How to ignore specific query parameter with varnish cache?

Question

/swatches/ajax/media/?product_id=17620&isAjax=true&_=1524469655019

I need to cache this request with varnish, but i need to ignore the last query parameter _=1524469655019.

I am not sure how varnish internally works, but i suppose it makes the cache uid key from the url requested. So in my case it would need it only to create the uid key from this url

/swatches/ajax/media/?product_id=17620&isAjax=true

Doing something like req.url ~ "^/swatches/(.*)$" would not work as varnish would still use the entire url for cache uid.

You can use this module https://github.com/NYTimes/libvmod-queryfilter — Ôrel, Apr 23 '18 at 14:48
https://serverfault.com/questions/112531/ignoring-get-parameters-in-varnish-vcl — Ôrel, Apr 23 '18 at 14:51
You can achieve this easily by nuster cache server, https://github.com/jiangwenyuan/nuster — nuster cache server, Apr 26 '18 at 05:04

score 1 · Accepted Answer · edited Jun 20 '20 at 09:12

just strip the _= from the QS.

sub vcl_recv {
  set req.url = regsuball(req.url,"\?_=[^&]+$",""); # strips when QS = "?_=AAA"
  set req.url = regsuball(req.url,"\?_=[^&]+&","?"); # strips when QS = "?_=AAA&foo=bar"

}

keep in mind this will strip the QS - and the QS is not forwarded to the backend. if you need it in the backend you'd need to do in in vcl_hash

beware if you have a custom vcl_hash, to include the default rules, as the custom removes the default hash parameters. http.host || client.ip

VCL hash is the part the generates the cache-uuid

sub vcl_hash {
  set req.http.hash_url = regsuball(req.url,"\?_=[^&]+$",""); # strips when QS = "?_=AAA"
  set req.http.hash_url = regsuball(req.http.hash_url,"\?_=[^&]+&","?"); # strips when QS = "?_=AAA&foo=bar"
  hash_data(req.http.hash_url);
  if (req.http.host) {
    hash_data(req.http.host);
  } else {
    hash_data(server.ip);
  }
}

this way, the request that produces a MISS also passes _= to the backend. and there is no explicit need for a vmod in such a simple case.

How to ignore specific query parameter with varnish cache?

1 Answers1