public static void createEventLoopPerClient(Configuration conf) {
    conf.set(EVENT_LOOP_CONFIG, "");
    EVENT_LOOP_CONFIG_MAP.clear();
  }
The {@link NettyRpcClient} will create its own {@code NioEventLoopGroup}.
hbase-client/src/main/java/org/apache/hadoop/hbase/ipc/NettyRpcClientConfigHelper.java