public Map<String, Long> getCallQueueSizeSummary() {
    return queues.stream().flatMap(Collection::stream)
      .map(callRunner -> new Pair<>(getMethodName(callRunner), getRpcCallSize(callRunner)))
      .collect(Collectors.groupingBy(Pair::getFirst, Collectors.summingLong(Pair::getSecond)));
  }
Return the {@link RpcCall#getSize()} from {@code callRunner} or 0L.
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/RpcExecutor.java