ActiveRecord execute SQL need to close connection? DEPRECATION WARNING: Database connections will not be closed automatically

First off, I am using Rails 3.2 on Puma (but with MRI), and am not doing any explicit threading by hand. I am in places using the `execute` method, like `MyModel.connection.execute` or I know `ActiveRecord::Base.connection.execute` can do the same thing since all connections are to the same DB for me right now. I recently started seeing ``` DEPRECATION WARNING: Database connections will not be closed automatically, please close your database connection at the end of the thread by calling `close` on your connection. For example ActiveRecord::Base.connection.close ``` This seems self-explanatory, but I can find very little information on it online, mostly about using ActiveRecord with Sinatra (ex ActiveRecord connection warning. (Database connections will not be closed automatically)). I read this: http://blog.daniel-azuma.com/archives/216 which suggests that Rack middleware does it for me as long as the DB execute transaction is done in a controller (if I understand correctly). Does this mean transactions done elsewhere (such as a model, or decorator - they're useful in many places, so I don't want to put them right in a single controller) must be explicitly closed? Even if it's a model method that does it which was called from a controller, ex: ``` class MyController def show MyModel.do_execute_sql_stuff end end class MyModel def self.do_execute_sql_stuff connection.execute("WHATEVER;") end end ``` Do I need to explicitly close here? If so, should I use `MyModel.connection.close` or `MyModel.clear_active_connections!` as the article suggests? Maybe because English is not my first language, but that method sounds dangerous! And how do I go do it? ``` conn = MyModel.connection result = conn.execute("STUFF") do_stuff_with(result) conn.close |or| MyModel.clear_active_connections! ``` Like that? What about when using `find_by_sql`? Will it return the connection to the pool, or do I have to explicitly do that? EDIT: Strangely, I only see this in my production logs. Not on development, nor staging (which should be identical to production).