Adding header depending on if request was fetched or passed

[Hugo Cisneiros (Eitch)]

On Fri, Aug 10, 2012 at 5:49 AM, Connor Walls
<connor.walls at skillpages.com> wrote:
> Hi all,
>
> So, as it stands we have the fairly common set up in our vcl_deliver to add a header to indicate whether or not the object was served from cache or not:
[...]
> Now, in addition to this, I was wondering if it would be possible to add a header to indicate whether or not we attempted to fetch the object from cache, i.e. if the request had gone through vcl_fetch or vcl_pass. My initial thought was to add some form of header in those subroutines but obviously I'm not able to access resp here. Is there anything that obj would be able to tell me in vcl_deliver about this?

Try setting http headers on vcl_miss (when it needs to fetch from
backend) and vcl_hit (when it doesn't). Then o vcl_deliver you set de
resp.http.* based on these. Example:

sub vcl_hit {
  set req.http.X-Varnish-TTL = obj.ttl;
  set req.http.X-Varnish-Cache = "hit";
}

sub vcl_miss {
  set req.http.X-Varnish-TTL = 0;
  set req.http.X-Varnish-Cache = "miss";
}

sub vcl_deliver {
  set resp.http.X-Varnish-TTL = req.http.X-Varnish-TTL;
  set resp.http.X-Varnish-Cache = req.http.X-Varnish-Cache;
}

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Hugo
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