Automatically clear related pages from Pantheon's Edge when you update content. High TTL. Fresh content. Visitors never wait.
For sites wanting fine-grained control over how their responses are represented in their edge cache, Pantheon Advanced Page Cache is the golden ticket. Here’s a high-level overview of how the plugin works:
WP_Query
object to “tag” the response with identifers for the data used in the response. See the “Adding Custom Keys” section for including your own surrogate keys.Because of its surrogate key technology, Pantheon Advanced Page Cache empowers WordPress sites with a significantly more accurate cache purge mechanism, and generally higher cache hit rate. It even works with the WordPress REST API.
Go forth and make awesome! And, once you’ve built something great, send us feature requests (or bug reports).
Pantheon Advanced Page Cache makes heavy use of surrogate keys, which enable responses to be “tagged” with identifiers that can then later be used in purge requests. For instance, a home page response might include the Surrogate-Key
header with these keys:
Surrogate-Key: front home post-43 user-4 post-41 post-9 post-7 post-1 user-1
Similarly, a GET
requests to /wp-json/wp/v2/posts
might include the Surrogate-Key
header with these keys:
Surrogate-Key: rest-post-collection rest-post-43 rest-post-43 rest-post-9 rest-post-7 rest-post-1
Because cached responses include metadata describing the data therein, surrogate keys enable more flexible purging behavior like:
There is a limit to the number of surrogate keys in a response, so we’ve optimized them based on a user’s expectation of a normal WordPress site. See the “Emitted Keys” section for full details on which keys are included, and the “Adding Custom Keys” section following for information on how to add your own.
By default, Pantheon Advanced Page Cache generates surrogate keys based on an interpretation of the main WP_Query
query object. Because WordPress sends headers before the page is rendered, you need to use the pantheon_wp_main_query_surrogate_keys
filter to include additional surrogate keys for any data present on the page.
For example, to include surrogate keys for a sidebar rendered on the homepage, you can filter the keys using the is_home()
template tag:
/** * Add surrogate key for the featured content sidebar rendered on the homepage. */ add_filter( 'pantheon_wp_main_query_surrogate_keys', function( $keys ){ if ( is_home() ) { $keys[] = 'sidebar-home-featured'; } return $keys; });
Then, when sidebars are updated, you can use the pantheon_wp_clear_edge_keys()
helper function to emit a purge event specific to the surrogate key:
/** * Trigger a purge event for the featured content sidebar when widgets are updated. */ add_action( 'update_option_sidebars_widgets', function() { pantheon_wp_clear_edge_keys( array( 'sidebar-home-featured' ) ); });
Similarly, to include surrogate keys for posts queried on the homepage, you can pre-fetch the posts before the page is rendered:
/** * An example of pre-fetching a WP_Query to tag the * response with queried data. You'd use `papcx_wp_query()` * a second time within your template to use the data. */ add_filter( 'pantheon_wp_main_query_surrogate_keys', function( $keys ) { if ( is_home() ) { $query = papcx_wp_query( array( 'post_type' => 'page', ) ); foreach( $query->posts as $post ) { $keys[] = 'post-' . $post->ID; } } return $keys; }); /** * Register a 'papc-non-persistent' cache group to cache data * in a non-persistent manner. We only want data in this group * to be cached within the page request. */ add_action( 'init', function(){ wp_cache_add_non_persistent_groups( array( 'papc-non-persistent' ) ); }); /** * Helper function to instantiate a WP_Query object only * once per page request. * * @param array $args Arguments to pass to WP_Query. * @return WP_Query */ function papcx_wp_query( $args = array() ) { $cache_key = md5( serialize( $args ) ); // WP_Query object will be in cache the second time we use the function. $cache_value = wp_cache_get( $cache_key, 'papc-non-persistent' ); if ( false !== $cache_value ) { return $cache_value; } $query = new WP_Query( $args ); wp_cache_set( $cache_key, $query, 'papc-non-persistent' ); return $query; }
Because Pantheon Advanced Page Cache already handles WordPress post purge events, there’s no additional call to pantheon_wp_clear_edge_keys()
.
Lastly, the pantheon_wp_rest_api_surrogate_keys
filter lets you filter surrogate keys present in a REST API response.
