Re: Introduce XID age and inactive timeout based replication slot invalidation

On Tue, Mar 26, 2024 at 1:24 AM Nathan Bossart <nathandbossart@gmail.com> wrote:
>
>
> On Sun, Mar 24, 2024 at 03:05:44PM +0530, Bharath Rupireddy wrote:
> > This commit particularly lets one specify the inactive_timeout for
> > a slot via SQL functions pg_create_physical_replication_slot and
> > pg_create_logical_replication_slot.
>
> Off-list, Bharath brought to my attention that the current proposal was to
> set the timeout at the slot level.  While I think that is an entirely
> reasonable thing to support, the main use-case I have in mind for this
> feature is for an administrator that wants to prevent inactive slots from
> causing problems (e.g., transaction ID wraparound) on a server or a number
> of servers.  For that use-case, I think a GUC would be much more
> convenient.  Perhaps there could be a default inactive slot timeout GUC
> that would be used in the absence of a slot-level setting.  Thoughts?
>

Yeah, that is a valid point. One of the reasons for keeping it at slot
level was to allow different subscribers/output plugins to have a
different setting for invalid_timeout for their respective slots based
on their usage. Now, having it as a GUC also has some valid use cases
as pointed out by you but I am not sure having both at slot level and
at GUC level is required. I was a bit inclined to have it at slot
level for now and then based on some field usage report we can later
add GUC as well.

--
With Regards,
Amit Kapila.