code: protected void stopRPC(boolean interruptClientHandlers)
        throws IOException, InterruptedException {
      // stop client handlers
      stopRPCInternal(server, "client", interruptClientHandlers);
  
      // stop datanode handlers
      stopRPCInternal(dnProtocolServer, "datanode", interruptClientHandlers);
  
      // waiting for the ongoing requests to complete
      stopWaitRPCInternal(server, "client");
      stopWaitRPCInternal(dnProtocolServer, "datanode");
    }
docs: Quiescess all communication to namenode cleanly.
  Ensures all RPC handlers have exited.
  
  @param interruptClientHandlers should the handlers be interrupted