no-conn-pool.rb

# Monkeypatch to disable connection pooling in ActiveRecord
module ActiveRecord
  module ConnectionAdapters
    class ConnectionPool
      def checkout
        c = ActiveRecord::Base.send(spec.adapter_method, spec.config.dup)
        c.verify!
        c
      end

      def checkin(conn)
        conn.disconnect!
      end

      # Disable @connection_mutex around these methods
      [:clear_reloadable_connections!, :verify_active_connections!,
       :connected?, :disconnect!].each do |m|
        aliased_method, punctuation = m.to_s.sub(/([?!=])$/, ''), $1
        alias_method m, "#{aliased_method}_without_synchronization#{punctuation}"
      end
    end
  end
end