Date: Wed, 27 Feb 2019 14:33:54 +0100
From: Johannes Truschnigg <johannes@truschnigg.info>
To: Achilleas Mantzios <achill@matrix.gatewaynet.com>
Cc: pgsql-admin@lists.postgresql.org
Subject: Re: Logical replication and wal segment retention
Message-ID: <20190227133350.rtmfaxyif43brugo@vault.lan>
References: <695C083D-AFB5-431B-B022-ED442CE94794@gmail.com>
 <20190227125242.6ixy4jkzcuj55cdl@vault.lan>
 <59567e0a-78e4-ed1c-f5b1-033aafcfb68a@matrix.gatewaynet.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha512;
	protocol="application/pgp-signature"; boundary="z2dl46zeu3zq2osa"
Content-Disposition: inline
In-Reply-To: <59567e0a-78e4-ed1c-f5b1-033aafcfb68a@matrix.gatewaynet.com>
User-Agent: NeoMutt/20170113 (1.7.2)
Precedence: bulk


--z2dl46zeu3zq2osa
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Wed, Feb 27, 2019 at 02:57:46PM +0200, Achilleas Mantzios wrote:
> > [...]
> A logical approach for replication slots would be to accept a parameter
> regarding max WAL files to retain, after which newer WALs will be removed
> and the primary server saved.=A0 Pretty much like : --archive-push-queue-=
max
> argument of pgbackrest .

Before replication slots where a thing, you had to carefully balance
wal_keep_segments in regard to WAL production or/and (usually and :)) set u=
p a
proper WAL archive for replication to be able to soldier on even after a WAL
receiver experienced service-interrupting trouble for a while.

The benefit of that was that the WAL producer remained unaffected (unless y=
ou
bungled the archiving process profoundly) of such calamities. To me, that w=
as
the preferred trade-off for all use-cases of replication that I personally
encountered.

If it were possible to have the best of both worlds (i.e. have a kind of "h=
igh
water mark number of WAL segments"-setting per replication slot, over which
the slot would be abandoned - with a heavy heart and lots of screaming in t=
he
logs, of course - by the producer), that sure would be awesome. But at this
time, we are where we are :)


--=20
with best regards:
- Johannes Truschnigg ( johannes@truschnigg.info )

www:   https://johannes.truschnigg.info/
phone: +43 650 2 133337
xmpp:  johannes@truschnigg.info

Please do not bother me with HTML-email or attachments. Thank you.

--z2dl46zeu3zq2osa
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=lSdU
-----END PGP SIGNATURE-----

--z2dl46zeu3zq2osa--