1、优先使用netty的 EpollServer

 

com.alipay.remoting.rpc.RpcServer#doInit

@Override
protected void doInit() {
    if (this.addressParser == null) {
        this.addressParser = new RpcAddressParser();
    }
    if (this.switches().isOn(GlobalSwitch.SERVER_MANAGE_CONNECTION_SWITCH)) {
        this.connectionEventHandler = new RpcConnectionEventHandler(switches());
        this.connectionManager = new DefaultConnectionManager(new RandomSelectStrategy());
        this.connectionEventHandler.setConnectionManager(this.connectionManager);
        this.connectionEventHandler.setConnectionEventListener(this.connectionEventListener);
    } else {
        this.connectionEventHandler = new ConnectionEventHandler(switches());
        this.connectionEventHandler.setConnectionEventListener(this.connectionEventListener);
    }
    initRpcRemoting(); // 初始化协议管理器等。。
    this.bootstrap = new ServerBootstrap();
    this.bootstrap.group(bossGroup, workerGroup)
        .channel(NettyEventLoopUtil.getServerSocketChannelClass()) // 选择server
        .option(ChannelOption.SO_BACKLOG, ConfigManager.tcp_so_backlog())
        .option(ChannelOption.SO_REUSEADDR, ConfigManager.tcp_so_reuseaddr())
        .childOption(ChannelOption.TCP_NODELAY, ConfigManager.tcp_nodelay())
        .childOption(ChannelOption.SO_KEEPALIVE, ConfigManager.tcp_so_keepalive());

    // set write buffer water mark
    initWriteBufferWaterMark();

    // init byte buf allocator
    if (ConfigManager.netty_buffer_pooled()) {
        this.bootstrap.option(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT)
            .childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT);
    } else {
        this.bootstrap.option(ChannelOption.ALLOCATOR, UnpooledByteBufAllocator.DEFAULT)
            .childOption(ChannelOption.ALLOCATOR, UnpooledByteBufAllocator.DEFAULT);
    }

    // enable trigger mode for epoll if need
    NettyEventLoopUtil.enableTriggeredMode(bootstrap); // 设置epoll触发方式

    final boolean idleSwitch = ConfigManager.tcp_idle_switch();
    final int idleTime = ConfigManager.tcp_server_idle();
    final ChannelHandler serverIdleHandler = new ServerIdleHandler();
    final RpcHandler rpcHandler = new RpcHandler(true, this.userProcessors);  // rpc处理器
    this.bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {

        @Override
        protected void initChannel(SocketChannel channel) {
            ChannelPipeline pipeline = channel.pipeline();
            pipeline.addLast("decoder", codec.newDecoder()); // 协议解析器
            pipeline.addLast("encoder", codec.newEncoder());
            if (idleSwitch) {
                pipeline.addLast("idleStateHandler", new IdleStateHandler(0, 0, idleTime,
                    TimeUnit.MILLISECONDS));
                pipeline.addLast("serverIdleHandler", serverIdleHandler);
            }
            pipeline.addLast("connectionEventHandler", connectionEventHandler);
            pipeline.addLast("handler", rpcHandler); // rpc处理器
            createConnection(channel);
        }

        /**
         * create connection operation<br>
         * <ul>
         * <li>If flag manageConnection be true, use {@link DefaultConnectionManager} to add a new connection, meanwhile bind it with the channel.</li>
         * <li>If flag manageConnection be false, just create a new connection and bind it with the channel.</li>
         * </ul>
         */
        private void createConnection(SocketChannel channel) {
            Url url = addressParser.parse(RemotingUtil.parseRemoteAddress(channel));
            if (switches().isOn(GlobalSwitch.SERVER_MANAGE_CONNECTION_SWITCH)) {
                connectionManager.add(new Connection(channel, url), url.getUniqueKey());
            } else {
                new Connection(channel, url);
            }
            channel.pipeline().fireUserEventTriggered(ConnectionEventType.CONNECT);
        }
    });
}

com.alipay.remoting.util.NettyEventLoopUtil

public class NettyEventLoopUtil {

    /** check whether epoll enabled, and it would not be changed during runtime. */
    private static boolean epollEnabled = ConfigManager.netty_epoll() && Epoll.isAvailable();

    /**
     * Create the right event loop according to current platform and system property, fallback to NIO when epoll not enabled.
     *
     * @param nThreads
     * @param threadFactory
     * @return an EventLoopGroup suitable for the current platform
     */
    public static EventLoopGroup newEventLoopGroup(int nThreads, ThreadFactory threadFactory) {
        return epollEnabled ? new EpollEventLoopGroup(nThreads, threadFactory)
            : new NioEventLoopGroup(nThreads, threadFactory);
    }

    /**
     * @return a SocketChannel class suitable for the given EventLoopGroup implementation
     */
    public static Class<? extends SocketChannel> getClientSocketChannelClass() {
        return epollEnabled ? EpollSocketChannel.class : NioSocketChannel.class;
    }

    /**
     * @return a ServerSocketChannel class suitable for the given EventLoopGroup implementation
     */
    public static Class<? extends ServerSocketChannel> getServerSocketChannelClass() {
        return epollEnabled ? EpollServerSocketChannel.class : NioServerSocketChannel.class;
    }

    /**
     * Use {@link EpollMode#LEVEL_TRIGGERED} for server bootstrap if level trigger enabled by system properties,
     *   otherwise use {@link EpollMode#EDGE_TRIGGERED}.
     * @param serverBootstrap server bootstrap
     */
    public static void enableTriggeredMode(ServerBootstrap serverBootstrap) {
        if (epollEnabled) {
            if (ConfigManager.netty_epoll_lt_enabled()) {
                serverBootstrap.childOption(EpollChannelOption.EPOLL_MODE,
                    EpollMode.LEVEL_TRIGGERED);
            } else {
                serverBootstrap
                    .childOption(EpollChannelOption.EPOLL_MODE, EpollMode.EDGE_TRIGGERED);
            }
        }
    }
}