How to print in Google App Engine?

Question

I am running a very simple Flask python App in Standard Environment Google App Engine. I am trying to view log information via the command: gcloud app logs tail -s default.

I tried printing using 3 different methods:

1. logging.info("Printing via Google App Engine Log")
2. print("Printing via python print")
3. app.logger.info("Printing via Flask Log")

Sadly, none of them worked.

So how do I print out lines in the live log stream?

Thanks

---

Edit: Added a section of my code

from flask import Flask
from flask import request

import requests
import json
import logging

app = Flask(__name__)

@app.route("/", methods=["GET"])
def webhook():

    app.logger.info("Printing via Flask Log")
    print("Printing via python print")
    logging.info("Printing via Google App Engine Log")

    if request.args.get("hub.mode") == "subscribe" and request.args.get("hub.challenge"):
        if not request.args.get("hub.verify_token") == VERIFICATION_TOKEN:
            return "Verification token mismatch", 403
        return request.args["hub.challenge"], 200

    return "Hello world", 200

If you think that showing other files such as .yaml file helps, please let me know. Thanks!

Answer 1

Per this Google Cloud Platform doc, the following is an example of how to use the different logging levels:

import logging

import webapp2


class MainPage(webapp2.RequestHandler):
    def get(self):
        logging.debug('This is a debug message')
        logging.info('This is an info message')
        logging.warning('This is a warning message')
        logging.error('This is an error message')
        logging.critical('This is a critical message')

        try:
            raise ValueError('This is a sample value error.')
        except ValueError:
            logging.exception('A example exception log.')

        self.response.out.write('Logging example.')


app = webapp2.WSGIApplication([
    ('/', MainPage)
], debug=True)

1- On your deployment, use --verbosity flag:

gcloud app deploy --verbosity debug

2- Run gcloud app logs tail -s default

3- Trigger any endpoint. In the above case, any GET call would do.