Flask logging not working at all
Question:
I’m trying to log messages in Flask both to file and to stdout. I’ve been reading the official Flask docs and came up with this:
from flask import Flask
import logging
from logging import Formatter, FileHandler
app = Flask(__name__)
@app.route('/')
def hello_world():
app.logger.debug('second test message...')
return 'Hello World!'
if __name__ == '__main__':
#Setup the logger
file_handler = FileHandler('output.log')
handler = logging.StreamHandler()
file_handler.setLevel(logging.DEBUG)
handler.setLevel(logging.DEBUG)
file_handler.setFormatter(Formatter(
'%(asctime)s %(levelname)s: %(message)s '
'[in %(pathname)s:%(lineno)d]'
))
handler.setFormatter(Formatter(
'%(asctime)s %(levelname)s: %(message)s '
'[in %(pathname)s:%(lineno)d]'
))
app.logger.addHandler(handler)
app.logger.addHandler(file_handler)
app.logger.error('first test message...')
app.run()
There are several problems:
- No
output.log file is generated
-
Only the first logging message works:
app.logger.error(‘testing…’)
And only in stdout…the one in the view “/” does not even print to stdout… am I doing something wrong?
This is the output from starting the app and going to /:
2015-03-08 11:33:27,183 ERROR: first test message... [in /home/mosquito/python_projects/flask_tst/flask_tst.py:31]
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [08/Mar/2015 11:33:43] "GET / HTTP/1.1" 200 -
Answers:
Your (debug) logging messages are getting suppressed by Flask as you’re not running in debug mode. If you set the following flag to True, your code will work.
app.run(debug=True)
The messages will now appear as expected.
BennyE$ python3 stackoverflow.py
2015-03-08 12:04:04,650 ERROR: firs test message... [in stackoverflow.py:31]
* Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
* Restarting with stat
2015-03-08 12:04:04,807 ERROR: firs test message... [in stackoverflow.py:31]
--------------------------------------------------------------------------------
DEBUG in stackoverflow [stackoverflow.py:11]:
second test message...
--------------------------------------------------------------------------------
2015-03-08 12:04:13,789 DEBUG: second test message... [in stackoverflow.py:11]
192.168.178.23 - - [08/Mar/2015 12:04:13] "GET / HTTP/1.1" 200 -
--------------------------------------------------------------------------------
DEBUG in stackoverflow [stackoverflow.py:11]:
second test message...
--------------------------------------------------------------------------------
2015-03-08 12:04:14,899 DEBUG: second test message... [in stackoverflow.py:11]
192.168.178.23 - - [08/Mar/2015 12:04:14] "GET / HTTP/1.1" 200 -
This is the output in the associated output file:
BennyE$ cat output.log
2015-03-08 11:58:22,226 ERROR: firs test message... [in stackoverflow.py:31]
2015-03-08 12:04:04,650 ERROR: firs test message... [in stackoverflow.py:31]
2015-03-08 12:04:04,807 ERROR: firs test message... [in stackoverflow.py:31]
2015-03-08 12:04:13,789 DEBUG: second test message... [in stackoverflow.py:11]
2015-03-08 12:04:14,899 DEBUG: second test message... [in stackoverflow.py:11]
Thansk BennyE_HH, it works.
But Flask didn’t suppressed ERROR level log message even debug mode is disable(default is disable).
I think we should call app.logger.setLevel(logging.DEBUG) to control log level even debug mode is false.
I had the same issue and following worked for me:
app.logger.setLevel(logging.INFO)
Set it on the root logger as described here
logging.getLogger().setLevel(logging.DEBUG)
in my case , I had need to set
logging.basicConfig(level=logging.DEBUG) in code
from flask import Flask, jsonify, request
from pathlib import Path
import json
import sys
import logging
import psycopg2
import re
# creating a Flask app
app = Flask(__name__)
logging.basicConfig(level=logging.DEBUG)
I’m trying to log messages in Flask both to file and to stdout. I’ve been reading the official Flask docs and came up with this:
from flask import Flask
import logging
from logging import Formatter, FileHandler
app = Flask(__name__)
@app.route('/')
def hello_world():
app.logger.debug('second test message...')
return 'Hello World!'
if __name__ == '__main__':
#Setup the logger
file_handler = FileHandler('output.log')
handler = logging.StreamHandler()
file_handler.setLevel(logging.DEBUG)
handler.setLevel(logging.DEBUG)
file_handler.setFormatter(Formatter(
'%(asctime)s %(levelname)s: %(message)s '
'[in %(pathname)s:%(lineno)d]'
))
handler.setFormatter(Formatter(
'%(asctime)s %(levelname)s: %(message)s '
'[in %(pathname)s:%(lineno)d]'
))
app.logger.addHandler(handler)
app.logger.addHandler(file_handler)
app.logger.error('first test message...')
app.run()
There are several problems:
- No
output.logfile is generated -
Only the first logging message works:
app.logger.error(‘testing…’)
And only in stdout…the one in the view “/” does not even print to stdout… am I doing something wrong?
This is the output from starting the app and going to /:
2015-03-08 11:33:27,183 ERROR: first test message... [in /home/mosquito/python_projects/flask_tst/flask_tst.py:31]
* Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [08/Mar/2015 11:33:43] "GET / HTTP/1.1" 200 -
Your (debug) logging messages are getting suppressed by Flask as you’re not running in debug mode. If you set the following flag to True, your code will work.
app.run(debug=True)
The messages will now appear as expected.
BennyE$ python3 stackoverflow.py
2015-03-08 12:04:04,650 ERROR: firs test message... [in stackoverflow.py:31]
* Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
* Restarting with stat
2015-03-08 12:04:04,807 ERROR: firs test message... [in stackoverflow.py:31]
--------------------------------------------------------------------------------
DEBUG in stackoverflow [stackoverflow.py:11]:
second test message...
--------------------------------------------------------------------------------
2015-03-08 12:04:13,789 DEBUG: second test message... [in stackoverflow.py:11]
192.168.178.23 - - [08/Mar/2015 12:04:13] "GET / HTTP/1.1" 200 -
--------------------------------------------------------------------------------
DEBUG in stackoverflow [stackoverflow.py:11]:
second test message...
--------------------------------------------------------------------------------
2015-03-08 12:04:14,899 DEBUG: second test message... [in stackoverflow.py:11]
192.168.178.23 - - [08/Mar/2015 12:04:14] "GET / HTTP/1.1" 200 -
This is the output in the associated output file:
BennyE$ cat output.log
2015-03-08 11:58:22,226 ERROR: firs test message... [in stackoverflow.py:31]
2015-03-08 12:04:04,650 ERROR: firs test message... [in stackoverflow.py:31]
2015-03-08 12:04:04,807 ERROR: firs test message... [in stackoverflow.py:31]
2015-03-08 12:04:13,789 DEBUG: second test message... [in stackoverflow.py:11]
2015-03-08 12:04:14,899 DEBUG: second test message... [in stackoverflow.py:11]
Thansk BennyE_HH, it works.
But Flask didn’t suppressed ERROR level log message even debug mode is disable(default is disable).
I think we should call app.logger.setLevel(logging.DEBUG) to control log level even debug mode is false.
I had the same issue and following worked for me:
app.logger.setLevel(logging.INFO)
Set it on the root logger as described here
logging.getLogger().setLevel(logging.DEBUG)
in my case , I had need to set
logging.basicConfig(level=logging.DEBUG) in code
from flask import Flask, jsonify, request
from pathlib import Path
import json
import sys
import logging
import psycopg2
import re
# creating a Flask app
app = Flask(__name__)
logging.basicConfig(level=logging.DEBUG)