Hi @velvia , I think it would be better to rename `config` to `configUpdater` to make the code clear. 

BTW, I think it would be better to create a `SparkConfiguration` class to wrap the TypeSafe config library and provide getter, setter functions for outside class, also hide `ConfigUpdater` into it, outside class need not explicitly call `ConfigUpdater` to update configuration.  I think it would be more reasonable from user's point of view.