At Skedulo we have a pretty sophisticated inventory set up that uses the generator plugin and hundreds of inventory directories to manage the configuration of dozens of different microservices and infrastructure services across several environments and regions.

ansible-inventory-diff is a tool that takes two git branches and runs ansible-inventory against both branches and compares the results, showing what hosts have inventory changes and what those changes are.

We’ve been using ansible-inventory-diff to protect ourselves from unexpected issues as a result of inventory changes for a while now. But with Github Actions being widely available for a while now, we wanted to make it more obvious in the pull request what will change

It took quite a lot of iterations to get the action behaviour correct but it’s now on the Github Marketplace

We use the configuration below to do the following:

• Check out the code
• See if any inventory files differ between the pull request and main branch
• If they do, run ansible-inventory-diff
• Output the full result in the action workflow (from the result output) to easily check that full output from the pull request
• Add a comment containing at most the first 200 lines (available as the snippet output)
• If there is no difference, or we didn’t run ansible-inventory-diff, explicitly comment to say that

Running ansible-inventory-diff against our inventory takes 5 minutes (I haven’t checked for a while how big the output from ansible-inventory is but I’m pretty sure it’s huge and rendering that is what takes the time) - I hope I can find some optimizations at some point before we run out of Github Action minutes!

on: pull_request

jobs:
  ansible_inventory_diff:
    runs-on: ubuntu-latest
    name: ansible-inventory-diff
    steps:
      - name: Checkout
        uses: actions/checkout@v2
        with:
          fetch-depth: 0
      - name: Check if ansible-inventory-diff should run
        run:
          echo "::set-output name=diff::$(git diff --name-only origin/main -- inventory)"
        id: check
      - name: Run ansible inventory diff
        id: run
        uses: Skedulo/ansible-inventory-diff@v1.5
        with:
          base-ref: origin/main
        if: ${{ steps.check.outputs.diff != '' }}
      - name: Ansible Inventory Diff output
        shell: bash
        run: echo "${{ steps.run.outputs.result }}"
        if: ${{ steps.check.outputs.diff != '' }}
      - name: Comment PR
        uses: unsplash/comment-on-pr@v1.2.0
        with:
          msg: "*ansible-inventory-diff*\n\n```${{ steps.run.outputs.snippet }}\n```"
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        if: ${{ steps.check.outputs.diff != '' && steps.run.outputs.snippet != '' }}
      - name: Comment PR when diff is empty
        uses: unsplash/comment-on-pr@v1.2.0
        with:
          msg: "*ansible-inventory-diff*\n\nEmpty diff"
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        if: ${{ steps.check.outputs.diff == '' || steps.run.outputs.snippet == '' }}