--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/modules/throttle/throttle.module	Tue Dec 23 14:28:28 2008 +0100
@@ -0,0 +1,128 @@
+<?php
+// $Id: throttle.module,v 1.83 2007/12/14 18:08:49 goba Exp $
+
+/**
+ * @file
+ * Allows configuration of congestion control auto-throttle mechanism.
+ */
+
+function throttle_menu() {
+  $items['admin/settings/throttle'] = array(
+    'title' => 'Throttle',
+    'description' => 'Control how your site cuts out content during heavy load.',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('throttle_admin_settings'),
+    'access arguments' => array('administer site configuration'),
+    'file' => 'throttle.admin.inc',
+  );
+  return $items;
+}
+
+/**
+ * Determine the current load on the site.
+ *
+ * Call the throttle_status() function from your own modules, themes, blocks,
+ * etc. as follows:
+ *
+ *   $throttle = module_invoke('throttle', 'status');
+ *
+ * to determine the current throttle status. Use module_invoke() so the
+ * call will still work if the throttle module is disabled. For example, in
+ * your theme you might choose to disable pictures when your site is too busy
+ * (reducing bandwidth), or in your modules you might choose to disable
+ * some complicated logic when your site is too busy (reducing CPU utilization).
+ *
+ * @return
+ *   0 or 1. 0 means that the throttle is currently disabled. 1 means that
+ *   the throttle is currently enabled. When the throttle is enabled, CPU
+ *   and bandwidth intensive functionality should be disabled.
+ */
+function throttle_status() {
+  return variable_get('throttle_level', 0);
+}
+
+/**
+ * Implementation of hook_exit().
+ *
+ * Changes the current throttle level based on page hits.
+ */
+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' => $message));
+    }
+  }
+}
+
+/**
+ * Implementation of hook_help().
+ */
+function throttle_help($path, $arg) {
+  switch ($path) {
+    case 'admin/help#throttle':
+      $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>';
+      $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>';
+      $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>';
+      return $output;
+    case 'admin/settings/throttle':
+      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>';
+  }
+}