基于Sagas模型的改进事务模型

An Improved Transaction Model Based on Sagas

在Sagas事务模型中,一个长事务是由一个预先定义好执行顺序的子事务集合和他们对应的补偿子事务集合组成的。子事务是按照顺序依次执行的,当其中的某个子事务出现异常时,就逆序执行已提交过的子事务对应的补偿事务来撤销他们的操作结果并退出。这样做会产生三个问题,第一是当一个不重要的子事务出现异常时,就需要撤销全部已提交的事务;第二是事务在完成补偿事务后会退出,而不是选择更有效的执行手段;第三是该模型只支持所有子事务都有相应的补偿子事务的情况。针对这三个问题,提出了相应的解决方案。

In Sagas transaction model, a long lived transaction is composed of ordered transactions set and compensate transactions set,the two sets are counterparts. A long lived transaction is implemented orderly. If a transaction is abnormal, the compensate transactions will be implemented in the opposite direction to remove the results and quit. It will cause three problems： the first is that when an unimportant transaction is abnormal, all results should be removed; the second is that if the compensate transactions were completed, the long lived transaction will quit, but not choose a better implement way; the third is that this model is only applicable in the condition that all compensate transactions are exist. In view of these three problems, the corresponding solutions are proposed.