learning-unlimited/ESP-Website — pull request #1182 by uakfdotb (2014-04-01 19:04:26+00:00)
Title: Add file lock for dbmail_cron.

This ensures that two dbmail_cron scripts don't run at the same time. If multiple do run at the same time this breaks the send delay feature and can also overload the system. Multiple may run at the same time without this lock since one may be processing a message and adding email text objects, while following executions lock the email text objects that have been constructed so far.