Re: Why don't we allow DNS names in pg_hba.conf?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Jon Jensen <jon(at)endpoint(dot)com>
Cc: Andreas Pflug <pgadmin(at)pse-consulting(dot)de>, "Marc G(dot) Fournier" <scrappy(at)postgresql(dot)org>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Why don't we allow DNS names in pg_hba.conf?
Date: 2006-01-02 19:06:38
Message-ID: 8029.1136228798@sss.pgh.pa.us
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

Jon Jensen <jon(at)endpoint(dot)com> writes:
> On Mon, 2 Jan 2006, Tom Lane wrote:
>> Can you demonstrate that this is actually a serious concern next to the
>> total time spent launching a backend? I can't measure any real change
>> in total time for "psql -l" when log_hostname is enabled, which should
>> be a comparable hit.

> The difference is negligible when using a UNIX socket (of course) or names
> listed in /etc/hosts. But it's certainly slower in my tests if you really
> use DNS. On a run of 1000 connections doing "psql -l", it takes 18.89s
> without the DNS lookup for log_hostname, and 31.5s with. Or run as a
> one-off, it's 0.032 to 0.041s.

Um --- I was testing a local-loopback connection, but now that I look at
the nsswitch.conf setup, it was going to /etc/hosts for that case.
Coming across the network so that a real DNS lookup is forced, there
seems to be a difference of about 4ms (note this is with a local DNS
daemon). I don't think that's significant. If it is, you've got other
performance problems anyway, and should switch to pooled connections to
reduce the number of backend launches.

regards, tom lane

In response to

Browse pgsql-hackers by date

  From Date Subject
Next Message Tom Lane 2006-01-02 19:12:03 Re: What bison versions are installed on buildfarm machines?
Previous Message Joshua D. Drake 2006-01-02 19:00:21 Re: What bison versions are installed on buildfarm machines?