Varnish only resolve the ip on startup

Justin Lloyd justinl at
Mon Oct 4 17:29:55 UTC 2021

I’m definitely watching this topic, considering I’m planning on moving to Varnish Enterprise next year and putting a cluster in ECS, if not Fargate, so being able to easily handle dynamic IPs would be extremely helpful.

From: varnish-misc < at> On Behalf Of Guillaume Quintard
Sent: Monday, October 4, 2021 10:16 AM
To: Dridi Boukelmoune <dridi at>
Cc: varnish-misc at
Subject: Re: Varnish only resolve the ip on startup

On Mon, Oct 4, 2021 at 9:49 AM Dridi Boukelmoune <dridi at<mailto:dridi at>> wrote:
One problem I have (and that you should be familiar with) is that
portable interfaces we have that *respect* the system configuration
(hosts file, nsswitch configuration etc) are not providing enough
information. For example it becomes cumbersome to resolve SRV records
or even get the TTL of individual records for a DNS resolution in a
*portable* fashion.

When you put it like this, it sounds simple enough (dare I say
simplistic?) but what I see is a sizeable can of worms.

That sounds like a bit of a strawman to me. getaddrinfo and connect are standard, and that's about all we should need. Applications are supposed (in general) to just use whatever gai give them. We can call them every time we need a new connection so we don't worry about TTL, and we just disregard SRV records.
The vast majority of users don't need SRV (yet?), and don't expect the application to optimize DNS calls, but they do complain that giving a hostname to VCL doesn't work.

Let's just provide basic, expected functionality out of the box, and leave the fancier features to vmod_goto and vmod_dynamic.

Guillaume Quintard
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