func (s *Simulator) emitHeartbeatFor(dea string) {
	hb := models.Heartbeat{
		DeaGuid:            dea,
		InstanceHeartbeats: make([]models.InstanceHeartbeat, len(s.DEAs[dea])),
	}

	for i, app := range s.DEAs[dea] {
		hb.InstanceHeartbeats[i] = app.InstanceAtIndex(0).Heartbeat()
		hb.InstanceHeartbeats[i].State = s.AppInstanceState[app.AppGuid]
	}

	s.messageBus.Publish("dea.heartbeat", hb.ToJSON())
}