/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.rocketmq.remoting.netty;

import io.netty.bootstrap.ServerBootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.PooledByteBufAllocator;
import io.netty.channel.Channel;
import io.netty.channel.ChannelDuplexHandler;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelOption;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.WriteBufferWaterMark;
import io.netty.channel.epoll.Epoll;
import io.netty.channel.epoll.EpollEventLoopGroup;
import io.netty.channel.epoll.EpollServerSocketChannel;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioServerSocketChannel;
import io.netty.handler.timeout.IdleState;
import io.netty.handler.timeout.IdleStateEvent;
import io.netty.handler.timeout.IdleStateHandler;
import io.netty.util.HashedWheelTimer;
import io.netty.util.Timeout;
import io.netty.util.TimerTask;
import io.netty.util.concurrent.DefaultEventExecutorGroup;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.security.cert.CertificateException;
import java.util.NoSuchElementException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import org.apache.rocketmq.common.Pair;
import org.apache.rocketmq.common.ThreadFactoryImpl;
import org.apache.rocketmq.common.constant.LoggerName;
import org.apache.rocketmq.common.utils.NetworkUtil;
import org.apache.rocketmq.logging.org.slf4j.Logger;
import org.apache.rocketmq.logging.org.slf4j.LoggerFactory;
import org.apache.rocketmq.remoting.ChannelEventListener;
import org.apache.rocketmq.remoting.InvokeCallback;
import org.apache.rocketmq.remoting.RemotingServer;
import org.apache.rocketmq.remoting.common.RemotingHelper;
import org.apache.rocketmq.remoting.common.TlsMode;
import org.apache.rocketmq.remoting.exception.RemotingSendRequestException;
import org.apache.rocketmq.remoting.exception.RemotingTimeoutException;
import org.apache.rocketmq.remoting.exception.RemotingTooMuchRequestException;
import org.apache.rocketmq.remoting.protocol.RemotingCommand;

@SuppressWarnings("NullableProblems")
public class NettyRemotingServer extends NettyRemotingAbstract implements RemotingServer {
    private static final Logger log = LoggerFactory.getLogger(LoggerName.ROCKETMQ_REMOTING_NAME);
    private static final Logger TRAFFIC_LOGGER = LoggerFactory.getLogger(LoggerName.ROCKETMQ_TRAFFIC_NAME);

    private final ServerBootstrap serverBootstrap;
    private final EventLoopGroup eventLoopGroupSelector;
    private final EventLoopGroup eventLoopGroupBoss;
    private final NettyServerConfig nettyServerConfig;

    private final ExecutorService publicExecutor;
    private final ScheduledExecutorService scheduledExecutorService;
    private final ChannelEventListener channelEventListener;

    private final HashedWheelTimer timer = new HashedWheelTimer(r -> new Thread(r, "ServerHouseKeepingService"));

    private DefaultEventExecutorGroup defaultEventExecutorGroup;

    /**
     * NettyRemotingServer may hold multiple SubRemotingServer, each server will be stored in this container with a
     * ListenPort key.
     */
    private final ConcurrentMap<Integer/*Port*/, NettyRemotingAbstract> remotingServerTable = new ConcurrentHashMap<>();

    public static final String HANDSHAKE_HANDLER_NAME = "handshakeHandler";
    public static final String TLS_HANDLER_NAME = "sslHandler";
    public static final String FILE_REGION_ENCODER_NAME = "fileRegionEncoder";

