[150741] in North American Network Operators' Group
Re: dns and software, was Re: Reliable Cloud host ?
daemon@ATHENA.MIT.EDU (Jared Mauch)
Fri Mar 2 14:33:11 2012
From: Jared Mauch <jared@puck.nether.net>
In-Reply-To: <4F4F8F3C.9090706@mtcc.com>
Date: Fri, 2 Mar 2012 14:32:03 -0500
To: Michael Thomas <mike@mtcc.com>
Cc: Nanog <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Mar 1, 2012, at 10:01 AM, Michael Thomas wrote:
> The real issue is that gethostbyxxx has been inadequate for a very
> long time. Moving it across the kernel boundary solves nothing and
> most likely causes even more trouble: what if I want, say, =
asynchronous
> name resolution? What if I want to use SRV records? What if a new DNS
> RR comes around -- do i have do recompile the kernel? It's for these
> reasons and probably a whole lot more that connect just confuses the
> actual issues.
<software-developer-hat-on>
My experience is that these calls are expensive and require a lot of =
work to get a true result. Some systems also have interim caching that =
happens as well (e.g. NSCD).
When building software that did a lot of dns lookups at once, I had to =
build my own internal cache to maintain performance. Startup costs were =
expensive, but maintaining it started to space out a bit more and be =
less of an issue.
I ended up caching these entries for 1 hour by default.
</hat ?xml-fail>
- jared=
