[GitHub] imlidian commented on a change in pull request #77: add saga quick start

[GitBox <gi...@apache.org>]

imlidian commented on a change in pull request #77:  add saga  quick start
URL: https://github.com/apache/servicecomb-docs/pull/77#discussion_r244125368
 
 

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 File path: saga-reference/zh_CN/quickstart.md
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+# Apache ServiceComb Pack
+Apache ServiceComb Pack QuickStart
+saga-servicecomb-demo中的Saga代码解读
+
+## 全局事务执行过程
+
+在SagaStartAnnotationProcessor
+Annotation被触发  
+1 当Request发送请求
+2 调用preIntercept 发送 SagaStartedEvent 开始事务  
+3 调用postIntercept 发送 SagaEndedEvent 事务结束执行  
+
+compensableAnnotationProcessor执行补偿  
+路径：servicecomb/saga/omega/transaction/
+
+### EnableOmega
+
+   ```
+   //BookingApplication Class 
+	@EnableOmega
+	public class BookingApplication {
+   ```
+* 当EnableOmega签注生效时TransactionAspectConfig同时被实例化
+* TransactionAspectConfig中的sagaStartAspect方法，返回初始化的SagaStartAspect对象。
+* SagaStartAspect在构造函数中初始化SagaStartAnnotationProcessor（参数：OmegaContext及SagaMessagerSende） 参考下面的代码： 
+
+   ```
+//SagaStartAspect Class
+@Around("execution(@org.apache.servicecomb.saga.omega.context.annotations.SagaStart * *(..)) && @annotation(sagaStart)")
+  Object advise(ProceedingJoinPoint joinPoint, SagaStart sagaStart) throws Throwable {
+    initializeOmegaContext();
+    Method method = ((MethodSignature) joinPoint.getSignature()).getMethod();
+
+  sagaStartAnnotationProcessor.preIntercept(sagaStart.timeout());
+
+    try {
+      Object result = joinPoint.proceed();
+      sagaStartAnnotationProcessor.postIntercept(context.globalTxId());
+      LOG.debug("Transaction with context {} has finished.", context);
+
+      return result;
+    } catch (Throwable throwable) {
+      if (!(throwable instanceof OmegaException)) {
+        sagaStartAnnotationProcessor.onError(method.toString(), throwable);
+      }
+      throw throwable;
+    } 
+  }
+   ```
+
+* 当全局事务开始时候
+* SagaStartAspect调用preIntercept来发送SagaStartedEvent表示事务的开始
+* SagaStartAspect调用postIntercept来发送SagaEndedEvent事件来结束全局事务
+* 在SagaStartAspect中会对签注SagaStart的对象发送Sender对象（Sender对象包含 globalTxId及localTxId）
+* 在事务执行出现异常的时候会发送TxAbortedEvent并通过反射调用compensationMethod  
+
+## 子事务执行过程
+
+在SagaStartAnnotationProcessor
+Annotation被触发  
+1 当Request发送请求
+2 调用preIntercept发送TxStartedEvent 开始事务   
+3 postIntercept 发送 TxEndedEvent 事务结束执行  
 
 Review comment:
   TxStartedEvent和 SagaStartedEvent 不一样

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