    // sharable handlers
    private HandshakeHandler handshakeHandler;
    private NettyEncoder encoder;
    private NettyConnectManageHandler connectionManageHandler;
    private NettyServerHandler serverHandler;
    private RemotingCodeDistributionHandler distributionHandler;

    public NettyRemotingServer(final NettyServerConfig nettyServerConfig) {
        this(nettyServerConfig, null);
    }

    public NettyRemotingServer(final NettyServerConfig nettyServerConfig,
        final ChannelEventListener channelEventListener) {
        super(nettyServerConfig.getServerOnewaySemaphoreValue(), nettyServerConfig.getServerAsyncSemaphoreValue());
        this.serverBootstrap = new ServerBootstrap();
        this.nettyServerConfig = nettyServerConfig;
        this.channelEventListener = channelEventListener;

        this.publicExecutor = buildPublicExecutor(nettyServerConfig);
        this.scheduledExecutorService = buildScheduleExecutor();

        this.eventLoopGroupBoss = buildBossEventLoopGroup();
        this.eventLoopGroupSelector = buildEventLoopGroupSelector();

        loadSslContext();
    }

    private EventLoopGroup buildEventLoopGroupSelector() {
        if (useEpoll()) {
            return new EpollEventLoopGroup(nettyServerConfig.getServerSelectorThreads(), new ThreadFactoryImpl("NettyServerEPOLLSelector_"));
        } else {
            return new NioEventLoopGroup(nettyServerConfig.getServerSelectorThreads(), new ThreadFactoryImpl("NettyServerNIOSelector_"));
        }
    }

    private EventLoopGroup buildBossEventLoopGroup() {
        if (useEpoll()) {
            return new EpollEventLoopGroup(1, new ThreadFactoryImpl("NettyEPOLLBoss_"));
        } else {
            return new NioEventLoopGroup(1, new ThreadFactoryImpl("NettyNIOBoss_"));
        }
    }

    private ExecutorService buildPublicExecutor(NettyServerConfig nettyServerConfig) {
        int publicThreadNums = nettyServerConfig.getServerCallbackExecutorThreads();
        if (publicThreadNums <= 0) {
            publicThreadNums = 4;
        }

        return Executors.newFixedThreadPool(publicThreadNums, new ThreadFactoryImpl("NettyServerPublicExecutor_"));
    }

    private ScheduledExecutorService buildScheduleExecutor() {
        return new ScheduledThreadPoolExecutor(1,
            new ThreadFactoryImpl("NettyServerScheduler_", true),
            new ThreadPoolExecutor.DiscardOldestPolicy());
    }

    public void loadSslContext() {
        TlsMode tlsMode = TlsSystemConfig.tlsMode;
        log.info("Server is running in TLS {} mode", tlsMode.getName());

        if (tlsMode != TlsMode.DISABLED) {
            try {
                sslContext = TlsHelper.buildSslContext(false);
                log.info("SSLContext created for server");
            } catch (CertificateException | IOException e) {
                log.error("Failed to create SSLContext for server", e);
            }
        }
    }

    private boolean useEpoll() {
        return NetworkUtil.isLinuxPlatform()
            && nettyServerConfig.isUseEpollNativeSelector()
            && Epoll.isAvailable();
    }

    @Override
    public void start() {
        this.defaultEventExecutorGroup = new DefaultEventExecutorGroup(nettyServerConfig.getServerWorkerThreads(),
            new ThreadFactoryImpl("NettyServerCodecThread_"));

        prepareSharableHandlers();

        serverBootstrap.group(this.eventLoopGroupBoss, this.eventLoopGroupSelector)
            .channel(useEpoll() ? EpollServerSocketChannel.class : NioServerSocketChannel.class)
            .option(ChannelOption.SO_BACKLOG, 1024)
            .option(ChannelOption.SO_REUSEADDR, true)
            .childOption(ChannelOption.SO_KEEPALIVE, false)
            .childOption(ChannelOption.TCP_NODELAY, true)
            .localAddress(new InetSocketAddress(this.nettyServerConfig.getBindAddress(),
                this.nettyServerConfig.getListenPort()))
            .childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) {
                    configChannel(ch);
                }
            });

        addCustomConfig(serverBootstrap);

