On 31Jul13, Jakub Hrozek allegedly wrote:
> On Wed, Jul 31, 2013 at 02:58:31PM +0000, Mark Delany wrote:
> > On 31Jul13, Daniel Pocock allegedly wrote:
> > > - if the application discovers new DNS servers (or if Ares has a way of
> >
> > Unfortunately that's what I've had to do. Monitor for DNS server changes and
> > create a new ares channel.
>
> In SSSD, we use this approach as well. Watch resolv.conf with inotify
> and just destroy and recreate the channel as appropriate.
Right. The good news is that ares_destroy is callback friendly in that
all the callbacks are called during the destroy process so you're not
left with any lingering or lost queries.
The bad news is that all the pending queries have to be re-initiated
on the new channel.
I imagine a clever implementation could have callbacks that test for
ARES_ECANCELLED/ARES_EDESTRUCTION and automatically re-add the
query to the newly constructed channel.
Really, the biggest problem for me is that my user code has to get
into the same business as ares_init() in that it has to know how to
detect the changed environment. The current approach is a simplistic
test on /etc/resolv.conf, but that doesn't work on all platforms.
Mark.
Received on 2013-07-31