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Flask is a web microframework for Python under the BSD license. On servers it is possible to run websites based on this framework thanks to the Phusion Passenger technology.

Initial setup

To run a website written in Flask you must first ensure the correct configuration of the environment and domain. Before proceeding with the next steps, make sure that:

  • Added virtualenv for Python environment and installed Flask with: pip install flask
  • The domain is properly added and configured in our DNS.
  • Added Python website and the path to the python binary inside the previously configured environment.

Project Flask

The root directory of the Flask project must be /usr/home/LOGIN/domains/DOMAIN/public_python. You should also delete the index.html file with the command: rm /usr/home/LOGIN/domains/DOMAIN/public_python/public/index.html

Configuration of Phusion Passenger

The last step is to create a configuration for the Phusion Passenger server, which is responsible for running the Flask application. In the Flask project directory (/usr/home/LOGIN/domains/DOMAIN/public_python) create a file and place the following content in it, modifying the import line:

import sys, os
from application import app as application

An example file (to be placed in the website directory to test Flask):

from flask import Flask
app = Flask(__name__)

def hello():
    return "Hello World!"

if __name__ == "__main__":


To disable buffering, send the X-Accel-Buffering: no header in the response header - for example, using stream_with_context():

resp = Response(stream_with_context(PARAMETERS))
    resp.headers['X-Accel-Buffering'] = 'no'