Re: Clarification in pg10's pgupgrade.html step 10 (upgrading standby servers)

On Tue, Sep 12, 2017 at 07:38:40PM -0400, Stephen Frost wrote:
> Further, really, I think we should provide a utility to do all of the
> above instead of using rsync- and that utility should do some additional
> things, such as:
>
> - Check that the control file on the primary and replica show that they
> reached the same point prior to the pg_upgrade. If they didn't, then
> things could go badly as there's unplayed WAL that the primary got
> through and the replica didn't.
>
> - Not copy over unlogged data, or any other information that shouldn't
> be copied across.
>
> - Allow the directory structures to be more different between the
> primary and the replica than rsync allows (wouldn't have to have a
> common subdirectory on the replica).
>
> - Perhaps other validation checks or similar.
>
> Unfortunately, this is a bit annoying as it necessairly involves running
> things on both the primary and the replica from the same tool, without
> access to PG, meaning we'd have to work through something else (such as
> SSH, like rsync does, but then what would we do for Windows...?).

Maybe pg_rewind's mechanism could be partially reused for this as it
seems to accomplish something vaguely similar AIUI?

Michael

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