Debugging cron

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    General

    There is an extensive page on drupal.org for solving problems with cron: Solving cron problems .

    There are a few modules aimed at helping debug cron. The one most commonly used is Cron debug .

    If you're having problems with cron and search (or think you might be), see Debugging Cron / Search Indexing.

    There are a number of ways explored here :

    Drush

    Drush offers a multitude of methods to troubleshoot cron and just about everything else.

    Modules

    The Drush Debug Tools are a group of extensions for Drush, written by Acquians, with more extensive cron debug capabilities.

    Note that this is only for Drupal 7.

    php-eval

    You can debug cron by using the Drush utility using php-eval.

    The code below runs drush php-eval using the respective functions :

    It logs each part of cron as cron runs, and then outputs that to the terminal.

    There is a version of drush php-eval for Drupal 7 and Drupal 8 :

    Drupal 7 Code

    drush php-eval 'global $timers; $return = $args = array();foreach (module_implements("cron") as $module) {  $function = $module . "_cron"; print($function ." - ");  timer_start($function); $result = call_user_func_array($function, $args);  if (isset($result) && is_array($result)) { $return = array_merge_recursive($return, $result); }  else if (isset($result)) { $return[] = $result; }  timer_stop  ($function);  print($timers[$function]["time"] ."\r\n");} '

    This code will return results like:

    ctools_cron - 9.74
field_cron - 83.14
node_cron - 3.91
search_cron - 1.97
system_cron - 1282.06
trigger_cron - 7.53
update_cron - 1036.85

    Drupal 8 Code

    drush php-eval 'use Drupal\Component\Utility\Timer;global $timers; $return = $args = array(); foreach (\Drupal::moduleHandler()->getImplementations("cron") as $module) { $function = $module . "_cron"; print("Starting execution of " . $module . " cron ... ");   Timer::start($function);$result = call_user_func_array($function, $args);if (isset($result) && is_array($result)) {$return = array_merge_recursive($return, $result);}  else if (isset($result)) {$return[] = $result;} Timer::stop($function); print("Execution of " . $module . " cron took " . Timer::read($function) . "ms\r\n"); }'

    This code will return results like:

    Starting execution of dblog cron .... Execution of dblog cron took 10.18ms 
Starting execution of field cron ..... Execution of field cron took 11.19ms 
Starting execution of file cron ..... Execution of file cron took 27.31ms 
Starting execution of history cron ..... Execution of history cron took 0.91ms 
Starting execution of node cron ..... Execution of node cron took 0.03ms 
Starting execution of scheduled_updates cron ..... Execution of scheduled_updates cron took 43.72ms 
Starting execution of search_api cron ..... Execution of search_api cron took 26.54ms 
Starting execution of system cron ..... Execution of system cron took 20.58ms 
Updater Publish multiple nodes at a certain time complete. Results: No updates were performed.                                                                         [status] 
Updater Publish single node at certain time complete. Results: No updates were performed.                                                                         [status]

    Modifying Drupal Core

    Alternately, you can use the following code to help you debug cron. The code is a replacement function that goes in includes/module.inc in place of the existing module_invoke_all() function (for Drupal 7). It logs each part of cron as cron runs, and then logs that to the system log.

    There is a version for Drupal 7 :

    <?php
/**
 * Invokes a hook in all enabled modules that implement it.
 *
 * @param $hook
 *   The name of the hook to invoke.
 * @param ...
 *   Arguments to pass to the hook.
 *
 * @return
 *   An array of return values of the hook implementations. If modules return
 *   arrays from their implementations, those are merged into one array.
 */
function module_invoke_all($hook) {
  $args = func_get_args();
  // Remove $hook from the arguments.
  unset($args[0]);
  $return = array();
  foreach (module_implements($hook) as $module) {
    // BEGIN CRON LOG
    if ($hook == "cron") {
      watchdog('cron', 'Running cron for: %module', array('%module' => $module), WATCHDOG_NOTICE);
    }
    // END CRON LOG
    $function = $module . '_' . $hook;
    if (function_exists($function)) {
      $result = call_user_func_array($function, $args);
      if (isset($result) && is_array($result)) {
        $return = array_merge_recursive($return, $result);
      }
      elseif (isset($result)) {
        $return[] = $result;
      }
    }
  }

  return $return;
}
?>

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