        try {
            ChannelFuture sync = serverBootstrap.bind().sync();
            InetSocketAddress addr = (InetSocketAddress) sync.channel().localAddress();
            if (0 == nettyServerConfig.getListenPort()) {
                this.nettyServerConfig.setListenPort(addr.getPort());
            }
            log.info("RemotingServer started, listening {}:{}", this.nettyServerConfig.getBindAddress(),
                this.nettyServerConfig.getListenPort());
            this.remotingServerTable.put(this.nettyServerConfig.getListenPort(), this);
        } catch (Exception e) {
            throw new IllegalStateException(String.format("Failed to bind to %s:%d", nettyServerConfig.getBindAddress(),
                nettyServerConfig.getListenPort()), e);
        }

        if (this.channelEventListener != null) {
            this.nettyEventExecutor.start();
        }

        TimerTask timerScanResponseTable = new TimerTask() {
            @Override
            public void run(Timeout timeout) {
                try {
                    NettyRemotingServer.this.scanResponseTable();
                } catch (Throwable e) {
                    log.error("scanResponseTable exception", e);
                } finally {
                    timer.newTimeout(this, 1000, TimeUnit.MILLISECONDS);
                }
            }
        };
        this.timer.newTimeout(timerScanResponseTable, 1000 * 3, TimeUnit.MILLISECONDS);

        scheduledExecutorService.scheduleWithFixedDelay(() -> {
            try {
                NettyRemotingServer.this.printRemotingCodeDistribution();
            } catch (Throwable e) {
                TRAFFIC_LOGGER.error("NettyRemotingServer print remoting code distribution exception", e);
            }
        }, 1, 1, TimeUnit.SECONDS);
    }

    /**
     * config channel in ChannelInitializer
     *
     * @param ch the SocketChannel needed to init
     * @return the initialized ChannelPipeline, sub class can use it to extent in the future
     */
    protected ChannelPipeline configChannel(SocketChannel ch) {
        return ch.pipeline()
            .addLast(defaultEventExecutorGroup, HANDSHAKE_HANDLER_NAME, handshakeHandler)
            .addLast(defaultEventExecutorGroup,
                encoder,
                new NettyDecoder(),
                distributionHandler,
                new IdleStateHandler(0, 0,
                    nettyServerConfig.getServerChannelMaxIdleTimeSeconds()),
                connectionManageHandler,
                serverHandler
            );
    }

    private void addCustomConfig(ServerBootstrap childHandler) {
        if (nettyServerConfig.getServerSocketSndBufSize() > 0) {
            log.info("server set SO_SNDBUF to {}", nettyServerConfig.getServerSocketSndBufSize());
            childHandler.childOption(ChannelOption.SO_SNDBUF, nettyServerConfig.getServerSocketSndBufSize());
        }
        if (nettyServerConfig.getServerSocketRcvBufSize() > 0) {
            log.info("server set SO_RCVBUF to {}", nettyServerConfig.getServerSocketRcvBufSize());
            childHandler.childOption(ChannelOption.SO_RCVBUF, nettyServerConfig.getServerSocketRcvBufSize());
        }
        if (nettyServerConfig.getWriteBufferLowWaterMark() > 0 && nettyServerConfig.getWriteBufferHighWaterMark() > 0) {
            log.info("server set netty WRITE_BUFFER_WATER_MARK to {},{}",
                nettyServerConfig.getWriteBufferLowWaterMark(), nettyServerConfig.getWriteBufferHighWaterMark());
            childHandler.childOption(ChannelOption.WRITE_BUFFER_WATER_MARK, new WriteBufferWaterMark(
                nettyServerConfig.getWriteBufferLowWaterMark(), nettyServerConfig.getWriteBufferHighWaterMark()));
        }

        if (nettyServerConfig.isServerPooledByteBufAllocatorEnable()) {
            childHandler.childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT);
        }
    }

