Seata服务端的启动过程学习记录

1.ServerRunner

ServerRunner类实现了CommandLineRunner与DisposableBean接口，将会在Spring容器启动和关闭的时间，分别执行

run 和 destory 方法。

而seata服务端的启动过程，都藏在run方法中

2.整体流程

io.seata.server.Server#start

 public static void start(String[] args) {// create loggerfinal Logger logger = LoggerFactory.getLogger(Server.class);//initialize the parameter parser//Note that the parameter parser should always be the first line to execute.//Because, here we need to parse the parameters needed for startup.//1.解析配置文件ParameterParser parameterParser = new ParameterParser(args);//2.初始化监控MetricsManager.get().init();System.setProperty(ConfigurationKeys.STORE_MODE, parameterParser.getStoreMode());ThreadPoolExecutor workingThreads = new ThreadPoolExecutor(NettyServerConfig.getMinServerPoolSize(),NettyServerConfig.getMaxServerPoolSize(), NettyServerConfig.getKeepAliveTime(), TimeUnit.SECONDS,new LinkedBlockingQueue<>(NettyServerConfig.getMaxTaskQueueSize()),new NamedThreadFactory("ServerHandlerThread", NettyServerConfig.getMaxServerPoolSize()), new ThreadPoolExecutor.CallerRunsPolicy());//3.创建netty用于服务端TC与客户端TM，RM通信NettyRemotingServer nettyRemotingServer = new NettyRemotingServer(workingThreads);//4.初始化UUID生成器（雪花算法），用于生成全局事务与分支事务idUUIDGenerator.init(parameterParser.getServerNode());//log store mode : file, db, redis//5.设置全局事务与分支事务持久化的三种方式SessionHolder.init(parameterParser.getSessionStoreMode());LockerManagerFactory.init(parameterParser.getLockStoreMode());//6.创建并初始化事务协调者 并绑定到NettyRemotingServer到TransactionMessageHandler，监听事务消息并处理DefaultCoordinator coordinator = DefaultCoordinator.getInstance(nettyRemotingServer);coordinator.init();nettyRemotingServer.setHandler(coordinator);//7.注册销毁事件// let ServerRunner do destroy instead ShutdownHook, see https://github.com/seata/seata/issues/4028ServerRunner.addDisposable(coordinator);//127.0.0.1 and 0.0.0.0 are not valid here.if (NetUtil.isValidIp(parameterParser.getHost(), false)) {XID.setIpAddress(parameterParser.getHost());} else {String preferredNetworks = ConfigurationFactory.getInstance().getConfig(REGISTRY_PREFERED_NETWORKS);if (StringUtils.isNotBlank(preferredNetworks)) {XID.setIpAddress(NetUtil.getLocalIp(preferredNetworks.split(REGEX_SPLIT_CHAR)));} else {XID.setIpAddress(NetUtil.getLocalIp());}}//8.启动nettyRemotingServernettyRemotingServer.init();}

1.解析配置文件

主要从三处地方获取配置

启动命令中

解析启动命令使用的是JCommander，主要有以下的命令
1. help 打印帮助信息
2. –host -h ：设置注册中心ip
3. “–port”, “-p” ：设置注册中心端口
4. “–storeMode”, “-m” ：设置日志存储模式
5. “–serverNode”, “-n” ：设置服务节点
6. “–seataEnv”, “-e” ： seata环境设置
7. “–sessionStoreMode”, “-ssm” ：设置会话存储模式，主要有三种文件，数据库，redis
8. “–lockStoreMode”, “-lsm” ：设置锁信息的存储，主要有三种文件，数据库，redis
容器中

