大纲
1.Seata TCC分布式事务案例配置
2.Seata TCC案例服务提供者启动分析
3.@TwoPhaseBusinessAction注解扫描源码
4.Seata TCC案例分布式事务入口分析
5.TCC核心注解扫描与代理创建入口源码
6.TCC动态代理拦截器TccActionInterceptor
7.Action拦截处理器ActionInterceptorHandler
8.Seata TCC分布式事务的注册提交回滚处理源码
1.Seata TCC分布式事务案例配置
(1)位于seata-samples的tcc模块下的Demo工程
(2)Demo工程的配置文件
(3)Demo工程运行说明
(1)位于seata-samples的tcc模块下的Demo工程
dubbo-tcc-sample模块主要演示了TCC模式下分布式事务的提交和回滚。该Demo中一个分布式事务内会有两个TCC事务参与者，这两个TCC事务参与者分别是TccActionOne和TccActionTwo。分布式事务提交则两者均提交，分布式事务回滚则两者均回滚。
这两个TCC事务参与者均是Dubbo远程服务。一个应用作为服务提供方，会实现这两个TCC参与者，并将它们发布成Dubbo服务。另外一个应用作为事务发起方，会订阅Dubbo服务，然后调用编排TCC参与者，执行远程Dubbo服务。
TccActionOne接口定义如下：
public interface TccActionOne {
@TwoPhaseBusinessAction(name = "DubboTccActionOne", commitMethod = "commit", rollbackMethod = "rollback")
public boolean prepare(BusinessActionContext actionContext,
@BusinessActionContextParameter(paramName = "a") int a);
public boolean commit(BusinessActionContext actionContext);
public boolean rollback(BusinessActionContext actionContext);
}TccActionTwo接口定义如下：
public interface TccActionTwo {
@TwoPhaseBusinessAction(name = "DubboTccActionTwo", commitMethod = "commit", rollbackMethod = "rollback")
public boolean prepare(BusinessActionContext actionContext,
@BusinessActionContextParameter(paramName = "b") String b,
@BusinessActionContextParameter(paramName = "c", index = 1) List list);
public boolean commit(BusinessActionContext actionContext);
public boolean rollback(BusinessActionContext actionContext);
}(2)Demo工程的配置文件
一.seata-tcc.xml
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://www.springframework.org/schema/beans"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd"
default-autowire="byName">
<!-- fescar bean scanner -->
<bean class="io.seata.spring.annotation.GlobalTransactionScanner">
<constructor-arg value="tcc-sample"/>
<constructor-arg value="my_test_tx_group"/>
</bean>
<bean id="tccActionOneImpl" class="io.seata.samples.tcc.dubbo.action.impl.TccActionOneImpl"/>
<bean id="tccActionTwoImpl" class="io.seata.samples.tcc.dubbo.action.impl.TccActionTwoImpl"/>
<bean id="tccTransactionService" class="io.seata.samples.tcc.dubbo.service.TccTransactionService"/>
</beans>二.seata-dubbo-provider.xml
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
xmlns="http://www.springframework.org/schema/beans"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://code.alibabatech.com/schema/dubbo
http://code.alibabatech.com/schema/dubbo/dubbo.xsd" default-autowire="byName">
<dubbo:application name="tcc-sample">
<dubbo:parameter key="qos.enable" value="false"/>
</dubbo:application>
<!--使用 zookeeper 注册中心暴露服务，注意要先开启 zookeeper-->
<dubbo:registry address="zookeeper://127.0.0.1:2181"/>
<dubbo:protocol name="dubbo" port="-1"/>
<dubbo:provider timeout="10000" threads="10" threadpool="fixed" loadbalance="roundrobin"/>
<!-- 第一个TCC 参与者服务发布 -->
<dubbo:service interface="io.seata.samples.tcc.dubbo.action.TccActionOne" ref="tccActionOneImpl"/>
<!-- 第二个TCC 参与者服务发布 -->
<dubbo:service interface="io.seata.samples.tcc.dubbo.action.TccActionTwo" ref="tccActionTwoImpl"/>
</beans>三.seata-dubbo-reference.xml
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
xmlns="http://www.springframework.org/schema/beans"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://code.alibabatech.com/schema/dubbo
http://code.alibabatech.com/schema/dubbo/dubbo.xsd" default-autowire="byName">
<dubbo:application name="tcc-sample-reference">
<dubbo:parameter key="qos.enable" value="false"/>
</dubbo:application>
<!--使用 zookeeper 注册中心暴露服务，注意要先开启 zookeeper-->
<dubbo:registry address="zookeeper://127.0.0.1:2181"/>
<dubbo:protocol name="dubbo" port="-1"/>
<dubbo:provider timeout="10000" threads="10" threadpool="fixed" loadbalance="roundrobin"/>
<!-- 第一个TCC参与者 服务订阅 -->
<dubbo:reference id="tccActionOne" interface="io.seata.samples.tcc.dubbo.action.TccActionOne" check="false" lazy="true"/>
<!-- 第二个TCC参与者 服务订阅 -->
<dubbo:reference id="tccActionTwo" interface="io.seata.samples.tcc.dubbo.action.TccActionTwo" check="false" lazy="true"/>
</beans>(3)Demo工程运行指南
一.启动Seata Server
二.启动Dubbo服务应用
运行DubboTccProviderStarter。该应用会发布Dubbo服务，并且实现了两个TCC参与者。
public class TccProviderStarter extends AbstractStarter {
public static void main(String[] args) throws Exception {
new TccProviderStarter().start0(args);
}
@Override
protected void start0(String[] args) throws Exception {
ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext(
new String[]{"spring/seata-tcc.xml", "spring/seata-dubbo-provider.xml"}
);
new ApplicationKeeper().keep();
}
}
public class TccActionOneImpl implements TccActionOne {
@Override
public boolean prepare(BusinessActionContext actionContext, int a) {
String xid = actionContext.getXid();
System.out.println("TccActionOne prepare, xid:" + xid + ", a:" + a);
return true;
}
@Override
