Level and formatting for logging.StreamHandler() changes after running subprocess

Question

I have some Python code that runs in an infinite loop, in which I do some logging, and depending on a certain condition, run a shell command using the subprocess module, and more logging is done afterwards. It looks approximately like this:

#!/usr/bin/env python

import logging
import subprocess
import time

TIME_FORMAT = '%a %b %-d %Y %-I:%M:%S %p'
logger = logging.getLogger(__name__)                                                                                                                                                                                                                                                                                
logger.setLevel(logging.DEBUG)                                                  
logformat = '%(asctime)s [%(levelname)s] %(name)s: %(message)s'                 
formatter = logging.Formatter(fmt=logformat, datefmt=TIME_FORMAT)               

file_handler = logging.FileHandler('/path/to/logfile.log')          
file_handler.setLevel(logging.DEBUG)                                            
file_handler.setFormatter(formatter)                                            
logger.addHandler(file_handler)                                                 

console = logging.StreamHandler()                                               
console.setLevel(logging.INFO)                                                  
console.setFormatter(formatter)                                                 
logger.addHandler(console) 

def main():
    if some_condition:
        return_code = subprocess.call(['./some_other_process'])
        if return_code == 0:
            logger.info('Just ran some_other_process')
    else:
        logger.debug('Sleeping for 60 seconds.')
        time.sleep(60)

if __name__ == '__main__':
    main()

When I first start executing this process, I notice that the output is correct; ie the log lines should look like this:

Fri Aug 22 2014 3:35:11 PM [DEBUG] __main__: Sleeping for 60 seconds.

But once the subprocess.call is made, I noticed that all the log lines (just the ones in the console; the output to the logfile is fine) revert to the default:

DEBUG:__main__:Sleeping for 60 seconds.

Not to mention that I shouldn't be seeing debug-level logging in the console, only info and up.

Why is this happening?

Answer 1

I'm not sure why this is happening, but I solved a similar issue with this procedure. Apparently, the getLogger and StreamHandler routines create two different StreamHandlers.

Try with this code:

#!/usr/bin/env python

import logging
import subprocess
import time

TIME_FORMAT = '%a %b %-d %Y %-I:%M:%S %p'
logformat = '%(asctime)s [%(levelname)s] %(name)s: %(message)s'                 
formatter = logging.Formatter(fmt=logformat, datefmt=TIME_FORMAT)               

file_handler = logging.FileHandler('/path/to/logfile.log')          
file_handler.setLevel(logging.DEBUG)                                            
file_handler.setFormatter(formatter)                                            
logging.getLogger('').addHandler(file_handler)                                                 

console = logging.StreamHandler()                                               
console.setLevel(logging.INFO)                                                  
console.setFormatter(formatter)                                                 
logging.getLogger('').addHandler(console) 

def main():
    if some_condition:
        return_code = subprocess.call(['./some_other_process'])
        if return_code == 0:
            logger.info('Just ran some_other_process')
    else:
        logger.debug('Sleeping for 60 seconds.')
        time.sleep(60)

if __name__ == '__main__':
    main()