JSON formatted logging with Flask and gunicorn : <p>I am trying to do something very similar to what's explained here: <a href="https://sebest.github.io/post/protips-using-gunicorn-inside-a-docker-image/" rel="noreferrer">https://sebest.github.io/post/protips-using-gunicorn-inside-a-docker-image/</a></p>

<p>I want to get my Flask app + gunicorn both outputting JSON formatted logging. I've got this working for the Flask app, but I can't seem to get it working with gunicorn.</p>

<p>Here's my current output:</p>

<pre><code> * Running on http://0.0.0.0:5000/ (Press CTRL+C to quit)
 * Restarting with stat
 * Debugger is active!
 * Debugger pin code: 317-187-130
192.168.99.1 - - [12/Jan/2016 20:09:29] "GET /nothing HTTP/1.1" 404 -
{"asctime": "2016-01-12 20:20:25,541", "levelname": "WARNING", "module": "app", "funcName": "err", "lineno": 17, "message": "will assert false..."}
192.168.99.1 - - [12/Jan/2016 20:20:25] "GET /err HTTP/1.1" 500 -
</code></pre>

<p>The line that begins <code>{"asctime":</code> is the output of the code <code>app.logger.warning('will assert false...')</code> which is being correctly logged as JSON. Yay. The lines that begin with <code>192.168.99.1</code> are output from my gunicorn WSGI server and, frustratingly, they are not JSON formatted.</p>

<p>Here's the command I am using to start gunicorn:</p>

<pre><code>gunicorn --log-config gunicorn_logging.conf -c gunicorn_config.py api.app:app
</code></pre>

<p>where the <code>gunicorn_logging.conf</code> file contains:</p>

<pre><code>[loggers]
keys=root, gunicorn.error

[handlers]
keys=console

[formatters]
keys=json

[logger_root]
level=INFO
handlers=console

[logger_gunicorn.error]
level=ERROR
handlers=console
propagate=0
qualname=gunicorn.error

[handler_console]
class=StreamHandler
formatter=json
args=(sys.stdout, )

[formatter_json]
class=jsonlogging.JSONFormatter
</code></pre>

<p>and the file <code>gunicorn_config.py</code> contains:</p>

<pre class="lang-python prettyprint-override"><code>import os
import multiprocessing

addr = os.environ.get('HTTP_ADDR', '0.0.0.0')
port = os.environ.get('HTTP_PORT', '5000')
loglevel = os.environ.get('LOG_LEVEL', 'info')

bind = '{0}:{1}'.format(addr, port)
workers = multiprocessing.cpu_count() * 5 + 1
worker_class = 'gevent'
timeout = 0
</code></pre>

<p>Here's the output of <code>pip freeze</code>:</p>

<pre><code>aniso8601==1.1.0
coverage==4.0.3
flake8==2.5.1
Flask==0.10.1
Flask-MySQLdb==0.2.0
Flask-RESTful==0.3.5
Flask-Script==2.0.5
gevent==1.1rc3
greenlet==0.4.9
gunicorn==19.4.5
itsdangerous==0.24
Jinja2==2.8
json-logging-py==0.2
MarkupSafe==0.23
marshmallow==2.4.2
mccabe==0.3.1
mysqlclient==1.3.7
nose==1.3.7
pep8==1.5.7
pyflakes==1.0.0
python-dateutil==2.4.2
python-json-logger==0.1.4
pytz==2015.7
six==1.10.0
SQLAlchemy==1.0.11
Werkzeug==0.11.3
</code></pre>
