分布式事务概述

短命女 2022-04-04 07:00 201阅读 0赞

A distributed transaction is a [database transaction][] in which two or more network hosts are involved. Usually, hosts provide transactional resources, while the transaction manager is responsible for creating and managing a global transaction that encompasses all operations against such resources. Distributed transactions, as any other [transactions][database transaction], must have all four [ACID (atomicity, consistency, isolation, durability)][ACID _atomicity_ consistency_ isolation_ durability] properties, where atomicity guarantees all-or-nothing outcomes for the unit of work (operations bundle).

摘自[wiki百科][wiki]，大致意思是分布式事务和普通事务一样拥有ACID特性，**只不过是涉及到多个网络节点的事务**。其中提到了Host和Transaction manager。

OpenGroup是一个供应商联盟，它提出了x/open分布式事务处理(DTP)模型(x/open xa)，成为事务模型组件行为的的标准。

In practice most commercial database systems use [strong strict two phase locking (SS2PL)][strong strict two phase locking _SS2PL] for [concurrency control][], which ensures global serializability, if all the participating databases employ it. (see also [commitment ordering][] for multidatabases.)

这里提到了**大多数商业数据库**系统使用强严格的两阶段锁定(Ss2pl)来进行并发控制，也就是俗说的二阶段提交。

但是2PC（二阶段提交并不适用所有场景），比方说预定机票和预订酒店这种，用2PC的方式并不合适，这种长时间的分布式事务会锁定较长的时间，而且有技术层面上锁的撤销操作，这种可以从业务上避免分布式事务，比方说业务上添加一个撤销操作。***通常，这些长时间的事务采用补偿事务、乐观和不锁定隔离的方案。***X/Open模型不适合长期存在的DTP。

[database transaction]: https://en.wikipedia.org/wiki/Database_transaction
[ACID _atomicity_ consistency_ isolation_ durability]: https://en.wikipedia.org/wiki/ACID
[wiki]: https://en.wikipedia.org/wiki/Distributed_transaction
[strong strict two phase locking _SS2PL]: https://en.wikipedia.org/wiki/Two_phase_locking#Strong_strict_two-phase_locking
[concurrency control]: https://en.wikipedia.org/wiki/Concurrency_control
[commitment ordering]: https://en.wikipedia.org/wiki/Commitment_ordering