CiviCRM cron job running twice

If you are new to both Drupal and CiviCRM, this is confusing. CiviCRM uses it's own cron process because it also works with WordPress and Joomla. In addition to running CiviCRM's cron, you also need to enable some jobs at /civicrm/admin/job?reset=1. Drupal doesn't include a UI to enable individual jobs, but you can add a module like https://drupal.org/project/ultimate_cron

Without ultimate_cron, every module using Drupal hook_cron will at least attempt to process every time Drupal's cron is called. In Drupal 7, Drupal's cron can be called a number of ways...

• Manually from /admin/reports/status
• Externally using a URL and Key list http://example.com/cron.php?cron_key=GzNFhXWZ7AV6_HNidUJXeHbJsRd95xJIRnR...
• As users browser the site. Drupal 7 includes functionality that used to be part of https://drupal.org/project/poormanscron

Now if you call Drupal's cron and several modules attempt to run jobs and then call cron again a few minutes later, you'll get the "Attempting to re-run cron while it is already running" error. Every time's Drupal's cron is called, civicrm_cron will also be called.... BUT the specific jobs that are executed by civicrm_cron will only run as often as they are configured to run at at /civicrm/admin/job?reset=1.

The only thing that is a bit odd is the URL included in the civicrm_cron log message. Not sure why that isn't a valid URL.

If your Drupal cron isn't finishing before you call it again after a reasonable amount of time (10-15 minutes), that's going to be an issue... but not one related to this module.