- Patch #331611 by sun, joshmiller, TheRec, Rob Loach, Damien Tournoud: add a poormanscron-like feature to core.

3 files changed, 185 insertions, 4 deletions

diff --git a/modules/system/system.admin.inc b/modules/system/system.admin.inc
index 88c8f2f70..9bd326ff2 100644
--- a/modules/system/system.admin.inc
+++ b/modules/system/system.admin.inc
@@ -1313,7 +1313,16 @@ function system_site_information_settings() {
     '#description' => t('Render all blocks on the default 404 (not found) page. Disabling blocks can help with performance but might leave users with a less functional site.'),
     '#default_value' => variable_get('site_404_blocks', 0)
   );
+  $form['cron_safe_threshold'] = array(
+    '#type' => 'select',
+    '#title' => t('Automatically run cron'),
+    '#default_value' => variable_get('cron_safe_threshold', DRUPAL_CRON_DEFAULT_THRESHOLD),
+    '#options' => array(0 => t('Never')) + drupal_map_assoc(array(3600, 10800, 21600, 43200, 86400, 604800), 'format_interval'),
+    '#description' => t('When enabled, the site will check whether cron has been run in the configured interval and automatically run it upon the next page request. For more information visit the <a href="@status-report-url">status report page</a>.', array('@status-report-url' => url('admin/reports/status'))),
+  );
+
   $form['#validate'][] = 'system_site_information_settings_validate';
+  $form['#submit'][] = 'system_site_information_settings_submit';
 
   return system_settings_form($form);
 }
@@ -1334,6 +1343,18 @@ function system_site_information_settings_validate($form, &$form_state) {
 }
 
 /**
+ * Form submit handler for the site-information form.
+ */
+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)) {
+    cache_clear_all();
+  }
+}
+
+/**
  * Form builder; Configure error reporting settings.
  *
  * @ingroup forms
diff --git a/modules/system/system.module b/modules/system/system.module
index 5088b4cf8..e768944e3 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -42,6 +42,11 @@ define('DRUPAL_MINIMUM_PGSQL',  '8.3');
 define('DRUPAL_MAXIMUM_TEMP_FILE_AGE', 21600);
 
 /**
+ * Default interval for automatic cron executions in seconds.
+ */
+define('DRUPAL_CRON_DEFAULT_THRESHOLD', 10800);
+
+/**
  * New users will be set to the default time zone at registration.
  */
 define('DRUPAL_USER_TIMEZONE_DEFAULT', 0);
@@ -196,6 +201,9 @@ function system_theme() {
       'arguments' => array('version' => NULL),
     ),
     'system_compact_link' => array(),
+    'system_run_cron_image' => array(
+      'arguments' => array('image_path' => NULL),
+    ),
   ));
 }
 
@@ -496,6 +504,12 @@ function system_menu() {
     'access callback' => TRUE,
     'type' => MENU_CALLBACK,
   );
+  $items['system/run-cron-image'] = array(
+    'title' => 'Execute cron',
+    'page callback' => 'system_run_cron_image',
+    'access callback' => 'system_run_cron_image_access',
+    'type' => MENU_CALLBACK,
+  );
   $items['admin'] = array(
     'title' => 'Administer',
     'access arguments' => array('access administration pages'),
@@ -2968,3 +2982,104 @@ function system_retrieve_file($url, $destination = NULL, $overwrite = TRUE) {
   