配置中心或者文件中

  private void init(String[] args) {try {//从命令行中获取配置信息getCommandParameters(args);//从环境（容器中）获取配置信息getEnvParameters();if (StringUtils.isNotBlank(seataEnv)) {System.setProperty(ENV_PROPERTY_KEY, seataEnv);}//从文件中获取配置信息if (StringUtils.isBlank(storeMode)) {storeMode = CONFIG.getConfig(ConfigurationKeys.STORE_MODE, SERVER_DEFAULT_STORE_MODE);}if (StringUtils.isBlank(sessionStoreMode)) {sessionStoreMode = CONFIG.getConfig(ConfigurationKeys.STORE_SESSION_MODE, storeMode);}if (StringUtils.isBlank(lockStoreMode)) {lockStoreMode = CONFIG.getConfig(ConfigurationKeys.STORE_LOCK_MODE, storeMode);}} catch (ParameterException e) {printError(e);}}

2. 初始化监控信息

MetricsManager.get().init();

默认是关闭的

3.创建netty用于服务端TC与客户端TM，RM通信

 ThreadPoolExecutor workingThreads = new ThreadPoolExecutor(NettyServerConfig.getMinServerPoolSize(),NettyServerConfig.getMaxServerPoolSize(), NettyServerConfig.getKeepAliveTime(), TimeUnit.SECONDS,new LinkedBlockingQueue<>(NettyServerConfig.getMaxTaskQueueSize()),new NamedThreadFactory("ServerHandlerThread", NettyServerConfig.getMaxServerPoolSize()), new ThreadPoolExecutor.CallerRunsPolicy());//3.创建netty用于服务端TC与客户端TM，RM通信NettyRemotingServer nettyRemotingServer = new NettyRemotingServer(workingThreads);

父抽象类 AbstractNettyRemotingServer 中设置消息处理器

 public AbstractNettyRemotingServer(ThreadPoolExecutor messageExecutor, NettyServerConfig nettyServerConfig) {super(messageExecutor);serverBootstrap = new NettyServerBootstrap(nettyServerConfig);serverBootstrap.setChannelHandlers(new ServerHandler());}

4.初始化UUID生成器（雪花算法），用于生成全局事务与分支事务id

      //4.初始化UUID生成器（雪花算法），用于生成全局事务与分支事务idUUIDGenerator.init(parameterParser.getServerNode());

5.初始化SessionManager与LockManager，管理会话与锁信息

SessionHolder.init(parameterParser.getSessionStoreMode());LockerManagerFactory.init(parameterParser.getLockStoreMode());

SessionManager有三个不同的实现，通过SPI机制加载

io.seata.server.storage.file.session.FileSessionManager
io.seata.server.storage.db.session.DataBaseSessionManager
io.seata.server.storage.redis.session.RedisSessionManager

