code: func (c *Conn) UpdateSettings(settingType string, key string, value int) (ClusterSettingsResponse, error) {
  	var retval ClusterSettingsResponse
  	if settingType != "transient" && settingType != "persistent" {
  		return retval, fmt.Errorf("settingType must be one of transient or persistent, you passed %s", settingType)
  	}
  	var url string = "/_cluster/state"
  	m := map[string]map[string]int{settingType: {key: value}}
  	body, err := c.DoCommand("PUT", url, nil, m)
  	if err != nil {
  		return retval, err
  	}
  	if err == nil {
  		// marshall into json
  		jsonErr := json.Unmarshal(body, &retval)
  		if jsonErr != nil {
  			return retval, jsonErr
  		}
  	}
  	return retval, err
  }
docs: // UpdateSettings allows to update cluster wide specific settings. Defaults to Transient setting
  // Settings updated can either be persistent (applied cross restarts) or transient (will not survive a full cluster restart).
  // http://www.elasticsearch.org/guide/reference/api/admin-cluster-update-settings.html