Re: unite recovery.conf and postgresql.conf

On Tue, Sep 20, 2011 at 1:01 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> I'll go further and say that we only want one trigger file by default,
> one which either enables or disables recovery.  I'll further suggest
> that we:
>
> a) have a standby.on file which puts the server in replica/recovery mode
> if it's detected on startup, and
> b) that we poll for the standby.on file going away as a trigger to stop
> recovery and bring up the server in master mode, and
> c) that pg_basebackup automatically create a standby.on file.

It seems a bit confusing to me to have a file that takes effect only
at startup when created but anytime when removed.

I think one of the insufficiently-lauded 9.1 features is Fujii Masao's
"pg_ctl promote". Now THAT is a good interface. Unlike
trigger_file, it doesn't require any advance preparation, or monkeying
with files on disk. You just tell it to promote, and it does. Sweet.
Now it turns out that it uses a file to make that happen behind the
scenes, but who cares? From the user's perspective It Just Works.

I like the idea of some kind of sentinel file that tells the server to
start up in recovery mode. But instead of having the user remove it
to cause a promotion, I think the server should remove it when it does
promote. That's more like what we've done in the past, and it ties in
very nicely with what pg_ctl promote already does.

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