【Seata源码学习 】篇三 seata客户端全局事务开启、提交与回滚

2023-12-28 12:40:40

1.GlobalTransactionalInterceptor 对事务方法对增强

我们已经知道 GlobalTransactionScanner 会给bean的类或方法上面标注有@GlobalTransactional 注解 和 @GlobalLock的 添加一个 advisor (DefaultPointcutAdvisor ,advisor = 绑定了PointCut 的 advise)

而此处的 DefaultPointcutAdvisor 的 advice 为 GlobalTransactionalInterceptor,PointCut 为 Pointcut.TRUE(匹配所有方法)

然后由 DynamicAdvisedInterceptor 回调函数 获取当前 bean对应的 AdvisedSupport , 从中遍历所有的 advisor,然后再获取 此 advisor 绑定的 PointCut 对目标方法进行匹配 ,如果满足,则添加到 拦截器链路中,后续递归调用

接下来我们看下 GlobalTransactionalInterceptor 对目标方法做了哪些增强

io.seata.spring.annotation.GlobalTransactionalInterceptor#invoke

 public Object invoke(final MethodInvocation methodInvocation) throws Throwable {
        Class<?> targetClass =
            methodInvocation.getThis() != null ? AopUtils.getTargetClass(methodInvocation.getThis()) : null;
        Method specificMethod = ClassUtils.getMostSpecificMethod(methodInvocation.getMethod(), targetClass);
        // Method.getDeclaringClass 获取方法声明的类 如果是静态方法,则返回方法所在类;如果是实例方法,则返回方法所在类的超类
        //!specificMethod.getDeclaringClass().equals(Object.class) 排除Object方法
        if (specificMethod != null && !specificMethod.getDeclaringClass().equals(Object.class)) {
            final Method method = BridgeMethodResolver.findBridgedMethod(specificMethod);
            //默认包装生成的DefaultPointcutAdvisor 拦截所有的方法
            // public DefaultPointcutAdvisor(Advice advice) {
            //		this(Pointcut.TRUE, advice);
            //	}
            //因此在此处对方法进行过滤  只处理标注了@GlobalTransactional 和 @GlobalLock 注解的方法
            final GlobalTransactional globalTransactionalAnnotation =
                getAnnotation(method, targetClass, GlobalTransactional.class);
            final GlobalLock globalLockAnnotation = getAnnotation(method, targetClass, GlobalLock.class);
            boolean localDisable = disable || (degradeCheck && degradeNum >= degradeCheckAllowTimes);
            if (!localDisable) {
                if (globalTransactionalAnnotation != null || this.aspectTransactional != null) {
                    //根据@GlobalTransactional 注解的属性封装事务切面信息
                    AspectTransactional transactional;
                    if (globalTransactionalAnnotation != null) {
                        transactional = new AspectTransactional(globalTransactionalAnnotation.timeoutMills(),
                            globalTransactionalAnnotation.name(), globalTransactionalAnnotation.rollbackFor(),
                            globalTransactionalAnnotation.rollbackForClassName(),
                            globalTransactionalAnnotation.noRollbackFor(),
                            globalTransactionalAnnotation.noRollbackForClassName(),
                            globalTransactionalAnnotation.propagation(),
                            globalTransactionalAnnotation.lockRetryInterval(),
                            globalTransactionalAnnotation.lockRetryTimes());
                    } else {
                        transactional = this.aspectTransactional;
                    }
                    //处理全局事务
                    return handleGlobalTransaction(methodInvocation, transactional);
                } else if (globalLockAnnotation != null) {
                    //处理全局锁
                    return handleGlobalLock(methodInvocation, globalLockAnnotation);
                }
            }
        }
        return methodInvocation.proceed();
    }

2.全局事务执行器 TransactionalExecutor 的匿名实现

io.seata.spring.annotation.GlobalTransactionalInterceptor#handleGlobalTransaction

  Object handleGlobalTransaction(final MethodInvocation methodInvocation,
        final AspectTransactional aspectTransactional) throws Throwable {
        boolean succeed = true;
        try {
            return transactionalTemplate.execute(new TransactionalExecutor() {
                @Override
                public Object execute() throws Throwable {
    								// 责任链模式 继续执行链路上的其他拦截器方法,如果已经执行到最后一个
    								// 则直接执行目标方法
                    return methodInvocation.proceed();
                }

                public String name() {
                    String name = aspectTransactional.getName();
                    if (!StringUtils.isNullOrEmpty(name)) {
                        return name;
                    }
                    return formatMethod(methodInvocation.getMethod());
                }

                @Override
                public TransactionInfo getTransactionInfo() {
                    //注解解析
                    // reset the value of timeout
                    int timeout = aspectTransactional.getTimeoutMills();
                    if (timeout <= 0 || timeout == DEFAULT_GLOBAL_TRANSACTION_TIMEOUT) {
                        timeout = defaultGlobalTransactionTimeout;
                    }

