Ghost BunnyCDN Perma-Cache Purger

Overview

This project acts as a proxy between a Ghost CMS instance and BunnyCDN. It efficiently forwards client requests to Ghost CMS and handles the responses. While doing so, it monitors responses for the X-Cache-Invalidate header, which signals the need to purge the cache.

In this project specifically, it is used to purge the cache of a specified BunnyCDN pull zone. This functionality ensures that the cache remains synchronized with the latest content updates from Ghost CMS.

Originally developed as part of the BunnyCDN Perma-Cache integration at Magic Pages, a managed Ghost CMS hosting service, this tool can also help self-hosters using BunnyCDN to keep their cache up-to-date with their Ghost CMS instance.

While designed for use within a Docker Compose environment, other usage configurations are technically possible but not tested.

Setting up BunnyCDN

If you don't have BunnyCDN set up yet, you can follow the tutorial on the Magic Pages blog to get started.

Usage

The magicpages/bunnycdn-perma-cache-purger Docker image is available on Docker Hub. It can be used to deploy the proxy as part of a Docker Compose stack alongside Ghost.

Environment Variables

Required variables

• GHOST_URL: The URL of your Ghost CMS instance. Ideally, the hostname of your Ghost container and the port it listens on (e.g., http://ghost:2368).
• BUNNYCDN_API_KEY: Your BunnyCDN API key.
• BUNNYCDN_PULL_ZONE_ID: The ID of the BunnyCDN pull zone that you wish to purge.

Optional variables

• PORT: The port on which the proxy listens for incoming requests. Defaults to 3000.
• BUNNYCDN_PURGE_OLD_CACHE: Set to trueto enable deleting old cache files from the storage zone.
• BUNNYCDN_STORAGE_ZONE_NAME: Required if BUNNYCDN_PURGE_OLD_CACHE is set to true. The name of the BunnyCDN storage zone connected to the pull zone.
• BUNNYCDN_STORAGE_ZONE_PASSWORD: Required if BUNNYCDN_PURGE_OLD_CACHE is set to true. The password of the BunnyCDN storage zone connected to the pull zone. This differs from the API key. See Bunny's Edge Storage API documentation for more information.

These variables must be set in the Docker Compose file or as part of your Docker container configuration.

Example Docker Compose Configuration

The docker-compose.yml is a functional example of how to deploy Ghost, MySQL, and the BunnyCDN Perma-Cache Purger as part of a Docker Compose stack.

version: '3.8'

services:
  mysql:
    image: mysql:8
    environment:
      MYSQL_ROOT_PASSWORD: example
      MYSQL_DATABASE: ghost
      MYSQL_USER: ghost
      MYSQL_PASSWORD: ghost
    volumes:
      - mysql_data:/var/lib/mysql
    healthcheck:
      test: ["CMD", "mysqladmin", "ping", "-h", "localhost"]
      interval: 30s
      timeout: 10s
      retries: 5
      start_period: 10s

  ghost:
    image: ghost:latest
    environment:
      url: http://localhost:2368
      database__client: mysql
      database__connection__host: mysql
      database__connection__user: ghost
      database__connection__password: ghost
      database__connection__database: ghost
    volumes:
      - ghost_data:/var/lib/ghost/content
    depends_on:
      mysql:
        condition: service_healthy

  bunnycdn-perma-cache-purger:
    image: magicpages/bunnycdn-perma-cache-purger:latest
    environment:
      GHOST_URL: http://ghost:2368
      BUNNYCDN_API_KEY: your_bunnycdn_api_key
      BUNNYCDN_PULL_ZONE_ID: your_pull_zone_id
      BUNNYCDN_PURGE_OLD_CACHE: "true"
      BUNNYCDN_STORAGE_ZONE_NAME: your_storage_zone_name
      BUNNYCDN_STORAGE_ZONE_PASSWORD: your_storage_zone_password
    depends_on:
      ghost:
        condition: service_started
    ports:
      - "2368:3000"

volumes:
  ghost_data:
  mysql_data:

In this example, the Ghost CMS instance is accessible at http://localhost:2368. Port 2368 is usually the default port on which Ghost listens, but since we want to catch the X-Cache-Invalidate header, we don't expose Ghost directly. Instead, the proxy listens on that port and forwards requests to Ghost.

How It Works

In a nutshell, this proxy forwards all incoming requests to the Ghost instance that's specified in the GHOST_URL environment variable. All responses from Ghost are forwarded back to the client, while the proxy monitors the responses for the X-Cache-Invalidate header.

If the header is present, the proxy sends a purge request to the BunnyCDN API to clear the cache of the specified pull zone. If BUNNYCDN_PURGE_OLD_CACHE is set to true, it also deletes old directories from the specified storage zone to manage storage costs effectively.

Under the Hood

The proxy is built using Node.js and a simple Express server. Nothing fancy, just a few lines of code to handle the requests and responses.

And yes, that is the exact code that's running in production at Magic Pages 😉

License

This project is licensed under the MIT License, so feel free to do whatever you want with it. If you find it useful, I'd love to hear about it!

Contributing

If you have any ideas for improvements or new features, feel free to open an issue or submit a pull request. Always happy to make things even better and more useful!