Get MongoDB running on AppHarbour - it's an AppSetting thing

I have been playing around a bit with MongoDB for the first time of my life. It's really a very nice experience and have a lot of the "just works"-feeling that I have started to get used to from frameworks like NancyFx and Simple.Data.

But when i pushed it to AppHarbor I ran into problems. That all had with me not reading stuff properly…



AppHarbor has a nice feature that replaces stuff in your .config files on deploy. That could be used for setting Production-environment values to your environment configuration. For example changing the connection string for a database.

The add-on for Mongo DB at AppHarbor has a nice article describing this in detail. But I read it quickly and put the connection string in the -node of the web.config. 

It should be added as an . As the documentation clearly points out. So you want this:

 
    key="MONGOHQ_URL" value="mongodb://localhost/DotVoter"/> 

That MONGOHQ_URL is a special name that the MongoDB add-on looks for at deploy time. It's replaced with your configuration variable (see AppHarbor->[Your application]->Configuration Variables) that is created for you when you add the MongoDB add on.

You can then read that value as simple as this:

private readonly MongoCollection _collection;

        public MongoRepository()
        {
            var connectionString = 
                   ConfigurationManager.AppSettings.Get("MONGOHQ_URL");

            var client = new MongoClient(connectionString);
            var server = client.GetServer();

            var con = new MongoUrlBuilder(connectionString);
            var db = server.GetDatabase(con.DatabaseName);
            _collection = db.GetCollection(typeof(T).Name.ToLower());
        }

With that in place … it just works!