Re: pg_rewind WAL segments deletion pitfall

> With archive_mode = always you can't reproduce it.
> It is very rarely people set it to always in production due to the overhead.
...
> The archive_mode has to be set to on and the archive_command should be
> failing when you do pg_ctl -D oldprim stop

Ah, I see.

What I don't still understand is why pg_rewind doesn't work for the
old primary in that case. When archive_mode=on, the old primary has
the complete set of WAL files counting both pg_wal and its archive. So
as the same to the privious repro, pg_rewind -c ought to work (but it
uses its own archive this time).  In that sense the proposed solution
is still not needed in this case.

A bit harder situation comes after the server successfully rewound; if
the new primary goes so far that the old primary cannot connect. Even
in that case, you can copy-in the requried WAL files or configure
restore_command of the old pimary so that it finds required WAL files
there.