---

mongodb::server::replicaset_members:
  'api-mongo-1':
  'api-mongo-2':
  'api-mongo-3':
  'api-mongo-4':

---

mongodb::server::replicaset_members:
  'api-mongo-1':
  'api-mongo-2':
  'api-mongo-3':
  'api-mongo-4':
    priority: 0

Set api-mongo-4 to be a priority 0 node.
Set api-mongo-4 to be a priority 0 node.