- Patch #566494 by Dave Reid, chx, JoshuaRogers, David_Rothstein, Rob Loach, TheRec, moshe weitzman: cron image does a full bootstrap on every page request so changing to a Javascript-based solution instead. Important performance fix -- what were we smoking? ;-)

includes/common.inc

@@ -4571,6 +4571,10 @@ function drupal_page_set_cache() {
     $header_names = _drupal_set_preferred_header_name();
     foreach (drupal_get_http_header() as $name_lower => $value) {
       $cache->headers[$header_names[$name_lower]] = $value;
+      if ($name_lower == 'expires') {
+        // Use the actual timestamp from an Expires header if available.
+        $cache->expire = strtotime($value);
+      }
     }
 
     if ($cache->data) {

modules/system/system.admin.inc

@@ -1496,7 +1496,7 @@ function system_site_information_settings_submit($form, &$form_state) {
   // Clear caches when the cron threshold is changed to ensure that the cron
   // image is not contained in cached pages.
   $cron_threshold = variable_get('cron_safe_threshold', DRUPAL_CRON_DEFAULT_THRESHOLD);
-  if (($cron_threshold > 0 && $form_state['input']['cron_safe_threshold'] == 0) || ($cron_threshold == 0 && $form_state['input']['cron_safe_threshold'] > 0)) {
+  if ($cron_threshold != $form_state['input']['cron_safe_threshold']) {
     cache_clear_all();
   }
 }

modules/system/system.cron.js

@@ -0,0 +1,20 @@
+// $Id$
+(function ($) {
+
+/**
+ * Checks to see if the cron should be automatically run.
+ */
+Drupal.behaviors.cronCheck = {
+  attach: function(context, settings) {
+    if (settings.cronCheck || false) {
+      $('body').once('cron-check', function() {
+        // Only execute the cron check if its the right time.
+        if (Math.round(new Date().getTime() / 1000.0) > settings.cronCheck) {
+          $.get(settings.basePath + 'system/run-cron-check');
+        }
+      });
+    }
+  }
+};
+
+})(jQuery);

modules/system/system.js

@@ -211,4 +211,3 @@ Drupal.behaviors.machineReadableValue = {
 };
 
 })(jQuery);
-

modules/system/system.module

@@ -190,9 +190,6 @@ function system_theme() {
     'system_compact_link' => array(
       'variables' => array(),
     ),
-    'system_run_cron_image' => array(
-      'variables' => array('image_path' => NULL),
-    ),
     'system_date_time_settings' => array(
       'render element' => 'form',
       'file' => 'system.admin.inc',
@@ -530,10 +527,10 @@ function system_menu() {
     'type' => MENU_CALLBACK,
     'file' => 'system.admin.inc',
   );
-  $items['system/run-cron-image'] = array(
+  $items['system/run-cron-check'] = array(
     'title' => 'Execute cron',
-    'page callback' => 'system_run_cron_image',
+    'page callback' => 'system_run_cron_check',
-    'access callback' => 'system_run_cron_image_access',
+    'access callback' => 'system_run_cron_check_access',
     'type' => MENU_CALLBACK,
     'file' => 'system.admin.inc',
   );
@@ -2420,6 +2417,10 @@ function system_region_list($theme_key, $show = REGIONS_ALL) {
 
   if (empty($list[$theme_key][$show])) {
     $themes = list_themes();
+    if (!isset($themes[$theme_key])) {
+      $list[$theme_key][$show] = array();
+      return $list[$theme_key][$show];
+    }
     $info = $themes[$theme_key]->info;
     // If requested, suppress hidden regions. @see block_admin_display_form().
     foreach ($info['regions'] as $name => $label) {
@@ -3066,17 +3067,23 @@ function system_retrieve_file($url, $destination = NULL, $overwrite = TRUE) {
  */
 function system_page_build(&$page) {
   // Automatic cron runs.
-  // @see system_run_cron_image()
+  $cron_threshold = variable_get('cron_safe_threshold', DRUPAL_CRON_DEFAULT_THRESHOLD);
-  if (system_run_cron_image_access()) {
+  if ($cron_threshold) {
     $page['page_bottom']['run_cron'] = array(
       // Trigger cron run via AJAX.
       '#attached' => array(
         'js' => array(
-          '(function($){ $.get(' . drupal_json_encode(url('system/run-cron-image')) . '); })(jQuery);' => array('type' => 'inline', 'scope' => 'header'),
+          drupal_get_path('module', 'system') . '/system.cron.js' => array('weight' => JS_DEFAULT - 5),
+          array(
+            'data' => array(
+              // Add the timestamp for the next automatic cron run.
+              'cronCheck' => variable_get('cron_last', 0) + $cron_threshold,
+            ),
+            'type' => 'setting',
+          ),
+
         ),
       ),
-      // Trigger cron run for clients not supporting JavaScript (fall-back).
-      '#markup' => theme('system_run_cron_image', array('image_path' => 'system/run-cron-image')),
     );
   }
 }
@@ -3097,27 +3104,18 @@ function system_page_alter(&$page) {
 }
 
