Purge Multiple Varnish Caches when pages are modified.
This was built and tested on Varnish 3.x, however it is reported to work on 2.x. It is only supported on v3 at this time.
The only pages that should purge are the post's page, the front page, categories, and tags. The reason why is a little philosophical.
When building out this plugin, there were a couple pathways on how best to handle purging caches and they boiled down to two: Decisions (the plugin purges what it purges when it purges) and Options (you decide what to purge, when and why). It's entirely possible to make this plugin purge everything, every time a 'trigger' happens, have it purge some things, or have it be so you can pick that purges.
In the interests of design, we decided that the KISS principle was key. Since you can configure your Varnish to always purge all pages recursively (i.e. purging http://example.com/ would purge all pages below it), if that's a requirement, you can set it yourself. There are also other Varnish plugins that allow for more granular control (including W3 Total Cache), however this plugin will not be gaining a whole bunch of options to handle that.
Because the plugin only purges your content when you edit it. That means if you edit a page/post, or someone leaves a comment, it'll change. Otherwise, you have to purge the whole cache. The plugin will do this for you if you change your theme, but not when you edit your theme.
That said, if you use Jetpack's CSS editor, it will purge the whole cache on save.
Click the 'Purge Varnish Cache' button on the "Right Now" Dashboard (see the screenshot if you can't find it).
Because PageSpeed likes to put in Caching headers to say not to cache. To fix this, you need to put this in your .htaccess section for PageSpeed:
If you're using nginx, it's
pagespeed ModifyCachingHeaders off;
Yes, but you'll need to make some additonal changes (see "Why aren't my changes showing when I use CloudFlare or another proxy?" below).
If you use the Jetpack CSS editor, however, your changes will show up.
When you use CloudFlare or any other similar servive, you've got a proxy in front of the Varnish proxy. In general this isn't a bad thing. The problem arises when the DNS shenanigans send the purge request to your domainname. When you've got an additional proxy like CloudFlare, you don't want the request to go to the proxy, you want it to go to Varnish server.
To fix this, add the following to your wp-config.php file:
Replace "18.104.22.168" with the IP of your Varnish Server (not CloudFlare, Varnish). DO NOT put in http in this define.
You can also set the option
vhp_varnish_ip in the database. This will NOT take precedence over the define, it's just there to let hosts who are using something like wp-cli do this for you in an automated fashion:
wp option add vhp_varnish_ip 22.214.171.124
wp option update vhp_varnish_ip 126.96.36.1990
add the following to your wp-config.php file:
Replace "188.8.131.52" and "266.600.33.1" with the IP addresses of your Varnish Servers (not CloudFlare, Varnish). DO NOT put in http in this define, you can list as many Varnish Servers as you have in this way.
you cannot use
wp option add or
wp option update to set more than one vhp_varnish_ip
Your Varnish IP must be one of the IPs that Varnish is listening on. If you use multiple IPs, or if you've customized your ACLs, you'll need to pick on that doesn't conflict with your other settings. For example, if you have Varnish listening on a public and private IP, you'll want to pick the private. On the other hand, if you told Varnish to listen on 0.0.0.0 (i.e. "listen on every interface you can") you would need to check what IP you set your purge ACL to allow (commonly 127.0.0.1 aka localhost), and use that (i.e. 127.0.0.1).
If your webhost set up Varnish for you, you may need to ask them for the specifics if they don't have it documented. I've listed the ones I know about here, however you should still check with them if you're not sure.
Make sure your Varnish VCL is configured correctly to purge all the right pages. This is normally an issue with Varnish 2, which is not supported.
The plugin sends a PURGE command of
X-Purge-Method in the header with a value of regex. If your Varnish server doesn't doesn't understand the wildcard, you can configure it to check for the header.
This is a beyond this plugin question in a way, since I don't offer any Varnish Config help. I will say this, you absolutely must have PURGE set up in your VCL. This is still supported in Varnish v3, though may not be set up by default. Also, here are some links to other people who use this plugin and have made public their VCLs:
All of these VCLs work with this plugin.