Cheaply Rebuilding an 11ty site on Netlify

So, you read Robb Knight's lovely article on implementing Webmentions on your 11ty site, and you even wrote some code to fetch reactions from brigdy and webmention.io; good for you! Thing is, Netlify provides 300 free build minutes per month, and it takes about a minute to build your site, door-to-door. That's about 720 minutes a month, or in layman's terms: $7 you could be spending on bourbon, or Nintendo games, or, I dunno, rent or something.

Luckily, our Cascadian software overlords in Redmond have deep pockets, and GitHub actions minutes are basically free. So instead of building our site on netlify's runners, let's build the site on their servers and just ship the _site dir to netlify to deploy. How? Easy-peasy:

Make .github/workflows/rebuild.yaml and plop this jaunty little ditty inside:

name: Rebuild

on:
  workflow_dispatch:
  schedule:
    - cron: '0 * * * *'

jobs:
  rebuild:
    runs-on: ubuntu-latest
    name: Rebuild site
    steps:
      - uses: actions/checkout@v3
      - uses: actions/setup-node@v3
        with:
          node-version: '18'
          cache: 'npm'
      - run: npm ci --prefer-offline
      - run: npm run build

      - name: Publish to Netlify
        env:
          NETLIFY_SITE_ID: ${{ secrets.NETLIFY_SITE_ID }}
          NETLIFY_AUTH_TOKEN: ${{ secrets.NETLIFY_AUTH_TOKEN }}
        run: npx netlify-cli deploy --prod --message "deploy from GitHub Action" --dir=_site

Let's break this down:

1. workflow_dispatch means the action runs whenever you click the right buttons in the GitHub web UI or by hitting a special URL GitHub generates. We can use that URL later on the rebuildPAT automatically whenever we get an incoming webmention.

2. schedule uses cron tab notation 0 * * * * to run every hour on the 0th minute, or if you're normal "once every hour".

3. We grab our site's UUID from the netlify web UI at https://app.netlify.com/sites/${your_site_slug}/settings/general and save it as a GitHub secret called NETLIFY_SITE_ID.

4. Likewise, we generate a PAT on the netlify user settings page and save it under NETLIFY_AUTH_TOKEN.

If your build uses any other env vars (for example WEBMENTION_IO_TOKEN), make sure to save those in GitHub as well. I mean, we might as well spread our secrets around amirite?

That having been accomplished, run the netlify-cli NPM package with the --prod flag to deploy to the main site and the --message flag to help our future selves understand just what's flying here.

How'd we do?

Not too shabby! With this trick we cut our build time down by about a fifth. If deploys take on average 15 seconds, and we automatically rebuild on the hour, that gives us a headroom of about 120 build minutes for regular main branch deploys and branch deploy previews.