Prerender Service (Dockerized)

This project provides a Dockerized prerender service based on prerender with an in-memory cache. It is designed to render JavaScript-heavy pages (e.g., for SEO or bots) using headless Chromium.

🚀 Features

• Headless Chromium rendering
• In-memory caching (prerender-memory-cache)
• Configurable cache TTL and size
• Lightweight Docker image (node:20-bullseye-slim)
• Ready to use with Docker Compose

📦 Project Structure

├── Dockerfile

├── server.js

└── docker-compose.yml

⚙️ Configuration

Environment Variables

Variable	Default	Description
PORT	3000	Port the service listens on
CACHE_MAXSIZE	1000	Maximum number of cached entries
CACHE_TTL	43200	Cache lifetime in seconds (12 hour)

---

🐳 Docker

Build Image

docker build -t prerender-service .

or check GitHub repository

ghcr.io/justcoded/dockerize-prerender:latest

with tag latest or number tag.

🧩 Docker Compose

Example docker-compose.yml:

services:
  webapp-prerender:
    build:
      context: .
      dockerfile: Dockerfile
    ports:
      - "3000:3000"
    shm_size: 512mb
    restart: unless-stopped
    environment:
      - PORT=3000

or

services:
  webapp-prerender:
    image: ghcr.io/justcoded/dockerize-prerender:latest
    shm_size: 512mb
    restart: unless-stopped
    environment:
      - PORT=3000

Run:

docker-compose up -d

🧠 How It Works

The service runs a prerender server using headless Chromium. Incoming requests are rendered as fully loaded HTML pages. Responses are cached in memory using prerender-memory-cache. Cache settings are controlled via environment variables.

🔧 Chromium Notes

Uses system-installed Chromium (/usr/bin/chromium) Required dependencies are installed in the Docker image --no-sandbox is enabled for compatibility inside containers

📈 Use Cases

SEO for SPA (React, Vue, Angular) Social media previews (Open Graph rendering) Rendering pages for bots/crawlers

🛠 Tips

Increase shm_size if Chromium crashes Tune CACHE_MAXSIZE based on memory limits Use a reverse proxy (e.g., Nginx) in production