Initial commit of version 0.6 from http://wordpress.org/extend/plugins/wp-cron-control/.

readme.txt

+=== WP-Cron Control ===
+Contributors: tott, automattic
+Tags: wp-cron, cron, cron jobs, post missed schedule, scheduled posts
+Donate link: http://hitchhackerguide.com
+Tested up to: 3.3
+Stable tag: trunk
+
+This plugin allows you to take control over the execution of cron jobs. 
+
+== Description ==
+
+This plugin allows you to take control over the execution of cron jobs. It's mainly useful for sites that either don't get enough comments to ensure a frequent execution of wp-cron or for sites where the execution of cron via regular methods can cause race conditions resulting in multiple execution of wp-cron at the same time. It can also help when you run into posts that missed their schedule.
+
+This plugin implements a secret parameter and ensures that cron jobs are only executed when this parameter is existing.
+
+== Installation ==
+
+* Install either via the WordPress.org plugin directory, or by uploading the files to your server.
+* Activate the Plugin and ensure that you enable the feature in the plugins' settings screen
+* Follow the instructions on the plugins' settings screen in order to set up a cron job that either calls `php wp-cron-control.php http://blog.address secret_string` or `wget -q "http://blog.address/wp-cron.php?doing_wp_cron&secret_string"`
+* If you like to have a global secret string you can define it in your wp-config.php by adding `define( 'WP_CRON_CONTROL_SECRET', my_secret_string' );`
+
+== Limitations ==
+
+This plugin performs a `remove_action( 'sanitize_comment_cookies', 'wp_cron' );` call in order to disable the spawning of new cron processes via the regular WordPress method. If `wp_cron` is hooked in an other action or called directly this might cause trouble.
+ 
+== Screenshots ==
+
+1. Settings screen to enable/disable various features.
+
+== ChangeLog ==
+
+= Version 0.6 =
+
+* Make sure that validated wp-cron-control requests also are valid in wp-cron.php by setting the global $doing_wp_cron value
+
+= Version 0.5 =
+
+* Adjustments for improved cron locking introduced in WordPress 3.3 http://core.trac.wordpress.org/changeset/18659
+
+= Version 0.4 =
+
+* Implementing feedback from Yoast http://yoast.com/wp-plugin-review/wp-cron-control/, fixing button classes, more inline comments 
+
+= Version 0.3 =
+
+* Added option to enable extra check that would search for missing jobs for scheduled posts and add them if necessary.
+
+= Version 0.2 =
+
+* Added capability check in settings page
+
+= Version 0.1 =
+
+* Initial version of this plugin.

wp-cron-control.php

+<?php
+/*
+ Plugin Name: WP-Cron Control
+ Plugin URI: http://wordpress.org/extend/plugins/wp-cron-control/
+ Description: get control over wp-cron execution.
+ Author: Thorsten Ott, Automattic
+ Version: 0.6
+ Author URI: http://hitchhackerguide.com
+ */
+
+class WP_Cron_Control {
+
+	private static $__instance = NULL;
+	
+	private $settings = array();
+	private $default_settings = array();
+	private $settings_texts = array();
+	
+	private $plugin_prefix = 'wpcroncontrol_';
+	private $plugin_name = 'WP-Cron Control';
+	private $settings_page_name ='WP-Cron Control Settings';
+	private $dashed_name = 'wp-cron-control';
+	private $js_version = '20110801';
+	private $css_version = '20110801';
+	
+	private $define_global_secret = NULL;	// if this is set, it's value will be used as secret instead of the option
+	
+	public function __construct() {
+		global $blog_id;
+		
+		// this allows overwriting of the default secret with a value set in the code. Useful If you don't want to give control to users.
