private void throttle(int credits) {
    long startNs = System.nanoTime();
    rateLimiter.acquire(Collections.singletonMap(tag, credits));
    if (waitTimeMetric != null) {
      waitTimeMetric.update(System.nanoTime() - startNs);
    }
  }
Set up waitTimeMetric metric for latency reporting due to throttling.
@param timer waitTimeMetric metric
samza-api/src/main/java/org/apache/samza/table/remote/TableRateLimiter.java