 /**
- * Menu callback; executes cron via an image callback.
+ * Menu callback; executes cron via an AJAX callback.
  *
  * This callback runs cron in a separate HTTP request to prevent "mysterious"
- * slow-downs of regular HTTP requests. It is either invoked via an AJAX request
+ * slow-downs of regular HTTP requests. It is invoked via an AJAX request and
- * (if the client's browser supports JavaScript) or by an IMG tag directly in
- * the page output (for clients not supporting JavaScript). For the latter case,
- * we need to output a transparent 1x1 image, so the browser does not render the
- * image's alternate text or a 'missing image placeholder'. The AJAX request
  * does not process the returned output.
  *
  * @see system_page_alter()
- * @see theme_system_run_cron_image()
+ * @see system_run_cron_check_access()
- * @see system_run_cron_image_access()
  */
-function system_run_cron_image() {
+function system_run_cron_check() {
-  drupal_page_is_cacheable(FALSE);
+  $cron_run = FALSE;
-
+  $cron_threshold = variable_get('cron_safe_threshold', DRUPAL_CRON_DEFAULT_THRESHOLD);
-  // Output a transparent 1x1 image to the browser; required for clients not
-  // supporting JavaScript.
-  drupal_add_http_header('Content-Type', 'image/gif');
-  echo "\x47\x49\x46\x38\x39\x61\x1\x0\x1\x0\x80\xff\x0\xc0\xc0\xc0\x0\x0\x0\x21\xf9\x4\x1\x0\x0\x0\x0\x2c\x0\x0\x0\x0\x1\x0\x1\x0\x0\x2\x2\x44\x1\x0\x3b";
 
   // Cron threshold semaphore is used to avoid errors every time the image
   // callback is displayed when a previous cron is still running.
@@ -3133,19 +3131,23 @@ function system_run_cron_image() {
     }
   }
   else {
-    // Run cron automatically if it has never run or threshold was crossed.
     $cron_last = variable_get('cron_last', NULL);
-    $cron_threshold = variable_get('cron_safe_threshold', DRUPAL_CRON_DEFAULT_THRESHOLD);
+    // Run cron automatically if it has never run or threshold was crossed.
     if (!isset($cron_last) || (REQUEST_TIME - $cron_last > $cron_threshold)) {
       // Lock cron threshold semaphore.
       variable_set('cron_threshold_semaphore', REQUEST_TIME);
-      drupal_cron_run();
+      $cron_run = drupal_cron_run();
       // Release the cron threshold semaphore.
       variable_del('cron_threshold_semaphore');
     }
   }
 
-  drupal_exit();
+  // Add an expires header with the time of the next cron run.
+  $cron_last = variable_get('cron_last', NULL);
+  drupal_add_http_header('Expires', gmdate(DATE_RFC1123, $cron_last + $cron_threshold));
+
+  drupal_json_output(array('cron_run' => $cron_run));
+  drupal_page_footer();
 }
 
 /**
@@ -3156,28 +3158,13 @@ function system_run_cron_image() {
  * @return
  *   TRUE if cron threshold is enabled, FALSE otherwise.
  *
- * @see system_run_cron_image()
+ * @see system_run_cron_check()
  * @see system_page_alter()
  */
-function system_run_cron_image_access() {
+function system_run_cron_check_access() {
   return variable_get('cron_safe_threshold', DRUPAL_CRON_DEFAULT_THRESHOLD) > 0;
 }
 
