code: func (r *EtcdRegistry) getUnitByHash(hash unit.Hash) *unit.UnitFile {
  	key := r.hashedUnitPath(hash)
  	opts := &etcd.GetOptions{
  		Recursive: true,
  	}
  	start := time.Now()
  	resp, err := r.kAPI.Get(context.Background(), key, opts)
  	if err != nil {
  		if isEtcdError(err, etcd.ErrorCodeKeyNotFound) {
  			err = nil
  		}
  		metrics.ReportRegistryOpFailure(metrics.Get)
  		return nil
  	}
  	metrics.ReportRegistryOpSuccess(metrics.Get, start)
  	return r.unitFromEtcdNode(hash, resp.Node)
  }
docs: // getUnitByHash retrieves from the Registry the Unit associated with the given Hash