Re: Delays between "connection received" and "connection authenticated" because of localhost entries in hba

On 10/29/24 09:30, Daniel Westermann (DWE) wrote:
> Delays between "connection received" and "connection authenticated" because of localhost entries in hba
>
> Hi,
>
> we're facing a strange issue with delays between "connection received" and "connection authenticated".
>
> # select version();
> version
> -----------------------------------------------------------------------------------------------------------------------------------
> PostgreSQL 15.6 (Ubuntu 15.6-1.pgdg22.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0, 64-bit
> (1 ligne)
>
> I know, this is not the latest minor version.
>
> # \! cat /etc/os-release | head -1
> PRETTY_NAME="Ubuntu 22.04.4 LTS"
>
> What we see in the log is this (around 4 seconds delay):
>
> 2024-05-07 15:29:50.244 CEST [369909] LOG: connection received: host=xx.xx.xx.100 port=48434
> 2024-05-07 15:29:54.518 CEST [369909] LOG: connection authenticated: identity="xxxxxx" method=md5 (/etc/postgresql/15/main/pg_hba.conf:121)

1) host=xx.xx.xx.100 = localhost?

2) In postgresql.conf what is listen_addresses set to?

3) What are the settings in /etc/hosts?

>
> The matching line is this ( I know md5 ):
> host all xxxxx xx.xx.xx.0/24 md5
>
> What we've found out so far is, that this only happens if we have a localhost(or any other hostname) line before the line matching our connection, something like this:
> host replication xxxxx localhost md5
> host all xxxxx xx.xx.xx.0/24 md5
>
> We don't see it if we do it like this:
> host all xxxxx xx.xx.xx.0/24 md5
> host replication xxxxx localhost md5
>
> Has anyone experienced such a behavior? It seems clear that this is somehow related to name resolution but we couldn't reproduce something like this on the OS using dig (in a loop several hundred of times). It is also only happening from time to time, and not constantly.
>
> What we're basically looking for is a way to prove the assumption without involving PostgreSQL at all, if that does make sense?
>
> Many thanks in advance
> Daniel
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com