Connect to 2 different MartenDB datastores with ASP.Net Core

user_22399 0
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When setting up a MartenDB datastore in ASP.Net Core, you normally put code like this in your Startup.cs:

services.AddMarten(o =>
{
    o.Connection(configuration.GetConnectionString("MyDatabase"));
    o.AutoCreateSchemaObjects = AutoCreate.All;
    o.Serializer(new JsonNetSerializer { EnumStorage = EnumStorage.AsString });
});

This allows you to then inject IDocumentSession and IDocumentStore into your various classes for working with that database.

Now what do you do if you have to connect to a second database? I looked at the ISessionFactory but it is not apparent that you can change the connection string from here. Do you need to manually create and register a new DocumentStore?

marten
1 Answers

To answer my own question, I wound up creating a custom DocumentStore and ISessionFactory for each database I wanted to connect to, and then injecting the custom SessionFactory.

Here's the code (only showing one instance of each class for the sake of brevity. Just replace Db1 with Db2 for the second version of each class):

The custom DocumentStore:

public class Db1Store : DocumentStore
{
    public Db1Store(StoreOptions options) : base(options)
    {
    }
}

The custom SessionFactory:

public class Db1SessionFactory : ISessionFactory
{
    private readonly Db1Store store;

    public Db1SessionFactory(Db1Store store)
    {
        this.store = store;
    }

    public IQuerySession QuerySession()
    {
        return store.QuerySession();
    }

    public IDocumentSession OpenSession()
    {
        return store.OpenSession();
    }
}

The service registration (this replaces the services.AddMarten call):

  services.AddSingleton(p =>
  {
      var options = new StoreOptions();
      options.Connection(configuration.GetConnectionString("DB1"));
      options.AutoCreateSchemaObjects = AutoCreate.All;
      options.Serializer(new JsonNetSerializer { EnumStorage = EnumStorage.AsString });
      return new Db1Store(options);
  });
  
  services.AddSingleton<Db1SessionFactory>();

Then you inject the Db1SessionFactory instance into your class, and run a query like this:

var result = await db1SessionFactory.QuerySession().Query<MyAwesomeTable>().ToListAsync();

Downsides:

  • I would prefer to inject the QuerySession or DocumentSession, but I can't see a way to do that without moving to Autofac or a similar DI Container that supports named instances.

  • I am not sure what downsides there will be creating these QuerySession/DocumentSessions in this manner. It may be a bad tradeoff.

user_223990
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