seata分布式事务TCC模式的源码分析

布满荆棘的人生 2022-12-27 05:00 109阅读 0赞

今天我们进行seata分布式事务TCC模式的源码分析：

首先其TCC源码和AT模式的源码基本都在一起，只是稍微有一些不同的地方，因此我们碰到以前详细分析过的地方就简单提一下，且TCC 的 TM 的源码跟 AT 是一样的，这里就不做分析了，下面我们就开始吧！

重点看一下  RM  那边的源码 RM 是通过  TM  这边的远程接口调用的，调用到了  RM 的代理对象，代理的生成：在 RM 的工程启动的时候，有@LocalTCC @TwoPhaseBusinessAction 注解的类（注解在接口中）就会走上述截图代码生成代理对象，代理对象的 advice 就是 TccActionInterceptor，所以当 TM 调用到远程的 RM 时，最终会调到 TccActionInterceptor 的 invoke 方法，我们只要看看 invoke 方法干了什么即可。

1、于是从这里开始：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70][]

2、根据策略模式判断是否TCC: TCCBeanParserUtils.isTccAutoProxy 方法进入

public static boolean isTccAutoProxy(Object bean, String beanName, ApplicationContext applicationContext) {
        boolean isRemotingBean = parserRemotingServiceInfo(bean, beanName);
        //get RemotingBean description
        RemotingDesc remotingDesc = DefaultRemotingParser.get().getRemotingBeanDesc(beanName);
        //is remoting bean
        if (isRemotingBean) {
            if (remotingDesc != null && remotingDesc.getProtocol() == Protocols.IN_JVM) {
                //LocalTCC
                return isTccProxyTargetBean(remotingDesc);
            } else {
                // sofa:reference / dubbo:reference, factory bean
                return false;
            }
        } else {
            if (remotingDesc == null) {
                //check FactoryBean
                if (isRemotingFactoryBean(bean, beanName, applicationContext)) {
                    remotingDesc = DefaultRemotingParser.get().getRemotingBeanDesc(beanName);
                    return isTccProxyTargetBean(remotingDesc);
                } else {
                    return false;
                }
            } else {
                return isTccProxyTargetBean(remotingDesc);
            }
        }
    }

3、进入  parserRemotingServiceInfo(bean, beanName);方法：

protected static boolean parserRemotingServiceInfo(Object bean, String beanName) {
        RemotingParser remotingParser = DefaultRemotingParser.get().isRemoting(bean, beanName);
        if (remotingParser != null) {
            return DefaultRemotingParser.get().parserRemotingServiceInfo(bean, beanName, remotingParser) != null;
        }
        return false;
    }

4、进入 parserRemotingServiceInfo 方法：

public RemotingDesc parserRemotingServiceInfo(Object bean, String beanName, RemotingParser remotingParser) {
        RemotingDesc remotingBeanDesc = remotingParser.getServiceDesc(bean, beanName);
        if (remotingBeanDesc == null) {
            return null;
        }
        remotingServiceMap.put(beanName, remotingBeanDesc);
    
        Class<?> interfaceClass = remotingBeanDesc.getInterfaceClass();
        Method[] methods = interfaceClass.getMethods();
        if (remotingParser.isService(bean, beanName)) {
            try {
                //service bean, registry resource
                Object targetBean = remotingBeanDesc.getTargetBean();
                for (Method m : methods) {
                    TwoPhaseBusinessAction twoPhaseBusinessAction = m.getAnnotation(TwoPhaseBusinessAction.class);
                    if (twoPhaseBusinessAction != null) {
                        TCCResource tccResource = new TCCResource();
                        tccResource.setActionName(twoPhaseBusinessAction.name());
                        tccResource.setTargetBean(targetBean);
                        tccResource.setPrepareMethod(m);
                        tccResource.setCommitMethodName(twoPhaseBusinessAction.commitMethod());
                        tccResource.setCommitMethod(ReflectionUtil
                            .getMethod(interfaceClass, twoPhaseBusinessAction.commitMethod(),
                                new Class[] {BusinessActionContext.class}));
                        tccResource.setRollbackMethodName(twoPhaseBusinessAction.rollbackMethod());
                        tccResource.setRollbackMethod(ReflectionUtil
                            .getMethod(interfaceClass, twoPhaseBusinessAction.rollbackMethod(),
                                new Class[] {BusinessActionContext.class}));
                        //registry tcc resource
                        DefaultResourceManager.get().registerResource(tccResource);
                    }
                }
            } catch (Throwable t) {
                throw new FrameworkException(t, "parser remoting service error");
            }
        }
        if (remotingParser.isReference(bean, beanName)) {
            //reference bean, TCC proxy
            remotingBeanDesc.setReference(true);
        }
        return remotingBeanDesc;
    }
    