resource下的META-INF文件夹中的service文件，根据要加载类的权限定类名找对应的文件，文件中存放着对应需要加载的类的权限定类型

io.seata.server.session.SessionHolder#init

public static void init(String mode) {if (StringUtils.isBlank(mode)) {mode = CONFIG.getConfig(ConfigurationKeys.STORE_SESSION_MODE,CONFIG.getConfig(ConfigurationKeys.STORE_MODE, SERVER_DEFAULT_STORE_MODE));}StoreMode storeMode = StoreMode.get(mode);if (StoreMode.DB.equals(storeMode)) {ROOT_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class, StoreMode.DB.getName());ASYNC_COMMITTING_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class, StoreMode.DB.getName(),new Object[]{ASYNC_COMMITTING_SESSION_MANAGER_NAME});RETRY_COMMITTING_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class, StoreMode.DB.getName(),new Object[]{RETRY_COMMITTING_SESSION_MANAGER_NAME});RETRY_ROLLBACKING_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class, StoreMode.DB.getName(),new Object[]{RETRY_ROLLBACKING_SESSION_MANAGER_NAME});DISTRIBUTED_LOCKER = DistributedLockerFactory.getDistributedLocker(StoreMode.DB.getName());} else if (StoreMode.FILE.equals(storeMode)) {String sessionStorePath = CONFIG.getConfig(ConfigurationKeys.STORE_FILE_DIR,DEFAULT_SESSION_STORE_FILE_DIR);if (StringUtils.isBlank(sessionStorePath)) {throw new StoreException("the {store.file.dir} is empty.");}ROOT_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class, StoreMode.FILE.getName(),new Object[]{ROOT_SESSION_MANAGER_NAME, sessionStorePath});ASYNC_COMMITTING_SESSION_MANAGER = ROOT_SESSION_MANAGER;RETRY_COMMITTING_SESSION_MANAGER = ROOT_SESSION_MANAGER;RETRY_ROLLBACKING_SESSION_MANAGER = ROOT_SESSION_MANAGER;DISTRIBUTED_LOCKER = DistributedLockerFactory.getDistributedLocker(StoreMode.FILE.getName());} else if (StoreMode.REDIS.equals(storeMode)) {ROOT_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class, StoreMode.REDIS.getName());ASYNC_COMMITTING_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class,StoreMode.REDIS.getName(), new Object[]{ASYNC_COMMITTING_SESSION_MANAGER_NAME});RETRY_COMMITTING_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class,StoreMode.REDIS.getName(), new Object[]{RETRY_COMMITTING_SESSION_MANAGER_NAME});RETRY_ROLLBACKING_SESSION_MANAGER = EnhancedServiceLoader.load(SessionManager.class,StoreMode.REDIS.getName(), new Object[]{RETRY_ROLLBACKING_SESSION_MANAGER_NAME});DISTRIBUTED_LOCKER = DistributedLockerFactory.getDistributedLocker(StoreMode.REDIS.getName());} else {// unknown storethrow new IllegalArgumentException("unknown store mode:" + mode);}reload(storeMode);}

EnhancedServiceLoader.load(SessionManager.class, xxxName）;

通过SPI机制获取所有需要装配的类后，通过参数二最终选择某一个类

@LoadLevel(name = "db", scope = Scope.PROTOTYPE)
public class DataBaseSessionManager extends AbstractSessionManager

@LoadLevel(name = "file", scope = Scope.PROTOTYPE)
public class FileSessionManager extends AbstractSessionManager implements Reloadable {

@LoadLevel(name = "redis", scope = Scope.PROTOTYPE)
public class RedisSessionManager extends AbstractSessionManager

除了META-INF/services/ 路径，还会找 META-INF/seata/路径下

io.seata.common.loader.EnhancedServiceLoader.InnerEnhancedServiceLoader#findAllExtensionDefinition

LockManager同样也有三个实现类，也是通过SPI机制加载

io.seata.server.storage.db.lock.DataBaseLockManager
io.seata.server.storage.file.lock.FileLockManager
io.seata.server.storage.redis.lock.RedisLockManager

6.创建并初始化事务协调者 DefaultCoordinator 并监听事务消息并处理

创建DefaultCoordinator实列

实列 DefaultCoordinator最重要的就是给两个属性赋值

remotingServer
core

remotingServer是用来TC与TM，RM通信的，而core则是真正的事务协调者（TC）

core的coreMap属性将缓存4个实现类，对应seata的四种模式，XA，AT，TCC，SAGA，实现类同样也是通过SPI机制加载，并在完成加载后缓存到coreMap中