public boolean commit(BusinessActionContext actionContext) {
String xid = actionContext.getXid();
System.out.println("TccActionOne commit, xid:" + xid + ", a:" + actionContext.getActionContext("a"));
ResultHolder.setActionOneResult(xid, "T");
return true;
}
@Override
public boolean rollback(BusinessActionContext actionContext) {
String xid = actionContext.getXid();
System.out.println("TccActionOne rollback, xid:" + xid + ", a:" + actionContext.getActionContext("a"));
ResultHolder.setActionOneResult(xid, "R");
return true;
}
}
public class TccActionTwoImpl implements TccActionTwo {
@Override
public boolean prepare(BusinessActionContext actionContext, String b, List list) {
String xid = actionContext.getXid();
System.out.println("TccActionTwo prepare, xid:" + xid + ", b:" + b + ", c:" + list.get(1));
return true;
}
@Override
public boolean commit(BusinessActionContext actionContext) {
String xid = actionContext.getXid();
System.out.println("TccActionTwo commit, xid:" + xid + ", b:" + actionContext.getActionContext("b") + ", c:" + actionContext.getActionContext("c"));
ResultHolder.setActionTwoResult(xid, "T");
return true;
}
@Override
public boolean rollback(BusinessActionContext actionContext) {
String xid = actionContext.getXid();
System.out.println("TccActionTwo rollback, xid:" + xid + ", b:" + actionContext.getActionContext("b") + ", c:" + actionContext.getActionContext("c"));
ResultHolder.setActionTwoResult(xid, "R");
return true;
}
}三.启动事务应用
运行TccConsumerStarter。该应用会订阅Dubbo服务，发起分布式事务，调用上述两个TCC参与者，内含TCC事务提交场景和TCC事务回滚场景的演示。
public class TccConsumerStarter extends AbstractStarter {
static TccTransactionService tccTransactionService = null;
public static void main(String[] args) throws Exception {
new TccConsumerStarter().start0(args);
}
@Override
protected void start0(String[] args) throws Exception {
ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext(
new String[]{"spring/seata-tcc.xml", "spring/seata-dubbo-reference.xml"}
);
tccTransactionService = (TccTransactionService) applicationContext.getBean("tccTransactionService");
//分布式事务提交demo
transactionCommitDemo();
//分布式事务回滚demo
transactionRollbackDemo();
}
private static void transactionCommitDemo() throws InterruptedException {
String txId = tccTransactionService.doTransactionCommit();
System.out.println(txId);
Assert.isTrue(StringUtils.isNotEmpty(txId), "事务开启失败");
System.out.println("transaction commit demo finish.");
}
private static void transactionRollbackDemo() throws InterruptedException {
Map map = new HashMap(16);
try {
tccTransactionService.doTransactionRollback(map);
Assert.isTrue(false, "分布式事务未回滚");
} catch (Throwable t) {
Assert.isTrue(true, "分布式事务异常回滚");
}
String txId = (String) map.get("xid");
System.out.println(txId);
System.out.println("transaction rollback demo finish.");
}
}
public class TccTransactionService {
private TccActionOne tccActionOne;
private TccActionTwo tccActionTwo;
//提交分布式事务
@GlobalTransactional
public String doTransactionCommit() {
//第一个TCC事务参与者
boolean result = tccActionOne.prepare(null, 1);
if (!result) {
throw new RuntimeException("TccActionOne failed.");
}
List list = new ArrayList();
list.add("c1");
list.add("c2");
//第二个TCC事务参与者
result = tccActionTwo.prepare(null, "two", list);
if (!result) {
throw new RuntimeException("TccActionTwo failed.");
}
return RootContext.getXID();
}
//回滚分布式事务
@GlobalTransactional
public String doTransactionRollback(Map map) {
//第一个TCC事务参与者
boolean result = tccActionOne.prepare(null, 1);
if (!result) {
throw new RuntimeException("TccActionOne failed.");
}
List list = new ArrayList();
list.add("c1");
list.add("c2");
//第二个TCC事务参与者
result = tccActionTwo.prepare(null, "two", list);
if (!result) {
throw new RuntimeException("TccActionTwo failed.");
}
map.put("xid", RootContext.getXID());
throw new RuntimeException("transacton rollback");
}
public void setTccActionOne(TccActionOne tccActionOne) {
this.tccActionOne = tccActionOne;
}
public void setTccActionTwo(TccActionTwo tccActionTwo) {
this.tccActionTwo = tccActionTwo;
}
}
2.Seata TCC案例服务提供者启动分析
添加了@TwoPhaseBusinessAction注解的接口发布成Dubbo服务：
3.@TwoPhaseBusinessAction注解扫描源码
(1)全局事务注解扫描器的wrapIfNecessary()方法扫描Spring Bean
(2)TCCBeanParserUtils的isTccAutoProxy()方法判断是否要创建TCC动态代理
(1)全局事务注解扫描器的wrapIfNecessary()方法扫描Spring Bean
全局事务注解扫描器GlobalTransactionScanner会在调用initClient()方法初始化Seata Client客户端后，通过wrapIfNecessary()方法扫描Spring Bean中含有@TwoPhaseBusinessAction注解的方法。
//AbstractAutoProxyCreator：Spring的动态代理自动创建者
//ConfigurationChangeListener：关注配置变更事件的监听器
//InitializingBean：Spring Bean初始化回调
//ApplicationContextAware：用来感知Spring容器
//DisposableBean：支持可抛弃Bean
public class GlobalTransactionScanner extends AbstractAutoProxyCreator
implements ConfigurationChangeListener, InitializingBean, ApplicationContextAware, DisposableBean {
...
