We TajoClient is opened, TajoClient initially tries to connect TajoMaster. This manner does not guarantee high availability. A known TajoMaster host may be not work anymore. So, this manner still has some failure point.
Also, this manner prohibits a Tajo cluster to run on some dynamic cluster environments like Yarn.
Tajo HA client should get directly TajoMaster addresses and others from HA component without contacting TajoMaster.