How do I get varnish to return in the http response header from which backend it took the response?

Question

I have three servers in the backend, with a round robin director.

I would like varnish to write a X-Server-By header with the name or ip of the server from which the response was fetched, how can this be done?

rossnz · Answer 1 · 2010-04-07 02:51:49Z

up vote 2 down vote

sub vcl_fetch {
    set obj.http.X-Backend = req.backend;
}

Tested on 2.0.6 in my (non round robin) setup. It should give you something to go on.

answered Apr 7 '10 at 2:04

that just displays the backend id, not the individual server – hoberion Nov 2 '10 at 11:26

feedback

Conor McDermottroe · Answer 2 · 2010-03-29 08:07:59Z

up vote 0 down vote

The following is not tested, but might get you started:

sub vcl_deliver {
    set resp.http.X-Served-By = server.hostname;
    deliver;
}

answered Mar 29 '10 at 8:07

that gives you the name of het varnish server – hoberion Nov 2 '10 at 11:35

feedback

Nirav24x7 · Answer 3 · 2011-06-17 20:01:50Z

You can set the header on your web server eg x-host: server2 and then varnish will return that as part of the response to a cache hit.

I have this working on apache and it works perfectly.

3 Answers