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?

thepearson · Accepted Answer · 2012-07-11 04:42:03Z

12

In Varnish 3.0.2 I use:

sub vcl_fetch {
    set beresp.http.X-Backend = beresp.backend.name;
}

Works perfectly.

answered Jul 11, 2012 at 4:42

thepearson

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2

For Varnish 4, vcl_fetch has been renamed vcl_backend_response. Otherwise this works there too.
– Pete
Jul 31, 2014 at 21:50

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

4

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, 2010 at 2:04

rossnz

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1

that just displays the backend id, not the individual server
– hoberion
Nov 2, 2010 at 11:26
In Varnish 3+ this should be: set beresp.http.X-Backend = req.backend;, however it will still only report the backend's id so it will not be that useful with round-robin backends.
– Martijn Heemels
Jul 4, 2012 at 13:39
This is not the way to do it. Set the header on the backend.
– Pax
Jul 11, 2012 at 19:13

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

3

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.

answered Jun 17, 2011 at 20:01

Nirav24x7

311 bronze badge

Do it this way, trying to set the header in Varnish doesn't make sense. Set it at the backend itself and Varnish will pass it on to the client.
– Pax
Jul 11, 2012 at 19:11

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

-1

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, 2010 at 8:07

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4 Answers 4