Re: Capturing both IP address and hostname in the log

On Thu, Apr 10, 2025 at 9:00 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> [ moving to -hackers ]
>
> Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com> writes:
> > On 4/10/25 05:22, Tefft, Michael J wrote:
> >> We have set log_hostname ON and we get hostname reported – but we do
> not
> >> get IP address. We would like to capture both.
> >> Is there a way to capture both IP address and hostname in the log
> >> messages? Or must we choose “one or the ootehr”?
>
> > I see the same thing. It seems either or.
>

cross-posting to -hackers now that it is here.

v19 plans aside the existing wording is incorrect (just here, other places
correctly point out the either-or aspect of the output).

The wording really should be more like:

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index fea683cb49..c545fee6c9 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7614,10 +7614,11 @@ local0.* /var/log/postgresql
</term>
<listitem>
<para>
- By default, connection log messages only show the IP address of the
- connecting host. Turning this parameter on causes logging of the
- host name as well. Note that depending on your host name
resolution
- setup this might impose a non-negligible performance penalty.
+ By default, for TCP/IP-originated connections, the identifier of
the host
+ making the connection is its IP address. Turning this parameter
on tells
+ the system to record the resolved host name instead. Note that
depending
+ on your host name resolution setup this might impose a
non-negligible
+ performance penalty.
This parameter can only be set in the
<filename>postgresql.conf</filename>
file or on the server command line.
</para>

Both the connection logging routine and log_line_prefix %h / %r simply
report the "identifier of the host making the connection".

David J.