# Seata
## 部署安装
- 集成nacos配置中心
下载 config ` https://github.com/seata/seata/blob/develop/script/config-center/config.txt`
下载 sh脚本 `https://github.com/seata/seata/blob/develop/script/config-center/nacos/nacos-config.sh`
本地修改config.txt 相关参数，修改nacos-config.sh 相关配置，并执行脚本，将配置推送到nacos
- Docker部署(需要指定当前宿主机IP)
```sh
docker run --name seata-server \
-p 8091:8091 \
-e SEATA_IP=10.113.206.85 \
-e SEATA_PORT=8091 \
seataio/seata-server
```
进入容器中，修改registry.conf 配置Nacos相关参数
```sh
registry {
# file 、nacos 、eureka、redis、zk、consul、etcd3、sofa
type = "nacos"
loadBalance = "RandomLoadBalance"
loadBalanceVirtualNodes = 10
nacos {
application = "serverAddr"
serverAddr = "10.113.206.34:8848"
group = "DEFAULT_GROUP"
namespace = ""
cluster = "default"
username = ""
password = ""
}
}
config {
# file、nacos 、apollo、zk、consul、etcd3
type = "nacos"
nacos {
serverAddr = "10.113.206.34:8848"
namespace = ""
group = "SEATA_GROUP"
username = ""
password = ""
# dataId = "seataServer.properties"
}
}
```
## 注入原理
- 添加注解 @EnableAutoDataSourceProxy 配置自动代理数据源
```java
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Import({AutoDataSourceProxyRegistrar.class})
@Documented
public @interface EnableAutoDataSourceProxy {
boolean useJdkProxy() default false;
String[] excludes() default {};
//设置工作模式 默认AT模式，可以选择TCC、XA、SAGA
String dataSourceProxyMode() default "AT";
}
```
@Import 引入配置类 AutoDataSourceProxyRegistrar.class 配置了代理数据源对象
```java
```
- 由于maven依赖了
```java
io.seata
seata-spring-boot-starter
1.4.1
```
1:由spring.factories 配置加载配置类 加载bean GlobalTransactionScanner
```java
@Configuration
@EnableConfigurationProperties({SeataProperties.class})
public class SeataAutoConfiguration {
.
.
.
@Bean
@DependsOn({"springApplicationContextProvider", "failureHandler"})
@ConditionalOnMissingBean({GlobalTransactionScanner.class})
public GlobalTransactionScanner globalTransactionScanner(SeataProperties seataProperties, FailureHandler failureHandler) {
if (LOGGER.isInfoEnabled()) {
LOGGER.info("Automatically configure Seata");
}
return new GlobalTransactionScanner(seataProperties.getApplicationId(), seataProperties.getTxServiceGroup(), failureHandler);
}
.
.
.
}
```
GlobalTransactionScanner 是个spring bean处理器，主要继承以及实现如下
```java
public class GlobalTransactionScanner extends AbstractAutoProxyCreator implements ConfigurationChangeListener, InitializingBean, ApplicationContextAware, DisposableBean {
}
public abstract class AbstractAutoProxyCreator extends ProxyProcessorSupport
implements SmartInstantiationAwareBeanPostProcessor, BeanFactoryAware {
}
```
由这部分判断是否有注解@GlobalTransactional 并创建代理对象，增强方法主要在有该注解的方法前，生成XID，在TC注册该全局事务；
```java
public Object postProcessAfterInitialization(@Nullable Object bean, String beanName) {
if (bean != null) {
Object cacheKey = getCacheKey(bean.getClass(), beanName);
if (this.earlyProxyReferences.remove(cacheKey) != bean) {
return wrapIfNecessary(bean, beanName, cacheKey);
}
}
return bean;
}
```
GlobalTransactionalInterceptor 判断 是否有@GlobalTransactional注解
```java
public Object invoke(MethodInvocation methodInvocation) throws Throwable {
Class targetClass = methodInvocation.getThis() != null ? AopUtils.getTargetClass(methodInvocation.getThis()) : null;
Method specificMethod = ClassUtils.getMostSpecificMethod(methodInvocation.getMethod(), targetClass);
if (specificMethod != null && !specificMethod.getDeclaringClass().equals(Object.class)) {
Method method = BridgeMethodResolver.findBridgedMethod(specificMethod);
GlobalTransactional globalTransactionalAnnotation = (GlobalTransactional)this.getAnnotation(method, targetClass, GlobalTransactional.class);
GlobalLock globalLockAnnotation = (GlobalLock)this.getAnnotation(method, targetClass, GlobalLock.class);
boolean localDisable = this.disable || degradeCheck && degradeNum >= degradeCheckAllowTimes;
if (!localDisable) {
if (globalTransactionalAnnotation != null) {
return this.handleGlobalTransaction(methodInvocation, globalTransactionalAnnotation);
}
if (globalLockAnnotation != null) {
return this.handleGlobalLock(methodInvocation, globalLockAnnotation);
}
}
}
return methodInvocation.proceed();
}
```
AT的增强类：SeataAutoDataSourceProxyAdvice
```java
public class SeataAutoDataSourceProxyAdvice implements MethodInterceptor, IntroductionInfo {
public Object invoke(MethodInvocation invocation) throws Throwable {
if (!RootContext.requireGlobalLock() && this.dataSourceProxyMode != RootContext.getBranchType()) {
return invocation.proceed();
} else {
Method method = invocation.getMethod();
Object[] args = invocation.getArguments();
Method m = BeanUtils.findDeclaredMethod(this.dataSourceProxyClazz, method.getName(), method.getParameterTypes());
if (m != null) {
SeataDataSourceProxy dataSourceProxy = DataSourceProxyHolder.get().putDataSource((DataSource)invocation.getThis(), this.dataSourceProxyMode);
return m.invoke(dataSourceProxy, args);
} else {
return invocation.proceed();
}
}
}
}
```
其中 RootContext.requireGlobalLock() 先判断了当前线程的该ThreadLocal中是否有 TX_LOCK ,如果有，执行代理方法
```
public static boolean requireGlobalLock() {
return CONTEXT_HOLDER.get("TX_LOCK") != null;
}
```
2:该spring.factories 配置也同时加载配置类 加载bean HttpAutoConfiguration
```java
@Configuration
@ConditionalOnWebApplication
public class HttpAutoConfiguration extends WebMvcConfigurerAdapter {
public HttpAutoConfiguration() {
}
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new TransactionPropagationInterceptor());
}
public void extendHandlerExceptionResolvers(List exceptionResolvers) {
exceptionResolvers.add(new HttpHandlerExceptionResolver());
}
}
```
新增了拦截器，用于拦截请求，构造上面的 线程ThreadLocal 变量，为之后数据源代理对象，判断是否是分布式事务
```java
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
String xid = RootContext.getXID();
String rpcXid = request.getHeader("TX_XID");
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("xid in RootContext[{}] xid in HttpContext[{}]", xid, rpcXid);
}
if (xid == null && rpcXid != null) {
RootContext.bind(rpcXid);
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("bind[{}] to RootContext", rpcXid);
}
}
return true;
}
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
if (RootContext.inGlobalTransaction()) {
XidResource.cleanXid(request.getHeader("TX_XID"));
}
}
```
- 未发现用feign拦截器进行request插入参数 XID的配置；对于请求的XID如何传递，暂时未看到源码。