//InitializingBean接口的回调方法
//Spring容器启动和初始化完毕后，会调用如下的afterPropertiesSet()方法进行回调
@Override
public void afterPropertiesSet() {
//是否禁用了全局事务，默认是false
if (disableGlobalTransaction) {
if (LOGGER.isInfoEnabled()) {
LOGGER.info("Global transaction is disabled.");
}
ConfigurationCache.addConfigListener(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION, (ConfigurationChangeListener)this);
return;
}
//通过CAS操作确保initClient()初始化动作仅仅执行一次
if (initialized.compareAndSet(false, true)) {
//initClient()方法会对Seata Client进行初始化，比如和Seata Server建立长连接
//seata-samples的tcc模块的seata-tcc.xml配置文件里都配置了GlobalTransactionScanner这个Bean
//而GlobalTransactionScanner这个Bean伴随着Spring容器的初始化完毕，都会回调其初始化逻辑initClient()
initClient();
}
}
//initClient()是核心方法，负责对Seata Client客户端进行初始化
private void initClient() {
if (LOGGER.isInfoEnabled()) {
LOGGER.info("Initializing Global Transaction Clients ... ");
}
if (DEFAULT_TX_GROUP_OLD.equals(txServiceGroup)) {
LOGGER.warn("...", DEFAULT_TX_GROUP_OLD, DEFAULT_TX_GROUP);
}
if (StringUtils.isNullOrEmpty(applicationId) || StringUtils.isNullOrEmpty(txServiceGroup)) {
throw new IllegalArgumentException(String.format("applicationId: %s, txServiceGroup: %s", applicationId, txServiceGroup));
}
//对于Seata Client来说，最重要的组件有两个：
//一个是TM，即Transaction Manager，用来管理全局事务
//一个是RM，即Resource Manager，用来管理各分支事务的数据源
//init TM
//TMClient.init()会对客户端的TM全局事务管理器进行初始化
TMClient.init(applicationId, txServiceGroup, accessKey, secretKey);
if (LOGGER.isInfoEnabled()) {
LOGGER.info("Transaction Manager Client is initialized. applicationId[{}] txServiceGroup[{}]", applicationId, txServiceGroup);
}
//init RM
//RMClient.init()会对客户端的RM分支事务资源管理器进行初始化
RMClient.init(applicationId, txServiceGroup);
if (LOGGER.isInfoEnabled()) {
LOGGER.info("Resource Manager is initialized. applicationId[{}] txServiceGroup[{}]", applicationId, txServiceGroup);
}
if (LOGGER.isInfoEnabled()) {
LOGGER.info("Global Transaction Clients are initialized. ");
}
//注册Spring容器被销毁时的回调钩子，释放TM和RM两个组件的一些资源
registerSpringShutdownHook();
}
//The following will be scanned, and added corresponding interceptor:
//添加了如下注解的方法会被扫描到，然后方法会添加相应的拦截器进行拦截
//TM:
//@see io.seata.spring.annotation.GlobalTransactional // TM annotation
//Corresponding interceptor:
//@see io.seata.spring.annotation.GlobalTransactionalInterceptor#handleGlobalTransaction(MethodInvocation, AspectTransactional) // TM handler
//GlobalLock:
//@see io.seata.spring.annotation.GlobalLock // GlobalLock annotation
//Corresponding interceptor:
//@see io.seata.spring.annotation.GlobalTransactionalInterceptor# handleGlobalLock(MethodInvocation, GlobalLock) // GlobalLock handler
//TCC mode:
//@see io.seata.rm.tcc.api.LocalTCC // TCC annotation on interface
//@see io.seata.rm.tcc.api.TwoPhaseBusinessAction // TCC annotation on try method
//@see io.seata.rm.tcc.remoting.RemotingParser // Remote TCC service parser
//Corresponding interceptor:
//@see io.seata.spring.tcc.TccActionInterceptor // the interceptor of TCC mode
@Override
//由于GlobalTransactionScanner继承了Spring提供的AbstractAutoProxyCreator，
//所以Spring会把Spring Bean传递给GlobalTransactionScanner.wrapIfNecessary()进行判断；
//让GlobalTransactionScanner来决定是否要根据Bean的Class、或者Bean的方法是否有上述注解，
//从而决定是否需要针对Bean的Class创建动态代理，来对添加了注解的方法进行拦截；
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
//do checkers
if (!doCheckers(bean, beanName)) {
return bean;
}
try {
synchronized (PROXYED_SET) {
if (PROXYED_SET.contains(beanName)) {
return bean;
}
interceptor = null;
//check TCC proxy
//判断传递进来的Bean是否是TCC动态代理
//服务启动时会把所有的Bean传递进来这个wrapIfNecessary()，检查这个Bean是否需要创建TCC动态代理
if (TCCBeanParserUtils.isTccAutoProxy(bean, beanName, applicationContext)) {
//init tcc fence clean task if enable useTccFence
TCCBeanParserUtils.initTccFenceCleanTask(TCCBeanParserUtils.getRemotingDesc(beanName), applicationContext);
//TCC interceptor, proxy bean of sofa:reference/dubbo:reference, and LocalTCC
interceptor = new TccActionInterceptor(TCCBeanParserUtils.getRemotingDesc(beanName));
ConfigurationCache.addConfigListener(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION, (ConfigurationChangeListener)interceptor);
} else {
//获取目标class的接口
Class<?> serviceInterface = SpringProxyUtils.findTargetClass(bean);
Class<?>[] interfacesIfJdk = SpringProxyUtils.findInterfaces(bean);
