Python scheduled task to run every 14 days

Question

I am currently working on a program that needs to run every 14 days. I have looked into Schedule which works fine, but I have a few doubts about how to go about this.

I will create a service which will handle the execution of the python program itself on a CentOS 7 system.

The issue here is that every 14 days I will run a function that generates a lot of email addresses and send them to a support entity. I am afraid that if something unintended happens, and the program restart - the support entity will get spammed with emails outside the time frame in which they should receive emails.

As far as I can tell, Schedule does not have any way of determining if the program has restarted, and therefore a reboot of either the system or the service will cause this behaviour.

Would it be a correct solution to write a date to a text file after each completed function run, and then check that text file once a day to determine whether the function should run or not? This method would survive a service and/or system reboot, but is it a "correct" way of doing it?

****UPDATE**** Having the cronjob run on specific days of the month (for example 1st and 15th.) is not sufficient. This could cause gaps in the data which the program processes. The script makes a call which pulls data from 14 days back, and this is the maximum number of days supported by the script (licensing and stuff, can't be changed so not that important except that it is a limitation). So it need to run on lets say odd or even week numbers (to get 14 days).

Any ideas on how to accomplish this given this new information?.

Answer 1

You should look into the use of cron (or google it yourself if you dont like the link).

I suggest creating a simple Python script that is called by cron every 14 days. The crontab entry could look like the following:

# this will run at 00:01 on the 15th and 30th of every month
1 0 */15 * * /path/to/python/script.py

# this will run at 00:01 on the 1st and 15th of every month
1 0 1,15 * * /path/to/python/script.py

You still could make your script write some sort of result (with maybe a timestamp) to a file, so that you could easily check that file to see if it ran correctly (or log some error info).

# this will run at 00:01 on the 1st and 15th of every month
1 0 1,15 * * /path/to/python/script.py >> /path/to/logfile.log 2>&1

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EDIT

You can also configure cron to run every Monday (or another day) if the 1st and 15th of every month are not sufficient. And the script could check a log file to see if it was run the previous Monday to assure it only executes your business logic every 2 weeks.

# this will run at 00:01 once a week on Mondays
1 0 * * 1 /path/to/python/script.py >> /path/to/logfile.log 2>&1