Making cachefu page purging work with vary headers : one solution nuke the Accept-Language <-- is this wise?

[Rob Rogers]

Thanks Laurence,

It looks like purge() instead of purge_url() and bans are the trick.

FYI, I did a purge("req.url == " req.url); wild card purges don't look  
necessary. i.e., == instead of ~

-rob
On Mar 17, 2010, at 4:57 AM, Laurence Rowe wrote:

> Take a look at my improved vcl for plone.recipe.varnish here:
>
> http://dev.plone.org/collective/browser/buildout/plone.recipe.varnish/branches/elro-better-vcl/plone/recipe/varnish/template.vcl
>
> While you do want to normalize Accept-Encoding (remember Zope only
> does gzip) you still have to account for browsers which do not handle
> gzip. As there is currently no way to invalidate varies, I use purge
> to add it to the ban list.
>
> You should just set English as the only allowed language in
> portal_languages to prevent internationalization of message strings.
>
> Laurence
>
> On 17 March 2010 10:21, Rob Rogers <robertbrogers at gmail.com> wrote:
>> The issue:
>> html type pages (think objects in zope) cached in varnish, were not  
>> purged
>> successfully with zope/plone/cachefu purging methods.
>> Images were purged. but html content was not.
>>
>> Given we depend on caching pages in accelerator/zope/plone this is  a
>> showstopper. (e.g. we use this:  cache-in-proxy-1-hour for (most)  
>> html
>> content)
>>
>> In order to make purging work, I had to normalize or unset a couple  
>> http.req
>> attributes. This is what I came up with.
>>
>> The 'working' solution:
>> sub vcl_recv {
>>        ...
>>        if (req.http.Accept-Encoding) { /* lifted from varnish site */
>>          if (req.url ~ "\.(jpg|png|gif|gz|tgz|bz2|tbz|mp3|ogg)$") {
>>                        # No point in compressing these
>>            remove req.http.Accept-Encoding;
>>          } elsif (req.http.Accept-Encoding ~ "gzip") {
>>            set req.http.Accept-Encoding = "gzip";
>>          } elsif (req.http.Accept-Encoding ~ "deflate") {
>>            set req.http.Accept-Encoding = "deflate";
>>          } else {
>>                        # unkown algorithm
>>            remove req.http.Accept-Encoding;
>>          }
>>        }
>>        unset req.http.Accept-Language; /* is this DANGEROUS? */
>>        unset req.http.user-agent;
>>        set req.http.host = "my.cashmoney.com";
>>        ...
>> }
>>
>> Based on what I have read, unsetting these attributes help keep  
>> multiple
>> cache objects to a minimum.
>> Which is the reasoning behind normalizing the Accept-Encoding per
>> http://varnish-cache.org/wiki/FAQ/Compression
>>
>> So, I guess I have 2 questions:
>> 1) Given the site is only served in english, is there a danger of  
>> serving up
>> the wrong hit for a browser with a different Accept-Language?
>> 2) Will I still get purge misses for objects  cached by some  
>> browsers, like
>> ones presenting deflate instead of gzip in the header?
>>
>>
>> Thanks,
>>
>> Rob
>>
>>
>>
>>
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>>