anchor.diff:  -export([code_change/3, terminate/2]).
   
   % changes callbacks
  --export([changes_reader/3, changes_reader_cb/2]).
  +-export([changes_reader/3, changes_reader_cb/3]).
   
   % config_listener callback
   -export([handle_config_change/5]).
  
positive.code:         {json_req, null},
          Db
      ),
      ChangesFeedFun({fun ?MODULE:changes_reader_cb/2, {Server, DbName}}).
  
  changes_reader_cb({change, Change}, {Server, DbName}) ->
      case has_valid_rep_id(Change) of
          true ->
              Msg = {rep_db_update, DbName, Change},
  
negative.code:             ok
      end,
      {ok, {Server, DbName}};
  changes_reader_cb({stop, EndSeq, _Pending}, _, {Server, DbName}) ->
      Msg = {rep_db_checkpoint, DbName, EndSeq},
      ok = gen_server:call(Server, Msg, infinity),
      {ok, {Server, DbName}};
  changes_reader_cb(_, _, Acc) ->
      {ok, Acc}.
  
  has_valid_rep_id({Change}) ->
  