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Message-ID: <792f687d-5188-4beb-b94b-3d3edeb384a3@aklaver.com>
Date: Tue, 29 Oct 2024 09:38:05 -0700
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Subject: Re: Delays between "connection received" and "connection
 authenticated" because of localhost entries in hba
To: "Daniel Westermann (DWE)" <daniel.westermann@dbi-services.com>,
 "pgsql-general@lists.postgresql.org" <pgsql-general@lists.postgresql.org>
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From: Adrian Klaver <adrian.klaver@aklaver.com>
In-Reply-To: <GV0P278MB0419EB5885DF99C5354804A9D24B2@GV0P278MB0419.CHEP278.PROD.OUTLOOK.COM>
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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.klaver@aklaver.com