This document provides a step-by-step guide for buiding a simple containerized RESTful API that returns the current server time in West Africa Time (WAT) using Docker. It will walk you through creating the API using Python and Flask, and then show you how to containerize it.

First, let's create the Flask application, which will be the same as in the previous example.

File: app.py

from flask import Flask, jsonify
from datetime import datetime
import pytz

app = Flask(__name__)

@app.route('/time', methods=['GET'])
def get_current_time():
    # Set the timezone to West Africa Time (WAT)
    wat_timezone = pytz.timezone('Africa/Lagos')  # Lagos, Nigeria is in WAT
    current_time = datetime.now(wat_timezone)
    
    # Format the time as a string
    formatted_time = current_time.strftime('%Y-%m-%d %H:%M:%S %Z')
    
    # Return the time in JSON format
    return jsonify({'current_time': formatted_time})

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

Now, let's create a Dockerfile to containerize the application.

File: Dockerfile

# Use an official Python runtime as a parent image
FROM python:3.9-slim

# Set the working directory in the container
WORKDIR /app

# Copy the current directory contents into the container at /app
COPY . /app

# Install any needed packages specified in requirements.txt
RUN pip install --no-cache-dir Flask pytz

# Make port 5000 available to the world outside this container
EXPOSE 5000

# Define environment variable
ENV NAME World

# Run app.py when the container launches
CMD ["python", "app.py"]

To specify the dependencies for your Flask application, create a requirements.txt file.

File: requirements.txt

Flask
pytz

Next, you need to build the Docker image. Open a terminal and navigate to the directory containing the Dockerfile, app.py, and requirements.txt. Then run the following command:

docker build -t wat-time-api .

After the image is built, you can run it as a container:

docker run -d -p 5000:5000 wat-time-api

This command runs the container in detached mode (-d) and maps port 5000 on your host to port 5000 in the container (-p 5000:5000).

Now you can access the API by navigating to http://localhost:5000/time in your web browser or using curl:

curl http://localhost:5000/time

The API should return the current server time in WAT in a JSON format like this:

{
    "StatusCode        : 200
     StatusDescription : OK
     Content           : {"current_time":"2024-08-26 14:37:28 WAT"}"
}

• Flask serves as the framework for the API.
• Docker containerizes the application, making it portable and easy to deploy.
• Dockerfile defines the environment and steps needed to run the application inside a container.