anchor.diff:  
   do_servant_call(Server, Request) ->
       get_servant_call_reply(initiate_servant_call(Server, Request)).
  -
  -get_tap_docs_estimate(Bucket, SrcNode, VBucket, TapName) ->
  -    RV = do_servant_call({server_name(Bucket), SrcNode},
  -                         {get_tap_docs_estimate, VBucket, TapName}),
  -    {ok, _} = RV,
  -    RV.
   
   -spec get_tap_docs_estimate_many_taps(bucket_name(), node(), vbucket_id(), [binary()]) ->
                                                [{ok, {non_neg_integer(), non_neg_integer(), binary()}}].
  
positive.code:     %% persisted seq no should not be possible here
      {ok, SeqNo} = ns_memcached:get_vbucket_high_seqno(Bucket, VBucket),
      {reply, SeqNo, State};
  handle_call({get_tap_docs_estimate, _VBucketId, _TapName} = Req, From, State) ->
      handle_call_via_servant(
        From, State, Req,
        fun ({_, VBucketId, TapName}, #state{bucket_name = Bucket}) ->
                ns_memcached:get_tap_docs_estimate(Bucket, VBucketId, TapName)
        end);
  handle_call({get_tap_docs_estimate_many_taps, _VBucketId, _TapName} = Req, From, State) ->
      handle_call_via_servant(
        From, State, Req,
  
negative.code:          complete_flush/3,
           get_replication_persistence_checkpoint_id/4,
           wait_checkpoint_persisted/5,
           get_tap_docs_estimate_many_taps/4,
           get_mass_tap_docs_estimate/3,
           get_dcp_docs_estimate/4,
  