allowStopNettyTimer = nettyConfig.getNettyTimer() == null;
nettyTimer = allowStopNettyTimer ? newNettyTimer() : nettyConfig.getNettyTimer();
channelManager = new ChannelManager(config, nettyConfig, nettyTimer);
requestSender = new NettyRequestSender(config, nettyConfig, channelManager, nettyTimer, closed);
channelManager.configureBootstraps(requestSender, closed);
}