← Today I Learned

Trigger a workflow run in another repo

This is kind of meta: I made a separate repo todayilearned with the website for the content in this repo, and I wanted to trigger a new deploy whenever I pushed a new TIL.

The TL;DR is that there needs to be a GitHub Actions workflow in each repo: one in the “source” to send a repository_dispatch event to the “destination”, and one in the destination to do the actual building/deploying/what have you.

I’m sure this has been written in a zillion different places, but it took me a bit of searching to figure out so here goes:

  1. Modify the destination repo’s workflow YAML file to run the workflow on repository_dispatch events:

        branches: [main]
      repository_dispatch: # this line tells the workflow to run on `repository_dispatch` events
        types: [deploy] # this tells what event types should trigger a workflow run; if it's omitted, it'll just run on every event
  2. Create a Personal Access Token.

    • The new fine-grained tokens require an expiration date with a max of two years, at which point I’ll definitely have forgotten about all this. But luckily I’ll be able to refer back to this TIL to figure it out again!
    • The only repository access needed is the destination (i.e. the one receiving the event).
    • The only required permissions are read and write access for content (which covers the dispatch event) and metadata (which I think is mandatory for all personal access tokens).
  3. At this point, you can test things out manually with a cURL (replace PERSONAL_ACCESS_TOKEN, USER and REPO with the appropriate values):

    curl --request POST \
     -H "Accept: application/vnd.github.everest-preview+json" \
     -H "Authorization: token PERSONAL_ACCESS_TOKEN" \
     --data '{ "event_type": "deploy" }' https://api.github.com/repos/USER/REPO/dispatches

    If things are set up correctly, this should trigger a workflow run.

  4. Add the personal access token in the Actions secrets settings of the source repo.

  5. Add a workflow YAML file to the source repo that runs the cURL command above:

    name: Deploy
          - main
        runs-on: ubuntu-latest
          - name: Dispatch to workflows
            run: |
              curl -H "Accept: application/vnd.github.everest-preview+json" \
              -H "Authorization: token ${{ secrets.PERSONAL_ACCESS_TOKEN }}" \
              --request POST \
              --data '{ "event_type": "deploy" }' https://api.github.com/repos/USER/REPO/dispatches