How can I add an id from flask's global 'g' object in the access log?

Question

I'm using gunicorn to run my Flask app.

I have an user_id on Flask's global g object that I want to log on each authenticated request.

Does anyone know a good way to do that? I tried adding a custom filter like this, but the request doesn't seem to be in scope at the time the logger is executed:

class MyFilter(logging.Filter):

    def filter(self, record):
        if hasattr(g, 'user_id'):
            record.msg = "User ID: {0} ".format(g.user_id) + record.msg
        return 1

I'm expecting something like this:

2014-11-08 21:52:15 [INFO] REQUESTLOG 127.0.0.1 User ID: 12345 "GET /v1.0/healthcheck HTTP/1.1" 200 51 "-" "curl/7.35.0"

Thanks!

Answer 1

You can subclass the Werkzeug request handler and provide your own version of the log_request() method. Here is an example:

from werkzeug.serving import BaseRequestHandler
from flask import Flask
app = Flask(__name__)

@app.route('/')
def index():
    return "hi"

class MyRequestHandler(BaseRequestHandler):
    def log_request(self, code='-', size='-'):
        self.log('info', 'custom log! "%s" %s %s', self.requestline, code, size)

if __name__ == '__main__':
    app.run(debug=True, request_handler=MyRequestHandler)