Unable to silence logging messages

[AlexKurek]

Im getting ~15 of:

127.0.0.1 - - [16/Mar/2024 12:10:13] "POST / HTTP/1.1" 200 -

in the terminal when Im running a Dash application.

server = flask.Flask(__name__)
app = dash.Dash(
    __name__,
    server=server,
    external_stylesheets=[dbc.themes.BOOTSTRAP],
    meta_tags=[
        {"name": "viewport", "content": "width=device-width, initial-scale=1"}
    ],
)

(https://github.com/AlexKurek/srt-py/blob/master/srt/dashboard/app.py#L53)

How do I silence them? I have found a lot of methods, e.g. Disable console messages in Flask server, but none of them worked. My guess is that since they worked in previous versions of Flask - could this be a regression?

Environment:

• Python version: 3.11
• Flask version: 3.0.2

[codespearhead]

Try this.

[AlexKurek]

@codespearhead I did:

    server = flask.Flask(__name__) # these messages "127.0.0.1 - - [16/Mar/2024 12:10:13] "POST / HTTP/1.1" 200 -"" are generated by Flask
    app = dash.Dash(
        __name__,
        server=server,
        external_stylesheets=[dbc.themes.BOOTSTRAP],
        meta_tags=[
            {"name": "viewport", "content": "width=device-width, initial-scale=1"}
        ],
    )
    app.logger.setLevel(logging.ERROR)
    server.logger.setLevel(logging.ERROR)

and there is no change, I still get these messages.
In general, this is the most recommended thing to do on the internet. People report that it worked in earlier versions of Flask.

[codespearhead]

Help us reproduce the error on our machines with a minimal reproducible example. This is what I got so far, but the errors I'm getting are unrelated to what's being reported.

mkdir myproject &&
cd myproject &&
python3 -m venv .venv &&
source .venv/bin/activate &&
pip install flask dash

cat > main.py <<'EOF'
server = flask.Flask(__name__)
app = dash.Dash(
    __name__,
    server=server,
    external_stylesheets=[dbc.themes.BOOTSTRAP],
    meta_tags=[
        {"name": "viewport", "content": "width=device-width, initial-scale=1"}
    ],
)
EOF

python main.py

[jtrip]

Perhaps it is the application server that is doing the logging, which wsgi server are you using? Check to see how to limit logging there.

[AlexKurek]

Its waitress, I found from waitress import serve.

[jtrip]

Great, have you tried to silence the logging at that level to see if that resolves the issue for you?

I've seen some related discussion here:
Pylons/waitress#151

and in the documentation:
https://docs.pylonsproject.org/projects/waitress/en/stable/logging.html

they suggest something like setup_console_handler = False as a parameter in serve()
but I've also seen something like:
serve(app, _quiet=True)
not sure if there is a version difference there or if either might work.

Edit:
Oh I also see:
"That _quiet parameter is a testing shim, and is not public API."
So that is not recommended, but one of the other solutions in that issue (151) should help.

[AlexKurek]

Not working:
logging.getLogger('waitress').setLevel(logging.ERROR)
and
logging.getLogger().addHandler(logging.NullHandler())
and
serve(app_server, _quiet=True)

[jtrip]

Can you provide a minimum reproducible example?
I don't know much about dash (maybe that is also doing some logging?) not sure how to set that up or how the waitress serve call integrates with the example in your original post.

Also it might be good to analyze the results of the things you've tried beyond does or does not work. The first solution you tried is setting the log level, does the app seem to be respecting that or are you seeing entries on a lower level?

[AlexKurek]

Can you provide a minimum reproducible example?

I will be difficult, since its not my code and its rather not small: MITHaystack/srt-py#19. Also its not trivial to install and run.

I dont think any other output is/was from dash.

[jtrip]

Ok yeah large applications can be a challenge when debugging.

I just made a simple flask + dash + waitress app. Like this:

from flask import Flask
from dash import Dash
from dash import html
from waitress import serve
import logging

waitress_logger = logging.getLogger('waitress')
waitress_logger.setLevel(logging.ERROR)

flask_app = Flask(__name__)
flask_app.logger.handlers = waitress_logger.handlers

app = Dash(__name__, server=flask_app, routes_pathname_prefix='/dash/')
app.layout = html.Div(children=[
    html.H1(children='Hello Dash'),
])

@flask_app.route('/')
def hello():
    return 'Hello, this is the Flask part! Navigate to /dash/ for the Dash app.'


if __name__ == '__main__':
    serve(flask_app, host='0.0.0.0', port=8080)
 

and I noticed that without the logging handlers setting the level properly I was getting INFO level messages about a task queue.

