static Pair<EventLoopGroup, Class<? extends Channel>> getEventLoopConfig(Configuration conf) {
    String name = conf.get(EVENT_LOOP_CONFIG);
    if (name == null) {
      return getDefaultEventLoopConfig(conf);
    }
    if (StringUtils.isBlank(name)) {
      return null;
    }
    return EVENT_LOOP_CONFIG_MAP.get(name);
  }
The {@link NettyRpcClient} will create its own {@code NioEventLoopGroup}.
hbase-client/src/main/java/org/apache/hadoop/hbase/ipc/NettyRpcClientConfigHelper.java