client = Mongo::MongoShardedClient.new("brandonblack-mbpr.local:3333", :read => :secondary_preferred)
client['database']['collection'].find_one()

client = Mongo::MongoShardedClient.new("brandonblack-mbpr.local:3333", :read => :primary)
client['database']['collection'].find_one()

client = Mongo::MongoShardedClient.new("brandonblack-mbpr.local:3333", :read => :secondary)
client['database']['collection'].find_one()
=> SystemStackError: stack level too deep

client = Mongo::MongoShardedClient.new("brandonblack-mbpr.local:3333", :read => :primary_preferred)
client['database']['collection'].find_one()
=> Mongo::OperationFailure: wrong type for field (mode) 14 != 2