GAE : how to output log messages to a file

By JackLok | Updated: August 28, 2012

Viewed: 1,934

Tags: gae logs

By default, all logging messages will output to log console. To change the logging settings, find this file – {Google App Engine SDK directory}\google\appengine\tools\dev_appserver_main.py.

File : dev_appserver_main.py – Find following pattern

#...
import getopt
import logging
import os
import signal
import sys
import tempfile
import traceback

logging.basicConfig(
    level=logging.INFO,
    format='%(levelname)-8s %(asctime)s %(filename)s:%(lineno)s] %(message)s')
#...

Output to File

In order to output log messages to a file, we can change the configuration of logging in dev_appserver_main.py like in below:

#...
import getopt
import logging
import os
import signal
import sys
import tempfile
import traceback

# default , comment out
#logging.basicConfig(
#    level=logging.INFO,
#    format='%(levelname)-8s %(asctime)s %(filename)s:%(lineno)s] %(message)s')

# new log settings , output to a file
logging.basicConfig(
    filename='/Users/lokjack/gae.log',
    filemode='a', 
    level=logging.DEBUG,
    format='%(levelname)-8s %(asctime)s %(filename)s:%(lineno)s] %(message)s')
#...

Restart the dev_appserver.py after changed the dev_appserver_main.py.

Now, the log console would not show any log messages, instead all output to a file (In this example, all log messages will be output to “/Users/lokjack/gae.log“).

Download Source Code

References

1. Logging to a file in Python
2. Does Google App Engine allow creation of files and folders on the server?