// Supports following actions:
// - restart (restarts all the MinIO instances in a setup)
// - stop (stops all the MinIO instances in a setup)
// - freeze (freezes all incoming S3 API calls)
// - unfreeze (unfreezes previously frozen S3 API calls)
func (a adminAPIHandlers) ServiceHandler(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	vars := mux.Vars(r)
	action := vars["action"]

	var serviceSig serviceSignal