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Getting started with self-hosted runners for GitHub CI on ExCL systems.

If you don’t want to run the runner as service then you can follow the steps posted at Adding self-hosted runners - GitHub Docs to create a self-hosted runner in ExCL.

Setup Runner as a service in ExCL

If you do want to register the runner as a service, the easiest way is to use systemd user services. To set this up follow the steps below.

Create a user systemd config which is unique to a single system.

mkdir -p /scratch/$USER/.config/systemd
ln -s /scratch/$USER/.config/systemd /home/$USER/.config/systemd

Notes:

  • If you are trying this on a system which doesn’t already have a /scratch folder the command will fail. Please send an email to excl-help@ornl.gov to create a folder for local storage.

  • If you setting up a second runner, the ln command will fail if the link already exists. Ensure that the link is a valid link pointing to scratch before continuing with these instructions.

Create a folder to store the GitHub Runner.

The steps are similar to that posted at Adding self-hosted runners - GitHub Docs with some changes. You will need to create one folder per machine and per repo so I recommend the following structure.

~/github-runners/<node>-<repo>

Download and Configure the Runner.

Once you create this directory and enter it, you will then download and configure the runner. The steps are reproduce below, but you should follow the instructions from the “add new self-hosted runner” page after clicking on “New self-hosted runner”.

curl -o actions-runner-linux-x64-2.311.0.tar.gz -L https://github.com/actions/runner/releases/download/v2.311.0/actions-runner-linux-x64-2.311.0.tar.gz
tar xzf ./actions-runner-linux-x64-2.311.0.tar.gz
./config.sh --url <url> --token <token>

Patch the Runner Folder for use as a User Systemd Service.

Apply this patch to modify the directory to use user systemd modules.

patch -p1 < /auto/software/github-runner/excl-patch.diff

Use the svc.sh script to install and manage the runner service.

After this patch is applied the svc.sh script works as documented in Configuring the self-hosted runner application as a service - GitHub Docs. However you don’t need to specify a username since it now defaults to the current user. The commands are reproduced below.

Install service

./svc.sh install

Start service and check status.

./svc.sh start
./svc.sh status

Note: The above install adds the service to auto start on reboot once you log back into the system. If you want to disable or enable this auto starting of the service run.

systemctl --user disable <service name

or

systemctl --user enable <service name>

To stop the service run

./svc.sh stop

To uninstall the service run

./svc.sh uninstall

Creating a secure, human-in-the-loop CI pipeline for public repos

GitHub Actions discourages the use of self-hosted runners for public repos. However, if you want to use an ExCL self-hosted runner for a public repo, you can use the following steps to create a secure CI pipeline that is triggered by an authorized user in a PR comment. This will prevent unauthorized users from running arbitrary code (e.g. attacks) automatically on ExCL systems from any PRs.

We follow the resulting workflow yaml file in the JACC.jl repo as an example that can be reused across repos.

  1. Select authorized users: those who can trigger the pipeline and store it in a GitHub secret in your repo using the following format: CI_GPU_ACTORS=;user1;user2;user3; and store another secret TOKENIZER=; to be used as a delimiter (it can be any character). Users should have a strong password and 2FA enabled.

  2. Trigger on issue_comment: this is the event that triggers the CI pipeline. The types: [created] ensures that the pipeline is triggered only when a new comment is made and not when an existing comment is edited.

    on:
  issue_comment:
    types: [created]

    NOTE: in GitHub Actions PRs are issues, so the issue_comment event is used to trigger the pipeline when a PR comment is made.

  3. Verify Actor: and "actor" is any user writing a comment on the PR. This step verifies that the actor is an authorized user to trigger the CI pipeline. The following is an example of how to verify the actor in the workflow yaml file. ACTOR_TOKEN puts the current "actor" within the delimiter and checks if it is in the list of authorized users. If it is, it triggers the pipeline. If not, it skips all subsequent steps.

    - name: Verify actor
      env:
        ACTOR_TOKEN: ${{secrets.TOKENIZER}}${{github.actor}}${{secrets.TOKENIZER}}
        SECRET_ACTORS: ${{secrets.CI_GPU_ACTORS}}
      if: contains(env.SECRET_ACTORS, env.ACTOR_TOKEN)
      id: check
      run: |
        echo "triggered=true" >> $GITHUB_OUTPUT

  4. Request PR info: since the event triggering the pipeline is a issue_comment the pipeline needs to retrieve information for the current PR. We use the official octokit/request-action action to get the PR information using the GITHUB_TOKEN available automatically from repo secrets. This is stored in a json format and available for future steps.

    - name: GitHub API Request
    if: steps.check.outputs.triggered == 'true'
    id: request
    uses: octokit/request-action@v2.1.9
    with:
      route: ${{github.event.issue.pull_request.url}}
    env:
      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

  5. Create PR status: this step creates a status check on the PR extracting information from the json information generated in the previous step. This steps allows for seamless integration with the typical checks interface for a PR along with other CI workflow. The status check is created as a "pending" status and the URL is linked to the current pipeline run before the actual tests run.

    - name: Create PR status
    if: steps.check.outputs.triggered == 'true'
    uses: geekdude/github-status-action-v2@v1.1.10
    with:
      authToken: ${{ secrets.GITHUB_TOKEN }}
      context: "ci-gpu-AMD ${{ matrix.jobname }}"
      state: "pending"
      sha: ${{fromJson(steps.request.outputs.data).head.sha}}
      target_url: https://github.com/${{github.repository}}/actions/runs/${{github.run_id}}

  6. Run tests: the following steps continue the pipeline tests and they are specific to each workflow reusing these steps.

  7. Report PR status: this step reports the status of the pipeline to the PR. The status is updated to "success" if the tests pass and "failure" if the tests fail. The URL is linked to the current pipeline run to update the PR status created in step 4.

    - name: Report PR status
    if: always() && steps.check.outputs.triggered == 'true'
    uses: geekdude/github-status-action-v2@v1.1.10
    with:
      authToken: ${{ secrets.GITHUB_TOKEN }}
      context: "ci-GPU-AMD ${{matrix.jobname}}"
      state: ${{job.status}}
      sha: ${{fromJson(steps.request.outputs.data).head.sha}}
      target_url: https://github.com/${{github.repository}}/actions/runs/${{github.run_id}}

    NOTE: in GitHub Actions statuses are different from checks, see the docs for a better explanation. The statuses generated by this pipeline get reported and stored in the Actions, and not in the PR checks tab. The important part is that the status from this workflow gets reported to the PR, users can see the status of the pipeline and admins can make these statuses mandatory or optional before merging.

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