code: protected Func1<HttpClientResponse<ByteBuf>, Integer> withBookkeeping(final int batchSize) {
      return response -> {
        boolean ok = response.getStatus().code() == 200;
        if (ok) {
          numMetricsSent.increment(batchSize);
        } else {
          LOGGER.info("Status code: {} - Lost {} metrics",
              response.getStatus().code(), batchSize);
          numMetricsDroppedHttpErr.increment(batchSize);
        }
  
        return batchSize;
      };
    }
docs: Utility function to map an Observable&lt;ByteBuf> to an Observable&lt;Integer> while also
  updating our counters for metrics sent and errors.