Re: Capturing both IP address and hostname in the log

On Thu, Apr 10, 2025 at 5:22 AM Tefft, Michael J <Michael(dot)J(dot)Tefft(at)snapon(dot)com>
wrote:

> The documentation for log_hostname says:
>
> log_hostname (boolean)
>
> 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. This parameter can only be set
> in the postgresql.conf file or on the server command line.
>
>
>
> https://www.postgresql.org/docs/14/runtime-config-logging.html
>
>
>
Yeah, 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.