Varnish keeps caching my tracking software

Question

I have a Varnish setup for one of my sites. I'm using the open source software Piwik for my stats tracking.

Piwik have an option of having a Proxy for tracking, which means that the URL of Piwik won't be revealed in my source code. Basically it's a PHP file that sits on my wordpress install and it sends CURL posts to my Piwik install...

Now, I set up my Varnish using: https://github.com/mattiasgeniar/varnish-3.0-configuration-templates

In vcl_fetch I added:

if (req.url ~ "piwik") {
    set beresp.ttl = 120s;
    return (hit_for_pass);
}

In vcl_recv I added:

if (req.url ~ "piwik") {
    return (pass);
}

What happens is, I see only 50% of the traffic I actually have on the website...

I'm afraid it's because of my vcl_fetch settings...

I read the differences between pass and hit_for_pass and from what I understand beresp.ttl is a config that I guides varnish to keep doing pass for 120s

One more thing, W3TotalCache on WP adds some caching headers like Max-Age & expires to my piwik.php file. Without Varnish it's still working well and tracking correctly. Is it possible that there is some sort of collision between Varnish and those headers?

Do I get it right? Why do you think 50% of my tracking is missed?

Thanks.

1. What's the PATH string of the PHP script? 2. Is the real "hidden" Piwik tracker also behind Varnish? If so, what is its PATH? — Ludwik Trammer
Hey, The Real PIWIK is not under Varnish. The path is /wp-content/wp-piwik/piwik.php Thanks. — tounano
Unfortunately I don't know what's wrong then. vcl_fetch code is completely redundant in you case, and the url regex should be more specific, but still - as far as I know what you have should work. — Ludwik Trammer

lkarsten lkarsten · Accepted Answer · 2013-11-06T14:29:16

The Varnish configuration for pass-ing in vcl_recv is correct.

The code you have in vcl_fetch can be removed, it doesn't make any difference at that point because of the code in recv.

Remember that any VCL code that filters response headers in vcl_fetch is also run for pass-ed responses. I'd guess that you are filtering the Set-Cookie that piwik sends.

Varnish keeps caching my tracking software

1 Answers