Implementation of hook_exit().

Changes the current throttle level based on page hits.

File

drupal-6.x/modules/throttle/throttle.module, line 48

Allows configuration of congestion control auto-throttle mechanism.

Code

function throttle_exit() {
  // The following logic determines what the current throttle level should
  //  be, and can be disabled by the admin. If enabled, the mt_rand() function
  //  returns a number between 0 and N, N being specified by the admin. If
  //  0 is returned, the throttle logic is run, adding two additional database
  //  queries. Otherwise, the following logic is skipped. This mechanism is
  //  referred to in the admin page as the 'probability limiter', roughly
  //  limiting throttle related database calls to 1 in N.
  if (!mt_rand(0, variable_get('throttle_probability_limiter', 9))) {

    // Count users with activity in the past n seconds.
    // This value is defined in the user module Who's Online block.
    $time_period = variable_get('user_block_seconds_online', 900);

    // When determining throttle status in your own module or theme, use
    // $throttle = module_invoke('throttle', 'status');
    // as that will still work when throttle.module is disabled.
    // Clearly here the module is enabled so we call throttle_status() directly.
    $throttle = throttle_status();

    if ($max_guests = variable_get('throttle_anonymous', 0)) {
      $guests = sess_count(time() - $time_period, TRUE);
    }
    else {
      $guests = 0;
    }
    if ($max_users = variable_get('throttle_user', 0)) {
      $users = sess_count(time() - $time_period, FALSE);
    }
    else {
      $users = 0;
    }

    // update the throttle status
    $message = '';
    if ($max_users && $users > $max_users) {
      if (!$throttle) {
        variable_set('throttle_level', 1);
        $message = format_plural($users, 
        '1 user accessing site; throttle enabled.', 
        '@count users accessing site; throttle enabled.');
      }
    }
    elseif ($max_guests && $guests > $max_guests) {
      if (!$throttle) {
        variable_set('throttle_level', 1);
        $message = format_plural($guests, 
        '1 guest accessing site; throttle enabled.', 
        '@count guests accessing site; throttle enabled.');
      }
    }
    else {
      if ($throttle) {
        variable_set('throttle_level', 0);
        // Note: unorthodox format_plural() usage due to Gettext plural limitations.
        $message = format_plural($users, '1 user', '@count users') . ', ';
        $message .= format_plural($guests, '1 guest accessing site; throttle disabled', '@count guests accessing site; throttle disabled');
      }
    }
    if ($message) {
      cache_clear_all();
      watchdog('throttle', 'Throttle: %message', array('%message' => $message));
    }
  }
}