    @Override
    public void shutdown() {
        try {
            this.timer.stop();

            this.eventLoopGroupBoss.shutdownGracefully();

            this.eventLoopGroupSelector.shutdownGracefully();

            this.nettyEventExecutor.shutdown();

            if (this.defaultEventExecutorGroup != null) {
                this.defaultEventExecutorGroup.shutdownGracefully();
            }
        } catch (Exception e) {
            log.error("NettyRemotingServer shutdown exception, ", e);
        }

        if (this.publicExecutor != null) {
            try {
                this.publicExecutor.shutdown();
            } catch (Exception e) {
                log.error("NettyRemotingServer shutdown exception, ", e);
            }
        }
    }

    @Override
    public void registerProcessor(int requestCode, NettyRequestProcessor processor, ExecutorService executor) {
        ExecutorService executorThis = executor;
        if (null == executor) {
            executorThis = this.publicExecutor;
        }

        Pair<NettyRequestProcessor, ExecutorService> pair = new Pair<>(processor, executorThis);
        this.processorTable.put(requestCode, pair);
    }

    @Override
    public void registerDefaultProcessor(NettyRequestProcessor processor, ExecutorService executor) {
        this.defaultRequestProcessorPair = new Pair<>(processor, executor);
    }

    @Override
    public int localListenPort() {
        return this.nettyServerConfig.getListenPort();
    }

    @Override
    public Pair<NettyRequestProcessor, ExecutorService> getProcessorPair(int requestCode) {
        return processorTable.get(requestCode);
    }

    @Override
    public Pair<NettyRequestProcessor, ExecutorService> getDefaultProcessorPair() {
        return defaultRequestProcessorPair;
    }

    @Override
    public RemotingServer newRemotingServer(final int port) {
        SubRemotingServer remotingServer = new SubRemotingServer(port,
            this.nettyServerConfig.getServerOnewaySemaphoreValue(),
            this.nettyServerConfig.getServerAsyncSemaphoreValue());
        NettyRemotingAbstract existingServer = this.remotingServerTable.putIfAbsent(port, remotingServer);
        if (existingServer != null) {
            throw new RuntimeException("The port " + port + " already in use by another RemotingServer");
        }
        return remotingServer;
    }

    @Override
    public void removeRemotingServer(final int port) {
        this.remotingServerTable.remove(port);
    }

    @Override
    public RemotingCommand invokeSync(final Channel channel, final RemotingCommand request, final long timeoutMillis)
        throws InterruptedException, RemotingSendRequestException, RemotingTimeoutException {
        return this.invokeSyncImpl(channel, request, timeoutMillis);
    }

    @Override
    public void invokeAsync(Channel channel, RemotingCommand request, long timeoutMillis, InvokeCallback invokeCallback)
        throws InterruptedException, RemotingTooMuchRequestException, RemotingTimeoutException, RemotingSendRequestException {
        this.invokeAsyncImpl(channel, request, timeoutMillis, invokeCallback);
    }

    @Override
    public void invokeOneway(Channel channel, RemotingCommand request, long timeoutMillis) throws InterruptedException,
        RemotingTooMuchRequestException, RemotingTimeoutException, RemotingSendRequestException {
        this.invokeOnewayImpl(channel, request, timeoutMillis);
    }

    @Override
    public ChannelEventListener getChannelEventListener() {
        return channelEventListener;
    }

    @Override
    public ExecutorService getCallbackExecutor() {
        return this.publicExecutor;
    }

    private void prepareSharableHandlers() {
        handshakeHandler = new HandshakeHandler(TlsSystemConfig.tlsMode);
        encoder = new NettyEncoder();
        connectionManageHandler = new NettyConnectManageHandler();
        serverHandler = new NettyServerHandler();
        distributionHandler = new RemotingCodeDistributionHandler();
    }

    private void printRemotingCodeDistribution() {
        if (distributionHandler != null) {
            String inBoundSnapshotString = distributionHandler.getInBoundSnapshotString();
            if (inBoundSnapshotString != null) {
                TRAFFIC_LOGGER.info("Port: {}, RequestCode Distribution: {}",
                    nettyServerConfig.getListenPort(), inBoundSnapshotString);
            }

