Sample Function: WAV to MP3 Converter

Introduction

This repository contains a sample serverless function written in Python that converts a WAV audio file to MP3 format. The function performs the following actions:

1. Downloads a WAV file from a specified DigitalOcean Spaces bucket.
2. Converts the WAV file to MP3 format using audioread and lameenc.
3. Uploads the converted MP3 file back to the Spaces bucket.
4. Sends a notification to a specified endpoint (config-proxy) with details of the converted file.

You can deploy this function on DigitalOcean's App Platform as a Serverless Function component. For more information, refer to the DigitalOcean Functions Documentation.

Requirements

• A DigitalOcean account.
• The DigitalOcean doctl CLI installed on your local machine.
• Access to a DigitalOcean Spaces bucket.
• The following environment variables set up:
  • DO_SPACES_REGION: Your Spaces region (e.g., nyc3, ams3).
  • DO_SPACES_BUCKET: Your Spaces bucket name.
  • DO_ACCESS_KEY: Your Spaces access key ID.
  • DO_SECRET_KEY: Your Spaces secret access key.
  • Optional: Any additional environment variables required by your config-proxy endpoint.

Deploying the Function

Clone the Repository

# Clone this repository
git clone <your-repo-url>
cd <your-repo-directory>

Install Dependencies

Ensure that your requirements.txt file includes the necessary dependencies:

audioread==2.1.9
boto3==1.26.60
lameenc==1.7.0
requests==2.28.2

Deploy the Function

Use the doctl CLI to deploy your function. The --remote-build flag ensures that the build and runtime environments match.

doctl serverless deploy <your-directory> --remote-build

Example:

doctl serverless deploy wav-to-mp3-converter --remote-build

Deployment Output:

Deploying 'wav-to-mp3-converter'
  to namespace 'fn-...'
  on host 'https://faas-...'
Submitted action 'convert' for remote building and deployment in runtime python:default
Processing of 'convert' is still running remotely ...
...
Deployed functions ('doctl sbx fn get <funcName> --url' for URL):
  - convert

Using the Function

Invoke the Function via HTTP Request

You can invoke the function by sending an HTTP POST request. Replace <FUNCTION_URL> with the URL of your deployed function. You can obtain the function URL using the doctl command:

doctl serverless functions get convert --url

Sample curl Command:

curl -X POST "<FUNCTION_URL>" \
  -H "Content-Type: application/json" \
  -H "Authorization: Basic <YOUR_BASE64_ENCODED_CREDENTIALS>" \
  -d '{
        "trackId": "your-track-id",
        "audioFileWAVKey": "path/to/your/audio.wav"
      }'

Parameters

• trackId: (string, required) The unique identifier for the track.
• audioFileWAVKey: (string, required) The key (path) to the WAV file in your Spaces bucket.

Response

On successful execution, the function will:

• Convert the WAV file to MP3 format.
• Upload the MP3 file to your Spaces bucket.
• Notify the config-proxy endpoint with the trackId and mp3Key.

Sample Successful Response:

{
  "statusCode": 200,
  "body": {
    "message": "Conversion successful",
    "mp3Key": "path/to/your/audio.mp3"
  }
}

Error Handling

If an error occurs during execution, the function will return a 500 status code with an error message.

Sample Error Response:

{
  "statusCode": 500,
  "body": "Error message detailing what went wrong"
}

Function Details

Code Breakdown

The function performs the following steps:

1. Input Validation: Checks for the required trackId and audioFileWAVKey parameters.
2. Download WAV File: Uses boto3 to download the WAV file from your Spaces bucket to a temporary location.
3. Convert to MP3: Utilizes audioread and lameenc to convert the WAV file to MP3 format.
4. Upload MP3 File: Uploads the converted MP3 file back to the Spaces bucket.
5. Cleanup: Deletes temporary files to free up resources.
6. Notify config-proxy: Sends a PUT request to the specified endpoint with the trackId and mp3Key.

Environment Variables

Ensure the following environment variables are set in your project.yml or function configuration:

environment:
  DO_SPACES_REGION: <your-spaces-region>
  DO_SPACES_BUCKET: <your-spaces-bucket-name>
  DO_ACCESS_KEY: <your-spaces-access-key>
  DO_SECRET_KEY: <your-spaces-secret-key>

Dependencies

List the dependencies in your requirements.txt file:

audioread==2.1.9
boto3==1.26.60
lameenc==1.7.0
requests==2.28.2

project.yml Configuration

Your project.yml should define the function and its runtime:

packages:
  - name: wav-to-mp3
    actions:
      - name: convert
        runtime: 'python:3.9'
        main: __main__.main
    environment:
      DO_SPACES_REGION: ${DO_SPACES_REGION}
      DO_SPACES_BUCKET: ${DO_SPACES_BUCKET}
      DO_ACCESS_KEY: ${DO_ACCESS_KEY}
      DO_SECRET_KEY: ${DO_SECRET_KEY}

build.sh Script

Include a build.sh script if you need to handle any build steps, especially for dependencies that require compilation:

#!/bin/bash

set -e

virtualenv --without-pip virtualenv
pip install -r requirements.txt --target virtualenv/lib/python3.9/site-packages

Testing the Function

Using doctl CLI

Invoke the function with test parameters:

doctl serverless functions invoke convert \
  --param trackId=your-track-id \
  --param audioFileWAVKey=path/to/your/audio.wav

Using Postman

1. Create a new POST request to <FUNCTION_URL>.
2. Headers:
   • Content-Type: application/json
   • Authorization: Basic <YOUR_BASE64_ENCODED_CREDENTIALS>
3. Body:

   {
     "trackId": "your-track-id",
     "audioFileWAVKey": "path/to/your/audio.wav"
   }

4. Send the request and verify the response.

Notes

• Authentication: The function requires Basic Authentication using credentials provided by DigitalOcean. Ensure you include the correct Authorization header in your requests.
• Timeouts: If processing large audio files, be mindful of function execution time limits. Optimize your code or adjust timeout settings as needed.
• Error Logging: Use print statements or logging to output debug information during development.

Learn More

• DigitalOcean Functions Documentation
• DigitalOcean Spaces Documentation
• doctl Serverless Reference

Contributing

Contributions are welcome! Please submit a pull request or open an issue to discuss improvements or bug fixes.

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Feel free to customize this README to suit your specific repository details, such as adding a link to your repository, adjusting the function name, or including additional information relevant to your use case.