+		if ( NULL <> $this->define_global_secret && !defined( 'WP_CRON_CONTROL_SECRET' ) )
+			define( 'WP_CRON_CONTROL_SECRET', $this->define_global_secret );
+		
+		add_action( 'admin_init', array( &$this, 'register_setting' ) );
+		add_action( 'admin_menu', array( &$this, 'register_settings_page' ) );
+		
+		/**
+		 * Default settings that will be used for the setup. You can alter these value with a simple filter such as this
+		 * add_filter( 'wpcroncontrol_default_settings', 'mywpcroncontrol_settings' );
+		 * function mywpcroncontrol_settings( $settings ) {
+		 * 		$settings['secret_string'] = 'i am more secret than the default';
+		 * 		return $settings;
+		 * }
+		 */
+		$this->default_settings = (array) apply_filters( $this->plugin_prefix . 'default_settings', array(
+			'enable'				=> 1,
+			'enable_scheduled_post_validation' => 0,
+			'secret_string'			=> md5( __FILE__ . $blog_id ),
+		) );
+		
+		/**
+		 * Define fields that will be used on the options page
+		 * the array key is the field_name the array then describes the label, description and type of the field. possible values for field types are 'text' and 'yesno' for a text field or input fields or 'echo' for a simple output
+		 * a filter similar to the default settings (ie wpcroncontrol_settings_texts) can be used to alter this values
+		 */
+		$this->settings_texts = (array) apply_filters( $this->plugin_prefix . 'settings_texts', array(
+			'enable'				=> array( 'label' => 'Enable ' . $this->plugin_name, 'desc' => 'Enable this plugin and allow requests to wp-cron.php only with the appended secret parameter.', 'type' => 'yesno' ),
+			'secret_string'			=> array( 'label' => 'Secret string', 'desc' => 'The secret parameter that needs to be appended to wp-cron.php requests.', 'type' => 'text' ),
+			'enable_scheduled_post_validation'	=> array( 'label' => 'Enable scheduled post validation', 'desc' => 'In some rare cases it can happen that even when running wp-cron via a scheduled system cron job posts miss their schedule. This feature makes sure that there is a scheduled event for each scheduled post.', 'type' => 'yesno' ),
+		) );
+					
+		$user_settings = get_option( $this->plugin_prefix . 'settings' );
+		if ( false === $user_settings )
+			$user_settings = array();
+		
+		// after getting default settings make sure to parse the arguments together with the user settings
+		$this->settings = wp_parse_args( $user_settings, $this->default_settings );	
+	
+		/**
+		 * If you define( 'WP_CRON_CONTROL_SECRET', 'my_super_secret_string' ); in your wp-config.php or your theme then
+		 * users are not allowed to change the secret, so we output the existing secret string rather than allowing to add a new one
+		 */ 
+		if ( defined( 'WP_CRON_CONTROL_SECRET' ) ) {
+			$this->settings_texts['secret_string']['type'] = 'echo';
+			$this->settings_texts['secret_string']['desc'] = $this->settings_texts['secret_string']['desc'] . " Cannot be changed as it is defined via WP_CRON_CONTROL_SECRET";
+			$this->settings['secret_string'] = WP_CRON_CONTROL_SECRET;
+		}
+
+	}
+	
+	public static function init() {	
+		if ( 1 == self::instance()->settings['enable'] ) {
+		}	
+		self::instance()->prepare();
+	}
+	
+	/*
+	 * Use this singleton to address methods
+	 */
+	public static function instance() {
+		if ( self::$__instance == NULL ) 
+			self::$__instance = new WP_Cron_Control;
+		return self::$__instance;
+	}
+
+	public function prepare() {
+		/**
+		 * If a css file for this plugin exists in ./css/wp-cron-control.css make sure it's included
+		 */
+		if ( file_exists( dirname( __FILE__ ) . "/css/" . $this->dashed_name . ".css" ) )