            String outBoundSnapshotString = distributionHandler.getOutBoundSnapshotString();
            if (outBoundSnapshotString != null) {
                TRAFFIC_LOGGER.info("Port: {}, ResponseCode Distribution: {}",
                    nettyServerConfig.getListenPort(), outBoundSnapshotString);
            }
        }
    }

    public DefaultEventExecutorGroup getDefaultEventExecutorGroup() {
        return defaultEventExecutorGroup;
    }

    public HandshakeHandler getHandshakeHandler() {
        return handshakeHandler;
    }

    public NettyEncoder getEncoder() {
        return encoder;
    }

    public NettyConnectManageHandler getConnectionManageHandler() {
        return connectionManageHandler;
    }

    public NettyServerHandler getServerHandler() {
        return serverHandler;
    }

    public RemotingCodeDistributionHandler getDistributionHandler() {
        return distributionHandler;
    }

    @ChannelHandler.Sharable
    public class HandshakeHandler extends SimpleChannelInboundHandler<ByteBuf> {

        private final TlsMode tlsMode;

        private static final byte HANDSHAKE_MAGIC_CODE = 0x16;

        HandshakeHandler(TlsMode tlsMode) {
            this.tlsMode = tlsMode;
        }

        @Override
        protected void channelRead0(ChannelHandlerContext ctx, ByteBuf msg) {

            // Peek the first byte to determine if the content is starting with TLS handshake
            byte b = msg.getByte(0);

            if (b == HANDSHAKE_MAGIC_CODE) {
                switch (tlsMode) {
                    case DISABLED:
                        ctx.close();
                        log.warn("Clients intend to establish an SSL connection while this server is running in SSL disabled mode");
                        break;
                    case PERMISSIVE:
                    case ENFORCING:
                        if (null != sslContext) {
                            ctx.pipeline()
                                .addAfter(defaultEventExecutorGroup, HANDSHAKE_HANDLER_NAME, TLS_HANDLER_NAME, sslContext.newHandler(ctx.channel().alloc()))
                                .addAfter(defaultEventExecutorGroup, TLS_HANDLER_NAME, FILE_REGION_ENCODER_NAME, new FileRegionEncoder());
                            log.info("Handlers prepended to channel pipeline to establish SSL connection");
                        } else {
                            ctx.close();
                            log.error("Trying to establish an SSL connection but sslContext is null");
                        }
                        break;

                    default:
                        log.warn("Unknown TLS mode");
                        break;
                }
            } else if (tlsMode == TlsMode.ENFORCING) {
                ctx.close();
                log.warn("Clients intend to establish an insecure connection while this server is running in SSL enforcing mode");
            }

            try {
                // Remove this handler
                ctx.pipeline().remove(this);
            } catch (NoSuchElementException e) {
                log.error("Error while removing HandshakeHandler", e);
            }

            // Hand over this message to the next .
            ctx.fireChannelRead(msg.retain());
        }
    }

    @ChannelHandler.Sharable
    public class NettyServerHandler extends SimpleChannelInboundHandler<RemotingCommand> {

        @Override
        protected void channelRead0(ChannelHandlerContext ctx, RemotingCommand msg) {
            int localPort = RemotingHelper.parseSocketAddressPort(ctx.channel().localAddress());
            NettyRemotingAbstract remotingAbstract = NettyRemotingServer.this.remotingServerTable.get(localPort);
            if (localPort != -1 && remotingAbstract != null) {
                remotingAbstract.processMessageReceived(ctx, msg);
                return;
            }
            // The related remoting server has been shutdown, so close the connected channel
            RemotingHelper.closeChannel(ctx.channel());
        }

