Netty简介
Netty是一个面向网络编程的Java基础框架，它基于异步的事件驱动，并且内置多种网络协议的支持，可以快速地开发可维护的高性能的面向协议的服务器和客户端。
安聊简介
安聊是一个即时聊天系统，服务端通过点对点与客户端建立TCP链接，接受来自客户端的请求，同时，也可以实时地将消息通知给客户端。
安聊为什么选择Netty
首先是性能和稳定性。在我们内部团队进行过测试，使用Netty框架，单台服务器可以维持10000个客户端长链接，并且稳定性非常高：我们的服务器曾经有过连续六个月稳定运行的记录，并且中断的原因还是因为服务端版本升级。
其次是应用程序的简洁性和易维护性。使用Netty进行网络开发，可以利用框架屏蔽那些网络底层的实现细节，让应用只关注于业务逻辑本身；同时因为pipeline的设计模式，让应用添加对数据/事件的额外处理变得非常简单。
安聊使用Netty的一些技术特点：
1、结合Spring，让端口侦听服务成为一个Bean，结合Bean的生命周期挂钩函数完成端口服务的安装/关闭行为
2、将终端长连接的ChannelHandleContext与对应的用户ID进行绑定，方便消息转发
3、使用自定义的编码/解码器对协议包进行处理
4、通过继承SimpleChannelInboundHandler的类，来处理客户端请求的协议包
5、因为处理客户端包的业务过程中，会涉及到数据库操作，磁盘读写操作，若直接在网络IO线程中处理，则会显著降低网络IO的处理能力，所以把每个业务处理都独立成为一个任务（Task）实例，然后放到线程池中去执行；当任务执行完毕，需要通知回网络IO线程时，使用userEvent的形式通知回去
一些关键代码：
网络服务初始化
public class IMClientServerInitializer extends ChannelInitializer<SocketChannel> { private final EventExecutorGroup execGroup; private final int pduTimeout; public IMClientServerInitializer(EventExecutorGroup execGroup, int pduTimeout) { this.execGroup = execGroup; this.pduTimeout = pduTimeout; } @Override protected void initChannel(SocketChannel ch) throws Exception { ChannelPipeline pipeline = ch.pipeline(); pipeline.addLast(new IdleStateHandler(this.pduTimeout, 0, 0, TimeUnit.SECONDS)); //pipeline.addLast(new LoggingHandler(LogLevel.DEBUG)); pipeline.addLast(new IMPacketEncoder()); pipeline.addLast(new IMPacketDecoder()); pipeline.addLast(new IMClientPacketHandler(execGroup)); } }
网络服务类
public class IMClientListenService implements InitializingBean, DisposableBean { private static final Logger logger = LoggerFactory.getLogger(IMClientListenService.class); @Value("${imcore.client.service.listen}") private String clientServiceListenAddress; @Value("${imcore.client.service.port}") private Integer clientServiceListenPort; @Value("${imcore.client.service.pdu.timeout}") private Integer clientServicePduTimeout; private EventLoopGroup bossEventLoopGroup; private EventLoopGroup childEventLoopGroup; private EventExecutorGroup eventExecutorGroup; private ServerBootstrap serverBootstrap; private Channel listenChannel; private final IMClientChannelManager imClientChannelManager = new IMClientChannelManager(); public IMClientChannelManager getImClientChannelManager() { return imClientChannelManager; } @Override public void afterPropertiesSet() { eventExecutorGroup = new DefaultEventExecutorGroup(128); bossEventLoopGroup = new NioEventLoopGroup(); childEventLoopGroup = new NioEventLoopGroup(); serverBootstrap = new ServerBootstrap(); serverBootstrap.group(bossEventLoopGroup, childEventLoopGroup); serverBootstrap.channel(NioServerSocketChannel.class); serverBootstrap.option(ChannelOption.SO_BACKLOG, 128); serverBootstrap.childHandler(new IMClientServerInitializer(eventExecutorGroup, clientServicePduTimeout)); } public void destroy() { logger.info("IMClientListenService destroy called"); } public void run() { try { listenChannel = serverBootstrap.bind(clientServiceListenPort).sync().channel(); logger.info("Client Listen Service started at port: " + clientServiceListenPort); listenChannel.closeFuture().sync(); } catch (InterruptedException e) { e.printStackTrace(); } } public void shutdown() { try { // // 先关闭侦听端口 // logger.info("close listen channel..."); ChannelFuture closeFuture = listenChannel.close(); closeFuture.sync(); logger.info("close listen channel...done!"); // // 再关闭所有客户端的连接 // List<ChannelHandlerContext> channels = imClientChannelManager.getAllChannels(); for (ChannelHandlerContext channel : channels) { channel.close().sync(); } logger.info("Client Listen Service stopped"); } catch (Exception ex) { logger.error("Client Listen Service close failed", ex); } finally { // // 最后关闭所有线程池 // childEventLoopGroup.shutdownGracefully(); bossEventLoopGroup.shutdownGracefully(); eventExecutorGroup.shutdownGracefully(); } } }
网络数据包处理Handler类
