Re: pg_stop_backup(wait_for_archive := true) on standby server

On Mon, Jul 24, 2017 at 11:40 AM, David Steele <david@pgmasters.net> wrote:
> Before reviewing the patch, I would note that it looks like this issue was
> introduced in b6a323a8c before the 9.6 release.  The documentation states
> that the pg_stop_backup() function will wait for all required WAL to be
> archived, which corresponds to the default in the new patch of
> waitforarchive = true.  The commit notes that the documentation needs
> updating, but since that didn't happen I think we should consider this a bug
> in 9.6 and back patch.
>
> While this patch brings pg_stop_backup() in line with the documentation, it
> also introduces a behavioral change compared to 9.6.  Currently, the default
> 9.6 behavior on a standby is to return immediately from pg_stop_backup(),
> but this patch will cause it to block by default instead.  Since action on
> the master may be required to unblock the process, I see this as a pretty
> significant change.  I still think we should fix and backpatch, but I wanted
> to point this out.

Hmm.  That seems to me like it could break backup scripts that are
currently working, which seems like a *very* unfriendly thing to do in
a minor release, especially since 9.6 has no option to override the
default behavior (nor can we add one, since it would require a change
to catalog contents).

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company