Dave has a question abtou Multisite and caching!
I asked about caching on multisite setups. I’ve got 10 of these, with between 10-50 sites added to each- and the content is static- never going to change it much. I have a feeling I could benefit from caching, you recommended server side. I could use some help here. I know your site says you’re maxed out time wise- I’m thinking I just need someone to help me with one site, and show me what to do. Or, if they want to set things up on all of them. Do you have any recommendations?
Thanks again for the help.
Dave
Caching! There are three main types: plugin, server, and proxy.
Plugin caching is WP Super Cache, or W3TC, and it’s letting WP make a static cache file on demand. Server caching is APC/Memecached and such, which lets the server make a dynamic cache. Proxy caching is Varnish and the like, which puts a cache before the WordPress server, kind of like a static file on another server.
Which one is best for Multisite with static content? Probably a proxy cache there. Though I’m going to go out on a limb and say if you’re not using WordPress for all it’s useful for, maybe you don’t need it at all. If you have a pretty static site, where you’re not changing content all that much, there’s nothing wrong with static HTML. But if you want to use WordPress (like you’re a WordPress only shop) then you have to consider the options. What is your site doing?
This is actually not a Multisite Question so much as a cache management question. The part that’s multisite specific is who to you let manage what aspect of the cache. I maintain a plugin called Varnish HTTP Purge, which is a pretty basic plugin that checks for common actions, like posting or commenting, and flushes your cache selectively on Varnish when those things happen. One of the Multisite specific issues with that code came up when I added in a new feature: Purge Cache.
That feature lets you press a button to flush the whole cache. Pretty cool, right? The problem was Multisite with Subfolders. See, the way the cache flushes is to say “Dump everything under domain.com!” which works fine with subdomain sites, as that will only flush domain.com and not foo.domain.com. On a subfolder, though, it’ll flush domain.com, domain.com/foo/ and domain.com/bar/ and everything else. That would suck! So the best thought I had was I should lock the flush down to Super Admins only on the main site on a subdomain setup. Normally I allow the site admin to flush their own cache, but this way only the Super Admin could make a full flush.
And that’s the crux of the issue with caching on Multisite. Do you want each admin to maintain their own cache? Do you want it to be something you control for everyone? W3 Total Cache can do that, by the way. You can do it both ways with that plugin, and only control what you want to control for the network. But what about if even I don’t want to do that? What if I want to be lazy and trust my tools? That’s when you look at the server itself and try to make it as brainless as possible. Decisions, not options, remember?
And that brings up another question. Why do I want to manage who flushes at all? In my Varnish example, it’s because careless flushing clears the whole cache, which means my server and site have to recache everything and it slows everyone down. Obviously I want to limit that as much as possible. The other reason is work. People who have a managed hosting site generally aren’t the most technical savvy users in the world. Some are, of course, but many are more likely the ones who don’t want to know about the crazy server stuff. This is great, but it means I want to make their life easier so I have to provide less support, then I want things that do their job and do it well, and that means taking options away and making decisions for them.
How would I cache a static Multisite network and fully control it as a network admin? Probably server side caching like Varnish or ZendAccelerator Memcache. If I can’t do that, I’d use W3TC and lock it down so only I, the super admin, in my fancy cape, can edit settings and purge the cache. And always, always, remember to only catch what should be caught in your cache. If you have a site that’s a store, account for that.