public class IMClientPacketHandler extends SimpleChannelInboundHandler<IMPacket> { private static final int NEED_LOGIN_FLAG = 1; private static final Logger logger = LoggerFactory.getLogger(IMClientPacketHandler.class); private final EventExecutorGroup eventExecutor; private final IMClientChannelManager imClientChannelManager; private final IMClientListenService imClientListenService; private int userId; private String loginName; ... public IMClientPacketHandler(EventExecutorGroup eventExecutor) { this.eventExecutor = eventExecutor; this.imClientListenService = Application.getInstance().getBean(IMClientListenService.class); this.imClientChannelManager = imClientListenService.getImClientChannelManager(); } @Override public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception { logger.error("ImPacketHandler exception caught, closing..."); if (cause != null) { logger.error(cause.getMessage(), cause); } else { logger.error("exception object is null"); } ctx.close(); this.imClientChannelManager.removeChannel(ctx); } @Override public void channelActive(ChannelHandlerContext ctx) throws Exception { super.channelActive(ctx); InetSocketAddress socketAddress = (InetSocketAddress)(ctx.channel().remoteAddress()); this.clientIP = socketAddress.getAddress().getHostAddress(); this.imClientChannelManager.addChannel(ctx); } @Override public void channelInactive(ChannelHandlerContext ctx) throws Exception { this.imClientChannelManager.removeChannel(ctx); if (this.userId != 0 && this.terminal != 0) { this.imClientChannelManager.removeLoginChannel(ctx, this.userId, this.terminal); } super.channelInactive(ctx); this.userId = 0; this.loginName = null; ... } @Override public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception { if (logger.isDebugEnabled()) { logger.debug("userEventTriggered:" + evt); } if (evt instanceof IdleStateEvent) { // 如果是长时间没有write事件，则尝试去从队列里拿出通知来发送 IdleStateEvent e = (IdleStateEvent) evt; if (e.state() == IdleState.READER_IDLE) { // close the channel ctx.close(); return; } } else if (evt instanceof IMUserLoginEvent) { logger.info("user login event thread id " + Thread.currentThread().getId()); IMUserLoginEvent loginEvent = (IMUserLoginEvent)evt; if (loginEvent.isSucceed()) { this.userId = loginEvent.getUserInfo().getUserId(); this.loginName = loginEvent.getUserInfo().getLoginName(); ... if (logger.isDebugEnabled()) { logger.debug("set login succeed in channel handler for user ‘" + this.loginName + "‘ with session ‘" + this.sessionKey + "‘"); } this.imClientChannelManager.addLoginChannel(ctx, this.userId, this.terminal); } } super.userEventTriggered(ctx, evt); } @Override protected void channelRead0(ChannelHandlerContext ctx, IMPacket msg) throws Exception { if (this.loginName == null && this.userId == 0) { if (msg.getCommandId() == IMBaseDefine.LoginCmdID.CID_USER_LOGIN_REQ_VALUE) { handleUserLoginRequest(ctx, msg); } else { // 如果未登录的情况下发送其他所有非登录命令，一律返回flag为1的响应头 IMPacket packet = new IMPacket(NEED_LOGIN_FLAG, null); ctx.channel().write(packet).addListener(ChannelFutureListener.CLOSE); } } else { if (msg.getCommandId() == IMBaseDefine.LoginCmdID.CID_USER_LOGIN_REQ_VALUE) { // 如果已登录的情况下发送登录命令，则返回 ERR_ALREADY_LOGGIN_VALUE 登录错误 IMLogin.IMLoginRsp.Builder loginRespBuilder = IMLogin.IMLoginRsp.newBuilder() .setErrorCode(IMBaseDefine.CommonErrors.ERR_DUPLICATE_LOGIN_VALUE) .setErrorMsg("duplicate login")); IMPacket packet = new IMPacket(loginRespBuilder.build().toByteArray()); ctx.channel().write(packet).addListener(ChannelFutureListener.CLOSE); } else { switch (msg.getCommandId()) { case IMBaseDefine.OtherCmdID.CID_OTHER_HEARTBEAT_VALUE: handleHeartbeatRequest(ctx, msg); break; case IMBaseDefine.LoginCmdID.CID_USER_LOGOUT_REQ_VALUE: handleUserLogoutRequest(ctx, msg); break; // 创建群聊 case IMBaseDefine.GroupCmdID.CID_GROUP_CREATE_REQ_VALUE: handleGroupCreateRequest(ctx, msg); break; ... default: logger.warn("unsupported command: " + msg.getCommandId()); break; } } } } private void handleUserLoginRequest(ChannelHandlerContext ctx, IMPacket msg) { if (logger.isDebugEnabled()) { logger.debug("user login received thread id " + Thread.currentThread().getId()); } TaskContext taskContext = new TaskContext(ctx, clientIP, userId, loginName, clientType, sessionKey, pushToken); try { UserLoginTask userLoginTask = new UserLoginTask(taskContext, msg); eventExecutor.submit(userLoginTask); } catch (CreateTaskException ex) { logger.error("create user login task