Re: Create replication slot in pg_basebackup if requested and not yet present

On Sun, Mar 19, 2017 at 12:01 PM, Magnus Hagander <magnus(at)hagander(dot)net> wrote:
> I think maybe we should output a message when the slot is created, at least
> in verbose mode, to make sure people realize that happened. Does that seem
> reasonable?

Slots are great until you leave one lying around by accident. I'm
afraid that no matter what we do, we're going to start getting
complaints from people who mess that up. For example, somebody
creates a replica using the new super-easy method, and then blows it
away without dropping the slot from the master, and then days or weeks
later pg_wal fills up and takes the server down. The user says, oh,
these old write-ahead log files should have gotten removed, and
removes them all. Oops.

So I tend to think that there should always be some explicit user
action to cause the creation of a slot, like --create-slot-if-needed
or --create-slot=name. That still won't prevent careless use of that
option but it's less dangerous than assuming that a user who refers to
a nonexistent slot intended to create it when, perhaps, they just
typo'd it.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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