2PCVariante

2PCVariante is a term used to describe any variant of the two-phase commit protocol (2PC) designed to coordinate distributed transactions across multiple nodes. In the standard 2PC, a transaction manager (the coordinator) requests votes from participating nodes (the participants) during a prepare phase. If all participants vote yes, the coordinator issues a commit; otherwise, it issues an abort. While 2PC ensures atomic commitment under certain failure conditions, it can be blocking: if the coordinator fails after a prepare, participants may lock resources until recovery.

2PCVariante covers modifications to the standard protocol to address specific environment needs, such as reducing blocking, improving failure handling, or adapting to heterogeneous systems. Common categories include:

- Presumed abort: treats a timeout as an abort, reducing blocking time at the cost of potentially more aborts.

- Presumed commit: treats a timeout as a commit, requiring compensation if the assumption proves incorrect.

- Optimized commit paths: techniques to shorten the critical window or streamline messaging in high-throughput settings.

Three-Phase Commit (3PC) is often discussed alongside 2PCVariante, though it is a distinct protocol that adds an extra phase to mitigate certain crash scenarios and reduce blocking.

Implementation considerations for 2PCVariante include durable logging for crash recovery, precise timeout management, and robust recovery procedures to re-establish agreement after failures. The choice of variant depends on system requirements such as tolerance for blocking, network reliability, latency constraints, and transaction load.

See also: Two-Phase Commit, Three-Phase Commit, distributed transactions, transaction manager, recovery mechanisms.