+			wp_enqueue_style( $this->dashed_name, plugins_url( "css/" . $this->dashed_name . ".css", __FILE__ ), $deps = array(), $this->css_version );
+		/**
+		 * If a js file for this plugin exists in ./js/wp-cron-control.css make sure it's included
+		 */
+		if ( file_exists( dirname( __FILE__ ) . "/js/" . $this->dashed_name . ".js" ) )
+			wp_enqueue_script( $this->dashed_name, plugins_url( "js/" . $this->dashed_name . ".js", __FILE__ ), array(), $this->js_version, true );
+		
+		/**
+		 * When the plugin is enabled make sure remove the default behavior for issueing wp-cron requests and add our own method
+		 * see: http://core.trac.wordpress.org/browser/trunk/wp-includes/default-filters.php#L236
+		 * and  http://core.trac.wordpress.org/browser/trunk/wp-includes/cron.php#L258
+		 */
+		if ( 1 == $this->settings['enable'] ) {
+			remove_action( 'sanitize_comment_cookies', 'wp_cron' );
+			add_action( 'init', array( &$this, 'validate_cron_request' ) );
+		}
+		
+	}
+
+	public function register_settings_page() {
+		add_options_page( $this->settings_page_name, $this->plugin_name, 'manage_options', $this->dashed_name, array( &$this, 'settings_page' ) );
+	}
+
+	public function register_setting() {
+		register_setting( $this->plugin_prefix . 'settings', $this->plugin_prefix . 'settings', array( &$this, 'validate_settings') );
+	}
+	
+	public function validate_settings( $settings ) {
+		// reset to defaults
+		if ( !empty( $_POST[ $this->dashed_name . '-defaults'] ) ) {
+			$settings = $this->default_settings;
+			$_REQUEST['_wp_http_referer'] = add_query_arg( 'defaults', 'true', $_REQUEST['_wp_http_referer'] );
+		// or do some custom validations
+		} else {
+			
+		}
+		return $settings;
+	}
+	
+	public function settings_page() { 
+		if ( !current_user_can( 'manage_options' ) )  {
+			wp_die( __( 'You do not permission to access this page' ) );
+		}
+		?>
+		<div class="wrap">
+		<?php if ( function_exists('screen_icon') ) screen_icon(); ?>
+			<h2><?php echo $this->settings_page_name; ?></h2>
+		
+			<form method="post" action="options.php">
+		
+			<?php settings_fields( $this->plugin_prefix . 'settings' ); ?>
+		
+			<table class="form-table">
+				<?php foreach( $this->settings as $setting => $value): ?>
+				<tr valign="top">
+					<th scope="row"><label for="<?php echo $this->dashed_name . '-' . $setting; ?>"><?php if ( isset( $this->settings_texts[$setting]['label'] ) ) { echo $this->settings_texts[$setting]['label']; } else { echo $setting; } ?></label></th>
+					<td>
+						<?php
+						/**
+						 * Implement various handlers for the different types of fields. This could be easily extended to allow for drop-down boxes, textareas and more 
+						 */
+						?>
+						<?php switch( $this->settings_texts[$setting]['type'] ):
+							case 'yesno': ?>
+								<select name="<?php echo $this->plugin_prefix; ?>settings[<?php echo $setting; ?>]" id="<?php echo $this->dashed_name . '-' . $setting; ?>" class="postform">
+									<?php 
+										$yesno = array( 0 => 'No', 1 => 'Yes' ); 
+										foreach ( $yesno as $val => $txt ) {
+											echo '<option value="' . esc_attr( $val ) . '"' . selected( $value, $val, false ) . '>' . esc_html( $txt ) . "&nbsp;</option>\n";
+										}
+									?>
+								</select><br />
+							<?php break;
+							case 'text': ?>
+								<div><input type="text" name="<?php echo $this->plugin_prefix; ?>settings[<?php echo $setting; ?>]" id="<?php echo $this->dashed_name . '-' . $setting; ?>" class="postform" value="<?php echo esc_attr( $value ); ?>" /></div>
+							<?php break;
+							case 'echo': ?>
+								<div><span id="<?php echo $this->dashed_name . '-' . $setting; ?>" class="postform"><?php echo esc_attr( $value ); ?></span></div>