        @Override
        public void channelWritabilityChanged(ChannelHandlerContext ctx) throws Exception {
            Channel channel = ctx.channel();
            if (channel.isWritable()) {
                if (!channel.config().isAutoRead()) {
                    channel.config().setAutoRead(true);
                    log.info("Channel[{}] turns writable, bytes to buffer before changing channel to un-writable: {}",
                        RemotingHelper.parseChannelRemoteAddr(channel), channel.bytesBeforeUnwritable());
                }
            } else {
                channel.config().setAutoRead(false);
                log.warn("Channel[{}] auto-read is disabled, bytes to drain before it turns writable: {}",
                    RemotingHelper.parseChannelRemoteAddr(channel), channel.bytesBeforeWritable());
            }
            super.channelWritabilityChanged(ctx);
        }
    }

    @ChannelHandler.Sharable
    public class NettyConnectManageHandler extends ChannelDuplexHandler {
        @Override
        public void channelRegistered(ChannelHandlerContext ctx) throws Exception {
            final String remoteAddress = RemotingHelper.parseChannelRemoteAddr(ctx.channel());
            log.info("NETTY SERVER PIPELINE: channelRegistered {}", remoteAddress);
            super.channelRegistered(ctx);
        }

        @Override
        public void channelUnregistered(ChannelHandlerContext ctx) throws Exception {
            final String remoteAddress = RemotingHelper.parseChannelRemoteAddr(ctx.channel());
            log.info("NETTY SERVER PIPELINE: channelUnregistered, the channel[{}]", remoteAddress);
            super.channelUnregistered(ctx);
        }

        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
            final String remoteAddress = RemotingHelper.parseChannelRemoteAddr(ctx.channel());
            log.info("NETTY SERVER PIPELINE: channelActive, the channel[{}]", remoteAddress);
            super.channelActive(ctx);

            if (NettyRemotingServer.this.channelEventListener != null) {
                NettyRemotingServer.this.putNettyEvent(new NettyEvent(NettyEventType.CONNECT, remoteAddress, ctx.channel()));
            }
        }

        @Override
        public void channelInactive(ChannelHandlerContext ctx) throws Exception {
            final String remoteAddress = RemotingHelper.parseChannelRemoteAddr(ctx.channel());
            log.info("NETTY SERVER PIPELINE: channelInactive, the channel[{}]", remoteAddress);
            super.channelInactive(ctx);

            if (NettyRemotingServer.this.channelEventListener != null) {
                NettyRemotingServer.this.putNettyEvent(new NettyEvent(NettyEventType.CLOSE, remoteAddress, ctx.channel()));
            }
        }

        @Override
        public void userEventTriggered(ChannelHandlerContext ctx, Object evt) {
            if (evt instanceof IdleStateEvent) {
                IdleStateEvent event = (IdleStateEvent) evt;
                if (event.state().equals(IdleState.ALL_IDLE)) {
                    final String remoteAddress = RemotingHelper.parseChannelRemoteAddr(ctx.channel());
                    log.warn("NETTY SERVER PIPELINE: IDLE exception [{}]", remoteAddress);
                    RemotingHelper.closeChannel(ctx.channel());
                    if (NettyRemotingServer.this.channelEventListener != null) {
                        NettyRemotingServer.this
                            .putNettyEvent(new NettyEvent(NettyEventType.IDLE, remoteAddress, ctx.channel()));
                    }
                }
            }

            ctx.fireUserEventTriggered(evt);
        }

        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
            final String remoteAddress = RemotingHelper.parseChannelRemoteAddr(ctx.channel());
            log.warn("NETTY SERVER PIPELINE: exceptionCaught {}", remoteAddress);
            log.warn("NETTY SERVER PIPELINE: exceptionCaught exception.", cause);

            if (NettyRemotingServer.this.channelEventListener != null) {
                NettyRemotingServer.this.putNettyEvent(new NettyEvent(NettyEventType.EXCEPTION, remoteAddress, ctx.channel()));
            }