//existsAnnotation()方法会判断Bean的Class或Method是否添加了@GlobalTransactional等注解
if (!existsAnnotation(new Class[]{serviceInterface}) && !existsAnnotation(interfacesIfJdk)) {
return bean;
}
if (globalTransactionalInterceptor == null) {
//构建一个GlobalTransactionalInterceptor，即全局事务注解的拦截器
globalTransactionalInterceptor = new GlobalTransactionalInterceptor(failureHandlerHook);
ConfigurationCache.addConfigListener(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION, (ConfigurationChangeListener)globalTransactionalInterceptor);
}
interceptor = globalTransactionalInterceptor;
}
LOGGER.info("Bean[{}] with name [{}] would use interceptor [{}]", bean.getClass().getName(), beanName, interceptor.getClass().getName());
if (!AopUtils.isAopProxy(bean)) {//如果这个Bean并不是AOP代理
//接下来会基于Spring的AbstractAutoProxyCreator创建针对目标Bean接口的动态代理
//这样后续调用到目标Bean的方法，就会调用到TccActionInterceptor拦截器
bean = super.wrapIfNecessary(bean, beanName, cacheKey);
} else {
AdvisedSupport advised = SpringProxyUtils.getAdvisedSupport(bean);
Advisor[] advisor = buildAdvisors(beanName, getAdvicesAndAdvisorsForBean(null, null, null));
int pos;
for (Advisor avr : advisor) {
//Find the position based on the advisor's order, and add to advisors by pos
pos = findAddSeataAdvisorPosition(advised, avr);
advised.addAdvisor(pos, avr);
}
}
PROXYED_SET.add(beanName);
return bean;
}
} catch (Exception exx) {
throw new RuntimeException(exx);
}
}
...
}(2)TCCBeanParserUtils的isTccAutoProxy()方法判断是否要创建TCC动态代理
public class TCCBeanParserUtils {
private TCCBeanParserUtils() {
}
//is auto proxy TCC bean
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
//创建一个local tcc代理
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);
}
}
}
...
//is TCC proxy-bean/target-bean: LocalTCC , the proxy bean of sofa:reference/dubbo:reference
public static boolean isTccProxyTargetBean(RemotingDesc remotingDesc) {
if (remotingDesc == null) {
return false;
}
//check if it is TCC bean
boolean isTccClazz = false;
//针对我们的class拿到一个接口class
Class<?> tccInterfaceClazz = remotingDesc.getInterfaceClass();
//获取我们的接口里定义的所有的方法
Method[] methods = tccInterfaceClazz.getMethods();
TwoPhaseBusinessAction twoPhaseBusinessAction;
//遍历所有的方法
for (Method method : methods) {
//获取的方法是否加了@TwoPhaseBusinessAction注解
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();
}
...
}
4.Seata TCC案例分布式事务入口分析
TccTransactionService作为分布式事务的入口，其提交事务和回滚事务的接口都会被添加上@GlobalTransactional注解。
所以应用启动时，TccTransactionService的Bean就会被GlobalTransactionScanner扫描，然后其下添加了@GlobalTransactional注解的接口就会被创建动态代理。
在TccTransactionService的提交分布式事务的接口中，会先后调用TccActionOne和TccActionTwo两个Dubbo服务。并且在调用两个Dubbo服务时，会通过ApacheDubboTransactionPropagationFilter传递xid。
public class TccTransactionService {
private TccActionOne tccActionOne;
private TccActionTwo tccActionTwo;
//提交分布式事务
@GlobalTransactional
public String doTransactionCommit() {
//第一个TCC事务参与者
boolean result = tccActionOne.prepare(null, 1);
if (!result) {
throw new RuntimeException("TccActionOne failed.");
}
List list = new ArrayList();
list.add("c1");
list.add("c2");
//第二个TCC事务参与者
result = tccActionTwo.prepare(null, "two", list);
if (!result) {
throw new RuntimeException("TccActionTwo failed.");
}
return RootContext.getXID();
}
//回滚分布式事务
@GlobalTransactional
public String doTransactionRollback(Map map) {
//第一个TCC事务参与者
boolean result = tccActionOne.prepare(null, 1);
if (!result) {
throw new RuntimeException("TccActionOne failed.");
}
List list = new ArrayList();
list.add("c1");
list.add("c2");
//第二个TCC事务参与者
result = tccActionTwo.prepare(null, "two", list);
if (!result) {
throw new RuntimeException("TccActionTwo failed.");
}
map.put("xid", RootContext.getXID());
throw new RuntimeException("transacton rollback");
}
public void setTccActionOne(TccActionOne tccActionOne) {
this.tccActionOne = tccActionOne;
}
public void setTccActionTwo(TccActionTwo tccActionTwo) {
this.tccActionTwo = tccActionTwo;
}
}
5.TCC核心注解扫描与代理创建入口源码
GlobalTransactionScanner的wrapIfNecessary()方法会扫描Spring Bean。TCCBeanParserUtils的isTccAutoProxy()方法会通过判断扫描的Spring Bean中的方法是否添加了TCC的注解，来决定是否要对Bean的方法进行TCC动态代理。
注意，其中TCC的注解有两个：@LocalTCC、@TwoPhaseBusinessAction
public class GlobalTransactionScanner extends AbstractAutoProxyCreator
implements ConfigurationChangeListener, InitializingBean, ApplicationContextAware, DisposableBean {
...
