anchor.diff:  leave(Node) ->
       gen_server:call(?MODULE, {leave, Node}, infinity).
   
  +%%%===================================================================
  +%%% debugging callbacks
  +%%%===================================================================
  +
   %% @doc Debugging.
   active() ->
       gen_server:call(?MODULE, active, infinity).
  
positive.code: handle_call({join, {_Name, _, _}=Node}, _From, State) ->
      gen_server:cast(?MODULE, {join, Node}),
      {reply, ok, State};
  
  handle_call(active, _From, #state{active=Active}=State) ->
      {reply, {ok, Active}, State};
  
negative.code:          receive_message/1,
           decode/1]).
  
  %% reservation specific API.
  -export([reserve/1]).
  
  %% debug.
  -export([active/0,
           passive/0]).
  