anchor.diff:                                _ ->
                                     false
                             end],
  -    wait_checkpoint_opened(Bucket, VBucket, NodesLeft, Sleeper, false).
  +    wait_checkpoint_opened(Bucket, VBucket, NodesLeft, Sleeper, SleepsSoFar+1).
  
positive.code:                         [fun build_replicas_main/6,
                           [Bucket, VBucket, SrcNode, ReplicateIntoNodes, JustBackfillNodes, AfterDone]]).
  
  -define(COMPLETION_POLLING_INTERVAL, 100).
  
  %% @doc works like try/after but when try has raised exception, any
  %% exception from AfterBody is logged and ignored. I.e. when we face
  
negative.code: 
  observe_wait_all_done(Bucket, VBucket, SrcNode, DstNodes, Sleeper) ->
      TapNames = sets:from_list([iolist_to_binary(tap_name(VBucket, SrcNode, DN)) || DN <- DstNodes]),
      observe_wait_all_done_tail(Bucket, SrcNode, Sleeper, TapNames, 0),
      wait_checkpoint_opened(Bucket, VBucket, DstNodes, Sleeper, 0).
  
  observe_wait_all_done_tail(Bucket, SrcNode, Sleeper, TapNames, SleepsSoFar) ->
      case sets:size(TapNames) of
          0 ->
              ok;
          _ ->
              if SleepsSoFar > 0 ->
                      system_stats_collector:increment_counter(replicas_builder_backfill_sleeps, 1),
                      Sleeper(SleepsSoFar);
                 true ->
                      ok
              end,
              {ok, PList} = ns_memcached:stats(SrcNode, Bucket, <<"tap">>),
              DoneTaps = extract_complete_taps(PList, TapNames),
              NewTapNames = sets:subtract(TapNames, DoneTaps),
              observe_wait_all_done_tail(Bucket, SrcNode, Sleeper, NewTapNames, SleepsSoFar+1)
      end.
  
  wait_checkpoint_opened(_Bucket, _VBucket, [], _Sleeper, _SleepsSoFar) ->
      ok;
  wait_checkpoint_opened(Bucket, VBucket, DstNodes, Sleeper, SleepsSoFar) ->
      case SleepsSoFar =:= 0 of
          false ->
              system_stats_collector:increment_counter(replicas_builder_checkpoint_sleeps, 1),
              ?log_debug("Incremented replicas_builder_checkpoint_sleeps"),
              Sleeper(SleepsSoFar);
          true -> ok
      end,
      Checkpoints = ns_memcached:get_vbucket_open_checkpoint(DstNodes, Bucket, VBucket),
  