Writing a fail-safe cron is an incredibly hard job as crons are infamous for failing rather silently. The cron script writer must take a very pessimist approach and handle every possibility of error. Even then, some scenarios are easy to miss. Following are some cases I have come across often:<p>1. <i>crash</i> - any runtime error that causes your script to stop execution abruptly.<p>2. <i>un-handled, non-crashing error</i> - db connection failure, remote api failure, file not found, etc. The script may continue execution, the results may not be logically correct.<p>3. <i>concurrent execution</i> - What if an instance of cron is not over by the time the next instance should start? crontab will simply start the next instance.<p>4. <i>internet connection error</i> - even the notification mechanism will fail if it depends on an active internet connection.<p>Your service is a very valuable one, and a challenging one too I believe. You can do a lot many things in cron monitoring and reporting.