From: Ernst Plüss
In D7 I discovered at the end of drupal_page_footer()[1] cron jobs are
started. On our website this triggers the search index being updated,
which can take minutes. Needles to say that the user doesn't want to
wait for this to be finished. http://api.drupal.org/api/drupal/includes--common.inc/function/drupal_page_footer/7