Is there a way to log python print statements in gunicorn?

With my Procfile like this:

web: gunicorn app:app \
    --bind "$HOST:$PORT" \
    --debug --error-logfile "-" \
    --enable-stdio-inheritance \
    --reload \
    --log-level "debug" 

is it in any way possible to get python print statements to be logged to stdout / bash? I am using the bottle framework here as well, if that affects anything.

It turns out the print statements were actually getting through, but with delay.

The gunicorn docs for --enable-stdio-inheritance note to set the PYTHONUNBUFFERED, which I thought I had, but it seems with wrong syntax.

I solved it using a .env file with my foreman setup to set the variable like this:

PYTHONUNBUFFERED=TRUE

In python 3, adding flush=True in each print statement works for my flask/gunicorn app.

E.g.

gunicorn --bind 0.0.0.0:8080 server --log-level debug

No particular flags are required.

See if this helps.

Please try below command:

gunicorn --workers 3 --bind 127.0.0.1:5000 --error-logfile /var/log/gunicorn/error.log --access-logfile /var/log/gunicorn/access.log --capture-output --log-level debug

It did work for me.

1. Specify --log-level to debug(default info).

2. Specify --capture-output flag (default false).

You should be able to watch logs in error log file.

I use Python3 along with Flask.

I use print('log info') directly instead of print('log info', flush=True).

I only set capture_output to True and set a errorlog file and it works.

Note that:

>### capture_output
> > --capture-output
> False
> Redirect stdout/stderr to specified file in errorlog >

I think it's that you need to specifiy a errorlog file to get the standard output.

---

Here's my config file gunicorn.config.py setting

accesslog = 'gunicorn.log'
errorlog = 'gunicorn.error.log'
capture_output = True

Then run with gunicorn app_py:myapp -c gunicorn.config.py

The equivaluent command line would be

gunicorn app_py:myapp --error-logfile gunicorn.error.log --access-logfile gunicorn.log --capture-output

Personally, I use a trick to print logs. I use file = sys.stderr as a parameter of the print statement. Following is the way out:

import sys
print("WHATEVER YOU WANT", file = sys.stderr)

Done!

This is working for me (I'm using a service called si-ct)

gunicorn --workers 3 --bind unix:si-ct.sock -m 007 wsgi:app --log-level debug --error-logfile - --access-logfile - --capture-output --reload 

With that, the print output shows in my service logs, which I read using

sudo journalctl -u si-ct -f