    5、进入  remotingParser.getServiceDesc(bean, beanName);方法：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 1][]

6、进入LocalTCCRemotingParser 解析器类：

@Override
    public RemotingDesc getServiceDesc(Object bean, String beanName) throws FrameworkException {
        if (!this.isRemoting(bean, beanName)) {
            return null;
        }
        RemotingDesc remotingDesc = new RemotingDesc();
        remotingDesc.setReference(true);
        remotingDesc.setProtocol(Protocols.IN_JVM);
        Class<?> classType = bean.getClass();
        Set<Class<?>> interfaceClasses = ReflectionUtil.getInterfaces(classType);
        for (Class<?> interClass : interfaceClasses) {
            if (interClass.isAnnotationPresent(LocalTCC.class)) {
                remotingDesc.setInterfaceClassName(interClass.getName());
                remotingDesc.setInterfaceClass(interClass);
                remotingDesc.setTargetBean(bean);
                return remotingDesc;
            }
        }
        throw new FrameworkException("Couldn't parser any Remoting info");
    }
    
    7、进入isService(bean, beanName) 方法：

8、进入  LocalTCCRemotingParser 解析器类：

@Override
    public boolean isService(Object bean, String beanName) {
        Class<?> classType = bean.getClass();
        Set<Class<?>> interfaceClasses = ReflectionUtil.getInterfaces(classType);
        for (Class<?> interClass : interfaceClasses) {
            if (interClass.isAnnotationPresent(LocalTCC.class)) {
                return true;
            }
        }
        return false;
    }

9、进入 isTccProxyTargetBean(remotingDesc);方法：

protected static boolean isTccProxyTargetBean(RemotingDesc remotingDesc) {
        if (remotingDesc == null) {
            return false;
        }
        //check if it is TCC bean
        boolean isTccClazz = false;
        Class<?> tccInterfaceClazz = remotingDesc.getInterfaceClass();
        Method[] methods = tccInterfaceClazz.getMethods();
        TwoPhaseBusinessAction twoPhaseBusinessAction;
        for (Method method : methods) {
            twoPhaseBusinessAction = method.getAnnotation(TwoPhaseBusinessAction.class);
            if (twoPhaseBusinessAction != null) {
                isTccClazz = true;
                break;
            }
        }
        if (!isTccClazz) {
            return false;
        }
        short protocols = remotingDesc.getProtocol();
        //LocalTCC
        if (Protocols.IN_JVM == protocols) {
            //in jvm TCC bean , AOP
            return true;
        }
        // sofa:reference /  dubbo:reference, AOP
        return remotingDesc.isReference();
    }

10、点击  TccActionInterceptor 类：

public TccActionInterceptor(RemotingDesc remotingDesc) {
        this.remotingDesc = remotingDesc;
    }
    
    @Override
    public Object invoke(final MethodInvocation invocation) throws Throwable {
        if (!RootContext.inGlobalTransaction()) {
            //not in transaction
            return invocation.proceed();
        }
        Method method = getActionInterfaceMethod(invocation);
        TwoPhaseBusinessAction businessAction = method.getAnnotation(TwoPhaseBusinessAction.class);
        //try method
        if (businessAction != null) {
            //save the xid
            String xid = RootContext.getXID();
            //clear the context
            RootContext.unbind();
            RootContext.bindInterceptorType(xid, BranchType.TCC);
            try {
                Object[] methodArgs = invocation.getArguments();
                //Handler the TCC Aspect 
                //跟 TC 通讯，注册 RM，把二阶段的 commit 和 rollback 方法名称传给 TC
                Map<String, Object> ret = actionInterceptorHandler.proceed(method, methodArgs, xid, businessAction,
                        invocation::proceed);//火炬传递，调用被代理方法，执行业务逻辑
                //return the final result
                return ret.get(Constants.TCC_METHOD_RESULT);
            } finally {
                //recovery the context
                RootContext.unbindInterceptorType();
                RootContext.bind(xid);
            }
        }
        return invocation.proceed();
    }

11、点击  actionInterceptorHandler.proceed方法：

public Map<String, Object> proceed(Method method, Object[] arguments, String xid, TwoPhaseBusinessAction businessAction,
                                       Callback<Object> targetCallback) throws Throwable {
        Map<String, Object> ret = new HashMap<>(4);
    
        //TCC name
        String actionName = businessAction.name();
        BusinessActionContext actionContext = new BusinessActionContext();
        actionContext.setXid(xid);
        //set action anme
        actionContext.setActionName(actionName);
    