However with the handlers added and level set like in this example I no longer see INFO messages, but would expect to see ERROR messages.

So I think that should work. Maybe you could share more details about the exact messages are trying to silence.

[AlexKurek]

It was easy to silence the queue messages: AlexKurek/srt-py@315ec8c.
I added:

  waitress_logger = logging.getLogger('waitress')
  waitress_logger.setLevel(logging.ERROR)
  server.logger.handlers = waitress_logger.handlers
  app.logger.handlers = waitress_logger.handlers

but:

127.0.0.1 - - [20/Mar/2024 16:47:25] "POST / HTTP/1.1" 200 -
127.0.0.1 - - [20/Mar/2024 16:47:25] "POST / HTTP/1.1" 200 -
127.0.0.1 - - [20/Mar/2024 16:47:26] "POST / HTTP/1.1" 200 -
127.0.0.1 - - [20/Mar/2024 16:47:26] "POST / HTTP/1.1" 200 -
127.0.0.1 - - [20/Mar/2024 16:47:26] "POST / HTTP/1.1" 200 -
[...]

is still there.

[jtrip]

Interesting, when I expand my example so the endpoints accept POST and use curl to POST to them I do not get anything in the console.

but that is because I am letting waitress do the serving in the conditional at the bottom, and running this via python main.py, are you by chance running this via the flask dev server instead? like flask run etc.?

[jtrip]

if so, that can be disabled with the werkzeug logger

werkzeug_logger = logging.getLogger('werkzeug')
werkzeug_logger.disabled = True

[AlexKurek]

@jtrip I dont think so, in the code I only see import flask.

werkzeug_logger = logging.getLogger('werkzeug')
werkzeug_logger.disabled = True

It didnt work :(

[AlexKurek]

If you look at some threads, you can see that more and more methods have stopped working over the years. For example:
https://stackoverflow.com/a/74137152

[AlexKurek]

I pasted it here:
https://github.com/MITHaystack/srt-py/blob/master/srt/dashboard/app.py#L63
but it did not work. I did that too:

  waitress_logger = logging.getLogger('waitress')
  waitress_logger.disabled = True
  app_server.logger.handlers = waitress_logger.handlers

here: https://github.com/MITHaystack/srt-py/blob/master/bin/srt_runner.py#L32
but this did not help either.

[AlexKurek]

This could be important:
https://stackoverflow.com/a/57086684/6764984

Flask apparently no longer uses logging for logging, and has switched to the click package

I pasted

log = logging.getLogger('werkzeug')
log.setLevel(logging.ERROR)

def secho(text, file=None, nl=None, err=None, color=None, **styles):
    pass

def echo(text, file=None, nl=None, err=None, color=None, **styles):
    pass

click.echo = echo
click.secho = secho

here: https://github.com/MITHaystack/srt-py/blob/master/srt/dashboard/app.py#L63 but also no result.

[jtrip]

I don't believe that would be important as it actually seems to be a misunderstanding or some confusion about what messages on the console are a flask app doing some logging and a flask/click command. Flask uses the standard python logging library as the documentation accurately describes and you can see in the flask source code.

https://flask.palletsprojects.com/en/3.0.x/logging/
https://github.com/pallets/flask/blob/b90a4f1f4a370e92054b9cc9db0efcb864f87ebe/src/flask/logging.py

I did notice this section that might be worth looking into:
https://flask.palletsprojects.com/en/3.0.x/logging/#removing-the-default-handler

Otherwise it might be worth looking into Dash to see if it might be creating a logger.

[AlexKurek]

I pasted:

app.logger.removeHandler(default_handler)
server.logger.removeHandler(default_handler)

here: https://github.com/MITHaystack/srt-py/blob/master/srt/dashboard/app.py#L63
but it didnt work. What do you mean by looking into Dash?

[jtrip]

Dash might be doing some logging, look to see if they document anything about working with logging.

You may also need to do more debugging, just trying to paste in some code will not help you understand what is going on.
Also maybe you have some other configuration impacting the application at runtime.