                    TransactionInfo transactionInfo = new TransactionInfo();
                    transactionInfo.setTimeOut(timeout);
                    transactionInfo.setName(name());
                    transactionInfo.setPropagation(aspectTransactional.getPropagation());
                    transactionInfo.setLockRetryInterval(aspectTransactional.getLockRetryInterval());
                    transactionInfo.setLockRetryTimes(aspectTransactional.getLockRetryTimes());
                    Set<RollbackRule> rollbackRules = new LinkedHashSet<>();
                    for (Class<?> rbRule : aspectTransactional.getRollbackFor()) {
                        rollbackRules.add(new RollbackRule(rbRule));
                    }
                    for (String rbRule : aspectTransactional.getRollbackForClassName()) {
                        rollbackRules.add(new RollbackRule(rbRule));
                    }
                    for (Class<?> rbRule : aspectTransactional.getNoRollbackFor()) {
                        rollbackRules.add(new NoRollbackRule(rbRule));
                    }
                    for (String rbRule : aspectTransactional.getNoRollbackForClassName()) {
                        rollbackRules.add(new NoRollbackRule(rbRule));
                    }
                    transactionInfo.setRollbackRules(rollbackRules);
                    return transactionInfo;
                }
            });
        } catch (TransactionalExecutor.ExecutionException e) {
            TransactionalExecutor.Code code = e.getCode();
            //根据异常类型执行不同的钩子方法
            switch (code) {
                case RollbackDone:
                    throw e.getOriginalException();
                case BeginFailure:
                    succeed = false;
                    failureHandler.onBeginFailure(e.getTransaction(), e.getCause());
                    throw e.getCause();
                case CommitFailure:
                    succeed = false;
                    failureHandler.onCommitFailure(e.getTransaction(), e.getCause());
                    throw e.getCause();
                case RollbackFailure:
                    failureHandler.onRollbackFailure(e.getTransaction(), e.getOriginalException());
                    throw e.getOriginalException();
                case RollbackRetrying:
                    failureHandler.onRollbackRetrying(e.getTransaction(), e.getOriginalException());
                    throw e.getOriginalException();
                default:
                    throw new ShouldNeverHappenException(String.format("Unknown TransactionalExecutor.Code: %s", code));
            }
        } finally {
            if (degradeCheck) {
                EVENT_BUS.post(new DegradeCheckEvent(succeed));
            }
        }
    }

将事务参数信息封装到TransactionInfo对象中,如事务传播行为,超时时间,超时重试次数,异常回滚类型等等,

如果出现异常,则根据异常类型分别执行不同的钩子方法

并且会继续回调拦截器链路上的其他拦截器方法

3.TransactionalTemplate 全局事务执行过程的模版方法

io.seata.tm.api.TransactionalTemplate#execute

public Object execute(TransactionalExecutor business) throws Throwable {
        // 1. Get transactionInfo
        //获取@GlobalTransation注解的属性封装的TransactionInfo
        TransactionInfo txInfo = business.getTransactionInfo();
        if (txInfo == null) {
            throw new ShouldNeverHappenException("transactionInfo does not exist");
        }
        // 1.1 Get current transaction, if not null, the tx role is 'GlobalTransactionRole.Participant'.
        // GlobalTransactionContext 全局事务上下文对象 用于创建一个新事务,或者获取当前事务
        // GlobalTransactionContext.getCurrent - > RootContext.getXID -> ContextCore.get
        // ContextCore 是一个接口 seata有两个实现  FastThreadLocalContextCore  ThreadLocalContextCore 都是基于ThreadLocal存储XID
        GlobalTransaction tx = GlobalTransactionContext.getCurrent();

        // 1.2 Handle the transaction propagation.
        // 获取当前事务的传播行为
        Propagation propagation = txInfo.getPropagation();
        // 用于存储被挂起的事务XID
        SuspendedResourcesHolder suspendedResourcesHolder = null;
        try {
            //处理事务的传播行为
            switch (propagation) {
                //如果当前事务的传播行为是 NOT_SUPPORTED 则以非事务的方式执行调用methodInvocation.proceed()
                // 如果当前拦截器不为拦截链的最后一个,则将获取下一个拦截器执行invoke方法,如果是最后一个,则直接执行目标方法
                case NOT_SUPPORTED:
                    // If transaction is existing, suspend it.
                    //如果当前存在全局事务,则挂起当前事务
                    if (existingTransaction(tx)) {
                        suspendedResourcesHolder = tx.suspend();
                    }
                    // Execute without transaction and return.
                    // 继续执行拦截器链
                    return business.execute();
                case REQUIRES_NEW:
                    // If transaction is existing, suspend it, and then begin new transaction.
                    // 如果当前存在事务 则挂起当前事务 并创建一个新的事务
                    if (existingTransaction(tx)) {
                        suspendedResourcesHolder = tx.suspend();
                        tx = GlobalTransactionContext.createNew();
                    }
                    // Continue and execute with new transaction
                    break;
                case SUPPORTS:
                    // If transaction is not existing, execute without transaction.
                    // 如果不存在事务 则跳过当前事务拦截器 执行拦截器链并返回
                    if (notExistingTransaction(tx)) {
                        return business.execute();
                    }
                    // Continue and execute with new transaction
                    break;
                case REQUIRED:
                    // If current transaction is existing, execute with current transaction,
                    // else continue and execute with new transaction.
                    break;
                case NEVER:
                    // If transaction is existing, throw exception.
                    // 有事务抛出异常
                    if (existingTransaction(tx)) {
                        throw new TransactionException(
                            String.format("Existing transaction found for transaction marked with propagation 'never', xid = %s"
                                    , tx.getXid()));
                    } else {
                        // Execute without transaction and return.
                        return business.execute();
                    }
                case MANDATORY:
                    // If transaction is not existing, throw exception.
                    // 要求必须有事务,没事务抛出异常
                    if (notExistingTransaction(tx)) {
                        throw new TransactionException("No existing transaction found for transaction marked with propagation 'mandatory'");
                    }
                    // Continue and execute with current transaction.
                    break;
                default:
                    throw new TransactionException("Not Supported Propagation:" + propagation);
            }