@Override
//由于GlobalTransactionScanner继承了Spring提供的AbstractAutoProxyCreator，
//所以Spring会把Spring Bean传递给GlobalTransactionScanner.wrapIfNecessary()进行判断；
//让GlobalTransactionScanner来决定是否要根据Bean的Class、或者Bean的方法是否有上述注解，
//从而决定是否需要针对Bean的Class创建动态代理，来对添加了注解的方法进行拦截；
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
//do checkers
if (!doCheckers(bean, beanName)) {
return bean;
}
try {
synchronized (PROXYED_SET) {
if (PROXYED_SET.contains(beanName)) {
return bean;
}
interceptor = null;
//check TCC proxy
//判断传递进来的Bean是否是TCC动态代理
//服务启动时会把所有的Bean传递进来这个wrapIfNecessary()，检查这个Bean是否需要创建TCC动态代理
if (TCCBeanParserUtils.isTccAutoProxy(bean, beanName, applicationContext)) {
//init tcc fence clean task if enable useTccFence
TCCBeanParserUtils.initTccFenceCleanTask(TCCBeanParserUtils.getRemotingDesc(beanName), applicationContext);
//TCC interceptor, proxy bean of sofa:reference/dubbo:reference, and LocalTCC
interceptor = new TccActionInterceptor(TCCBeanParserUtils.getRemotingDesc(beanName));
ConfigurationCache.addConfigListener(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION, (ConfigurationChangeListener)interceptor);
} else {
//获取目标class的接口
Class<?> serviceInterface = SpringProxyUtils.findTargetClass(bean);
Class<?>[] interfacesIfJdk = SpringProxyUtils.findInterfaces(bean);
//existsAnnotation()方法会判断Bean的Class或Method是否添加了@GlobalTransactional等注解
if (!existsAnnotation(new Class[]{serviceInterface}) && !existsAnnotation(interfacesIfJdk)) {
return bean;
}
if (globalTransactionalInterceptor == null) {
//构建一个GlobalTransactionalInterceptor，即全局事务注解的拦截器
globalTransactionalInterceptor = new GlobalTransactionalInterceptor(failureHandlerHook);
ConfigurationCache.addConfigListener(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION, (ConfigurationChangeListener)globalTransactionalInterceptor);
}
interceptor = globalTransactionalInterceptor;
}
LOGGER.info("Bean[{}] with name [{}] would use interceptor [{}]", bean.getClass().getName(), beanName, interceptor.getClass().getName());
if (!AopUtils.isAopProxy(bean)) {//如果这个Bean并不是AOP代理
//接下来会基于Spring的AbstractAutoProxyCreator创建针对目标Bean接口的动态代理
//这样后续调用到目标Bean的方法，就会调用到TccActionInterceptor拦截器
bean = super.wrapIfNecessary(bean, beanName, cacheKey);
} else {
AdvisedSupport advised = SpringProxyUtils.getAdvisedSupport(bean);
Advisor[] advisor = buildAdvisors(beanName, getAdvicesAndAdvisorsForBean(null, null, null));
int pos;
for (Advisor avr : advisor) {
//Find the position based on the advisor's order, and add to advisors by pos
pos = findAddSeataAdvisorPosition(advised, avr);
advised.addAdvisor(pos, avr);
}
}
PROXYED_SET.add(beanName);
return bean;
}
} catch (Exception exx) {
throw new RuntimeException(exx);
}
}
...
}
public class TCCBeanParserUtils {
private TCCBeanParserUtils() {
}
//is auto proxy TCC bean
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
//创建一个local tcc代理
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);
}
}
}
...
//is TCC proxy-bean/target-bean: LocalTCC , the proxy bean of sofa:reference/dubbo:reference
public static boolean isTccProxyTargetBean(RemotingDesc remotingDesc) {
if (remotingDesc == null) {
return false;
}
//check if it is TCC bean
boolean isTccClazz = false;
//针对我们的class拿到一个接口class
Class<?> tccInterfaceClazz = remotingDesc.getInterfaceClass();
//获取我们的接口里定义的所有的方法
Method[] methods = tccInterfaceClazz.getMethods();
TwoPhaseBusinessAction twoPhaseBusinessAction;
//遍历所有的方法
for (Method method : methods) {
//获取的方法是否加了@TwoPhaseBusinessAction注解
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();
}
...
}
6.TCC动态代理拦截器TccActionInterceptor
如果调用添加了TCC的注解的方法，就会执行TccActionInterceptor的invoke()方法，此外只有分支事务的方法才会有可能被TCC动态代理。
在TccActionInterceptor的invoke()方法中，会通过ActionInterceptorHandler的proceed()方法来执行具体拦截逻辑。
public class TccActionInterceptor implements MethodInterceptor, ConfigurationChangeListener, Ordered {
//Action拦截处理器
private ActionInterceptorHandler actionInterceptorHandler = new ActionInterceptorHandler();
private volatile boolean disable = ConfigurationFactory.getInstance().getBoolean(ConfigurationKeys.DISABLE_GLOBAL_TRANSACTION, DEFAULT_DISABLE_GLOBAL_TRANSACTION);
...
