set is considered failed:
  UNKNOWN - agent lost track of worker group state, unrecoverable
  INIT - worker group object created not yet started
  HEALTHY - workers running and healthy
  UNHEALTHY - workers running and unhealthy
  STOPPED - workers stopped (interrupted) by the agent
  SUCCEEDED - workers finished running (exit 0)
  FAILED - workers failed to successfully finish (exit !0)

A worker group starts from an initial "INIT" state, then progresses
   to "HEALTHY" or "UNHEALTHY" states, and finally reaches a terminal
   "SUCCEEDED" or "FAILED" state.
Worker groups can be interrupted and temporarily put into "STOPPED"
   state by the agent. Workers in "STOPPED" state are scheduled to be
   restarted in the near future by the agent. Some examples of workers
   being put into "STOPPED" state are:


Worker group failure|unhealthy observed


Membership change detected


When actions (start, stop, rdzv, retry, etc) on worker group fails