   return $local;
 }
+
+/**
+ * Implement hook_page_alter().
+ */
+function system_page_alter(&$page) {
+  // Automatic cron runs.
+  // @see system_run_cron_image()
+  if (system_run_cron_image_access()) {
+    $page['page_bottom']['run_cron'] = array(
+      // Trigger cron run via AJAX.
+      '#attached_js' => array(
+        '(function($){ $.get(' . drupal_to_js(url('system/run-cron-image')) . '); })(jQuery);' => array('type' => 'inline', 'scope' => 'header'),
+      ),
+      // Trigger cron run for clients not supporting JavaScript (fall-back).
+      '#markup' => theme('system_run_cron_image', 'system/run-cron-image'),
+    );
+  }
+}
+
+/**
+ * Menu callback; executes cron via an image 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
+ * (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_image_access()
+ */
+function system_run_cron_image() {
+  drupal_page_is_cacheable(FALSE);
+
+  // Output a transparent 1x1 image to the browser; required for clients not
+  // supporting JavaScript.
+  drupal_set_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.
+  $threshold_semaphore = variable_get('cron_threshold_semaphore', FALSE);
+  if ($threshold_semaphore) {
+    if (REQUEST_TIME - $threshold_semaphore > 3600) {
+      // Either cron has been running for more than an hour or the semaphore
+      // was not reset due to a database error.
+      watchdog('cron', 'Cron has been running for more than an hour and is most likely stuck.', array(), WATCHDOG_ERROR);
+
+      // Release the cron threshold semaphore.
+      variable_del('cron_threshold_semaphore');
+    }
+  }
+  else {
+    // Run cron automatically if it has never run or threshold was crossed.
+    $cron_last = variable_get('cron_last', NULL);
+    $cron_threshold = variable_get('cron_safe_threshold', DRUPAL_CRON_DEFAULT_THRESHOLD);
+    if (!isset($cron_last) || (REQUEST_TIME - $cron_last > $cron_threshold)) {
+      // Lock cron threshold semaphore.
+      variable_set('cron_threshold_semaphore', REQUEST_TIME);
+      drupal_cron_run();
+      // Release the cron threshold semaphore.
+      variable_del('cron_threshold_semaphore');
+    }
+  }
+
+  exit;
+}
+
+/**
+ * Checks if the feature to automatically run cron is enabled.
+ *
+ * Also used as a menu access callback for this feature.
+ *
+ * @return
+ *   TRUE if cron threshold is enabled, FALSE otherwise.
+ *
+ * @see system_run_cron_image()
+ * @see system_page_alter()
+ */
+function system_run_cron_image_access() {
+  return variable_get('cron_safe_threshold', DRUPAL_CRON_DEFAULT_THRESHOLD) > 0;
+}
+
+/**
+ * Display image used to run cron automatically.
+ *
+ * Renders an image pointing to the automatic cron run menu callback for
+ * graceful degradation when Javascript is not available. The wrapping NOSCRIPT
+ * tag ensures that only browsers not supporting JavaScript render the image.
+ *
+ * @see system_page_alter()
+ * @see system_run_cron_image()
+ * @ingroup themeable
+ */
+function theme_system_run_cron_image($image_path) {
+  return '<noscript><div id="system-cron-image">' . theme('image', $image_path, '', '', array(), FALSE) . '</div></noscript>';
+}
+
diff --git a/modules/system/system.test b/modules/system/system.test
index 2c642adff..92d0e32dc 100644
--- a/modules/system/system.test
+++ b/modules/system/system.test
@@ -372,6 +372,7 @@ class CronRunTestCase extends DrupalWebTestCase {
    */
   function testCronRun() {
     global $base_url;
+
     // Run cron anonymously without any cron key.
     $this->drupalGet($base_url . '/cron.php', array('external' => TRUE));
     $this->assertResponse(403);
@@ -391,13 +392,57 @@ class CronRunTestCase extends DrupalWebTestCase {
   }
 
   /**
+   * Follow every image paths in the previously retrieved content.
+   */
+  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() {
+    // Ensure cron does not run when the cron threshold is enabled and was
+    // not passed.
+    $start_cron_last = time();
+    variable_set('cron_last', $start_cron_last);
+    variable_set('cron_safe_threshold', 10);
+    $this->drupalGet('');
+    // Follow every image path on the page.
+    $this->drupalGetAllImages();
+    $this->assertTrue($start_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;
+    variable_set('cron_last', $start_cron_last);
+    $this->drupalGet('');
+    // Follow every image path on the page.
+    $this->drupalGetAllImages();
+    $this->assertTrue(variable_get('cron_last', NULL) > $start_cron_last, t('Cron runs when the cron threshold is passed.'));
+
+    // Test if cron does not run when the cron threshold was is disabled.
+    $start_cron_last = time() - 15;
+    variable_set('cron_safe_threshold', 0);
+    variable_set('cron_last', $start_cron_last);
+    $this->drupalGet('');
+    // Follow every image path on the page.
+    $this->drupalGetAllImages();
+    $this->assertTrue($start_cron_last == variable_get('cron_last', NULL), t('Cron does not run when the cron threshold is disabled.'));
+  }
+
+  /**
    * Ensure that temporary files are removed.
+   *
+   * Create files for all the possible combinations of age and status. We are
+   * using UPDATE statments rather than file_save() because it would set the
+   * timestamp.
    */
   function testTempFileCleanup() {
-    // Create files for all the possible combinations of age and status. We're
-    // using UPDATE statments rather than file_save() because it would set the
-    // timestamp.
-
     // Temporary file that is older than DRUPAL_MAXIMUM_TEMP_FILE_AGE.
     $temp_old = file_save_data('');
     db_update('file')