optional string topologyKey = 2;

  // WhenUnsatisfiable indicates how to deal with a pod if it doesn't satisfy
  // the spread constraint.
  // - DoNotSchedule (default) tells the scheduler not to schedule it.
  // - ScheduleAnyway tells the scheduler to schedule the pod in any location,
  //   but giving higher precedence to topologies that would help reduce the
  //   skew.