anchor.diff:      Node1#metric{heartbeats=Node1#metric.heartbeats + 1}.
   
   
  +-spec evaluate_node_health(Node::#metric{}) -> {reset | should_die, #metric{} }.
   evaluate_node_health(Node) ->
       Node1 = maybe_advance_interval(Node),
       #metric{node_pid=Pid, avg=NAvg} = Node1,
  
positive.code: 
  -record(metric, {node_pid :: pid(),
                   avg=down_threshold() * 2 :: float(),
                   interval_start=pushy_time:timestamp() :: pos_integer(),
                   heartbeats=1 :: pos_integer()}).
  
  %% These two weights must total to 1.0
  -define(NOW_WEIGHT, (1.0/decay_window())).
  
negative.code:                 {reset, Node2} ->
                      ets:insert(?MODULE, Node2),
                      ok;
                  {should_die, _Node2} ->
                      ets:delete_object(?MODULE, Node1),
                      should_die
  