Forum: NGINX DNS TTLs being ignored

I have recently come across several related issues which I have tracked 
down
to nginx and the way it handles DNS.
I run nginx as a proxy for several back end services. It works really 
well,
except for 1 thing.
My proxy_pass refers to an upstream which points to a DNS entry.
That DNS entry is a CNAME with a TTL of 60 seconds.
Nginx doesn't appear to be honoring that TTL. This has happened twice 
now.
My upstream DNS information has changed, pointing to a new IP address.
Instead of recovering withing 1 minute (which would happen if TTLs were
being honored), I have had to restart nginx.
When I searched for it, I found that nginx doesn't appear to honor TTLs, 
at
all (http://www.ruby-forum.com/topic/2657341).

What I'm hoping to find out, is why?
Why does nginx cache DNS entries, instead of referring to the operating
system? The OS has DNS handling built in. It respects TTLs, and it works
perfectly. Nginx, on the other hand, is effectively broken as a load
balancer, since upstreams might change IP addresses at any time (which 
is
why we're using DNS names, instead of IP addresses.

Thanks,
Noah

Noah,

Right, thanks for your observation. It really took a while, but we're 
actually about to fix this one shortly.

Thanks for the reply Andrew. Do you have any idea when it's likely to be 
generally available? This is a pretty big nuisance for us, and I'd like 
to be able to figure out if I need to look at using a new reverse proxy, 
at least for the time being.

--Noah

Noah,

This fix/improvement be introduced in 1.1.8 which will come out around 
Nov 14.

Hope this helps

On Nov 3, 2011, at 1:50 PM, Andrew Alexeev wrote:

> Noah,
>
> This fix/improvement be introduced in 1.1.8 which will come out around Nov 14.

Apologies, it didn't get in either 1.1.8 (yesterday) or 1.1.10 (today). 
It's almost ready and would hopefully get into the next dev and stable 
releases in a couple of weeks.

On Nov 15, 2011, at 1:50 PM, Andrew Alexeev wrote:

> On Nov 3, 2011, at 1:50 PM, Andrew Alexeev wrote:
>
>> Noah,
>>
>> This fix/improvement be introduced in 1.1.8 which will come out around Nov 14.
>
> Apologies, it didn't get in either 1.1.8 (yesterday) or 1.1.10 (today). It's 
almost ready and would hopefully get into the next dev and stable releases in a 
couple of weeks.

Jfyi, it went committed today

http://mailman.nginx.org/pipermail/nginx-devel/201...
http://nginx.org/en/docs/http/ngx_http_core_module...

and will be included in 1.1.9.

That's great news. Thank you very much. I'll be sure to get hold of it 
as soon as 1.1.9 is released.

--Noah

On 16 November 2011 14:00, Andrew Alexeev <andrew@nginx.com> wrote:
> Jfyi, it went committed today
>
> http://mailman.nginx.org/pipermail/nginx-devel/201...
> http://nginx.org/en/docs/http/ngx_http_core_module...
>
> and will be included in 1.1.9.

You mentioned it'd be in stable at some point.
I can't find it in any subsequent 1.0.x announcement - could you
clarify the status of this feature in stable please?

Many thanks,
Jonathan
--
Jonathan Matthews
London, UK
http://www.jpluscplusm.com/contact.html

Hello!

On Mon, Feb 06, 2012 at 03:03:14PM +0000, Jonathan Matthews wrote:

> >
> > Jfyi, it went committed today
> >
> > http://mailman.nginx.org/pipermail/nginx-devel/201...
> > http://nginx.org/en/docs/http/ngx_http_core_module...
> >
> > and will be included in 1.1.9.
>
> You mentioned it'd be in stable at some point.
> I can't find it in any subsequent 1.0.x announcement - could you
> clarify the status of this feature in stable please?

It's not in 1.0.x, and probably won't be.  The 1.1.x branch is
expected to become stable in near future.

Maxim Dounin