anchor.diff:  
   -export([behaviour_info/1]).
   
  --export([maybe_create_hashtrees/3,
  +-export([maybe_create_hashtrees/4,
            update_hashtree/4]).
   
   -export([request_hashtree_pid/2,
  
positive.code: %% created hashtree so it should listen for
  %% `{'DOWN', _, _, Pid, _}` where Pid is the pid of the created hashtree
  %% to recreate a new one if this should die.
  -spec maybe_create_hashtrees(atom(), integer(), pid()|undefined) ->
                                      pid()|undefined.
  maybe_create_hashtrees(Service, Index, Last) ->
      maybe_create_hashtrees(riak_core_entropy_manager:enabled(), Service, Index,
                             Last).
  
  -spec maybe_create_hashtrees(boolean(), atom(), integer(), pid()|undefined) ->
                                      pid()|undefined.
  maybe_create_hashtrees(false, _Service, _Index, Last) ->
      lager:info("sniffle_dtrace: Hashtree not enabled."),
      Last;
  
  maybe_create_hashtrees(true, Service, Index, Last) ->
      %% Only maintain a hashtree if a primary vnode
      {ok, Ring} = riak_core_ring_manager:get_my_ring(),
      lager:debug("~p/~p: creating hashtree.", [Service, Index]),
  
negative.code:         primary ->
              RP = riak_core_util:responsible_preflists(Index),
              case riak_core_index_hashtree:start(Service, Index, RP, self(),
                                                  VNode) of
                  {ok, Trees} ->
                      lager:debug("~p/~p: hashtree created: ~p.",
                                  [Service, Index, Trees]),
  