Changeset 8901 for sites/trunk/wordpress.org/public_html/wp-content/plugins/plugin-directory/libs/site-search/jetpack-search.php

Timestamp:

05/31/2019 06:33:07 AM (6 years ago)

Author:

dd32

Message:

Plugin Directory: Search: Tweak the 'search stampede' code to allow two concurrent search requests.

Currently the locked-with-no-stale-response warning is triggered far too often, this relaxes it a bit while hopefully not overloading things.

File:

• sites/trunk/wordpress.org/public_html/wp-content/plugins/plugin-directory/libs/site-search/jetpack-search.php (modified) (2 diffs)

sites/trunk/wordpress.org/public_html/wp-content/plugins/plugin-directory/libs/site-search/jetpack-search.php

@@ -230 +230 @@
         $response = wp_cache_get( $cache_key, self::CACHE_GROUP );
 
-        // Use a temporary lock to prevent cache stampedes. This ensures only one process (per search term per memcache instance) will run the remote post.
+
+        // Use a temporary lock to prevent cache stampedes.
+        // This will ensure that a maximum of two processes are performing the search, or one when the stale value is still known.
         // Other processes will use the stale cached value if it's present, even for a while after the expiration time if a fresh value is still being fetched.
+        $do_fresh_request = false;
         if ( wp_cache_add( $lock_key, 1, self::CACHE_GROUP, 15 ) ) {
+            $do_fresh_request = true;
+        } elseif ( ! $response && 2 === wp_cache_incr( $lock_key, 1, self::CACHE_GROUP ) ) {
+            // If we don't have cached data, this is the second request and, error volume is low, still perform the request.
+            $do_fresh_request = $this->error_volume_is_low();
+        }
+
+        if ( $do_fresh_request ) {
             // Keep track of the number of concurrent requests for this key
             wp_cache_set( $count_key, 1, self::CACHE_GROUP, 60 );
@@ -257 +267 @@
 
                 // Lock further requests for the same search for 3-7 seconds. We probably don't need anything more complex like exponential backoff here because this is per search.
-                wp_cache_set( $lock_key, 1, self::CACHE_GROUP, mt_rand( 3, 7 ) );
+                wp_cache_set( $lock_key, 2, self::CACHE_GROUP, mt_rand( 3, 7 ) );
 
                 if ( is_wp_error( $request ) ) {