mysql connection handling

[SWSAmor]

May i ask a theoretical noob questions here? Or there is another channel for these?

I'd like to group mysql functions into a module. But if they are in a module, how could i call these from other modules. Should i declare the 'conn' (= mysql_connect()) variable as a global? Or should i pass it to all functions as parameter?
Generally the mysql connection is permanent in tarantool? Need to be permanent (relate to performance)? Or need to be open a new connection for every operation?
Thank you.