SQLite Object Cache vs WeAmp Cache Control for ModPageSpeed

A persistent object cache helps your site perform well. This one uses the widely available SQLite3 extension, and optionally the igbinary and APCu extensions to php. Many hosting services offer those extensions, and they are easy to install on a server you control. What is this about? It’s about making your site’s web server perform better. An object cache does that by reducing the workload on your MariaDB or MySQL database. This is not a page cache; these persistent objects go into a different kind of cache. These objects aren’t chunks of web pages ready for people to view in their browsers, they are data objects for use by the WordPress software. Caches are ubiquitous in computing, and WordPress has its own caching subsystem. Caches contain short-term copies of the results of expensive database lookups or computations, and allow software to use the copy rather than repeating the expensive operation. This plugin (like other object-caching plugins) extends WordPress’s caching subsystem to save those short-term copies from page view to page view. WordPress’s cache happens to be a memoization cache. Without a persistent object cache, every WordPress page view must use your MariaDB or MySQL database server to retrieve everything about your site. When a user requests a page, WordPress starts from scratch and loads everything it needs from your database server. Only then can it deliver content to your user. With a persistent object cache, WordPress immediately loads much of the information it needs. This lightens the load on your database server and delivers content to your users faster. Who should use this? If your site runs on a single web server machine, and that server provides the SQLite3 and igbinary extensions to php, this plugin will almost certainly make your site work faster. And if that server provides the APCu extension, this plugin uses it too. Some hosting providers offer redis cache servers. If your provider offers redis, it may be a good choice. You can use it via the Redis Object Cache plugin. Sites using redis have one SQL database and another non-SQL storage server: redis. Other hosting providers offer memcached, which has the Memcached Object Cache plugin. And some large multipurpose cache plugins, such as the LiteSpeed Cache, also offer object caching based on one of those cache server software packages. The cache-server approach to object caching comes into its own when you have multiple load-balanced web server machines handling your site. SQLite doesn’t work correctly in a multiple-web-server environment. But, for single-server site configurations, SQLite, possibly assisted by APCu, performs well. And the vast majority of sites are single-server. APCu APCu is an in-memory storage medium. It lets php programs, like WordPress, store data in shared memory so it’s very fast to retrieve when needed. If APCu is available on your host server, you can configure this plugin to use it. It reduces the typical cache lookup time to one-fifth or less of the SQLite lookup time, which is itself a few tens of microseconds. Performance counts, especially on busy web sites. Please look at Installation to learn how to configure this plugin to use APCu. The plugin works fast without it, and faster with it. WP-CLI: Even if APCu is in use, caching with SQLite is necessary when your web site uses WP-CLI, because WP-CLI programs do not have access to the APCu cache. This plugin writes all cached data both to APCu and to SQLite and makes sure the two are synchronized. WP-CLI You can control this plugin via WP-CLI once you activate it. Please type this command into your shell for details. wp help sqlite-object-cache Credits Thanks to Till Krüss. His Redis Object Cache plugin serves as a model for this one. And thanks to Ari Stathopoulos and Jonny Harris for reviewing this. Props to Matt Jones for finding and fixing a bug that appeared on a heavily loaded system. Thanks to Massimo Villa for testing help, and to nickchomey for a comprehensive code review. All defects are, of course, entirely the author’s responsibility. And thanks to Jetbrains for the use of their software development tools, especially PhpStorm. It’s hard to imagine how a plugin like this one could be developed without PhpStorm’s tools for exploring epic code bases like WordPress’s. How can I learn more about making my WordPress site more efficient? We offer several plugins to help with your site’s database efficiency. You can read about them here.

This plugin is the control panel for ModPageSpeed — a web server optimization module for nginx and Apache. ModPageSpeed must be installed and running on your server for this plugin to function. It is not a standalone caching plugin. The plugin does three things: Enables full-page caching — adds Cache-Control: public, max-age=N to anonymous page responses (WordPress does not send this by default), with explicit bypasses for logged-in users, WooCommerce cart/checkout/account pages, search, feeds, and 404s. Keeps the cache fresh — calls the ModPageSpeed purge API when you publish, update, or delete content, when comments change, when stock levels change, and when terms or theme settings change. Gives you control in WP Admin and WP-CLI — per-post-type TTLs, cookie bypass list, excluded URL patterns, a first-run setup wizard, and wp pagespeed flush|status|test-connection commands. Works with both ModPageSpeed product lines (auto-detected), with one important difference: ModPageSpeed 2.0 caches full HTML pages itself — the plugin’s headers and purge calls drive the module’s page cache directly. mod_pagespeed / ngx_pagespeed 1.1 does not cache HTML (it is a streaming rewriter; its in-place optimization caches only images, CSS, and JS). Full-page caching on 1.1 requires an external cache layer in front (nginx proxy_cache, Varnish, or a CDN) plus ModifyCachingHeaders off or DownstreamCachePurgeLocationPrefix — with 1.1’s default ModifyCachingHeaders on, the module replaces this plugin’s Cache-Control header on rewritten HTML. On 1.1, the plugin’s purge calls evict optimized sub-resources and metadata, not HTML pages. Server requirements ModPageSpeed 1.1 (v1.15.0+r3 or later) or ModPageSpeed 2.0 (v2.0.0 or later) installed on your web server. For 2.0: the worker admin API enabled (--api-port). For full logged-in-user correctness an nginx cookie-bypass map block is required — the setup wizard provides a copy-paste snippet and verifies it. WP-CLI wp pagespeed flush [--url= ] — purge the home page (and posts page), or one specific URL on this site. wp pagespeed status — detected product, version, license tier, purge prerequisites, and last-purge status. wp pagespeed test-connection — verify the admin API is reachable and correctly configured (read-only, never purges). License This plugin is free software, licensed under the GNU General Public License v2.0 or later. The full GPL-2.0 license text is bundled with the plugin in the LICENSE file. Third Party Services This plugin makes HTTP requests to the operator-configured ModPageSpeed admin API URL. Data sent includes page URLs (for cache purging) and an API key (for authentication). No data is sent to We-Amp or any third party.