Need a bit more power? In addition to pantheon_wp_clear_edge_keys()
, there are two additional helper functions you can use:
pantheon_wp_clear_edge_paths( $paths = array() )
– Purge cache for one or more paths.pantheon_wp_clear_edge_all()
– Warning! With great power comes great responsibility. Purge the entire cache, but do so wisely.By default, Pantheon Advanced Page Cache is pretty aggressive in how it clears its surrogate keys. Specifically, any time wp_insert_post
is called (which can include any time a post of any type is added or updated, even private post types), it will purge a variety of keys including home
, front
, 404
and feed
. To bypass or override this behavior, since 1.5.0-dev we have a filter allowing an array of post types to ignore to be passed before those caches are purged. By default, the revision
post type is ignored, but others can be added:
/** * Add a custom post type to the ignored post types. * * @param array $ignored_post_types The array of ignored post types. * @return array */ function filter_ignored_posts( $ignored_post_types ) { $ignored_post_types[] = 'my-post-type'; // Ignore my-post-type from cache purges. return $ignored_post_types; } add_filter( 'pantheon_purge_post_type_ignored', 'filter_ignored_posts' );
This will prevent the cache from being purged if the given post type is updated.
The cache max age setting is controlled by the Pantheon Page Cache admin page. As of 2.0.0, there are three cache age options by default — 1 week, 1 month, 1 year. Pantheon Advanced Page Cache automatically purges the cache of updated and related posts and pages, but you might want to override the cache max age value and set it programmatically. In this case, you can use the pantheon_cache_default_max_age
filter added in Pantheon MU plugin 1.4.0+. For example:
add_filter( 'pantheon_cache_default_max_age', function() { return 10 * DAY_IN_SECONDS; } );
When the cache max age is filtered in this way, the admin option is disabled and a notice is displayed.
The cache max age setting is controlled by the Pantheon Page Cache admin page. As of 2.0.0, there are three cache age options by default — 1 week, 1 month, 1 year. Pantheon Advanced Page Cache automatically purges the cache of updated and related posts and pages, but you might want to override the cache max age value and set it programmatically. In this case, you can use the pantheon_cache_default_max_age
filter added in Pantheon MU plugin 1.4.0+. For example:
add_filter( 'pantheon_cache_default_max_age', function() { return 10 * DAY_IN_SECONDS; } );
When the cache max age is filtered in this way, the admin option is disabled and a notice is displayed.
This plugin implements a variety of WP-CLI commands. All commands are grouped into the wp pantheon cache
namespace.
$ wp help pantheon cache NAME wp pantheon cache DESCRIPTION Manage the Pantheon Advanced Page Cache. SYNOPSIS wp pantheon cache <command> SUBCOMMANDS purge-all Purge the entire page cache. purge-key Purge one or more surrogate keys from cache. purge-path Purge one or more paths from cache.
Use wp help pantheon cache <command>
to learn more about each command.
By default, Pantheon’s infrastructure strips out the Surrogate-Key
response header before responses are served to clients. The contents of this header can be viewed as Surrogate-Key-Raw
by adding on a debugging header to the request.
A direct way of inspecting headers is with curl -I
. This command will make a request and show just the response headers. Adding -H "Pantheon-Debug:1"
will result in Surrogate-Key-Raw
being included in the response headers. The complete command looks like this:
curl -IH "Pantheon-Debug:1" https://scalewp.io/
Piping to grep
will filter the output down to just the Surrogate-Key-Raw
header:
curl -IH "Pantheon-Debug:1" https://scalewp.io/ | grep -i Surrogate-Key-Raw
Tada!
Home /
home
, front
, post-<id>
(all posts in main query)Single post /2016/10/14/surrogate-keys/
single
, post-<id>
, post-user-<id>
, post-term-<id>
(all terms assigned to post)Author archive /author/pantheon/
archive
, user-<id>
, post-<id>
(all posts in main query)Term archive /tag/cdn/
archive
, term-<id>
, post-<id>
(all posts in main query)Day archive /2016/10/14/
archive
, date
, post-<id>
(all posts in main query)Month archive /2016/10/
archive
, date
, post-<id>
(all posts in main query)Year archive /2016/
archive
, date
, post-<id>
(all posts in main query)Search /?s=<search>
search
, either search-results
or search-no-results
, post-<id>
(all posts in main query)Not found (404)
404
Posts
/wp-json/wp/v2/posts
emits surrogate keys: rest-post-collection
, rest-post-<id>
/wp-json/wp/v2/posts/<id>
emits surrogate keys: rest-post-<id>
Pages
/wp-json/wp/v2/pages
emits surrogate keys: rest-page-collection
, rest-post-<id>
/wp-json/wp/v2/pages/<id>
emits surrogate keys: rest-post-<id>
Categories
/wp-json/wp/v2/categories
emits surrogate keys: rest-category-collection
, rest-term-<id>
/wp-json/wp/v2/categories/<id>
emits surrogate keys: rest-term-<id>
Tags
/wp-json/wp/v2/tags
emits surrogate keys: rest-post_tag-collection
, rest-term-<id>
/wp-json/wp/v2/tags/<id>
emits surrogate keys: rest-term-<id>
Comments
/wp-json/wp/v2/comments
emits surrogate keys: rest-comment-collection
, rest-comment-post-<post-id>
, rest-comment-<id>
/wp-json/wp/v2/comments/<id>
emits surrogate keys: rest-comment-post-<post-id>
, rest-comment-<id>
Users
/wp-json/wp/v2/users
emits surrogate keys: rest-user-collection
, rest-user-<id>
/wp-json/wp/v2/users/<id>
emits surrogate keys: rest-user-<id>
Settings
/wp-json/wp/v2/settings
emits surrogate keys: rest-setting-<name>
Different WordPress actions cause different surrogate keys to be purged, documented here.
