anchor.diff:  
   update(Key, Value) ->
       update([{Key, Value}]).
  +
  +update_txn(Props) ->
  +    fun (Config, SetFn) ->
  +            JSON = fetch_settings_json(Config),
  +            Current = decode_settings_json(JSON),
  +
  +            New = build_settings_json(Props, Current),
  +            {commit, SetFn(?INDEX_CONFIG_KEY, New, Config), New}
  +    end.
   
   config_upgrade() ->
       [{set, ?INDEX_CONFIG_KEY, build_settings_json(default_settings())}].
  
positive.code:          get/1, get/2,
           get_from_config/3,
           update/1, update/2,
           config_upgrade/0]).
  
  start_link() ->
  
negative.code:       end).
  
  do_update(Props) ->
      RV = ns_config:run_txn(update_txn(Props)),
      case RV of
          {commit, _, NewJSON} ->
              populate_ets_table(NewJSON),
  