anchor.diff:                     {error, commit_failed | invalid_attribute_value |
                              invalid_url_object | unknown_attribute |
                              replication_failed | unauthorized} |
  -                   {ok, [binary(),...]} | ok) -> [any()].
  +                   {ok, [url()]} | ok) -> [any()].
   send_replies(ReplyTo, Message) when is_tuple(ReplyTo) ->
       send_replies([ReplyTo], Message);
   send_replies(ReplyToList, Message) ->
  
positive.code:                         {missing, notfound} |
                          {missing, deleted} |
                          {error, _} |
                          {ok, #tagcontent{}},
                  ddfs_data :: path(),
                  timeout :: non_neg_integer(),
                  delayed   = false :: false | gb_tree(),
  
negative.code:     Url.
  
  -spec get_tagdata(tagname(), path()) -> {missing, notfound} | {error, _}
                                              | {ok, tagname(), [node()], [url()]}.
  get_tagdata(TagName, DdfsData) ->
      {ok, ReadableNodes, RBSize} = ddfs_master:get_read_nodes(),
      TagMinK = get(min_tagk),
  