Re: Python and /etc/resolv.conf changes
On Wed, 2009-01-21 at 09:26 -0500, Colin Walters wrote:
On Tue, Jan 20, 2009 at 8:19 PM, Colin Walters
<walters(a)verbum.org> wrote:
>
> Both Debian/Ubuntu
> (http://patches.ubuntu.com/g/glibc/extracted/any/local-dynamic-resolvconf....)
> and OpenSUSE
(http://download.opensuse.org/distribution/11.0/repo/src-oss/suse/src/glib...,
> resolv.dynamic.diff) ship a patch to glibc which stats() resolv.conf.
> We do not.
Thinking about this a bit more this morning on the shuttle, there's a
strong argument that this is a glibc bug, and that the stat() approach
is a correct fix, if not necessarily the most ideal one. That
argument is simply that glibc is caching data without a mechanism for
invalidation; and a cache without invalidation is always a bug.
This was discussed with the glibc maintainers a long time ago, and was
rejected for various reasons (see below). Their answer at the time was
to use "lwresd", a lightweight caching nameserver, or nscd to provide
this functionality. This was back in 2004, so perhaps things have
changed, and maybe it's time to strike up the conversation again.
However, I suspect the answer is still "use nscd".
Dan
--------------------------------------
On Fri, 2004-06-04 at 07:48 -0700, Ulrich Drepper wrote:
Dan Williams wrote:
> 1) make glibc stat() /etc/resolv.conf on every call that does name
> lookups
> 2) make glibc re-read /etc/resolv.conf every time something does a name
> lookup
> 3) use nscd instead, and modify ncsd to do either (1) or (2)?
None of this is an option. There is no way we are going to make
everybody pay the price for the needs of a few people who wants
everything to happen automatically.
The solution is to use nscd and have some external code explicitly flush
the cache with
service nscd reload
This is already possible for, I guess, 5-6 years.