Feedback-ID: idd01497b:Fastmail
Mime-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset=UTF-8
Date: Fri, 05 Jun 2026 20:34:01 +0000
Message-Id: <DJ1EI730WLNK.NJ6O9XYWV2R0@partin.io>
Subject: Re: Prevent remote libpq notices from being sent to clients
To: "Chao Li" <li.evan.chao@gmail.com>
From: "Tristan Partin" <tristan@partin.io>
Cc: "Fujii Masao" <masao.fujii@gmail.com>, "vignesh C"
 <vignesh21@gmail.com>, "Postgres hackers"
 <pgsql-hackers@lists.postgresql.org>
References: <396C3BEE-CD4D-450A-8D28-E708E9AA4075@gmail.com>
In-Reply-To: <396C3BEE-CD4D-450A-8D28-E708E9AA4075@gmail.com>
Archived-At: 
 <https://www.postgresql.org/message-id/DJ1EI730WLNK.NJ6O9XYWV2R0%40partin.io>
Precedence: bulk

On Fri Jun 5, 2026 at 9:32 AM UTC, Chao Li wrote:
> Hi,
>
> This is another issue with =E2=80=9C[112faf137] Log remote NOTICE, WARNIN=
G, and similar messages using ereport()=E2=80=9D. From the commit message, =
the intention of the feature is to log remote messages with ereport() to ge=
t better formatting:
> ```
>     Log remote NOTICE, WARNING, and similar messages using ereport().
>
>     Previously, NOTICE, WARNING, and similar messages received from remot=
e
>     servers over replication, postgres_fdw, or dblink connections were pr=
inted
>     directly to stderr on the local server (e.g., the subscriber). As a r=
esult,
>     these messages lacked log prefixes (e.g., timestamp), making them har=
der
>     to trace and correlate with other log entries.
>
>     This commit addresses the issue by introducing a custom notice receiv=
er
>     for replication, postgres_fdw, and dblink connections. These messages
>     are now logged via ereport(), ensuring they appear in the logs with p=
roper
>     formatting and context, which improves clarity and aids in debugging.
> ```
>
> So remote messages should only be output to the server log, but currently=
 they can leak to the client if client_min_messages is set to log.
>
> This is a simple repro:
> ```
> evantest=3D# set client_min_messages=3Dlog;
> SET
> evantest=3D# select * from dblink('host=3Dlocalhost dbname=3Dpostgres=E2=
=80=99,
> 'do $$ begin raise warning ''hello, client!!!''; end $$; select 1=E2=80=
=99)
> as t(x int);
> LOG:  received message via remote connection: WARNING:  hello, client!!!
>  x
> ---
>  1
> (1 row)
> ```
>
> The one-line fix is straightforward, just change the ereport() level from=
 LOG to LOG_SERVER_ONLY. I also added a test in the patch.

This looks good to me. Do you think we should also copy the test to=20
postgres_fdw? Or, I wonder if there is an even better location for the=20
test outside of either's regression suite.

--=20
Tristan Partin
PostgreSQL Contributors Team
AWS (https://aws.amazon.com)