Using GitHub to host recurring jobs

I manage my own server, and while I appreciate the sense of ownership and the learning that goes along with it, it can still increase the sense of friction.

For example, a few times lately I've had an idea for a simple little program, to run regularly and email me something. The programs aren't large, and the effort in developing and testing my Ansible playbook to host the program (including probably checking out from source, setting up deploy keys, etc) is probably about the same… so nothing gets done. Yes, I'm lazy.

Then suddenly I realised that GitHub¹ had free "Actions" (they'll run some code for you), and that these include cron-like scheduled triggers. That was all I needed!

At my day-job we use Harvest for time and budget tracking on projects. Try as I might, my instincts to bury myself in a technical problem mean that periodically reviewing budgets doesn't happen anywhere nearly as often as it should. Naturally this sounds like a technical problem to me! I'd like an email that gets sent every week to tell me how my projects are going: it's in my Inbox, and harder to ignore or forget. Zero-friction.

Skipping ahead, the result is on GitHub. Harvest have an API that's fairly easy to work with. I wrote a simple Python program that invokes it, formats the results using Mako, and writes to a file. For everything else, we will use GitHub's infrastructure.

Setting up GitHub Actions is fairly simple and covered elsewhere.

The key point I want to focus on here is the trigger ("on:") that invokes your workflow, which normally is a repository action such as pushing a new commit, or a pull request. It turns out, you can also define a schedule, using a cron-style syntax. Also worth noting, you probably want to include workflow_dispatch: in your workflows, which means you can invoke them on-demand for testing.

name: Harvest Budget Summary Report
on:
  workflow_dispatch:            # Enable manual invocation for testing
  schedule:
    - cron: "0 22 * * THU"      # 8am Fri, AEST

There is some boilerplate to create my python environment, then a simple entry to run the program, configured by environment variables²:

      - run: python projects_status.py
        env:
          HARVEST_ID: ${{ secrets.HARVEST_ID }}
          HARVEST_TOKEN: ${{ secrets.HARVEST_TOKEN }}
          ACCOUNT_EMAIL: ${{ secrets.ACCOUNT_EMAIL }}

Finally, we can lean on a third-party contribution to send the email, and we are done!

      - uses: dawidd6/action-send-mail@v3
        with:
          server_address: smtp.gmail.com
          server_port: 465
          username: ${{ secrets.SMTP_USERNAME }}
          password: ${{ secrets.SMTP_PASSWORD }}
          subject: "[Harvest] Project Budget Tracking"
          html_body: file://email.html
          from: ${{ secrets.ACCOUNT_EMAIL }}
          to: ${{ secrets.ACCOUNT_EMAIL }}