+							<?php break;
+							default: ?>
+								<?php echo $this->settings_texts[$setting]['type']; ?>
+							<?php break;
+						endswitch; ?>
+						<?php if ( !empty( $this->settings_texts[$setting]['desc'] ) ) { echo $this->settings_texts[$setting]['desc']; } ?>
+					</td>
+				</tr>
+				<?php endforeach; ?>
+				<?php if ( 1 == $this->settings['enable'] ): ?>
+					<tr>
+						<td colspan="3">
+							<p>You enabled wp-cron-control. To make sure that scheduled tasks are still executed correctly you will need to setup a system cron job that will call wp-cron.php with the secret parameter defined in the settings.</p>
+							<p>
+								You can either use the function defined in this script and setup a cron job that calls either
+							</p>
+							<p><code>php <?php echo __FILE__; ?> <?php echo get_site_url(); ?> <?php echo $this->settings['secret_string']; ?></code></p>
+							<p>or</p>
+							<p><code>wget -q "<?php echo get_site_url(); ?>/wp-cron.php?doing_wp_cron&<?php echo $this->settings['secret_string']; ?>"</code></p>
+							<p>You can setup an interval as low as one minute, but should consider a reasonable value of 5-15 minutes as well.</p>
+							<p>If you need help setting up a cron job please refer to the documentation that your provider offers.</p>
+							<p>Anyway, chances are high that either <a href="http://docs.cpanel.net/twiki/bin/view/AllDocumentation/CpanelDocs/CronJobs#Adding a cron job" target="_blank">the CPanel</a>, <a href="http://download1.parallels.com/Plesk/PP10/10.3.1/Doc/en-US/online/plesk-administrator-guide/plesk-control-panel-user-guide/index.htm?fileName=65208.htm" target="_blank">Plesk</a> or <a href="http://www.thegeekstuff.com/2011/07/php-cron-job/" target="_blank">the crontab</a> documentation will help you.</p>
+						</td>
+					</tr>
+				<?php endif; ?>
+			</table>
+			
+			<p class="submit">
+		<?php
+				if ( function_exists( 'submit_button' ) ) {
+					submit_button( null, 'primary', $this->dashed_name . '-submit', false );
+					echo ' ';
+					submit_button( 'Reset to Defaults', '', $this->dashed_name . '-defaults', false );
+				} else {
+					echo '<input type="submit" name="' . $this->dashed_name . '-submit" class="button-primary" value="Save Changes" />' . "\n";
+					echo '<input type="submit" name="' . $this->dashed_name . '-defaults" id="' . $this->dashed_name . '-defaults" class="button-primary" value="Reset to Defaults" />' . "\n";
+				}
+		?>
+			</p>
+		
+			</form>
+		</div>
+		
+		<?php
+	}
+	
+	/**
+	 * Alternative function to the current wp_cron function that would usually executed on sanitize_comment_cookies
+	 */
+	public function validate_cron_request() {
+		// make sure we're in wp-cron.php
+		if ( false !== strpos( $_SERVER['REQUEST_URI'], '/wp-cron.php' ) ) {
+			// grab the necessary secret string
+			if ( defined( 'WP_CRON_CONTROL_SECRET' ) )
+				$secret = WP_CRON_CONTROL_SECRET;
+			else 
+				$secret = $this->settings['secret_string'];
+				
+			// make sure a secret string is provided in the ur
+			if ( isset( $_GET[$secret] ) ) {
+			
+				// check if there is already a cron request running
+				$local_time = time();
+				if ( function_exists( '_get_cron_lock' ) )
+					$flag = _get_cron_lock();
+				else
+					$flag = get_transient('doing_cron');
+					
+				if ( defined( 'WP_CRON_LOCK_TIMEOUT' ) )
+					$timeout = WP_CRON_LOCK_TIMEOUT;
+				else 
+					$timeout = 60;
+					
+				if ( $flag > $local_time + 10 * $timeout )
+					$flag = 0;
+					
+				// don't run if another process is currently running it or more than once every 60 sec.
