Coding the App

In this tutorial, we'll take advantage of the FastAPI library in Python. If you are familiar with any other language and framework, feel free to just replace the code samples in this section with your preferred alternative.

Creating the Required Files

First, create a new git repository with GitHub. We'll need to add the following files:

├── api.py 
├── requirements.txt 
├── Dockerfile 
├── README.md (optional)
└── .gitignore (optional)

Fill in the Code

Next, we'll fill in the code just like we would do if we were planning to run on a normal server.

A Simple Server

Next, we can write the simplest of FastAPI servers:

from fastapi import FastAPI, Header
from typing import Optional

app = FastAPI()

@app.get("/say_hello")
async def say_hello(x_oblv_user_name: Optional[str] = Header(None)):
    return {"message": "Hello " + x_oblv_user_name}

The only thing that may look unfamiliar from a standard FastAPI server is that we are reading the optional header field X-OBLV-User-Name which gets autocast to be snake case (lowercase with underscores) as x_oblv_user_name. When we use PKI pre-shared keys (PSK) with field is added by the proxy so the application can know who it was who made the request.

The simple server above will reply to a request by responding Hello to the user's name.

Requirements

In the requirements.txt file, add the requirements for a basic FastAPI server:

fastapi>=0.68.0,<0.69.0
pydantic>=1.8.0,<2.0.0
uvicorn>=0.15.0,<0.16.0

Dockerfile

As a last step, let's write a simple Dockerfile to package the api. It should look something like this:

FROM python:3.9
 
WORKDIR /code
 
COPY ./requirements.txt /code/requirements.txt
 
RUN pip install --no-cache-dir --upgrade -r /code/requirements.txt
 
COPY ./api.py /code/api.py

CMD ["uvicorn", "api:app", "--host", "0.0.0.0", "--port", "80"]

To build and run the above packaged application we can simply do the following:

docker build -t example .  

docker run -p 1234:80 -t example 

Quick Test

The above should make a simple api when we build and deploy it with docker. To test it from the command line you can use a curl command as follows:

curl --header "X-OBLV-User-Name: Bob" localhost:1234/say_hello 

Equally, if you use Postman or equivalent, simply call localhost:1234 with the header field set from your Postman application:

Push to GitHub

Finally push your code to GitHub as a new repository. For the sake of simplicity let's call is my-first-oblivious-app.