@Override
      public void run() {
        task.setStatus(RpcServer.getStatus());
        task.run();
        queueSize.decrementAndGet();
      }
A very simple {@code }RpcScheduler} that serves incoming requests in order. This can be used for
HMaster, where no prioritization is needed.
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/FifoRpcScheduler.java