code: func (r *Orchestrator) initCluster(readTx store.ReadTx) error {
  	clusters, err := store.FindClusters(readTx, store.ByName(store.DefaultClusterName))
  	if err != nil {
  		return err
  	}
  
  	if len(clusters) != 1 {
  		// we'll just pick it when it is created.
  		return nil
  	}
  
  	r.cluster = clusters[0]
  	return nil
  }
docs: // This file provices service-level orchestration. It observes changes to
  // services and creates and destroys tasks as necessary to match the service
  // specifications. This is different from task-level orchestration, which
  // responds to changes in individual tasks (or nodes which run them).