failed", ex); } } private void handleHeartbeatRequest(ChannelHandlerContext ctx, IMPacket msg) { if (logger.isDebugEnabled()) { logger.debug("heartbeat received"); } TaskContext taskContext = new TaskContext(ctx, clientIP, userId, loginName, clientType, sessionKey, pushToken); try { HeartbeatTask heartbeatTask = new HeartbeatTask(taskContext, msg); eventExecutor.submit(heartbeatTask); } catch (CreateTaskException ex) { logger.error("create heartbeat task failed", ex); } } private void handleUserLogoutRequest(ChannelHandlerContext ctx, IMPacket msg) { if (logger.isDebugEnabled()) { logger.debug("session logout received"); } TaskContext taskContext = new TaskContext(ctx, clientIP, userId, loginName, clientType, sessionKey, pushToken); try { UserLogoutTask userLogoutTask = new UserLogoutTask(taskContext, msg); eventExecutor.submit(userLogoutTask); } catch (CreateTaskException ex) { logger.error("create logout task failed", ex); } } private void handleGroupCreateRequest(ChannelHandlerContext ctx, IMPacket msg) { if (logger.isDebugEnabled()) { logger.debug("group creation received"); } TaskContext taskContext = new TaskContext(ctx, clientIP, userId, loginName, clientType, sessionKey, pushToken); try { GroupCreationTask groupCreationTask = new GroupCreationTask(taskContext, msg); eventExecutor.submit(groupCreationTask); } catch (CreateTaskException ex) { logger.error("create group creation task failed", ex); } } }
用户登录Task类
/** * Task executed in thread pool for user login */ public class UserLoginTask extends TaskBase { private static final Logger logger = LoggerFactory.getLogger(UserLoginTask.class); private final IMPacket request; private final IMLogin.IMLoginReq reqBody; private final IMUserService userService; private int errorCode; private String errorMessage; public UserLoginTask(TaskContext taskContext, IMPacket request) throws CreateTaskException { super(taskContext); this.request = request; try { this.reqBody = IMLogin.IMLoginReq.parseFrom(request.getPayload()); } catch (InvalidProtocolBufferException e) { throw new CreateTaskException("parse pb failed", e); } this.userService = Application.getInstance().getBean(IMUserService.class); } @Override protected void taskRun() { this.errorCode = 0; this.errorMessage = "ok"; IMUserRecord user = userService.findUserByLoginName(reqBody.getUserName()); if (user == null) { this.errorCode = IMBaseDefine.CommonErrors.ERR_USERNAME_OR_PASSWD_INVALID_VALUE; this.errorMessage = "bad username or password"; handleErrorResponse(); return; } if (!user.getPassword().equals(reqBody.getPassword())) { this.errorCode = IMBaseDefine.CommonErrors.ERR_USERNAME_OR_PASSWD_INVALID_VALUE; this.errorMessage = "bad username or password"; handleErrorResponse(); return; } handleSucceedResponse(user); return; } private void handleErrorResponse() { logger.error("user ‘" + reqBody.getUserName() + "‘ login failed with code " + this.errorCode + " ‘" + this.errorMessage + "‘"); IMLogin.IMLoginRsp.Builder loginResp = IMLogin.IMLoginRsp.newBuilder() .setErrorCode(this.errorCode) .setErrorMsg(this.errorMessage); IMPacket packetResp = new IMPacket(loginResp.build().toByteArray()); getContext().getChannelContext().writeAndFlush(packetResp); } private void handleSucceedResponse(IMUserRecord user) { IMLogin.IMLoginRsp.Builder loginResp = IMLogin.IMLoginRsp.newBuilder() .setErrorCode(0) .setErrorMsg("succeed") .setUserInfo(IMUserProtobufUtils.toProtobuf(user)); IMPacket packetResp = new IMPacket(loginResp.build().toByteArray()); getContext().getChannelContext().writeAndFlush(packetResp); // ??触发 user event 通知 IO 线程：我们可以异步的改变相关 pipeline 的状态 IMUserLoginEvent event = new IMUserLoginEvent(); event.setSucceed(true); event.setUserInfo(user); getContext().getChannelContext().pipeline().fireUserEventTriggered(event); } }
踩过的一个坑备注一下：
之前使用ChannelHandlerContext向客户端写数据的时候，都是这样子的：
getContext().getChannelContext().write(packetResp);
写完之后，发现有概率性的客户端收不到响应包，原来是写完数据，还需要flush一下：
getContext().getChannelContext().writeAndFlush(packetResp);
这样子就没有问题了。
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本人在企业做过五年的即时聊天系统开发，关注这一块开发的同学，可以一起探讨。
另外，本人独自开发了一套安聊系统，感兴趣的同学可以去下载demo试用一下：安聊系统1.0发布