Setting up docker and requirements for websocket

In this tutorial, we are going to do some initial setup necessary for WebSockets. We would need FastAPI for sure and internally we are going to use Redis for its pub-sub capabilities. FastAPI when combined with Docker, a powerful containerization platform, it becomes even easier to deploy, manage, and scale FastAPI applications.
Docker is a containerization platform that simplifies the packaging and distribution of applications, making them portable and consistent across different environments. Containers provide a lightweight and isolated runtime environment for your applications, reducing conflicts and compatibility issues.

Before we dive into Dockerizing our FastAPI application, let's first set up a basic FastAPI project. Make sure you have Python installed on your system. create a file named codeshare/main.py

from fastapi import FastAPI 

app = FastAPI()

We also have some requirements for FastAPI, WebSockets and Redis too. Let's create a requirements.txt for it.

fastapi==0.100.0
uvicorn==0.23.1 

Now, coming to the docker part, We are going to create a Dockerfile that will have steps on starting the fastapi server. Since fastapi will not be the only service, we might have a Redis service, maybe a Postgres service. So, we also going to have a docker-compose.yml file to manage the different services together. Create a file named Dockerfile (without any file extension) in the project directory and add the following content:

FROM python:3.9

# Set the working directory in the container
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
EXPOSE 8000
CMD ["uvicorn", "main:app", "--host", "0.0.0.0", "--port", "8000"]

Docker Compose, on the other hand, is a tool for defining and running multi-container Docker applications. It simplifies the process of managing multiple containers and their interactions. Now, let's give wings to our FastAPI app with Docker Compose. Create a new file named docker-compose.yml in the project directory and let the creativity flow. This is our docker-compose.yml file.

version: '3.8'

services:
  web:
    build:
      context: ./
      dockerfile: Dockerfile
    ports:
      - "8000:8000"
    environment:
      - ENV_VAR_NAME=VALUE
    depends_on:
      - redis

  redis:
    image: redis:latest
    ports:
      - "6379:6379"

Now, we can start the docker container by using : docker compose up --build

Note that the --build flag will be needed once we make a change in the code and we need the changes to be picked up by docker. Normally, we do not want to install the requirements everytime. So, we simply use:

docker compose up