+				if ( $flag + $timeout > $local_time )
+					die( 'another cron process running or previous not older than 60 secs' );
+				
+				// set a transient to allow locking down parallel requests
+				set_transient( 'doing_cron', $local_time );
+				
+				// make sure the request also validates in wp-cron.php
+				global $doing_wp_cron;
+				$doing_wp_cron = $local_time;
+			
+				// if settings allow it validate if there are any scheduled posts without a cron event
+				if ( 1 == self::instance()->settings['enable_scheduled_post_validation'] ) {
+					$this->validate_scheduled_posts();
+				}
+				return true;
+			}
+			// something went wrong
+			die( 'invalid secret string' );
+		}
+		
+		// for all other cases disable wp-cron.php and spawn_cron() by telling the system it's already running
+		if ( !defined( 'DOING_CRON' ) )
+			define( 'DOING_CRON', true );
+			
+		// and also disable the wp_cron() call execution
+		if ( !defined( 'DISABLE_WP_CRON' ) )
+			define( 'DISABLE_WP_CRON', true );
+		return false;
+	}
+	
+	public function validate_scheduled_posts() {
+		global $wpdb;
+		
+		// grab all scheduled posts from posts table
+		$sql = $wpdb->prepare( "SELECT ID, post_date_gmt FROM $wpdb->posts WHERE post_status = 'future' " );
+		$results = $wpdb->get_results( $sql );
+		$return = true;
+
+		// if none exists just return
+		if ( empty( $results ) )
+			return true;
+
+		// otherwise check each of them
+		foreach ( $results as $r ) {
+
+			$gmt_time  = strtotime( $r->post_date_gmt . ' GMT' );
+			
+			// grab the scheduled job for this post
+			$timestamp = wp_next_scheduled( 'publish_future_post', array( (int) $r->ID ) );
+			if ( $timestamp === false ) {
+				// if none exists issue one
+				wp_schedule_single_event( $gmt_time, 'publish_future_post', array( (int) $r->ID ) );
+				$return = false;
+			} else {
+				// if one exists update timestamp to adjust for daylights savings change, when necessary
+				if ( $timestamp != $gmt_time ) {
+					wp_clear_scheduled_hook( 'publish_future_post', array( (int) $r->ID ) );
+					wp_schedule_single_event( $gmt_time, 'publish_future_post', array( (int) $r->ID ) );
+
+					$new_date = date( 'Y-m-d H:i:s', $gmt_time );
+					$sql_u = $wpdb->prepare( "UPDATE $wpdb->posts SET post_date_gmt=%s WHERE ID=%d", $new_date, $r->ID );
+					$wpdb->query( $sql_u );
+					$return = false;
+				}
+			}
+		}
+		
+		return $return;
+	}
+}
+
+/**
+ * This method can be used to initiate a cron call via cli
+ */
+function wp_cron_control_call_cron( $blog_address, $secret ) {
+ 	$cron_url = $blog_address . '/wp-cron.php?doing_wp_cron&' . $secret;
+ 	$ch = curl_init( $cron_url );
+ 	curl_setopt( $ch, CURLOPT_RETURNTRANSFER, 0 );
+	curl_setopt( $ch, CURLOPT_TIMEOUT, '3' );
+	$result = curl_exec( $ch );
+	curl_close( $ch );
+	return $result;
+}
+
+// if we loaded wp-config then ABSPATH is defined and we know the script was not called directly to issue a cli call
+if ( defined('ABSPATH') ) {
+	WP_Cron_Control::init();
+} else {
+	// otherwise parse the arguments and call the cron. 
+	if ( !empty( $argv ) && $argv[0] == basename( __FILE__ ) || $argv[0] == __FILE__ ) {
+		if ( isset( $argv[1] ) && isset( $argv[2] ) ) {
+			wp_cron_control_call_cron( $argv[1], $argv[2] );
+		} else {
+			echo "Usage: php " . __FILE__ . " <blog_address> <secret_string>\n";
+			echo "Example: php " . __FILE__ . " http://my.blog.com efe18b0e53498e737da9b91cf4ca3d25\n";
+			exit;
+		}  
+	}
+}
+