key为枚举类BranchType到值，value为SPI加载到对应类

io.seata.server.coordinator.DefaultCore#DefaultCore

DefaultCoordinator 初始化

初始化即启动5个周期线程

			//周期重试回滚事务retryRollbacking.scheduleAtFixedRate(() -> SessionHolder.distributedLockAndExecute(RETRY_ROLLBACKING, this::handleRetryRollbacking), 0,ROLLBACKING_RETRY_PERIOD, TimeUnit.MILLISECONDS);//周期重试提交事务retryCommitting.scheduleAtFixedRate(() -> SessionHolder.distributedLockAndExecute(RETRY_COMMITTING, this::handleRetryCommitting), 0,COMMITTING_RETRY_PERIOD, TimeUnit.MILLISECONDS);//周期异步提交事务asyncCommitting.scheduleAtFixedRate(() -> SessionHolder.distributedLockAndExecute(ASYNC_COMMITTING, this::handleAsyncCommitting), 0,ASYNC_COMMITTING_RETRY_PERIOD, TimeUnit.MILLISECONDS);//周期超时检测timeoutCheck.scheduleAtFixedRate(() -> SessionHolder.distributedLockAndExecute(TX_TIMEOUT_CHECK, this::timeoutCheck), 0,TIMEOUT_RETRY_PERIOD, TimeUnit.MILLISECONDS);//周期清理回滚日志undoLogDelete.scheduleAtFixedRate(() -> SessionHolder.distributedLockAndExecute(UNDOLOG_DELETE, this::undoLogDelete),UNDO_LOG_DELAY_DELETE_PERIOD, UNDO_LOG_DELETE_PERIOD, TimeUnit.MILLISECONDS);

每个线程池的任务逻辑基本都是一样的，只不过针对不同的事务状态

 protected void handleRetryRollbacking() {//条件对象，只处理对应状态的事务会话SessionCondition sessionCondition = new SessionCondition(rollbackingStatuses);sessionCondition.setLazyLoadBranch(true);//查找所有的全局会话 如果当前事务会话持久方式是DB，则从表中条件查找Collection<GlobalSession> rollbackingSessions =SessionHolder.getRetryRollbackingSessionManager().findGlobalSessions(sessionCondition);//如果为空，表示当前没有事务，则直接返回if (CollectionUtils.isEmpty(rollbackingSessions)) {return;}long now = System.currentTimeMillis();//遍历所有的事务会话SessionHelper.forEach(rollbackingSessions, rollbackingSession -> {try {//如果是正在回滚中的或者已经死亡的事务会话，跳过// prevent repeated rollbackif (rollbackingSession.getStatus().equals(GlobalStatus.Rollbacking)&& !rollbackingSession.isDeadSession()) {// The function of this 'return' is 'continue'.return;}//如果超时if (isRetryTimeout(now, MAX_ROLLBACK_RETRY_TIMEOUT.toMillis(), rollbackingSession.getBeginTime())) {//有锁则释放全局锁if (ROLLBACK_RETRY_TIMEOUT_UNLOCK_ENABLE) {rollbackingSession.clean();}//删除全局事务会话// Prevent thread safety issuesSessionHolder.getRetryRollbackingSessionManager().removeGlobalSession(rollbackingSession);LOGGER.error("Global transaction rollback retry timeout and has removed [{}]", rollbackingSession.getXid());SessionHelper.endRollbackFailed(rollbackingSession, true);// rollback retry timeout eventMetricsPublisher.postSessionDoneEvent(rollbackingSession, GlobalStatus.RollbackRetryTimeout, true, false);//The function of this 'return' is 'continue'.return;}rollbackingSession.addSessionLifecycleListener(SessionHolder.getRootSessionManager());//如果没有超时，执行回滚core.doGlobalRollback(rollbackingSession, true);} catch (TransactionException ex) {LOGGER.info("Failed to retry rollbacking [{}] {} {}", rollbackingSession.getXid(), ex.getCode(), ex.getMessage());}});}

nettyRemotingServer 通信服务类设置handler

将创建的TC绑定到nettyRemotingServer

7.注册销毁事件

        // let ServerRunner do destroy instead ShutdownHook, see https://github.com/seata/seata/issues/4028ServerRunner.addDisposable(coordinator);

