Fescar

2019 年 1 月，阿里巴巴中间件团队发起了开源项目 Fescar（Fast & EaSy Commit And Rollback），和社区一起共建开源分布式事务解决方案。

Fescar 的愿景是让分布式事务的使用像本地事务的使用一样，简单和高效，并逐步解决开发者们遇到的分布式事务方面的所有难题。

Fescar 开源后，蚂蚁金服加入 Fescar 社区参与共建，并在 Fescar 0.4.0 版本中贡献了 TCC 模式。

Seata

为了打造更中立、更开放、生态更加丰富的分布式事务开源社区，经过社区核心成员的投票，大家决定对 Fescar 进行品牌升级，并更名为 Seata。

意为：Simple Extensible Autonomous Transaction Architecture，是一套一站式分布式事务解决方案。

Seata 融合了阿里巴巴和蚂蚁金服在分布式事务技术上的积累，并沉淀了新零售、云计算和新金融等场景下丰富的实践经验，但要实现适用于所有的分布式事务场景的愿景，仍有很长的路要走。

因此，我们决定建立一个完全中立的分布式事务组织，希望更多的企业、开发者能够加入我们，一起打造 Seata。

DTX

Distributed Transaction Problem in Microservices

Let’s imagine a traditional monolithic application.

Its business is built up with 3 modules.

They use a single local data source.

Naturally, data consistency will be guaranteed by the local transaction.

Things have changed in microservices architecture. The 3 modules mentioned above are designed to be 3 services on top of 3 different data sources (Pattern: Database per service). Data consistency within every single service is naturally guaranteed by the local transaction.

But how about the whole business logic scope?

How Seata do?

Seata is just a solution to the problem mentioned above.

Firstly, how to define a Distributed Transaction?

We say, a Distributed Transaction is a Global Transaction which is made up with a batch of Branch Transaction, and normally Branch Transaction is just Local Transaction.

basic components

There are 3 basic components in Seata 大专栏 Seata-一站式分布式事务解决方案:

Transaction Coordinator(TC): Maintain status of global and branch transactions, drive the global commit or rollback.

Transaction Manager(TM): Define the scope of global transaction: begin a global transaction, commit or rollback a global transaction.

Resource Manager(RM): Manage resources that branch transactions working on, talk to TC for registering branch transactions and reporting status of branch transactions, and drive the branch transaction commit or rollback.

执行过程

A typical lifecycle of Seata managed distributed transaction:

TM asks TC to begin a new global transaction. TC generates an XID representing the global transaction.
XID is propagated through microservices’ invoke chain.
RM register local transaction as a branch of the corresponding global transaction of XID to TC.
TM asks TC for committing or rollbacking the corresponding global transaction of XID.
TC drives all branch transactions under the corresponding global transaction of XID to finish branch committing or rollbacking.