Python logging: Flask + uWsgi + nginx

By accessing application.logger.addHandler(handler) you initialized Flask's logger. However, in the lines after you're using root logger with logging.debug('Debug Message'), instead of application logger with application.logger.debug('Debug Message').

Also, app.logger.setLevel(logging.DEBUG).

Full example:

from flask import Flaskapp = Flask(__name__)formatter = logging.Formatter(  # pylint: disable=invalid-name    '%(asctime)s %(levelname)s %(process)d ---- %(threadName)s  '    '%(module)s : %(funcName)s {%(pathname)s:%(lineno)d} %(message)s','%Y-%m-%dT%H:%M:%SZ')handler = StreamHandler()handler.setFormatter(formatter)app.logger.setLevel(logging.DEBUG)app.logger.addHandler(handler)app.logger.removeHandler(default_handler)app.logger.debug('Debug Message')app.logger.info('Info Message')app.logger.warning('Warning Message')app.logger.error('Error Message')app.logger.critical('Critical ')

prints:

...2020-10-26T14:13:27Z DEBUG 3197 ---- MainThread  test_log : <module> {test_log.py:77} Debug Message2020-10-26T14:13:27Z INFO 3197 ---- MainThread  test_log : <module> {test_log.py:78} Info Message2020-10-26T14:13:27Z WARNING 3197 ---- MainThread  test_log : <module> {test_log.py:79} Warning Message2020-10-26T14:13:27Z ERROR 3197 ---- MainThread  test_log : <module> {test_log.py:80} Error Message2020-10-26T14:13:27Z CRITICAL 3197 ---- MainThread  test_log : <module> {test_log.py:81} Critical ...

Please update your Flask version to 1.0.2. Here is a small example using the app.logger behind uwsgi-emperor and nginx:

def create_app(**kwargs):    app = Flask(__name__)    app.logger.setLevel(logging.DEBUG)    @app.route('/ping/', methods=['GET'])    def ping_pong():        app.logger.critical('Healthcheck called')        app.logger.error('Healthcheck called')        app.logger.warning('Healthcheck called')        app.logger.info('Healthcheck called')        app.logger.debug('Healthcheck called')        return jsonify({            'status': 'Epic success',            'message': 'pong!'        })

All log messages appear in syslog:

[2018-05-14 08:43:33,778] CRITICAL in __init__: Healthcheck called[2018-05-14 08:43:33,779] ERROR in __init__: Healthcheck called[2018-05-14 08:43:33,779] WARNING in __init__: Healthcheck called[2018-05-14 08:43:33,779] INFO in __init__: Healthcheck called[2018-05-14 08:43:33,779] DEBUG in __init__: Healthcheck called

Hope that helps.