Re: WAL recycled despite logical replication slot

On Fri, Sep 20, 2019 at 6:25 PM Andres Freund <andres(at)anarazel(dot)de> wrote:

> Hi,
>
> On September 20, 2019 5:45:34 AM PDT, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
> wrote:
> >While testing something else (whether "terminating walsender process
> >due to
> >replication timeout" was happening spuriously), I had logical
> >replication
> >set up streaming a default pgbench transaction load, with the publisher
> >being 13devel-e1c8743 and subscriber being 12BETA4. Eventually I
> >started
> >getting errors about requested wal segments being already removed:
> >
> >10863 sub idle 00000 2019-09-19 17:14:58.140 EDT LOG: starting logical
> >decoding for slot "sub"
> >10863 sub idle 00000 2019-09-19 17:14:58.140 EDT DETAIL: Streaming
> >transactions committing after 79/EB0B17A0, reading WAL from
> >79/E70736A0.
> >10863 sub idle 58P01 2019-09-19 17:14:58.140 EDT ERROR: requested WAL
> >segment 0000000100000079000000E7 has already been removed
> >10863 sub idle 00000 2019-09-19 17:14:58.144 EDT LOG: disconnection:
> >session time: 0:00:00.030 user=jjanes database=jjanes host=10.0.2.2
> >port=40830
> >
> >It had been streaming for about 50 minutes before the error showed up,
> >and
> >it showed right when streaming was restarting after one of the
> >replication
> >timeouts.
> >
> >Is there an innocent explanation for this? I thought logical
> >replication
> >slots provided an iron-clad guarantee that WAL would be retained until
> >it
> >was no longer needed. I am just using pub/sub, none of the lower level
> >stuff.
>
> It indeed should. What's the content of
> pg_replication_slot for that slot?
>

Unfortunately I don't think I have that preserved. If I can reproduce the
issue, would preserving data/pg_replslot/sub/state help as well?

Cheers,

Jeff