Thread

Re: Timeline switching with partial WAL records can break replica recovery

Artem Gavrilov <artem.gavrilov@percona.com> — 2025-12-25T15:11:15Z

Hello Alyona,

Your solution, if I understood it correctly, violates the main idea of
timelines, as it creates an "alternative" version for timeline N.
It's possible that primary finished contrecord and whole segment was
archived. Currently, replica always has subset of timeline N, so it's safe
to start new timeline from any point. But with your timeline finalization
logic it will create its own version timeline N that will conflict with
already archived version. If replica will archive timeline N+1 you may end
up with two different "tails" of timeline N in the same archive. Also I
assume some third party tools that rely on WAL may be broken by such change.


-- 

Artem Gavrilov

Senior Software Engineer, Percona

artem.gavrilov@percona.com
percona.com <http://www.percona.com>