Find error in Python script running inside Screen

Question

I have written a python script that runs infinite using loops. The script is started inside a screen session. However sometimes, after a few hours or even days, it breaks down for a reason i dont now, because screen session closes when that happends.

I have also created a "watchdog" script with the following code, which also runs inside a screen session:

from subprocess import check_output
import os
import time
import random
time.sleep(20)
def screen_present(name):
    try:
            var = check_output(["screen -ls; true"],shell=True)
            if "."+name+"\t(" in var:
                    print name+" is running"
            else:
                    print name+" is not running"
                    print "RESTARTING"
                    os.system("screen -dmS player python /var/www/updater.py > /dev/null 2> /dev/null & echo $")
    except:
            return true


while True:
    screen_present("updater")
    time.sleep(random.uniform(6, 10))

So when i check my scripts after leaving them running a night or so, i sometimes find, that

the screen session with the original code is not there anymore, because my script must have thrown an exception but i can't find out which to fix it
the screen session of my watchdog is marked as "dead"

What would you guys do to find the error and guarantee a stable running?

Instead of running inside screen, you could run your original script inside supervisord — Simon Fraser
– Simon Fraser, Commented Mar 11, 2016 at 8:32

DevShark · Accepted Answer · 2016-03-11 08:37:58Z

1

When you start your python process, make it output to a file. Like this:

python myfile.py >> log.txt 2>&1

You will be able to access that file even after it dies.

answered Mar 11, 2016 at 8:37

DevShark

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