Varnish Cache Configuration

Manage the Varnish page cache

When Varnish is installed on your server, its card on the Services tab has a Configure button. It opens two tabs: Cache Exclusions for everyday rules, and Edit Raw VCL for everything else. Both check your change before it goes live, so a typo cannot take your sites down.

01 · Cache Exclusions

Some pages must never come from a shared cache: carts, compare pages, anything that keeps a visitor's choices in cookies. Addresses that match a rule here always skip the cache: they go to your site with their cookies, and the answer is never stored.

1. Type a regular expression in URL Pattern (regex) and, in the label field, why the rule exists.
2. Click Add Rule.
3. Type an address in Test a URL against your rules to see which rule it matches, as you type.
4. Keep Also purge already-cached URLs matching new rules ticked, so the rule works at once.
5. Click Save & Apply.

Patterns are matched against the path and query string, for example /products/compare?selected=1,2. They are not anchored: use ^ and $. Write a literal ? or . as \? or \.. Double quotes are not allowed.

The rules live in their own file, included from the main VCL. If that include line goes missing after a manual edit, it is put back at the next save.

02 · Edit Raw VCL

The full /etc/varnish/default.vcl, for cache lifetimes, grace mode, cookies and anything else VCL can do. Save & Apply:

• keeps a dated copy of the current file (the last 10);
• compiles the new VCL first: on an error you see the compiler's message and the running configuration stays;
• loads the new VCL without restarting Varnish and without emptying the cache.

03 · First-time setup

When Varnish is installed but not yet set up for a site, Edit Raw VCL opens with a guide in comments and a reference VCL to uncomment. The chain it sets up:

visitor → Apache :80/:443 (TLS) → Varnish 127.0.0.1:6081 → Apache 127.0.0.1:8080 → PHP-FPM

1. Make Varnish listen on 127.0.0.1:6081.
2. Move the site's virtual host to 127.0.0.1:8080, keeping real visitor addresses in the logs and telling PHP when the request came over HTTPS.
3. Create a front virtual host on ports 80 and 443 that keeps the certificate and passes everything to Varnish.
4. Uncomment and adapt the reference VCL, then Save & Apply.

The guide has the full examples for each step. A file with only comments does not compile, so the editor asks you to uncomment the VCL part first.

04 · Check it works

The reference VCL adds an X-Cache header to every answer:

curl -sI https://www.example.com/some-page | grep X-Cache

• MISS, then HIT on the next request: the page is cached.
• MISS every time: the address is excluded or cannot be cached. That is what you want for a page with an exclusion rule.

The Stats button on the Varnish card shows the hit rate, memory and evictions: see Cache stats.