Re: pgsql: Introduce replication slots.

On 2014-02-01 18:33:08 +0900, Fujii Masao wrote:
> On Sat, Feb 1, 2014 at 6:09 PM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> > On 2014-02-01 16:47:47 +0900, Fujii Masao wrote:
> >> This patch changed basebackup.c so that it skips pg_replslot. It's OK
> >> to skip all files in that directory, but an empty pg_replslot must be
> >> included in the backup. Otherwise we cannot start PostgreSQL from
> >> the backup taken via pg_basebackup. Attached patch fixes this problem.
> >
> > That's a pretty fair point. Not sure how that could escape my
> > notice. The patch does look sane to me.
> >
> > I wonder if we additionally should add code to recreate pg_replslot on
> > startup, similar to pg_xlog?
>
> Similar to pg_xlog/archive_status, not pg_xlog? That might be an option.
> But I'm not inclined to do that for now. The fact that the essential
> directory like pg_replslot doesn't exist indicates the symptom of
> something strange. And, changing that way might prevent us from
> detecting such symptom.

The reason I am wondering is that it makes a fair bit of sense to
exclude it in open-coded base backups as well, and excluding the
entire directory might be the easiest way there. But I guess people
manage for pg_xlog/, so it's really not something that would reduce pain
measurably.

> BTW, we should add the setting of primary_slotname into
> recovery.conf.sample?

Yes.

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services