{"id":749,"date":"2017-07-10T00:16:55","date_gmt":"2017-07-09T16:16:55","guid":{"rendered":"https:\/\/www.techcoil.com\/blog\/?p=749"},"modified":"2018-09-05T00:34:52","modified_gmt":"2018-09-04T16:34:52","slug":"how-to-host-your-python-3-flask-mvp-with-supervisor-on-ubuntu-server-16-04","status":"publish","type":"post","link":"https:\/\/www.techcoil.com\/blog\/how-to-host-your-python-3-flask-mvp-with-supervisor-on-ubuntu-server-16-04\/","title":{"rendered":"How to host your Python 3 Flask MVP with Supervisor on Ubuntu Server 16.04"},"content":{"rendered":"

Due to its minimalistic design, the Python Flask<\/a> framework is ideal for building the web server layer of minimal viable products (MVP) to validate customers' needs. However, development work is just one part of the user validation efforts. To ensure that our customer can access our Flask MVP and provide feedback as and when they are available, we will need to get it running with as a server daemon. <\/p>\n

Supervisor<\/a> is a convenient tool for running applications as a server daemon. <\/p>\n

This post documents the steps that I took to host a Python 3 Flask MVP with Supervisor on an Ubuntu Server 16.04 instance.<\/p>\n

Creating a simple Python 3 Flask application as a proof of concept<\/h2>\n

To proof that it is possible to host a Python 3 Flask application with Supervisor on a Ubuntu Server 16.04 instance, I first created a \"Hello World\" application with minimal Python 3 dependencies.<\/p>\n

Project structure<\/h3>\n

This \"Hello World\" application consists of a folder and three files within the folder:<\/p>\n

\r\nmvpapp\r\n|--requirements.txt\r\n|--start.sh\r\n|--app.py\r\n<\/pre>\n
The requirements.txt<\/h3>\n
The requirements.txt is for specifying the Python 3 dependencies that our Python 3 Flask application is going to need. Since this is a minimalistic application, the requirements.txt contains only the following line:<\/p>\n
\r\nFlask==0.12.2\r\n<\/pre>\n
Shell script to start the Python 3 Flask Application: start.sh<\/h3>\n
The shell script is intended for the Supervisor daemon to start the \"Hello World\" Python 3 Flask application. The shell script contains the following content:<\/p>\n
\r\nsource mvpappenv\/bin\/activate\r\npython app.py\r\ndeactivate\r\n<\/pre>\n
The mvpappenv<\/code> folder contains a virtual environment that we will created later with virtualenv<\/a>. In this shell script, we first get into the virtual environment by sourcing the activate script that resides in mvpappenv\/bin<\/code> folder. We then use the python binary to run the Python 3 Flask Application. The deactivate command will be run when the Python 3 Flask application got terminated by whatever reason. In such a case, the executor of the shell script will get out of the virtual environment.<\/p>\n
The Python 3 Flask source code: app.py<\/h3>\n
To test drive the approach to hosting a Python 3 Flask MVP with Supervisor on a Ubuntu Server 16.04 instance, we can simply create a Python 3 Flask application that will run a development server with a simple endpoint that returns a simple string as a response to HTTP GET requests:<\/p>\n
\r\nfrom flask import Flask\r\napp = Flask(__name__)\r\n\r\n@app.route('\/')\r\ndef mvp_hello():\r\n    return 'Hello there, I am a MVP!'\r\n\r\napp.run(host='0.0.0.0', port=80)\r\n<\/pre>\n
Copying the project files over to the server instance<\/h2>\n
Once we had provisioned an instance of Ubuntu Server 16.04 for our minimal viable product, we can then copy over the project folder from our machine to the Ubuntu Server 16.04 instance. Assuming that we got an instance of Ubuntu Server 16.04 running at 55.12.32.45<\/strong> and we are at the folder that contains the mvpapp<\/code> folder, we will run the following shell command to perform the copy:<\/p>\n
\r\nscp -r mvpapp root@55.12.32.45:\/var\/flaskapp\/\r\n<\/pre>\n
Logging into the Ubuntu Server 16.04 instance through ssh<\/h2>\n
After we get the mvpapp folder into the Ubuntu Server 16.04 instance, we can use ssh to get into the Ubuntu Server 16.04 instance to perform the necessary configurations:<\/p>\n
\r\nssh root@55.12.32.45\r\n<\/pre>\n
Installing Python 3 Package Manager (pip3)<\/h2>\n
If you do not have the Python 3 Package Manager in your Ubuntu Server 16.04 instance, you can install it via the following command:<\/p>\n
\r\nsudo apt-get install python3-pip\r\n<\/pre>\n
Installing virtualenv<\/h2>\n
If you do not have virtualenv in your Ubuntu Server 16.04 instance, you can install it via the following command: <\/p>\n
\r\nsudo apt-get install virtualenv\r\n<\/pre>\n
Installing Supervisor<\/h2>\n
To install Supervisor, we can run the following command:<\/p>\n
\r\nsudo apt-get install supervisor -y && sudo supervisord\r\n<\/pre>\n
After the command completes, Supervisor will be installed and started on the Ubuntu Server 16.04 instance.<\/p>\n
Preparing the virtual environment for running our Python 3 Flask MVP<\/h2>\n
After installing Supervisor, we can then proceed to prepare the virtual environment that our Python 3 Flask MVP will need. To do so, we run the following commands:<\/p>\n
\r\ncd \/var\/flaskapp\/mvpapp\r\nvirtualenv -p python3 mvpappenv\r\nsource mvpappenv\/bin\/activate\r\npip install -r requirements.txt\r\ndeactivate\r\n<\/pre>\n
The above commands does the following:<\/p>\n