anchor.diff:      %% Schedule periodic plumtree refresh.
       schedule_plumtree_peer_refresh(),
   
  -    {ok, #state{gossip_peers=[], store=Store, actor=Actor}}.
  +    BlockingSyncs = dict:new(),
  +
  +    {ok, #state{gossip_peers=[],
  +                blocking_syncs=BlockingSyncs,
  +                store=Store,
  +                actor=Actor}}.
   
   %% @private
   -spec handle_call(term(), {pid(), term()}, #state{}) ->
       {reply, term(), #state{}}.
  +
  +handle_call({blocking_sync, ObjectFilterFun}, From,
  +            #state{gossip_peers=GossipPeers,
  +                   store=Store,
  +                   blocking_syncs=BlockingSyncs0}=State) ->
  +    %% Get the peers to synchronize with.
  +    Members = case ?SYNC_BACKEND:broadcast_tree_mode() of
  +        true ->
  +            GossipPeers;
  +        false ->
  +            {ok, Members1} = ?SYNC_BACKEND:membership(),
  +            Members1
  +    end,
  +
  +    %% Remove ourself and compute exchange peers.
  +    Peers = ?SYNC_BACKEND:compute_exchange(?SYNC_BACKEND:without_me(Members)),
  +
  +    %% Send the object.
  +    SyncFun = fun(Peer) ->
  +                      {Peer, init_state_sync(Peer, ObjectFilterFun, Store)}
  +              end,
  +    Objects = lists:flatmap(SyncFun, Peers),
  +
  +    %% Mark response as waiting.
  +    BlockingSyncs = dict:store(From, Objects, BlockingSyncs0),
  +
  +    {noreply, State#state{blocking_syncs=BlockingSyncs}};
   
   handle_call(Msg, _From, State) ->
       _ = lager:warning("Unhandled messages: ~p", [Msg]),
  
positive.code:                     end
                 end,
      %% TODO: Should this be parallel?
      {ok, _} = lasp_storage_backend:do(fold, [Store, Function, []]),
      lasp_logger:extended("Completed state synchronization with peer: ~p", [Peer]),
      ok.
  
  %% @private
  plumtree_gossip_peers(Root) ->
  
negative.code: start_link(Opts) ->
      gen_server:start_link({local, ?MODULE}, ?MODULE, Opts, []).
  
  blocking_sync(ObjectFilterFun) ->
      gen_server:call(?MODULE, {blocking_sync, ObjectFilterFun}, infinity).
  
  %%%===================================================================
  %%% gen_server callbacks
  %%%===================================================================
  