private void updateMetrics(Call result) {
    if (result == null) {
      return;
    }
    metrics.incTimeInQueue(result.timeInQueue());
    metrics.setCallQueueLen(this.size());
  }
A BlockingQueue reports waiting time in queue and queue length to ThriftMetrics.
hbase-thrift/src/main/java/org/apache/hadoop/hbase/thrift/CallQueue.java