            // 1.3 If null, create new transaction with role 'GlobalTransactionRole.Launcher'.
            // 如果当前的事务上下文中不存在事务,实例化默认全局事务对象 且此次事务发起为 TM 角色为 Launcher
            if (tx == null) {
                tx = GlobalTransactionContext.createNew();
            }

            // set current tx config to holder
            // 记录当前的全局锁配置,存放到 ThreadLocal
            GlobalLockConfig previousConfig = replaceGlobalLockConfig(txInfo);

            try {
                // 2. If the tx role is 'GlobalTransactionRole.Launcher', send the request of beginTransaction to TC,
                //    else do nothing. Of course, the hooks will still be triggered.
                // 执行全局事务开启的前后置钩子方法
                // 如果当前事务的角色是 Participant 也就是 RM ,判断当前事务上下文RootContext是否存在XID,如果不存在,抛出异常
                // 如果当前事务的角色是 launcher 也就是 TM ,判断当前事务上下文RootContext是否存在XID,如果存在,抛出异常
                // 如果不存在,则通过TmNettyRemotingClient  向TC发送一个 GlobalBeginRequest 同步消息,并获取TC返回的XID,绑定到RootContext
                beginTransaction(txInfo, tx);

                Object rs;
                try {
                    // Do Your Business
                    // 执行执行拦截器链路
                    rs = business.execute();
                } catch (Throwable ex) {
                    // 3. The needed business exception to rollback.
                    // 如果抛出异常,判断异常是否在指定的范围中(默认为Throwable类及其子类)
                    // 执行异常回滚的前后钩子方法
                    // 如果当前事务的角色是 launcher 也就是 TM ,通过TmNettyRemotingClient  向TC发送一个 GlobalRollbackRequest 同步消息
                    // 并记录TC返回的当前事务状态Status
                    completeTransactionAfterThrowing(txInfo, tx, ex);
                    throw ex;
                }

                // 4. everything is fine, commit.
                //  如果方法执行过程中没有出现异常
                //  执行事务提交的前后置方法
                //  如果当前事务的角色是 launcher 也就是 TM ,通过TmNettyRemotingClient  向TC发送一个 GlobalCommitRequest 同步消息
                // 并记录TC返回的当前事务状态Status
                commitTransaction(tx);

                return rs;
            } finally {
                //5. clear
                // 恢复以前的全局锁配置
                resumeGlobalLockConfig(previousConfig);
                // 执行整个事务完成的前后置方法
                triggerAfterCompletion();
                // 移除当前绑定的事务钩子对象
                cleanUp();
            }
        } finally {
            // If the transaction is suspended, resume it.
            // 当前事务执行完毕后,恢复挂起的事务,
            // 获取suspendedResourcesHolder关联的xid,由RootContext重新绑定
            if (suspendedResourcesHolder != null) {
                tx.resume(suspendedResourcesHolder);
            }
        }
    }

判断RootContext中是否绑定了XID,如果没有绑定,说明当前不存在事务返回null,如果有绑定XID,则返回默认的GlobalTransaction实现,记录当前全局事务的状态为beging,且为事务的参与者participate。接下来根据全局事务不同的传播行为,进一步判断需不需要挂起当前的全局事务,或者跳过事务处理,如果当前的传播行为要求有一个事务,而当前不存在全局事务(GlobalTransaction对象为null),则无参实例化GlobalTransaction,默认为事务的发起者luancher,事务状态未知

接着执行不同的钩子方法,且都是由事务发起者luancher使用 TmNettyRemotingClient 与 TC 通信,发送GlobalReportRequest消息,如果链路执行顺利,则发送GlobalCommitRequest消息,如果出现异常,发送GlobalRollbackRequest

4.总结与流程图

seata客户端模版方法执行

文章来源:https://blog.csdn.net/JAVAlife2021/article/details/135246205
本文来自互联网用户投稿,该文观点仅代表作者本人,不代表本站立场。本站仅提供信息存储空间服务,不拥有所有权,不承担相关法律责任。