Re: BUG #19029: Replication Slot size keeps increasing while logical subscription works fine

Hi,

In case my previous emails didn't make it clear, we started having this
issue after upgrading to 17.6 only.

Thadeus Anand.

On Mon, 25 Aug, 2025, 3:36 pm vignesh C, <vignesh21(at)gmail(dot)com> wrote:

> On Mon, 25 Aug 2025 at 12:59, Thadeus Anand <thadeus(at)rmkv(dot)com> wrote:
> >
> > Hi,
> >
> > > Can you share an example as to what you mean by folder keeps
> > > increasing? Is the slot size on disk is increasing?
> >
> > The size on the disk keeps increasing. Last week, it went upto 35 GB per
> slot, then I had to put a 20GB limit on max_slot_wal_keep_size. After
> reaching the size limit, the subscriptions went inactive. Then I dropped
> the subscriptions and freed up the replication slots.
> >
> > > To understand the problem you are facing, we need to see some real
> > > data on the size. Can you share the output of pg_replication_slots
> > > both before and after the folder's size increase?
> >
> > I cannot share the real data right now because I have dropped the
> subscriptions and publications altogether. I can create them again tonight
> (I am in India) and share the details tomorrow.
> >
> > > Is it possible to share a reproducer or some steps to reproduce the
> problem?
> >
> > What I had was a straightforward logical replication setup. We had two
> publications and six subscribing servers. Please also note that this setup
> was working fine with PostgreSQL 15. During May we upgraded to 17.5, and
> ran into a bug which is described in the following release notes section of
> 17.6
>
> Have you tested this on PG16 or any other PG17 versions where it works
> successfully? I’m trying to determine which specific version has this
> issue.
>
> Regards,
> Vignesh
>