cancerian0684/flask-tutorial

Flask API Development to Deployment Tutorial

Flask API Tutorial

Install virtual environment

$ pip install virtualenv

Create virtual environment by any name. Lets say venv

$ virtualenv -p python3.6 venv

Activate virtual environment

$ source venv/bin/activate

After activating the virtual environment, install requirements by using following command.

$ cd app
$ pip install -r requirements.txt

Freeze requirements for virtual environment

$ pip freeze > requirements.txt

Running the python flask application

$ python src/main.py

Running wsgi gunicorn

$ gunicorn --workers 4 --bind 0.0.0.0:5000 src.wsgi:app
$ gunicorn -w 6 -b 127.0.0.1:5000  src.wsgi:app

Deactivate the virtual environment

$ deactivate

Architecture diagram

Architecture diagram for nginx setup with wsgi unicorn & flask app.

Figure 1: Nginx as a reverse proxy for WSGI gunicorn

Get host information using sidecar

Sidecar app exposes host information about all the hosts registered in eureka service registry. This could be very convenient for non-JVM app.

Retrieve Host Information for sidecar-pdf service

GET http://localhost:5678/hosts/sidecar-pdf

Response

[
    {
        "host": "localhost",
        "port": 8058,
        "secure": false,
        "uri": "http://localhost:8058",
        "serviceId": "SIDECAR-PDF",
    }
]

In a similar fashion we can retrieve host information about any other service registered in Spring Cloud Eureka Registry - be it JVM app or non-JVM app.

Docker containerization

Creating a docker image:

$ docker build -t flask_tutorial .

Running docker container:

$ docker run -p 80:8058 flask_tutorial:latest