            RemotingHelper.closeChannel(ctx.channel());
        }
    }

    /**
     * The NettyRemotingServer supports bind multiple ports, each port bound by a SubRemotingServer. The
     * SubRemotingServer will delegate all the functions to NettyRemotingServer, so the sub server can share all the
     * resources from its parent server.
     */
    class SubRemotingServer extends NettyRemotingAbstract implements RemotingServer {
        private volatile int listenPort;
        private volatile Channel serverChannel;

        SubRemotingServer(final int port, final int permitsOnway, final int permitsAsync) {
            super(permitsOnway, permitsAsync);
            listenPort = port;
        }

        @Override
        public void registerProcessor(final int requestCode, final NettyRequestProcessor processor,
            final ExecutorService executor) {
            ExecutorService executorThis = executor;
            if (null == executor) {
                executorThis = NettyRemotingServer.this.publicExecutor;
            }

            Pair<NettyRequestProcessor, ExecutorService> pair = new Pair<>(processor, executorThis);
            this.processorTable.put(requestCode, pair);
        }

        @Override
        public void registerDefaultProcessor(final NettyRequestProcessor processor, final ExecutorService executor) {
            this.defaultRequestProcessorPair = new Pair<>(processor, executor);
        }

        @Override
        public int localListenPort() {
            return listenPort;
        }

        @Override
        public Pair<NettyRequestProcessor, ExecutorService> getProcessorPair(final int requestCode) {
            return this.processorTable.get(requestCode);
        }

        @Override
        public Pair<NettyRequestProcessor, ExecutorService> getDefaultProcessorPair() {
            return this.defaultRequestProcessorPair;
        }

        @Override
        public RemotingServer newRemotingServer(final int port) {
            throw new UnsupportedOperationException("The SubRemotingServer of NettyRemotingServer " +
                "doesn't support new nested RemotingServer");
        }

        @Override
        public void removeRemotingServer(final int port) {
            throw new UnsupportedOperationException("The SubRemotingServer of NettyRemotingServer " +
                "doesn't support remove nested RemotingServer");
        }

        @Override
        public RemotingCommand invokeSync(final Channel channel, final RemotingCommand request,
            final long timeoutMillis) throws InterruptedException, RemotingSendRequestException, RemotingTimeoutException {
            return this.invokeSyncImpl(channel, request, timeoutMillis);
        }

        @Override
        public void invokeAsync(final Channel channel, final RemotingCommand request, final long timeoutMillis,
            final InvokeCallback invokeCallback) throws InterruptedException, RemotingTooMuchRequestException, RemotingTimeoutException, RemotingSendRequestException {
            this.invokeAsyncImpl(channel, request, timeoutMillis, invokeCallback);
        }

        @Override
        public void invokeOneway(final Channel channel, final RemotingCommand request,
            final long timeoutMillis) throws InterruptedException, RemotingTooMuchRequestException, RemotingTimeoutException, RemotingSendRequestException {
            this.invokeOnewayImpl(channel, request, timeoutMillis);
        }

        @Override
        public void start() {
            try {
                if (listenPort < 0) {
                    listenPort = 0;
                }
                this.serverChannel = NettyRemotingServer.this.serverBootstrap.bind(listenPort).sync().channel();
                if (0 == listenPort) {
                    InetSocketAddress addr = (InetSocketAddress) this.serverChannel.localAddress();
                    this.listenPort = addr.getPort();
                }
            } catch (InterruptedException e) {
                throw new RuntimeException("this.subRemotingServer.serverBootstrap.bind().sync() InterruptedException", e);
            }
        }

        @Override
        public void shutdown() {
            if (this.serverChannel != null) {
                try {
                    this.serverChannel.close().await(5, TimeUnit.SECONDS);
                } catch (InterruptedException ignored) {
                }
            }
        }

        @Override
        public ChannelEventListener getChannelEventListener() {
            return NettyRemotingServer.this.getChannelEventListener();
        }

        @Override
        public ExecutorService getCallbackExecutor() {
            return NettyRemotingServer.this.getCallbackExecutor();
        }
    }
}
