anchor.diff:                  nodes = [],
                   write_blacklist = [],
                   read_blacklist = []}}.
  -
  -get_readable_nodes(Nodes, ReadBlacklist) ->
  -    NodeSet = gb_sets:from_ordset(lists:sort([Node || {Node, _} <- Nodes])),
  -    BlackSet = gb_sets:from_ordset(ReadBlacklist),
  -    ReadableNodeSet = gb_sets:subtract(NodeSet, BlackSet),
  -    {gb_sets:to_list(ReadableNodeSet), gb_sets:size(BlackSet)}.
   
   handle_call(dbg_get_state, _, S) ->
       {reply, S, S};
  
positive.code:                 tag_cache :: 'false' | gb_set(),
                  write_blacklist :: [node()],
                  read_blacklist :: [node()]}).
  
  start_link() ->
      error_logger:info_report([{"DDFS master starts"}]),
  
negative.code: -module(ddfs_master).
  -behaviour(gen_server).
  
  -export([start_link/0, stop/0]).
  -export([init/1,
           handle_call/3,
           handle_cast/2,
           handle_info/2,
           terminate/2,
           code_change/3]).
  
  -define(WEB_PORT, 8011).
  
  