//如果调用添加了TCC的注解的方法，就会执行如下invoke()方法
@Override
public Object invoke(final MethodInvocation invocation) throws Throwable {
//当前必须是在全局事务里，也就是说分支事务的方法才会有可能被TCC动态代理
if (!RootContext.inGlobalTransaction() || disable || RootContext.inSagaBranch()) {
//not in transaction, or this interceptor is disabled
return invocation.proceed();
}
//本次调用的是哪个方法，在class接口里找到这个方法
Method method = getActionInterfaceMethod(invocation);
//然后才能找到接口里定义的那个方法上面加的一个注解
TwoPhaseBusinessAction businessAction = method.getAnnotation(TwoPhaseBusinessAction.class);
//try method
if (businessAction != null) {
//save the xid
String xid = RootContext.getXID();
//save the previous branchType
BranchType previousBranchType = RootContext.getBranchType();
//if not TCC, bind TCC branchType
if (BranchType.TCC != previousBranchType) {
RootContext.bindBranchType(BranchType.TCC);
}
try {
//Handler the TCC Aspect, and return the business result
//传入actionInterceptorHandler的参数分别是：方法、调用方法传递进来的参数、全局事务xid、分支事务注解、目标方法执行
return actionInterceptorHandler.proceed(method, invocation.getArguments(), xid, businessAction, invocation::proceed);
} finally {
//if not TCC, unbind branchType
if (BranchType.TCC != previousBranchType) {
RootContext.unbindBranchType();
}
//MDC remove branchId
MDC.remove(RootContext.MDC_KEY_BRANCH_ID);
}
}
//not TCC try method
return invocation.proceed();
}
//get the method from interface
protected Method getActionInterfaceMethod(MethodInvocation invocation) {
Class<?> interfaceType = null;
try {
if (remotingDesc == null) {
interfaceType = getProxyInterface(invocation.getThis());
} else {
interfaceType = remotingDesc.getInterfaceClass();
}
if (interfaceType == null && remotingDesc != null && remotingDesc.getInterfaceClassName() != null) {
interfaceType = Class.forName(remotingDesc.getInterfaceClassName(), true, Thread.currentThread().getContextClassLoader());
}
if (interfaceType == null) {
return invocation.getMethod();
}
return interfaceType.getMethod(invocation.getMethod().getName(), invocation.getMethod().getParameterTypes());
} catch (NoSuchMethodException e) {
if (interfaceType != null && !"toString".equals(invocation.getMethod().getName())) {
LOGGER.warn("no such method '{}' from interface {}", invocation.getMethod().getName(), interfaceType.getName());
}
return invocation.getMethod();
} catch (Exception e) {
LOGGER.warn("get Method from interface failed", e);
return invocation.getMethod();
}
}
//get the interface of proxy
@Nullable
protected Class<?> getProxyInterface(Object proxyBean) throws Exception {
if (DubboUtil.isDubboProxyName(proxyBean.getClass().getName())) {
//dubbo javaassist proxy
return DubboUtil.getAssistInterface(proxyBean);
} else {
//jdk/cglib proxy
return SpringProxyUtils.getTargetInterface(proxyBean);
}
}
...
}
7.Action拦截处理器ActionInterceptorHandler
Action拦截处理器ActionInterceptorHandler的主要工作是：设置业务动作上下文 + 注册分支事务 + 执行目标方法。
注意：设置业务动作上下文时，会判断执行方法入参中是否有业务动作上下文。注册分支事务前，会从执行方法入参中提取数据设置到业务动作上下文。
//Handler the TCC Participant Aspect : Setting Context, Creating Branch Record
public class ActionInterceptorHandler {
...
public Object proceed(Method method, Object[] arguments, String xid, TwoPhaseBusinessAction businessAction, Callback<Object> targetCallback) throws Throwable {
//1.设置业务动作上下文
//Get action context from arguments, or create a new one and then reset to arguments
BusinessActionContext actionContext = getOrCreateActionContextAndResetToArguments(method.getParameterTypes(), arguments);
//Set the xid
actionContext.setXid(xid);
//Set the action name，我们自己定义的tcc业务动作名称
String actionName = businessAction.name();
actionContext.setActionName(actionName);
//Set the delay report，延迟report上报
actionContext.setDelayReport(businessAction.isDelayReport());
//Creating Branch Record
//2.发起分支事务的注册，注册成功才会获取到一个branchId
String branchId = doTccActionLogStore(method, arguments, businessAction, actionContext);
actionContext.setBranchId(branchId);
//MDC put branchId
MDC.put(RootContext.MDC_KEY_BRANCH_ID, branchId);
//save the previous action context
BusinessActionContext previousActionContext = BusinessActionContextUtil.getContext();
try {
//share actionContext implicitly
BusinessActionContextUtil.setContext(actionContext);
if (businessAction.useTCCFence()) {
try {
//Use TCC Fence, and return the business result
return TCCFenceHandler.prepareFence(xid, Long.valueOf(branchId), actionName, targetCallback);
} catch (SkipCallbackWrapperException | UndeclaredThrowableException e) {
Throwable originException = e.getCause();
if (originException instanceof FrameworkException) {
LOGGER.error("[{}] prepare TCC fence error: {}", xid, originException.getMessage());
}
throw originException;
}
} else {
//Execute business, and return the business result
//3.执行目标方法
return targetCallback.execute();
}
} finally {
try {
//to report business action context finally if the actionContext.getUpdated() is true
BusinessActionContextUtil.reportContext(actionContext);
} finally {
if (previousActionContext != null) {
//recovery the previous action context
BusinessActionContextUtil.setContext(previousActionContext);
} else {
//clear the action context
BusinessActionContextUtil.clear();
}
}
}
}
...