将会在Sping容器关闭的时候调用coordinator的destory方法

    @Overridepublic void destroy() {// 1. first shutdown timed taskretryRollbacking.shutdown();retryCommitting.shutdown();asyncCommitting.shutdown();timeoutCheck.shutdown();undoLogDelete.shutdown();branchRemoveExecutor.shutdown();try {retryRollbacking.awaitTermination(TIMED_TASK_SHUTDOWN_MAX_WAIT_MILLS, TimeUnit.MILLISECONDS);retryCommitting.awaitTermination(TIMED_TASK_SHUTDOWN_MAX_WAIT_MILLS, TimeUnit.MILLISECONDS);asyncCommitting.awaitTermination(TIMED_TASK_SHUTDOWN_MAX_WAIT_MILLS, TimeUnit.MILLISECONDS);timeoutCheck.awaitTermination(TIMED_TASK_SHUTDOWN_MAX_WAIT_MILLS, TimeUnit.MILLISECONDS);undoLogDelete.awaitTermination(TIMED_TASK_SHUTDOWN_MAX_WAIT_MILLS, TimeUnit.MILLISECONDS);branchRemoveExecutor.awaitTermination(TIMED_TASK_SHUTDOWN_MAX_WAIT_MILLS, TimeUnit.MILLISECONDS);} catch (InterruptedException ignore) {}// 2. second close netty flowif (remotingServer instanceof NettyRemotingServer) {((NettyRemotingServer) remotingServer).destroy();}// 3. third destroy SessionHolderSessionHolder.destroy();instance = null;}

8.启动NettyRemotingServer，处理TM与RM消息

    @Overridepublic void init() {// registry processorregisterProcessor();if (initialized.compareAndSet(false, true)) {super.init();}}

registerProcessor 方法主要是注册一系列消息处理器

 private void registerProcessor() {// 1. registry on request message processorServerOnRequestProcessor onRequestProcessor =new ServerOnRequestProcessor(this, getHandler());ShutdownHook.getInstance().addDisposable(onRequestProcessor);super.registerProcessor(MessageType.TYPE_BRANCH_REGISTER, onRequestProcessor, messageExecutor);super.registerProcessor(MessageType.TYPE_BRANCH_STATUS_REPORT, onRequestProcessor, messageExecutor);super.registerProcessor(MessageType.TYPE_GLOBAL_BEGIN, onRequestProcessor, messageExecutor);super.registerProcessor(MessageType.TYPE_GLOBAL_COMMIT, onRequestProcessor, messageExecutor);super.registerProcessor(MessageType.TYPE_GLOBAL_LOCK_QUERY, onRequestProcessor, messageExecutor);super.registerProcessor(MessageType.TYPE_GLOBAL_REPORT, onRequestProcessor, messageExecutor);super.registerProcessor(MessageType.TYPE_GLOBAL_ROLLBACK, onRequestProcessor, messageExecutor);super.registerProcessor(MessageType.TYPE_GLOBAL_STATUS, onRequestProcessor, messageExecutor);super.registerProcessor(MessageType.TYPE_SEATA_MERGE, onRequestProcessor, messageExecutor);// 2. registry on response message processorServerOnResponseProcessor onResponseProcessor =new ServerOnResponseProcessor(getHandler(), getFutures());super.registerProcessor(MessageType.TYPE_BRANCH_COMMIT_RESULT, onResponseProcessor, branchResultMessageExecutor);super.registerProcessor(MessageType.TYPE_BRANCH_ROLLBACK_RESULT, onResponseProcessor, branchResultMessageExecutor);// 3. registry rm message processorRegRmProcessor regRmProcessor = new RegRmProcessor(this);super.registerProcessor(MessageType.TYPE_REG_RM, regRmProcessor, messageExecutor);// 4. registry tm message processorRegTmProcessor regTmProcessor = new RegTmProcessor(this);super.registerProcessor(MessageType.TYPE_REG_CLT, regTmProcessor, null);// 5. registry heartbeat message processorServerHeartbeatProcessor heartbeatMessageProcessor = new ServerHeartbeatProcessor(this);super.registerProcessor(MessageType.TYPE_HEARTBEAT_MSG, heartbeatMessageProcessor, null);}

调用 super.registerProcessor 方法将消息处理器与线程池封装成一个Pair，然后在放到map中，map的key为消息类型，value为Pair。

