You can't. Sessions are designed to operate on a single database.

However, you can get two sessions to participate in the same transaction.

var documentStore = new DocumentStore { Url = "http://server:8080/" };

using (var ts = new TransactionScope())
{
   using (var session = documentStore.OpenSession("database1"))
   {
      session.Store(user);
      session.SaveChanges();
   }

   using (var session = documentStore.OpenSession("database2"))
   {
      session.Store(widget);
      session.SaveChanges();
   }

   ts.Complete();
}

If the second operation fails for any reason, the first will also be rolled back - even though you've saved changes and completed the session.