Re: [HACKERS] [bug fix] PG10: libpq doesn't connect to alternativehosts when some errors occur

Tom, Robert,

* Tom Lane (tgl@sss.pgh.pa.us) wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > Yeah, you have a point.  I'm willing to admit that we may have defined
> > the behavior of the feature incorrectly, provided that you're willing
> > to admit that you're proposing a definition change, not just a bug
> > fix.
>
> > Anybody else want to weigh in with an opinion here?
>
> I'm not really on board with "try each server until you find one where
> this dbname+username+password combination works".  That's just a recipe
> for trouble, especially the password angle.

Agreed.

> I think it's a good point that there are certain server responses that
> we should take as equivalent to "server down", but by the same token
> there are responses that we should not take that way.

Right.

> I suggest that we need to conditionalize the decision based on what
> SQLSTATE is reported.  Not sure offhand if it's better to have a whitelist
> of SQLSTATEs that allow failing over to the next server, or a blacklist of
> SQLSTATEs that don't.

No particular comment on this.  I do wonder about forward/backwards
compatibility in such lists and if SQLSTATE really covers all
cases/distinctions which are interesting when it comes to making this
decision.

Thanks!

Stephen