ServerOnRequestProcessor 的 transactionMessageHandler 成员变量为第6步创建的TC

super.init 方法则是启动netty

   @Overridepublic void init() {//启动超时检测super.init();//启动nettyserverBootstrap.start();}

 @Overridepublic void start() {this.serverBootstrap.group(this.eventLoopGroupBoss, this.eventLoopGroupWorker).channel(NettyServerConfig.SERVER_CHANNEL_CLAZZ).option(ChannelOption.SO_BACKLOG, nettyServerConfig.getSoBackLogSize()).option(ChannelOption.SO_REUSEADDR, true).childOption(ChannelOption.SO_KEEPALIVE, true).childOption(ChannelOption.TCP_NODELAY, true).childOption(ChannelOption.SO_SNDBUF, nettyServerConfig.getServerSocketSendBufSize()).childOption(ChannelOption.SO_RCVBUF, nettyServerConfig.getServerSocketResvBufSize()).childOption(ChannelOption.WRITE_BUFFER_WATER_MARK,new WriteBufferWaterMark(nettyServerConfig.getWriteBufferLowWaterMark(),nettyServerConfig.getWriteBufferHighWaterMark())).localAddress(new InetSocketAddress(getListenPort())).childHandler(new ChannelInitializer<SocketChannel>() {@Overridepublic void initChannel(SocketChannel ch) {ch.pipeline().addLast(new IdleStateHandler(nettyServerConfig.getChannelMaxReadIdleSeconds(), 0, 0)).addLast(new ProtocolV1Decoder()).addLast(new ProtocolV1Encoder());if (channelHandlers != null) {addChannelPipelineLast(ch, channelHandlers);}}});try {this.serverBootstrap.bind(getListenPort()).sync();XID.setPort(getListenPort());LOGGER.info("Server started, service listen port: {}", getListenPort());RegistryFactory.getInstance().register(new InetSocketAddress(XID.getIpAddress(), XID.getPort()));initialized.set(true);} catch (SocketException se) {throw new RuntimeException("Server start failed, the listen port: " + getListenPort(), se);} catch (Exception exx) {throw new RuntimeException("Server start failed", exx);}}

在第3步时，创建并设置了双向通道消息处理器 io.seata.core.rpc.netty.AbstractNettyRemotingServer.ServerHandler

 public AbstractNettyRemotingServer(ThreadPoolExecutor messageExecutor, NettyServerConfig nettyServerConfig) {super(messageExecutor);serverBootstrap = new NettyServerBootstrap(nettyServerConfig);serverBootstrap.setChannelHandlers(new ServerHandler());}

ChannelDuplexHandler是Netty框架中的一个双向通道处理器，用于处理网络通信中的读写事件。它继承自ChannelInboundHandler和ChannelOutboundHandler，可以同时处理入站和出站事件。

当通道中有消息时，将调用io.seata.core.rpc.netty.AbstractNettyRemotingServer.ServerHandler#channelRead方法

处理消息

    protected void processMessage(ChannelHandlerContext ctx, RpcMessage rpcMessage) throws Exception {if (LOGGER.isDebugEnabled()) {LOGGER.debug(String.format("%s msgId:%s, body:%s", this, rpcMessage.getId(), rpcMessage.getBody()));}Object body = rpcMessage.getBody();if (body instanceof MessageTypeAware) {MessageTypeAware messageTypeAware = (MessageTypeAware) body;//根据消息的类型，获取Pair，找到消息处理器final Pair<RemotingProcessor, ExecutorService> pair = this.processorTable.get((int) messageTypeAware.getTypeCode());if (pair != null) {if (pair.getSecond() != null) {try {pair.getSecond().execute(() -> {try {//处理消息pair.getFirst().process(ctx, rpcMessage);} catch (Throwable th) {LOGGER.error(FrameworkErrorCode.NetDispatch.getErrCode(), th.getMessage(), th);} finally {MDC.clear();}});} catch (RejectedExecutionException e) {LOGGER.error(FrameworkErrorCode.ThreadPoolFull.getErrCode(),"thread pool is full, current max pool size is " + messageExecutor.getActiveCount());if (allowDumpStack) {String name = ManagementFactory.getRuntimeMXBean().getName();String pid = name.split("@")[0];long idx = System.currentTimeMillis();try {String jstackFile = idx + ".log";LOGGER.info("jstack command will dump to " + jstackFile);Runtime.getRuntime().exec(String.format("jstack %s > %s", pid, jstackFile));} catch (IOException exx) {LOGGER.error(exx.getMessage());}allowDumpStack = false;}}} else {try {pair.getFirst().process(ctx, rpcMessage);} catch (Throwable th) {LOGGER.error(FrameworkErrorCode.NetDispatch.getErrCode(), th.getMessage(), th);}}} else {LOGGER.error("This message type [{}] has no processor.", messageTypeAware.getTypeCode());}} else {LOGGER.error("This rpcMessage body[{}] is not MessageTypeAware type.", body);}}

