code: public void onSuccessfulWrite(long startTimeNanos) {
      Instrumented.updateTimer(this.dataWriterTimer, System.nanoTime() - startTimeNanos, TimeUnit.NANOSECONDS);
      Instrumented.markMeter(this.successfulWritesMeter);
    }
docs: Called after a successful write of a record.
  @param startTimeNanos time at which writing started.