code: func (b *Backend) TriggerChord(groupUUID string) (bool, error) {
  	groupMeta, err := b.getGroupMeta(groupUUID)
  	if err != nil {
  		return false, err
  	}
  
  	// Chord has already been triggered, return false (should not trigger again)
  	if groupMeta.ChordTriggered {
  		return false, nil
  	}
  
  	// If group meta is locked, wait until it's unlocked
  	for groupMeta.Lock {
  		groupMeta, _ = b.getGroupMeta(groupUUID)
  		log.WARNING.Print("Group meta locked, waiting")
  		time.Sleep(time.Millisecond * 5)
  	}
  
  	// Acquire lock
  	if err = b.lockGroupMeta(groupMeta); err != nil {
  		return false, err
  	}
  	defer b.unlockGroupMeta(groupMeta)
  
  	// Update the group meta data
  	groupMeta.ChordTriggered = true
  	encoded, err := json.Marshal(&groupMeta)
  	if err != nil {
  		return false, err
  	}
  	if err = b.getClient().Replace(&gomemcache.Item{
  		Key:        groupUUID,
  		Value:      encoded,
  		Expiration: b.getExpirationTimestamp(),
  	}); err != nil {
  		return false, err
  	}
  
  	return true, nil
  }
docs: // TriggerChord flags chord as triggered in the backend storage to make sure
  // chord is never trigerred multiple times. Returns a boolean flag to indicate
  // whether the worker should trigger chord (true) or no if it has been triggered
  // already (false)