假设此次消息是TM开启全局事务的单条消息，则将交由ServerOnRequestProcessor处理,ServerOnRequestProcessor处理的消息类型如下

 * RM:* 1) {@link MergedWarpMessage}* 2) {@link BranchRegisterRequest}* 3) {@link BranchReportRequest}* 4) {@link GlobalLockQueryRequest}* TM:* 1) {@link MergedWarpMessage}* 2) {@link GlobalBeginRequest}* 3) {@link GlobalCommitRequest}* 4) {@link GlobalReportRequest}* 5) {@link GlobalRollbackRequest}* 6) {@link GlobalStatusRequest}

 @Overridepublic void process(ChannelHandlerContext ctx, RpcMessage rpcMessage) throws Exception {if (ChannelManager.isRegistered(ctx.channel())) {onRequestMessage(ctx, rpcMessage);} else {try {if (LOGGER.isInfoEnabled()) {LOGGER.info("closeChannelHandlerContext channel:" + ctx.channel());}ctx.disconnect();ctx.close();} catch (Exception exx) {LOGGER.error(exx.getMessage());}if (LOGGER.isInfoEnabled()) {LOGGER.info(String.format("close a unhandled connection! [%s]", ctx.channel().toString()));}}}

 private void onRequestMessage(ChannelHandlerContext ctx, RpcMessage rpcMessage) {Object message = rpcMessage.getBody();RpcContext rpcContext = ChannelManager.getContextFromIdentified(ctx.channel());if (LOGGER.isDebugEnabled()) {LOGGER.debug("server received:{},clientIp:{},vgroup:{}", message,NetUtil.toIpAddress(ctx.channel().remoteAddress()), rpcContext.getTransactionServiceGroup());} else {try {BatchLogHandler.INSTANCE.getLogQueue().put(message + ",clientIp:" + NetUtil.toIpAddress(ctx.channel().remoteAddress()) + ",vgroup:"+ rpcContext.getTransactionServiceGroup());} catch (InterruptedException e) {LOGGER.error("put message to logQueue error: {}", e.getMessage(), e);}}if (!(message instanceof AbstractMessage)) {return;}//处理多条消息// the batch send request messageif (message instanceof MergedWarpMessage) {if (NettyServerConfig.isEnableTcServerBatchSendResponse() && StringUtils.isNotBlank(rpcContext.getVersion())&& Version.isAboveOrEqualVersion150(rpcContext.getVersion())) {List<AbstractMessage> msgs = ((MergedWarpMessage)message).msgs;List<Integer> msgIds = ((MergedWarpMessage)message).msgIds;for (int i = 0; i < msgs.size(); i++) {AbstractMessage msg = msgs.get(i);int msgId = msgIds.get(i);if (PARALLEL_REQUEST_HANDLE) {CompletableFuture.runAsync(() -> handleRequestsByMergedWarpMessageBy150(msg, msgId, rpcMessage, ctx, rpcContext));} else {handleRequestsByMergedWarpMessageBy150(msg, msgId, rpcMessage, ctx, rpcContext);}}} else {List<AbstractResultMessage> results = new CopyOnWriteArrayList<>();List<CompletableFuture<Void>> completableFutures = null;for (int i = 0; i < ((MergedWarpMessage)message).msgs.size(); i++) {if (PARALLEL_REQUEST_HANDLE) {if (completableFutures == null) {completableFutures = new ArrayList<>();}int finalI = i;completableFutures.add(CompletableFuture.runAsync(() -> {results.add(finalI, handleRequestsByMergedWarpMessage(((MergedWarpMessage)message).msgs.get(finalI), rpcContext));}));} else {results.add(i,handleRequestsByMergedWarpMessage(((MergedWarpMessage)message).msgs.get(i), rpcContext));}}if (CollectionUtils.isNotEmpty(completableFutures)) {try {CompletableFuture.allOf(completableFutures.toArray(new CompletableFuture[0])).get();} catch (InterruptedException | ExecutionException e) {LOGGER.error("handle request error: {}", e.getMessage(), e);}}MergeResultMessage resultMessage = new MergeResultMessage();resultMessage.setMsgs(results.toArray(new AbstractResultMessage[0]));remotingServer.sendAsyncResponse(rpcMessage, ctx.channel(), resultMessage);}} else {//处理单条消息// the single send request messagefinal AbstractMessage msg = (AbstractMessage) message;AbstractResultMessage result = transactionMessageHandler.onRequest(msg, rpcContext);remotingServer.sendAsyncResponse(rpcMessage, ctx.channel(), result);}}

