Starting flask server in background

Question

I have a flask application which I am currently starting up in the following way:

#phantom.py __author__ = 'uruddarraju' from phantom.api.v1 import app app.run(host='0.0.0.0', port=8080, debug=True) 

and when I run this script, it executes successfully by printing:

loading config from /home/uruddarraju/virtualenvs/PHANTOMNEW/Phantom/etc/phantom/phantom.ini * Running on http://0.0.0.0:8080/ 

But it never returns and if I do a CTRL-C the server stops. I am trying to deploy this to production and want to run this startup on the background, where the process stays up as long as the server is up.

What is the best way to do this?

Answer 1

$ python phantom.py & 

Is probably the easiest way to make it run in the background. That said you should not be using the app.run() server to serve your flask app if you are moving it into production as @LukasGraf mentions (as well as I believe their documentation)

Answer 2

My favorite way of doing it in production is to combine flask with uwsgi and nginx to keep persistence. Here are nice setup instructions to get you started: http://www.markjberger.com/flask-with-virtualenv-uwsgi-nginx/

Jist:

First make sure that your vps has the latest updates:

sudo apt-get update sudo apt-get upgrade 

Now install python and virtualenv:

sudo apt-get install build-essential python-dev python-pip sudo pip install virtualenv 

Make a folder for your website:

sudo mkdir -p /var/www/mysite sudo chown -R <your user id> /var/www/mysite cd /var/www/mysite 

Setup virtualenv and install flask:

virtualenv .env --no-site-packages source .env/bin/activate pip install flask 

Place your flask app in this folder. Make sure that your host is set to 0.0.0.0 and that your app is under if __name__ == '__main__':. If your app is in a function, uwsgi will not be able to call it.

Now is a good time to test your app with the flask development server to see if everything is working so far. If everything runs smoothly, install nginx and uwsgi:

deactivate sudo apt-get install nginx uwsgi uwsgi-plugin-python 

Next we must create a socket file for nginx to communicate with uwsgi:

cd /tmp/ touch mysite.sock sudo chown www-data mysite.sock 

By changing the owner of mysite.sock to www-data, nginx will be able to write to the socket. Now all we have to do is add our configuration files for nginx and uwsgi. First delete the default configuration for nginx:

cd /etc/nginx/sites-available sudo rm default 

Create a new configuration file mysite and add the following:

server {     listen 80;     server_tokens off;     server_name www.mysite.com mysite.com;       location / {          include uwsgi_params;          uwsgi_pass unix:/tmp/mysite.sock;      }       location /static {          alias /var/www/mysite/static;      }       ## Only requests to our Host are allowed      if ($host !~ ^(mysite.com|www.mysite.com)$ ) {         return 444;      } } 

In order to enable the site, we must link our configuration file to /etc/nginx/sites-enabled/:

sudo ln -s /etc/nginx/sites-available/mysite /etc/nginx/sites-enabled/mysite 

The process is similar for uwsgi. Create the file /etc/uwsgi/apps-available/mysite.ini and add the following:

[uwsgi] vhost = true socket = /tmp/mysite.sock venv = /var/www/mysite/.env chdir = /var/www/mysite module = app callable = app 

Module is the name of your python script and callable is the name of your flask instance. So if your flask site was in a file called mysite.py that looked like this:

from flask import Flask my_app = Flask(__name__)  @my_app.route('/') def hello_world():     return 'Hello World!'  if __name__ == '__main__':     my_app.run(host='0.0.0.0') 

Your mysite.ini file would be:

module = mysite callable = my_app 

Link the configuration file to the enabled-apps folder:

sudo ln -s /etc/uwsgi/apps-available/mysite.ini /etc/uwsgi/apps-enabled/mysite.ini 

Finally, restart nginx and uwsgi:

sudo service nginx restart sudo service uwsgi restart