if tgt.Empty() {
			writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErrWithErr(ErrInvalidRequest, fmt.Errorf("invalid arn : '%s'", opts.ARN)), r.URL)
			return
		}
	}

	keepAliveTicker := time.NewTicker(500 * time.Millisecond)
	defer keepAliveTicker.Stop()

	diffCh, err := getReplicationDiff(ctx, objectAPI, bucket, opts)
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return