Master node, or cluster master, is a unified endpoint within a cluster which oversees activity on each node.
Master node responsibilities consist of scheduling deployment and distributing work to be installed on the nodes. Worker nodes that run the services can run or stop based on master node requests.
Worker nodes self-report statuses and activities to the master node which determines whether nodes need to be repaired, upgraded, or removed. The master node can add or remove nodes if a node fails.