-/**
- * Display image used to run cron automatically.
- *
- * Renders an image pointing to the automatic cron run menu callback for
- * graceful degradation when Javascript is not available. The wrapping NOSCRIPT
- * tag ensures that only browsers not supporting JavaScript render the image.
- *
- * @see system_page_alter()
- * @see system_run_cron_image()
- * @ingroup themeable
- */
-function theme_system_run_cron_image($variables) {
-  return '<noscript><div id="system-cron-image">' . theme('image', array('path' => $variables['image_path'], 'getsize' => FALSE)) . '</div></noscript>';
-}
-
 /**
  * Get the list of available date types and attributes.
  *

modules/system/system.test

@@ -415,47 +415,61 @@ class CronRunTestCase extends DrupalWebTestCase {
   }
 
   /**
-   * Follow every image paths in the previously retrieved content.
+   * Ensure that the automatic cron run callback is working.
-   */
-  function drupalGetAllImages() {
-    foreach ($this->xpath('//img') as $image) {
-      $this->drupalGet($this->getAbsoluteUrl($image['src']));
-    }
-  }
-
-  /**
-   * Ensure that the cron image callback to run it automatically is working.
    *
    * In these tests we do not use REQUEST_TIME to track start time, because we
    * need the exact time when cron is triggered.
    */
-  function testCronThreshold() {
+  function testAutomaticCron() {
     // Ensure cron does not run when the cron threshold is enabled and was
     // not passed.
-    $start_cron_last = time();
+    $cron_last = time();
-    variable_set('cron_last', $start_cron_last);
+    $cron_safe_threshold = 100;
-    variable_set('cron_safe_threshold', 10);
+    variable_set('cron_last', $cron_last);
+    variable_set('cron_safe_threshold', $cron_safe_threshold);
     $this->drupalGet('');
-    // Follow every image path on the page.
+    $this->assertRaw('"cronCheck":' . ($cron_last + $cron_safe_threshold));
-    $this->drupalGetAllImages();
+    $this->drupalGet('system/run-cron-check');
-    $this->assertTrue($start_cron_last == variable_get('cron_last', NULL), t('Cron does not run when the cron threshold is not passed.'));
+    $this->assertExpiresHeader($cron_last + $cron_safe_threshold);
+    $this->assertTrue($cron_last == variable_get('cron_last', NULL), t('Cron does not run when the cron threshold is not passed.'));
 
     // Test if cron runs when the cron threshold was passed.
-    $start_cron_last = time() - 15;
+    $cron_last = time() - 200;
-    variable_set('cron_last', $start_cron_last);
+    variable_set('cron_last', $cron_last);
     $this->drupalGet('');
-    // Follow every image path on the page.
+    $this->assertRaw('"cronCheck":' . ($cron_last + $cron_safe_threshold));
-    $this->drupalGetAllImages();
+    sleep(1);
-    $this->assertTrue(variable_get('cron_last', NULL) > $start_cron_last, t('Cron runs when the cron threshold is passed.'));
+    $this->drupalGet('system/run-cron-check');
+    $this->assertExpiresHeader(variable_get('cron_last', NULL) + $cron_safe_threshold);
+    $this->assertTrue($cron_last < variable_get('cron_last', NULL), t('Cron runs when the cron threshold is passed.'));
 
-    // Test if cron does not run when the cron threshold was is disabled.
+    // Disable the cron threshold through the interface.
-    $start_cron_last = time() - 15;
+    $admin_user = $this->drupalCreateUser(array('administer site configuration'));
-    variable_set('cron_safe_threshold', 0);
+    $this->drupalLogin($admin_user);
-    variable_set('cron_last', $start_cron_last);
+    $this->drupalPost('admin/config/system/site-information', array('cron_safe_threshold' => 0), t('Save configuration'));
+    $this->assertText(t('The configuration options have been saved.'));
+    $this->drupalLogout();
+
+    // Test if cron does not run when the cron threshold is disabled.
+    $cron_last = time() - 200;
+    variable_set('cron_last', $cron_last);
     $this->drupalGet('');
-    // Follow every image path on the page.
+    $this->assertNoRaw('cronCheck');
-    $this->drupalGetAllImages();
+    $this->drupalGet('system/run-cron-check');
-    $this->assertTrue($start_cron_last == variable_get('cron_last', NULL), t('Cron does not run when the cron threshold is disabled.'));
+    $this->assertResponse(403);
+    $this->assertTrue($cron_last == variable_get('cron_last', NULL), t('Cron does not run when the cron threshold is disabled.'));
+  }
+
+  /**
+   * Assert that the Expires header is a specific timestamp.
+   *
+   * @param $timestamp
+   *   The timestamp value to match against the header.
+   */
+  private function assertExpiresHeader($timestamp) {
+    $expires = $this->drupalGetHeader('Expires');
+    $expires = strtotime($expires);
+    $this->assertEqual($expires, $timestamp, t('Expires header expected @expected got @actual.', array('@expected' => $timestamp, '@actual' => $expires)));
   }
 
   /**