Ticket #17462: 17462.6.diff

Index: wp-includes/default-constants.php
===================================================================
--- wp-includes/default-constants.php   (revision 18653)
+++ wp-includes/default-constants.php   (working copy)
@@ -268,6 +268,12 @@
 
        if ( !defined('WP_POST_REVISIONS') )
                define('WP_POST_REVISIONS', true);
+
+       /**
+        * @since 3.3.0
+        */
+       if ( !defined( 'WP_CRON_LOCK_TIMEOUT' ) )
+               define('WP_CRON_LOCK_TIMEOUT', 60);  // In seconds
 }
 
 /**
Index: wp-includes/cache.php
===================================================================
--- wp-includes/cache.php       (revision 18653)
+++ wp-includes/cache.php       (working copy)
@@ -102,13 +102,14 @@
  *
  * @param int|string $key What the contents in the cache are called
  * @param string $group Where the cache contents are grouped
+ * @param bool $force Whether to force an update of the local cache from the persistent cache (default is false)
  * @return bool|mixed False on failure to retrieve contents or the cache
  *             contents on success
  */
-function wp_cache_get($key, $group = '') {
+function wp_cache_get( $key, $group = '', $force = false ) {
        global $wp_object_cache;
 
-       return $wp_object_cache->get($key, $group);
+       return $wp_object_cache->get( $key, $group, $force );
 }
 
 /**
@@ -403,10 +404,11 @@
         *
         * @param int|string $key What the contents in the cache are called
         * @param string $group Where the cache contents are grouped
+        * @param string $force Whether to force a refetch rather than relying on the local cache (default is false)
         * @return bool|mixed False on failure to retrieve contents or the cache
         *              contents on success
         */
-       function get($key, $group = 'default') {
+       function get( $key, $group = 'default', $force = false) {
                if ( empty ($group) )
                        $group = 'default';
 
Index: wp-includes/cron.php
===================================================================
--- wp-includes/cron.php        (revision 18653)
+++ wp-includes/cron.php        (working copy)
@@ -204,13 +204,13 @@
        * multiple processes on multiple web servers can run this code concurrently
        * try to make this as atomic as possible by setting doing_cron switch
        */
-       $flag = get_transient('doing_cron');
+       $lock = get_transient('doing_cron');
 
-       if ( $flag > $local_time + 10*60 )
-               $flag = 0;
+       if ( $lock > $local_time + 10*60 )
+               $lock = 0;
 
        // don't run if another process is currently running it or more than once every 60 sec.
-       if ( $flag + 60 > $local_time )
+       if ( $lock + WP_CRON_LOCK_TIMEOUT > $local_time )
                return;
 
        //sanity check
@@ -226,10 +226,11 @@
                if ( !empty($_POST) || defined('DOING_AJAX') )
                        return;
 
-               set_transient( 'doing_cron', $local_time );
+               $doing_wp_cron = $local_time;
+               set_transient( 'doing_cron', $doing_wp_cron );
 
                ob_start();
-               wp_redirect( add_query_arg('doing_wp_cron', '', stripslashes($_SERVER['REQUEST_URI'])) );
+               wp_redirect( add_query_arg('doing_wp_cron', $doing_wp_cron, stripslashes($_SERVER['REQUEST_URI'])) );
                echo ' ';
 
                // flush any buffers and send the headers
@@ -240,9 +241,10 @@
                return;
        }
 
-       set_transient( 'doing_cron', $local_time );
+       $doing_wp_cron = $local_time;
+       set_transient( 'doing_cron', $doing_wp_cron );
 
-       $cron_url = get_option( 'siteurl' ) . '/wp-cron.php?doing_wp_cron';
+       $cron_url = get_option( 'siteurl' ) . '/wp-cron.php?doing_wp_cron=' . $doing_wp_cron;
        wp_remote_post( $cron_url, array('timeout' => 0.01, 'blocking' => false, 'sslverify' => apply_filters('https_local_ssl_verify', true)) );
 }
 
Index: wp-cron.php
===================================================================
--- wp-cron.php (revision 18653)
+++ wp-cron.php (working copy)
@@ -26,6 +26,24 @@
        require_once('./wp-load.php');
 }
 
+// Uncached doing_cron transient fetch
+function _get_cron_lock() {
+       global $_wp_using_ext_object_cache, $wpdb;
+
+       $value = 0;
+       if ( $_wp_using_ext_object_cache ) {
+               // Skip local cache and force refetch of doing_cron transient in case
+               // another processs updated the cache
+               $value = wp_cache_get( 'doing_cron', 'transient', true );
+       } else {
+               $row = $wpdb->get_row( $wpdb->prepare( "SELECT option_value FROM $wpdb->options WHERE option_name = %s LIMIT 1", '_transient_doing_cron' ) );
+               if ( is_object( $row ) )
+                       $value = $row->option_value;
+       }
+
+       return $value;
+}
+
 if ( false === $crons = _get_cron_array() )
        die();
 
@@ -35,26 +53,52 @@
 if ( isset($keys[0]) && $keys[0] > $local_time )
        die();
 
-foreach ($crons as $timestamp => $cronhooks) {
+$doing_cron_transient = get_transient( 'doing_cron');
+
+// Use global $doing_wp_cron lock otherwise use the GET lock. If no lock, trying grabbing a new lock.
+if ( empty( $doing_wp_cron ) ) {
+       if ( empty( $_GET[ 'doing_wp_cron' ] ) ) {
+               // Called from external script/job. Try setting a lock.
+               if ( $doing_cron_transient && ( $doing_cron_transient + WP_CRON_LOCK_TIMEOUT > $local_time ) )
+                       return;
+               $doing_cron_transient = $doing_wp_cron = time();
+               set_transient( 'doing_cron', $doing_wp_cron );
+       } else {
+               $doing_wp_cron = $_GET[ 'doing_wp_cron' ];
+       }
+}
+
+// Check lock
+if ( $doing_cron_transient != $doing_wp_cron )
+       return;
+
+foreach ( $crons as $timestamp => $cronhooks ) {
        if ( $timestamp > $local_time )
                break;
 
-       foreach ($cronhooks as $hook => $keys) {
+       foreach ( $cronhooks as $hook => $keys ) {
 
-               foreach ($keys as $k => $v) {
+               foreach ( $keys as $k => $v ) {
 
                        $schedule = $v['schedule'];
 
-                       if ($schedule != false) {
+                       if ( $schedule != false ) {
                                $new_args = array($timestamp, $schedule, $hook, $v['args']);
                                call_user_func_array('wp_reschedule_event', $new_args);
                        }
 
-                       wp_unschedule_event($timestamp, $hook, $v['args']);
+                       wp_unschedule_event( $timestamp, $hook, $v['args'] );
 
-                       do_action_ref_array($hook, $v['args']);
+                       do_action_ref_array( $hook, $v['args'] );
+
+                       // If the hook ran too long and another cron process stole the lock, quit.
+                       if ( _get_cron_lock() != $doing_wp_cron )
+                               return;
                }
        }
 }
 
+if ( _get_cron_lock() == $doing_wp_cron )
+       delete_transient( 'doing_cron' );
+
 die();