wp_insert_post / transition_post_status / before_delete_post / delete_attachment
home
, front
, 404
, post-<id>
, user-<id>
, term-<id>
, rest-<type>-collection
, rest-comment-post-<id>
clean_post_cache
post-<id>
, rest-post-<id>
created_term / edited_term / delete_term
term-<id>
, post-term-<id>
, rest-<taxonomy>-collection
clean_term_cache
term-<id>
, rest-term-<id>
wp_insert_comment / transition_comment_status
rest-comment-collection
, rest-comment-<id>
clean_comment_cache
rest-comment-<id>
clean_user_cache
user-<id>
, rest-user-<id>
updated_option
rest-setting-<name>
Setting surrogate keys for posts with large numbers of taxonomies (such as WooCommerce products with a large number of global attributes) can suffer from slower queries. Surrogate keys can be skipped for ‘product’ post types’ taxonomy terms (or any other criteria you see fit) with the following filter:
function custom_should_add_terms($should_add_terms, $wp_query) { if ( $wp_query->is_singular( 'product' ) ) { return false; } return $should_add_terms; } add_filter('pantheon_should_add_terms', 'custom_should_add_terms', 10, 2);<h3>Other Filters</h3>
Since 2.0.0, Pantheon Advanced Page Cache displays a number of admin notices about your current cache max age value. You can disable these notices with the pantheon_apc_disable_admin_notices
filter.
add_filter( 'pantheon_apc_disable_admin_notices', '__return_true' );
Alternately, the function callback is passed into the pantheon_apc_disable_admin_notices
filter, allowing you to specify precisely which notice to disable, for example:
add_filter( 'pantheon_apc_disable_admin_notices', function( $disable_notices, $callback ) { if ( $callback === '\\Pantheon_Advanced_Page_Cache\\Admin_Interface\\admin_notice_maybe_recommend_higher_max_age' ) { return true; } return $disable_notices; }, 10, 2 );
The above example would disable only the admin notice recommending a higher cache max age.
Since 2.0.0, Pantheon Advanced Page Cache displays a number of admin notices about your current cache max age value. You can disable these notices with the pantheon_apc_disable_admin_notices
filter.
add_filter( 'pantheon_apc_disable_admin_notices', '__return_true' );
Alternately, the function callback is passed into the pantheon_apc_disable_admin_notices
filter, allowing you to specify precisely which notice to disable, for example:
add_filter( 'pantheon_apc_disable_admin_notices', function( $disable_notices, $callback ) { if ( $callback === '\\Pantheon_Advanced_Page_Cache\\Admin_Interface\\admin_notice_maybe_recommend_higher_max_age' ) { return true; } return $disable_notices; }, 10, 2 );
The above example would disable only the admin notice recommending a higher cache max age.
Pantheon Advanced Page Cache integrates with WordPress plugins, including:
See CONTRIBUTING.md for information on contributing.
To install Pantheon Advanced Page Cache, follow these steps:
To install Pantheon Advanced Page Cache in one line with WP-CLI:
wp plugin install pantheon-advanced-page-cache --activate
nonce_life
filter when nonces are created on the front-end to set the pantheon_cache_default_max_age
to less than the nonce lifetime to avoid nonces expiring before the cache does. [#282] props @ryanshooverpantheon_purge_post_type_ignored
to allow an array of post types to ignore before purging cache [#258]pantheon_should_add_terms
to allow disabling surrogate keys for posts’ taxonomy terms [239]WPGraphQL\Model\Model
class [#212].?_embed
emits correct surrogate keys [#103].feed
surrogate key for RSS feeds, and purges when posts are created, modified, or deleted.$rest_base
property of post types and taxonomies when set.delete_others_posts
capability has been deleted.