Hi,
On Sat, Aug 4, 2018 at 1:50 AM, K3 <[email protected]> wrote:
> Hi,
> We are running into a problem and would like to hear any advice.
>
> Our Setup:
> We use haproxy 1.7.7 with two backends.
> One of the backends is AWS ELB
> The haproxy is running on a linux machine in our data center (on premises)
>
> Problem:
> The ELB is available on 3 AZ so the endpoint can resolve to 3 IPs at a
> given time.
> After startup, when one of the ELB's IP changes, our haproxy shows the ELB
> as down with L4TMOUT and never recovers the backend.
>
> From 1.7.7 doc, under section 5.3.1 we see the below
> "A few other events can trigger a name resolution at run time:
>
> - when a server's health check ends up in a connection timeout: this may be
> because the server has a new IP address. So we need to trigger a name
> resolution to know this new IP."
>
> Its not clear if the resolvers section is required for the above statement to
> be true.
>
> Unfortunately, we cannot define name server's IPs in our configuration since
> these IPs can change.
>
> On the system (/etc/resolv.conf), these are automatically updated by dhclient.
>
> Question:
>
> 1. Is there any way by which haproxy can use the latest DNS entries from the
> system config and use it during the runtime?
>
> I just saw this announced in 1.9-dev1
- the "resolvers" section can now be fed directly from resolv.conf
using the "parse-resolv-conf" directive. The DNS code also supports
new options to enable/disable address deduplication within a farm.
so you might give it a try.
> 2. Is there any way to configure haproxy to expire name resolution after X
> secs without defining the nameserver IPs?
>
> There is "hold valid" option for the "resolvers" section to tell haproxy
to refresh the resolved names lets say every 10 seconds. Makes sense in
case of
reading from resolv.conf to re-read its content as well but not sure, maybe
it does it once on startup and then it's cached, we need someone from
haproxy team to comment on this.
> Please advice.
>
> Thanks,
> Karthik
>
