Systemd launches duplicate python processes

Question

I am using systemd to start a python flask app on raspberry pi zero(Raspbian buster).

Every time I start a service, it launches two python processes instead of one. Why does this happen?

The first process is the parent of the second process.

Here is my service definition in /etc/systemd/system/website.service:

[Unit]
Description=Website
After=network.target

[Service]
User=root
WorkingDirectory=/home/pi/dev
ExecStart=python /home/pi/dev/app.py
Restart=always

[Install]
WantedBy=multi-user.target

Here is the flask app in /home/pi/dev/app.py

from flask import Flask
app = Flask(__name__)


@app.route('/')
def hello():
    return "Hello World!"

if __name__ == '__main__':
    app.run(host='0.0.0.0', debug=True)

What is the result of `ps -ef | grep python` when you stop the systemd servic? — Berkay, May 06 '20 at 10:53
After I stop the service, both processes get killed so `ps -ef | grep python` returns nothing. — Maugrim, May 07 '20 at 07:51
Check this wiki: https://wiki.archlinux.org/index.php/cgroups — Berkay, May 07 '20 at 14:06
**DO NOT post images of code, data, error messages, etc.** - copy or type the text into the question. [ask] — Rob, May 11 '20 at 13:16

score 3 · Accepted Answer · answered May 09 '20 at 08:06

I found the answer, Flask's dev server is running with the reloader so it's launching two processes. If I add use_reloader=False when starting the Flask app, it will only start one process.

app.run(host='0.0.0.0', debug=True, use_reloader=False)

More info here: Why does a Flask app create two process?

Systemd launches duplicate python processes

1 Answers1