manipulating page content

[dtownrobbrown at gmail.com]

On May 12, 2010 1:41pm, Laurence Rowe <l at lrowe.co.uk> wrote:
> On 12 May 2010 08:40, Rob Brown dtownrobbrown at gmail.com> wrote:

> >> If we are talking about stuff in the body of the object, the anwer is

> >> no.

> >

> >

> > yes, unfortunately that is what I am looking for. I am trying to see if

> > varnish can "replicate" the functionality of a commercial cache  
> appliance

> > from a "well-known" vendor.

> >

> >>

> >> You could always use ESI for it, but apart from that, there's currently

> >> no way to manipulate the content of a page.

> >

> > ESI would probably work and be much easier, but reading the wiki

> > (http://varnish-cache.org/wiki/ESIfeatures) it seems like Varnish  
> doesn't

> > yet support the "Content substitution based on variables" functionality.

> > I am not well versed in ESI, but I think would be looking to do  
> something

> > like this:

> >

> >
> >  
> href="http://www.example.com/getpage?sessionKey=$(QUERY_STRING{'sessionKey'})"/>get

> > page

> >

> > In the wiki, it says "For now we have deemed this feature  
> uninteresting, but

> > adding it is just a matter of programming." What are the chances of  
> getting

> > support for variables in a future release?



> It might be possible to make this work with just ESI includes.

> Assuming that the ESI subrequests reuse the same req object as the

> parent request (I'm not sure about this point), all you need do is

> generate the key as a synthetic response in vcl_error. Something like:



> sub vcl_recv {

> if (req.url == "/_esi/sessionKey") {

> error 701;

> } else {

> set req.http.X-Session-Key = # regexp to extract session key from url

> }

> }

> sub vcl_error {

> if (obj.status == 701) {

> synthetic {

> "http://www.example.com/getpage?sessionKey="

> req.http.X-Session-Key "%34>get page"

> };

> }

> }



> And use in your page:
> <esi:include src="/_esi/sessionKey"/>

> Laurence


That's pretty cool... Will have to try it!
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