Varnish only resolve the ip on startup

Dridi Boukelmoune dridi at
Mon Oct 4 16:48:36 UTC 2021

On Mon, Oct 4, 2021 at 3:45 PM Guillaume Quintard
<guillaume.quintard at> wrote:
> I think it makes sense for Varnish to natively support backends changing their IPs. I do get the performance argument but now that there is a cloud/container market and that Varnish has proven to be useful in it, this basic functionality should be brought in.

I would assume the primary argument was simplicity, not performance,
but I wasn't around. One could argue it's turned into simplism in
today's cloudy cloud cloudy world.

> Would it be acceptable to add a "host_string" to vrt_endpoint and fill it if the VCL backend isn't an IP, then, we can add another cp_methods to cache_conn_pool.c to use it? This way IPs are still super fast, and hostnames become actually useful and a bit less confusing?

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.

I do think we could do something about it, I don't know what would be


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