GitHub App Preview Trigger

A Cloudflare Worker that listens for /preview comments on pull requests and triggers GitHub Actions workflows for preview deployments.

Setup

Prerequisites

• Cloudflare account
• Node.js 18+
• Wrangler CLI: npm install -g wrangler

1. Deploy Worker

wrangler login
npm install
wrangler deploy

2. Create GitHub App

1. Go to GitHub Settings > Developer settings > GitHub Apps
2. Click "New GitHub App"
3. Fill in:
   • GitHub App name: Preview Deploy Bot
   • Webhook URL: https://your-worker.your-subdomain.workers.dev/webhook
   • Webhook secret: Generate a secure random string
4. Set permissions:
   • Actions: Read & Write
   • Contents: Read
   • Issues: Write
   • Metadata: Read
   • Pull requests: Write
   • Subscribe to: Issue comments
5. Note down: App ID, private key, webhook secret

3. Configure Secrets

wrangler secret put GITHUB_APP_ID
wrangler secret put GITHUB_PRIVATE_KEY
wrangler secret put WEBHOOK_SECRET

4. Install GitHub App

1. Go to "Install App" tab in GitHub App settings
2. Install on your account/organization
3. Select repositories

Usage

1. Comment /preview on any pull request
2. Worker triggers GitHub Actions workflow
3. Results are posted back as a comment

Local Development

wrangler dev

Troubleshooting

• Webhook not working: Check URL in GitHub App settings
• Auth errors: Verify secrets are set correctly
• Workflow not triggering: Ensure .github/workflows/preview-deploy.yml exists
• View logs: wrangler tail