@Override
          public void onRemoval(RemovalNotification<String, ProtocolType> arg) {
            if (arg == null) return;
            shutdownProtocolImpl(arg.getValue());
          }
Asynchronous request to a node. The request must override {@link #callInternal()}
@param <REQUEST>
@param <RESPONSE>
llap-common/src/java/org/apache/hadoop/hive/llap/AsyncPbRpcProxy.java