//Get or create action context, and reset to arguments
@Nonnull
protected BusinessActionContext getOrCreateActionContextAndResetToArguments(Class<?>[] parameterTypes, Object[] arguments) {
BusinessActionContext actionContext = null;
//get the action context from arguments
int argIndex = 0;
//遍历方法调用时传入的参数类型
for (Class<?> parameterType : parameterTypes) {
//如果某个参数类型是BusinessActionContext，因为prepare方法是可以接收一个BusinessActionContext类型的入参的
if (BusinessActionContext.class.isAssignableFrom(parameterType)) {
//尝试获取这个位置的参数对象，但基本是空的
actionContext = (BusinessActionContext) arguments[argIndex];
if (actionContext == null) {
//If the action context exists in arguments but is null, create a new one and reset the action context to the arguments
//创建一个BusinessActionContext对象，把一个空的上下文传递到方法入参里
actionContext = new BusinessActionContext();
arguments[argIndex] = actionContext;
} else {
//Reset the updated, avoid unnecessary reporting
actionContext.setUpdated(null);
}
break;
}
argIndex++;
}
//if null, create a new one
if (actionContext == null) {
actionContext = new BusinessActionContext();
}
return actionContext;
}
...
//Creating Branch Record
protected String doTccActionLogStore(Method method, Object[] arguments, TwoPhaseBusinessAction businessAction, BusinessActionContext actionContext) {
String actionName = actionContext.getActionName();
String xid = actionContext.getXid();
//region fetch context and init action context
//从方法入参里提取出来一些数据放入到上下文里去
Map<String, Object> context = fetchActionRequestContext(method, arguments);
context.put(Constants.ACTION_START_TIME, System.currentTimeMillis());
//Init business context
initBusinessContext(context, method, businessAction);
//Init running environment context
initFrameworkContext(context);
Map<String, Object> originContext = actionContext.getActionContext();
if (CollectionUtils.isNotEmpty(originContext)) {
//Merge context and origin context if it exists.
//@since: above 1.4.2
originContext.putAll(context);
context = originContext;
} else {
actionContext.setActionContext(context);
}
//endregion
//Init applicationData
Map<String, Object> applicationContext = Collections.singletonMap(Constants.TCC_ACTION_CONTEXT, context);
String applicationContextStr = JSON.toJSONString(applicationContext);
try {
//registry branch record
//分支事务注册
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);
}
}
...
//Extracting context data from parameters, add them to the context
protected Map<String, Object> fetchActionRequestContext(Method method, Object[] arguments) {
Map<String, Object> context = new HashMap<>(8);
Annotation[][] parameterAnnotations = method.getParameterAnnotations();
//方法的入参也是可以添加注解的
for (int i = 0; i < parameterAnnotations.length; i++) {
for (int j = 0; j < parameterAnnotations[i].length; j++) {
//如果某个入参添加了一个@BusinessActionContextParameter注解
if (parameterAnnotations[i][j] instanceof BusinessActionContextParameter) {
//get annotation
BusinessActionContextParameter annotation = (BusinessActionContextParameter) parameterAnnotations[i][j];
if (arguments[i] == null) {
throw new IllegalArgumentException("@BusinessActionContextParameter 's params can not null");
}
//get param
Object paramObject = arguments[i];
if (paramObject == null) {
continue;
}
//load param by the config of annotation, and then put into the context
//根据注解的配置提取入参的名称和值，把这个名称和值放入到BusinessActionContext里
ActionContextUtil.loadParamByAnnotationAndPutToContext(ParamType.PARAM, "", paramObject, annotation, context);
}
}
}
return context;
}
}
8.Seata TCC分布式事务的注册提交回滚处理源码
(1)TCC分支事务的注册
(2)TCC分支事务的提交
(3)TCC分支事务的回滚
从TCC的分支事务注册提交回滚过程可知：TCC和AT是可以混合使用的。
(1)TCC分支事务的注册
Action拦截处理器在注册TCC的分支事务时，会调用DefaultResourceManager的branchRegister()方法。
public class DefaultResourceManager implements ResourceManager {
//all resource managers
protected static Map<BranchType, ResourceManager> resourceManagers = new ConcurrentHashMap<>();
private static class SingletonHolder {
private static DefaultResourceManager INSTANCE = new DefaultResourceManager();
}
public static DefaultResourceManager get() {
return SingletonHolder.INSTANCE;
}
private DefaultResourceManager() {
initResourceManagers();
}
protected void initResourceManagers() {
//init all resource managers
//通过SPI加载所有的ResourceManager资源管理器
//比如：DataSourceManager、TCCResourceManager、SagaResourceManager、ResourceManagerXA
List<ResourceManager> allResourceManagers = EnhancedServiceLoader.loadAll(ResourceManager.class);
if (CollectionUtils.isNotEmpty(allResourceManagers)) {
for (ResourceManager rm : allResourceManagers) {
resourceManagers.put(rm.getBranchType(), rm);
}
}
}
...
//注册分支事务
@Override
public Long branchRegister(BranchType branchType, String resourceId, String clientId, String xid, String applicationData, String lockKeys) throws TransactionException {
return getResourceManager(branchType).branchRegister(branchType, resourceId, clientId, xid, applicationData, lockKeys);
}
public ResourceManager getResourceManager(BranchType branchType) {
ResourceManager rm = resourceManagers.get(branchType);
if (rm == null) {
throw new FrameworkException("No ResourceManager for BranchType:" + branchType.name());
}
return rm;
}
...
}
public class TCCResourceManager extends AbstractResourceManager {
...
...
