webmaster@1: <?php
webmaster@1: // $Id: throttle.module,v 1.83 2007/12/14 18:08:49 goba Exp $
webmaster@1: 
webmaster@1: /**
webmaster@1:  * @file
webmaster@1:  * Allows configuration of congestion control auto-throttle mechanism.
webmaster@1:  */
webmaster@1: 
webmaster@1: function throttle_menu() {
webmaster@1:   $items['admin/settings/throttle'] = array(
webmaster@1:     'title' => 'Throttle',
webmaster@1:     'description' => 'Control how your site cuts out content during heavy load.',
webmaster@1:     'page callback' => 'drupal_get_form',
webmaster@1:     'page arguments' => array('throttle_admin_settings'),
webmaster@1:     'access arguments' => array('administer site configuration'),
webmaster@1:     'file' => 'throttle.admin.inc',
webmaster@1:   );
webmaster@1:   return $items;
webmaster@1: }
webmaster@1: 
webmaster@1: /**
webmaster@1:  * Determine the current load on the site.
webmaster@1:  *
webmaster@1:  * Call the throttle_status() function from your own modules, themes, blocks,
webmaster@1:  * etc. as follows:
webmaster@1:  *
webmaster@1:  *   $throttle = module_invoke('throttle', 'status');
webmaster@1:  *
webmaster@1:  * to determine the current throttle status. Use module_invoke() so the
webmaster@1:  * call will still work if the throttle module is disabled. For example, in
webmaster@1:  * your theme you might choose to disable pictures when your site is too busy
webmaster@1:  * (reducing bandwidth), or in your modules you might choose to disable
webmaster@1:  * some complicated logic when your site is too busy (reducing CPU utilization).
webmaster@1:  *
webmaster@1:  * @return
webmaster@1:  *   0 or 1. 0 means that the throttle is currently disabled. 1 means that
webmaster@1:  *   the throttle is currently enabled. When the throttle is enabled, CPU
webmaster@1:  *   and bandwidth intensive functionality should be disabled.
webmaster@1:  */
webmaster@1: function throttle_status() {
webmaster@1:   return variable_get('throttle_level', 0);
webmaster@1: }
webmaster@1: 
webmaster@1: /**
webmaster@1:  * Implementation of hook_exit().
webmaster@1:  *
webmaster@1:  * Changes the current throttle level based on page hits.
webmaster@1:  */
webmaster@1: function throttle_exit() {
webmaster@1:   // The following logic determines what the current throttle level should
webmaster@1:   //  be, and can be disabled by the admin. If enabled, the mt_rand() function
webmaster@1:   //  returns a number between 0 and N, N being specified by the admin. If
webmaster@1:   //  0 is returned, the throttle logic is run, adding two additional database
webmaster@1:   //  queries. Otherwise, the following logic is skipped. This mechanism is
webmaster@1:   //  referred to in the admin page as the 'probability limiter', roughly
webmaster@1:   //  limiting throttle related database calls to 1 in N.
webmaster@1:   if (!mt_rand(0, variable_get('throttle_probability_limiter', 9))) {
webmaster@1: 
webmaster@1:     // Count users with activity in the past n seconds.
webmaster@1:     // This value is defined in the user module Who's Online block.
webmaster@1:     $time_period = variable_get('user_block_seconds_online', 900);
webmaster@1: 
webmaster@1:     // When determining throttle status in your own module or theme, use
webmaster@1:     // $throttle = module_invoke('throttle', 'status');
webmaster@1:     // as that will still work when throttle.module is disabled.
webmaster@1:     // Clearly here the module is enabled so we call throttle_status() directly.
webmaster@1:     $throttle = throttle_status();
webmaster@1: 
webmaster@1:     if ($max_guests = variable_get('throttle_anonymous', 0)) {
webmaster@1:       $guests = sess_count(time() - $time_period, TRUE);
webmaster@1:     }
webmaster@1:     else {
webmaster@1:       $guests = 0;
webmaster@1:     }
webmaster@1:     if ($max_users = variable_get('throttle_user', 0)) {
webmaster@1:       $users = sess_count(time() - $time_period, FALSE);
webmaster@1:     }
webmaster@1:     else {
webmaster@1:       $users = 0;
webmaster@1:     }
webmaster@1: 
webmaster@1:     // update the throttle status
webmaster@1:     $message = '';
webmaster@1:     if ($max_users && $users > $max_users) {
webmaster@1:       if (!$throttle) {
webmaster@1:         variable_set('throttle_level', 1);
webmaster@1:         $message = format_plural($users,
webmaster@1:                                  '1 user accessing site; throttle enabled.',
webmaster@1:                                  '@count users accessing site; throttle enabled.');
webmaster@1:       }
webmaster@1:     }
webmaster@1:     elseif ($max_guests && $guests > $max_guests) {
webmaster@1:       if (!$throttle) {
webmaster@1:         variable_set('throttle_level', 1);
webmaster@1:         $message = format_plural($guests,
webmaster@1:                                  '1 guest accessing site; throttle enabled.',
webmaster@1:                                  '@count guests accessing site; throttle enabled.');
webmaster@1:       }
webmaster@1:     }
webmaster@1:     else {
webmaster@1:       if ($throttle) {
webmaster@1:         variable_set('throttle_level', 0);
webmaster@1:         // Note: unorthodox format_plural() usage due to Gettext plural limitations.
webmaster@1:         $message = format_plural($users, '1 user', '@count users') .', ';
webmaster@1:         $message .= format_plural($guests, '1 guest accessing site; throttle disabled', '@count guests accessing site; throttle disabled');
webmaster@1:       }
webmaster@1:     }
webmaster@1:     if ($message) {
webmaster@1:       cache_clear_all();
webmaster@1:       watchdog('throttle', 'Throttle: %message', array('%message' => $message));
webmaster@1:     }
webmaster@1:   }
webmaster@1: }
webmaster@1: 
webmaster@1: /**
webmaster@1:  * Implementation of hook_help().
webmaster@1:  */
webmaster@1: function throttle_help($path, $arg) {
webmaster@1:   switch ($path) {
webmaster@1:     case 'admin/help#throttle':
webmaster@1:       $output = '<p>'. t('The throttle module provides a congestion control mechanism that automatically adjusts to a surge in incoming traffic. If your site is referenced by a popular website, or experiences a "Denial of Service" (DoS) attack, your webserver might become overwhelmed. The throttle mechanism is utilized by modules to temporarily disable CPU-intensive functionality, increasing performance. For instance, via the throttle module, modules may choose to disable resource-intensive blocks or the code within the site theme may temporarily disable user pictures in posts.') .'</p>';
webmaster@1:       $output .= '<p>'. t('The congestion control throttle can be automatically enabled when the number of anonymous or authenticated users currently visiting the site exceeds a specified threshold.') .'</p>';
webmaster@1:       $output .= '<p>'. t('For more information, see the online handbook entry for <a href="@throttle">Throttle module</a>.', array('@throttle' => 'http://drupal.org/handbook/modules/throttle/')) .'</p>';
webmaster@1:       return $output;
webmaster@1:     case 'admin/settings/throttle':
webmaster@1:       return '<p>'. t('The throttle module provides a congestion control mechanism that automatically adjusts to a surge in incoming traffic. If your site is referenced by a popular website, or experiences a "Denial of Service" (DoS) attack, your webserver might become overwhelmed. The throttle mechanism is utilized by modules to temporarily disable CPU-intensive functionality, increasing performance.') .'</p>';
webmaster@1:   }
webmaster@1: }