        //Creating Branch Record 远程调用通知TC
        String branchId = doTccActionLogStore(method, arguments, businessAction, actionContext);
        actionContext.setBranchId(branchId);
    
        //set the parameter whose type is BusinessActionContext
        Class<?>[] types = method.getParameterTypes();
        int argIndex = 0;
        for (Class<?> cls : types) {
            if (cls.getName().equals(BusinessActionContext.class.getName())) {
                arguments[argIndex] = actionContext;
                break;
            }
            argIndex++;
        }
        //the final parameters of the try method
        ret.put(Constants.TCC_METHOD_ARGUMENTS, arguments);
        //the final result
        ret.put(Constants.TCC_METHOD_RESULT, targetCallback.execute());
        return ret;
    }

12、点击 doTccActionLogStore 方法：

protected String doTccActionLogStore(Method method, Object[] arguments, TwoPhaseBusinessAction businessAction,
                                         BusinessActionContext actionContext) {
        String actionName = actionContext.getActionName();
        String xid = actionContext.getXid();
        //核心
        Map<String, Object> context = fetchActionRequestContext(method, arguments);
        context.put(Constants.ACTION_START_TIME, System.currentTimeMillis());
    
        //init business context  核心
        initBusinessContext(context, method, businessAction);
        //Init running environment context
        initFrameworkContext(context);
        actionContext.setActionContext(context);
    
        //init applicationData
        Map<String, Object> applicationContext = new HashMap<>(4);
        applicationContext.put(Constants.TCC_ACTION_CONTEXT, context);
        String applicationContextStr = JSON.toJSONString(applicationContext);
        try {
            //registry branch record  和TC通信
            Long branchId = DefaultResourceManager.get().branchRegister(BranchType.TCC, actionName, null, xid,
                applicationContextStr, null);
            return String.valueOf(branchId);
        } catch (Throwable t) {
            String msg = String.format("TCC branch Register error, xid: %s", xid);
            LOGGER.error(msg, t);
            throw new FrameworkException(t, msg);
        }
    }
    
    
    13、点击fetchActionRequestContext方法：

protected Map<String, Object> fetchActionRequestContext(Method method, Object[] arguments) {
        Map<String, Object> context = new HashMap<>(8);
    
        Annotation[][] parameterAnnotations = method.getParameterAnnotations();
        for (int i = 0; i < parameterAnnotations.length; i++) {
            for (int j = 0; j < parameterAnnotations[i].length; j++) {
                if (parameterAnnotations[i][j] instanceof BusinessActionContextParameter) {
                    BusinessActionContextParameter param = (BusinessActionContextParameter)parameterAnnotations[i][j];
                    if (null == arguments[i]) {
                        throw new IllegalArgumentException("@BusinessActionContextParameter 's params can not null");
                    }
                    Object paramObject = arguments[i];
                    int index = param.index();
                    //List, get by index
                    if (index >= 0) {
                        @SuppressWarnings("unchecked")
                        Object targetParam = ((List<Object>)paramObject).get(index);
                        if (param.isParamInProperty()) {
                            context.putAll(ActionContextUtil.fetchContextFromObject(targetParam));
                        } else {
                            context.put(param.paramName(), targetParam);
                        }
                    } else {
                        if (param.isParamInProperty()) {
                            context.putAll(ActionContextUtil.fetchContextFromObject(paramObject));
                        } else {
                            context.put(param.paramName(), paramObject);
                        }
                    }
                }
            }
        }
        return context;
    }

14、点击 initBusinessContext方法：

protected void initBusinessContext(Map<String, Object> context, Method method,
                                       TwoPhaseBusinessAction businessAction) {
        if (method != null) {
            //the phase one method name
            context.put(Constants.PREPARE_METHOD, method.getName());
        }
        if (businessAction != null) {
            //the phase two method name
            context.put(Constants.COMMIT_METHOD, businessAction.commitMethod());
            context.put(Constants.ROLLBACK_METHOD, businessAction.rollbackMethod());
            context.put(Constants.ACTION_NAME, businessAction.name());
        }
    }

15、这是TCC一阶段提交的提交的流程，正式提交和回滚思路和也是和AT模式类似的，大家可以试着查看一下。

这里也可以看到，TCC 模式的 RM 的代理主要就是注册了 RM，封 BusinessActionContext 对象传递给 TC，TC 二阶段回调的时候又把 BusinessActionContext 对象传递回 RM，所以就感觉一阶段和二阶段方法共享了 BusinessActionContext 对象的错 觉。

到此结束，下篇我们分析sage模式的使用，敬请期待！

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