}
public abstract class AbstractResourceManager implements ResourceManager {
//registry branch record
@Override
public Long branchRegister(BranchType branchType, String resourceId, String clientId, String xid, String applicationData, String lockKeys) throws TransactionException {
try {
BranchRegisterRequest request = new BranchRegisterRequest();
request.setXid(xid);//xid是全局事务id
request.setLockKey(lockKeys);//这次分支事务要更新数据全局锁keys
request.setResourceId(resourceId);//分支事务对应的资源id
request.setBranchType(branchType);//分支事务类型
request.setApplicationData(applicationData);//应用数据
BranchRegisterResponse response = (BranchRegisterResponse) RmNettyRemotingClient.getInstance().sendSyncRequest(request);
if (response.getResultCode() == ResultCode.Failed) {
throw new RmTransactionException(response.getTransactionExceptionCode(), String.format("Response[ %s ]", response.getMsg()));
}
return response.getBranchId();
} catch (TimeoutException toe) {
throw new RmTransactionException(TransactionExceptionCode.IO, "RPC Timeout", toe);
} catch (RuntimeException rex) {
throw new RmTransactionException(TransactionExceptionCode.BranchRegisterFailed, "Runtime", rex);
}
}
...
}(2)TCC分支事务的提交
public class TCCResourceManager extends AbstractResourceManager {
...
//TCC branch commit，分支事务的提交
@Override
public BranchStatus branchCommit(BranchType branchType, String xid, long branchId, String resourceId, String applicationData) throws TransactionException {
TCCResource tccResource = (TCCResource) tccResourceCache.get(resourceId);
if (tccResource == null) {
throw new ShouldNeverHappenException(String.format("TCC resource is not exist, resourceId: %s", resourceId));
}
//获取到目标的Bean
Object targetTCCBean = tccResource.getTargetBean();
//获取到目标Bean的commit方法
Method commitMethod = tccResource.getCommitMethod();
if (targetTCCBean == null || commitMethod == null) {
throw new ShouldNeverHappenException(String.format("TCC resource is not available, resourceId: %s", resourceId));
}
try {
//BusinessActionContext
BusinessActionContext businessActionContext = getBusinessActionContext(xid, branchId, resourceId, applicationData);
Object[] args = this.getTwoPhaseCommitArgs(tccResource, businessActionContext);
Object ret;
boolean result;
//add idempotent and anti hanging
if (Boolean.TRUE.equals(businessActionContext.getActionContext(Constants.USE_TCC_FENCE))) {
try {
result = TCCFenceHandler.commitFence(commitMethod, targetTCCBean, xid, branchId, args);
} catch (SkipCallbackWrapperException | UndeclaredThrowableException e) {
throw e.getCause();
}
} else {
ret = commitMethod.invoke(targetTCCBean, args);
if (ret != null) {
if (ret instanceof TwoPhaseResult) {
result = ((TwoPhaseResult) ret).isSuccess();
} else {
result = (boolean) ret;
}
} else {
result = true;
}
}
LOGGER.info("TCC resource commit result : {}, xid: {}, branchId: {}, resourceId: {}", result, xid, branchId, resourceId);
return result ? BranchStatus.PhaseTwo_Committed : BranchStatus.PhaseTwo_CommitFailed_Retryable;
} catch (Throwable t) {
String msg = String.format("commit TCC resource error, resourceId: %s, xid: %s.", resourceId, xid);
LOGGER.error(msg, t);
return BranchStatus.PhaseTwo_CommitFailed_Retryable;
}
}
...
}(3)TCC分支事务的回滚
public class TCCResourceManager extends AbstractResourceManager {
...
//TCC branch rollback，分支事务的回滚
@Override
public BranchStatus branchRollback(BranchType branchType, String xid, long branchId, String resourceId, String applicationData) throws TransactionException {
TCCResource tccResource = (TCCResource) tccResourceCache.get(resourceId);
if (tccResource == null) {
throw new ShouldNeverHappenException(String.format("TCC resource is not exist, resourceId: %s", resourceId));
}
Object targetTCCBean = tccResource.getTargetBean();
Method rollbackMethod = tccResource.getRollbackMethod();
if (targetTCCBean == null || rollbackMethod == null) {
throw new ShouldNeverHappenException(String.format("TCC resource is not available, resourceId: %s", resourceId));
}
try {
//BusinessActionContext
BusinessActionContext businessActionContext = getBusinessActionContext(xid, branchId, resourceId, applicationData);
Object[] args = this.getTwoPhaseRollbackArgs(tccResource, businessActionContext);
Object ret;
boolean result;
//add idempotent and anti hanging
if (Boolean.TRUE.equals(businessActionContext.getActionContext(Constants.USE_TCC_FENCE))) {
try {
result = TCCFenceHandler.rollbackFence(rollbackMethod, targetTCCBean, xid, branchId, args, tccResource.getActionName());
} catch (SkipCallbackWrapperException | UndeclaredThrowableException e) {
throw e.getCause();
}
} else {
ret = rollbackMethod.invoke(targetTCCBean, args);
if (ret != null) {
if (ret instanceof TwoPhaseResult) {
result = ((TwoPhaseResult) ret).isSuccess();
} else {
result = (boolean) ret;
}
} else {
result = true;
}
}
LOGGER.info("TCC resource rollback result : {}, xid: {}, branchId: {}, resourceId: {}", result, xid, branchId, resourceId);
return result ? BranchStatus.PhaseTwo_Rollbacked : BranchStatus.PhaseTwo_RollbackFailed_Retryable;
} catch (Throwable t) {
String msg = String.format("rollback TCC resource error, resourceId: %s, xid: %s.", resourceId, xid);
LOGGER.error(msg, t);
return BranchStatus.PhaseTwo_RollbackFailed_Retryable;
}
}
...
}
