A Simple API for downloading files from a Linux Server

You can implement a Flask API endpoint to send a file from a local directory to the client and delete the file after it's been sent. Use the send_from_directory function provided by Flask to send the file.

Here's how you can modify the app.py to do this:

from flask import Flask, jsonify, send_from_directory
import os

app = Flask(__name__)

@app.route('/download/<id>', methods=['GET'])
def download_file(id):
    # Map the ID to a specific filename
    filename = f"{id}"
    directory = "/mnt/files/"

    # Check if the file exists and send it
    if os.path.exists(os.path.join(directory, filename)):
        # Send the file and delete it after sending
        try:
            return send_from_directory(directory, filename, as_attachment=True, attachment_filename=filename)
        finally:
            os.remove(os.path.join(directory, filename))
    else:
        return jsonify({"error": "File not found"}), 400


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

The send_from_directory function sends the specified file to the client. The as_attachment=True argument makes the file download as an attachment (which triggers the file download dialog), and attachment_filename=filename sets the name of the downloaded file. The try/finally block ensures that the file is deleted even if an error occurs while sending the file.

The rest of the steps (creating the Dockerfile, building the Docker image, and running the Docker container) would remain the same as in the previous examples.

With this setup, you can request to download and delete a file like so:

curl http://localhost:5000/download/<id> --output <output_filename>

Replace <id> with the name of the file you want to download and delete, and replace <output_filename> with the name you want to give to the downloaded file.

As before, this is a simple example and does not include comprehensive error handling or security precautions. Be sure to secure your API and handle potential errors in a production setting.

Dockerise the app and deploy

You can use Docker Compose to define and run your multi-container Docker applications. Here's an example of how to use it to mount a local directory to a directory in a Docker container.

Create a docker-compose.yml file in your project directory:

version: '3.8'
services:
  my-app:
    image: my-app:latest
    ports:
      - 5000:5000
    volumes:
      - /mnt/host/files/:/mnt/files/

In this docker-compose.yml file:

• my-app is the name of the service. This can be anything you like.
• image: my-app:latest specifies the Docker image to use for the container. Replace my-app:latest with the name and tag of your Docker image.
• ports is a list of port mappings. This example maps port 5000 on the host to port 5000 in the container. Adjust this to fit your needs.
• volumes is a list of volume mappings. This example maps the /mnt/host/files directory on the host to the /mnt/files directory in the container. Replace with the default download directory in your container if it's different.

Base Image for building my app if no external network access

You can then run your Docker container with Docker Compose:

docker-compose up

This will start your container and mount the specified local directory to the specified directory in the container.

Please note that you must have Docker Compose installed on your system to use this. If it's not installed, you can install it following the instructions on the official Docker Compose installation guide.

You can create a base image that has Flask pre-installed. Here are the steps:

1. Create a Dockerfile for your base image:

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

# Install Flask
RUN pip install --no-cache-dir flask

2. Build the Docker image:

docker build -t my-python-flask-base .

This command will create a Docker image named my-python-flask-base with Flask pre-installed.

3. Now, you can use this base image in your application's Dockerfile:

dockerfileCopy

# Use the base image with Flask pre-installed
FROM my-python-flask-base

# Set the working directory in the container to /app
WORKDIR /app

# Add the current directory contents into the container at /app
ADD . /app

# Make port 80 available to the world outside this container
EXPOSE 80

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

With this setup, your application's Docker image is built from a base image that already has Flask installed, so it doesn't need to install Flask itself. This can speed up the build process for your application's Docker image.

Note that the base image my-python-flask-base needs to be available on the machine where you're building the application's Docker image. If you're building on a different machine, you'll need to push my-python-flask-base to a Docker registry (like Docker Hub) and pull it on the machine where you're building the application's Docker image.