Re: recovery_connections cannot start (was Re: master in standby mode croaks)

Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> Tom Lane wrote:
>> We realized some time ago that it was a good idea to separate
>> archive_mode (what to put in WAL) from archive_command (whether we are
>> actually archiving right now). If we fail to apply that same principle
>> to Hot Standby, I think we'll come to regret it.

> The recovery_connections GUC does that. If you enable it, the extra
> information required for hot standby is written to the WAL, otherwise
> it's not.

No, driving it off recovery_connections is exactly NOT that. It's
confusing the transport mechanism with the desired WAL contents.
I maintain that this design is exactly isomorphic to our original PITR
GUC design wherein what got written to WAL was determined by the current
state of archive_command. We eventually realized that was a bad idea.
So is this.

As a concrete example, there is nothing logically wrong with driving
a hot standby slave from WAL records shipped via old-style pg_standby.
Or how about wanting to turn off recovery_connections temporarily, but
not wanting the archived WAL to be unable to support HS?

regards, tom lane