How to add stdout and stderr to logger file in flask

Question

I want to log the stdout & stderr to log files, and this is what I tried.

app = Flask(__name__)
app.logger.setLevel(logging.INFO)  # use the native logger of flask
app.logger.disabled = False
handler = logging.handlers.RotatingFileHandler(
    SYSTEM_LOG_FILENAME,
    'a',
    maxBytes=1024 * 1024 * 100,
    backupCount=20
    )

formatter = logging.Formatter(\
    "%(asctime)s - %(levelname)s - %(name)s: \t%(message)s")
handler.setFormatter(formatter)
app.logger.addHandler(handler)

@app.route('/')
def hello():

    return 'Hello World'
if __name__ == '__main__':
    app.run()        

Then I would like to log the console output in files. such as

* Running on http://127.0.0.1:5000/
127.0.0.1 - - [24/May/2013 14:55:14] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [24/May/2013 14:55:14] "GET /favicon.ico HTTP/1.1" 404 -

what can I do?

Answer 1

The logging messages you mention don't come from flask's logger, the come from werkzeug 's logger , that means you also need to add your handler to that logger instance to make it work, eg:

log = logging.getLogger('werkzeug')
log.setLevel(logging.INFO)
log.addHandler(handler)

If you look at how werkzeug initializes its logger, you'll see that it adds a default handler only if logging wasn't already set up. That means if you set it up before wekzeug does, it won't use the default StreamHandler but the handler you supply.