最终将调用io.seata.server.coordinator.DefaultCoordinator#doGlobalBegin

    @Overrideprotected void doGlobalBegin(GlobalBeginRequest request, GlobalBeginResponse response, RpcContext rpcContext)throws TransactionException {//获取全局事务id放入response中response.setXid(core.begin(rpcContext.getApplicationId(), rpcContext.getTransactionServiceGroup(),request.getTransactionName(), request.getTimeout()));if (LOGGER.isInfoEnabled()) {LOGGER.info("Begin new global transaction applicationId: {},transactionServiceGroup: {}, transactionName: {},timeout:{},xid:{}",rpcContext.getApplicationId(), rpcContext.getTransactionServiceGroup(), request.getTransactionName(), request.getTimeout(), response.getXid());}}

core.begin方法

    @Overridepublic String begin(String applicationId, String transactionServiceGroup, String name, int timeout)throws TransactionException {GlobalSession session = GlobalSession.createGlobalSession(applicationId, transactionServiceGroup, name,timeout);MDC.put(RootContext.MDC_KEY_XID, session.getXid());session.addSessionLifecycleListener(SessionHolder.getRootSessionManager());session.begin();// transaction start eventMetricsPublisher.postSessionDoingEvent(session, false);return session.getXid();}

    public GlobalSession(String applicationId, String transactionServiceGroup, String transactionName, int timeout, boolean lazyLoadBranch) {this.transactionId = UUIDGenerator.generateUUID();this.status = GlobalStatus.Begin;this.lazyLoadBranch = lazyLoadBranch;if (!lazyLoadBranch) {this.branchSessions = new ArrayList<>();}this.applicationId = applicationId;this.transactionServiceGroup = transactionServiceGroup;this.transactionName = transactionName;this.timeout = timeout;this.xid = XID.generateXID(transactionId);}

首先通过雪花算法生成事务id，然后调用 XID.generateXID(transactionId)

最终格式为 ip：端口号：事务id

public static String generateXID(long tranId) {return new StringBuilder().append(ipAddress).append(IP_PORT_SPLIT_CHAR).append(port).append(IP_PORT_SPLIT_CHAR).append(tranId).toString();}

【大部分内容来源于https://saint.blog.csdn.net/article/details/126457129。推荐各位学习seata的朋友看一看】