TajoMaster has various roles: query coordinator, resource manager, and client API service. Please see TajoMaster section in https://cwiki.apache.org/confluence/display/TAJO/Tajo+Internal.
But, the current implementation does not have any bound for these roles. So, the code readability is not good and some part is too messy. So, I'm going to explicitly separate these roles into packages and improve their cohesion.