Events: Cache event queries for performance.

Co-Authored-By: Paul Kevan <[email protected]>

public_html/wp-content/themes/wporg-events-2023/inc/event-getters.php

@@ -5,6 +5,72 @@
 
 defined( 'WPINC' ) || die();
 
+
+add_action( 'init', __NAMESPACE__ . '\schedule_cron_jobs' );
+add_action( 'events_landing_prime_query_cache', __NAMESPACE__ . '\prime_query_cache' );
+
+/**
+ * Schedule cron jobs.
+ */
+function schedule_cron_jobs(): void {
+	if ( ! wp_next_scheduled( 'events_landing_prime_query_cache' ) ) {
+		wp_schedule_event( time(), 'hourly', 'events_landing_prime_query_cache' );
+	}
+}
+
+/**
+ * Prime the caches of events.
+ *
+ * Without this, users would have to wait for new results to be generated every time the cache expires. That could
+ * make the front end very slow. This will refresh the cache before it expires, so that the front end can always
+ * load cached results.
+ */
+function prime_query_cache(): void {
+	get_all_upcoming_events( true );
+
+	$city_landing_uris = get_known_city_landing_request_uris();
+
+	foreach ( $city_landing_uris as $request_uri ) {
+		get_city_landing_page_events( $request_uri, true );
+	}
+}
+
+/**
+ * Get a list of all known city landing page request URIs.
+ *
+ * For example, `/rome/`, `/rome/training/`, `/rome/2023/`.
+ */
+function get_known_city_landing_request_uris(): array {
+	$city_landing_pages = array();
+
+	$city_sites = get_sites( array(
+		'network_id'   => EVENTS_NETWORK_ID,
+		'path__not_in' => array( '/' ),
+		'number'       => false,
+		'public'       => 1,
+		'archived'     => 0,
+		'deleted'      => 0,
+	) );
+
+	foreach ( $city_sites as $site ) {
+		$parts = explode( '/', trim( $site->path, '/' ) );
+
+		if ( 3 !== count( $parts ) ) {
+			continue;
+		}
+
+		$city  = $parts[0];
+		$year  = absint( $parts[1] );
+		$title = preg_replace( '#^(.*)(-\d+)$#', '$1', $parts[2] ); // Strip any `-2`, `-3`, `-n` suffixes.
+
+		$city_landing_pages[ sprintf( '/%s/', $city ) ]            = true;
+		$city_landing_pages[ sprintf( '/%s/%s/', $city, $year ) ]  = true;
+		$city_landing_pages[ sprintf( '/%s/%s/', $city, $title ) ] = true;
+	}
+
+	return array_keys( $city_landing_pages );
+}
+
 /**
  * Query a table that's encoded with the `latin1` charset.
  *
@@ -13,6 +79,8 @@
  * `utf8mb4`, you'll get Mojibake.
  *
  * @param string $prepared_query ⚠️ This must have already be ran through `$wpdb->prepare()` if needed.
+ *
+ * @return object|null
  */
 function get_latin1_results_with_prepared_query( string $prepared_query ) {
 	global $wpdb;
@@ -33,8 +101,16 @@ function get_latin1_results_with_prepared_query( string $prepared_query ) {
 /**
  * Get a list of all upcoming events across all sites.
  */
-function get_all_upcoming_events(): array {
-	global $wpdb;
+function get_all_upcoming_events( bool $force_refresh = false ): array {
+	$cache_key = 'event_landing_all_upcoming_events';
+
+	if ( ! $force_refresh ) {
+		$cached_events = get_transient( $cache_key );
+
+		if ( $cached_events ) {
+			return $cached_events;
+		}
+	}
 
 	$events = get_latin1_results_with_prepared_query( '
 		SELECT
@@ -62,6 +138,9 @@ function get_all_upcoming_events(): array {
 		unset( $event->date_utc );
 	}
 
+	// `prime_query_cache()` should update this hourly, but expire after a day just in case it doesn't.
+	set_transient( $cache_key, $events, DAY_IN_SECONDS );
+
 	return $events;
 }
 
@@ -70,8 +149,22 @@ function get_all_upcoming_events(): array {
  *
  * See `get_city_landing_sites()` for how request URIs map to events.
  */
-function get_city_landing_page_events( string $request_uri ): array {
-	$limit = 300;
+function get_city_landing_page_events( string $request_uri, bool $force_refresh = false ): array {
+	$limit     = 300;
+	$cache_key = 'event_landing_city_events_' . md5( $request_uri );
+
+	if ( empty( $request_uri ) || '/' === $request_uri ) {
+		return array();
+	}
+
+	if ( ! $force_refresh ) {
+		$cached_events = get_transient( $cache_key );
+
+		if ( $cached_events ) {
+			return $cached_events;
+		}
+	}
+
 	$sites = get_city_landing_sites( $request_uri, $limit );
 
 	switch_to_blog( WORDCAMP_ROOT_BLOG_ID );
@@ -109,14 +202,31 @@ function get_city_landing_page_events( string $request_uri ): array {
 
 	restore_current_blog();
 
+	// `prime_query_cache()` should update this hourly, but expire after a day just in case it doesn't find all the
+	// valid request URIs.
+	set_transient( $cache_key, $events, DAY_IN_SECONDS );
+
 	return $events;
 }
 
+/**
+ * Standardize request URIs so they can be reliably used as cache keys.
+ *
+ * For example, `/rome`, `/rome/` and `/rome/?foo=bar` should all be `/rome/`.
+ */
+function normalize_request_uri( $raw_uri, $query_string ) {
+	$clean_uri = str_replace( '?' . $query_string, '', $raw_uri );
+	$clean_uri = trailingslashit( $clean_uri );
+	$clean_uri = '/' . ltrim( $clean_uri, '/' );
+
+	return $clean_uri;
+}
+
 /**
  * Get sites that match the given request URI.
  *
  * /rome/          -> All sites in Rome
- * /rome/training/ -> All training sites in Rome
+ * /rome/training/ -> All training sites in Rome (including those with slugs like `training-2`)
  * /rome/2023/     -> All sites in Rome in 2023
  */
 function get_city_landing_sites( string $request_uri, int $limit ): array {

public_html/wp-content/themes/wporg-events-2023/patterns/city-landing-page-map.php

@@ -14,8 +14,8 @@
 	return;
 }
 
-// Can't use $wp->request because Gutenberg calls this on `init`, before `parse_request`.
-$request_uri = str_replace( '?' . $_SERVER['QUERY_STRING'], '', $_SERVER['REQUEST_URI'] );
+// Can't use `$wp->request` because Gutenberg calls this on `init`, before `parse_request`.
+$request_uri = normalize_request_uri( $_SERVER['REQUEST_URI'], $_SERVER['QUERY_STRING'] );
 
 $map_options = array(
 	'id'      => 'city-landing-page',