Continuous Integration and Continuous Delivery (CI/CD)

The provided codebase for the Balena Prometheus Exporter, while not explicitly incorporating CI/CD, has a clear foundation for automation.

Workflow:

1. Build: The Dockerfile defines the process for building the Docker image.

   FROM python:3.10-alpine
             
             WORKDIR /usr/src/app
             
             COPY requirements.txt ./
             RUN pip install --no-cache-dir -r requirements.txt
             
             COPY main.py .
             
             USER nobody
             
             CMD [ "python", "./main.py" ]
             

2. Test: Tests are provided in tests/test_exporter.py.

   import unittest
             from unittest import mock
             
             from main import BalenaCollector
             
             class TestBalenaCollector(unittest.TestCase):
                 def setUp(self):
                     self.collector = BalenaCollector()
             
                 @mock.patch("main.BalenaCollector.get_fleet_metrics")
                 def test_collect(self, mock_metrics):
                     with mock.patch.object(self.collector, "get_balena_fleets") as mock_fleets:
                         mock_fleets.return_value = ["fleet1", "fleet2"]
                         mock_metrics.side_effect = [("test_fleet", 3), ("test_fleet", 3)]
             
                         result = list(self.collector.collect()[0].samples)
                         expected = [('balena_devices_online', {'fleet_name': 'test_fleet'}, 3),
                                     ('balena_devices_online', {'fleet_name': 'test_fleet'}, 3)]
             
                         result = [(s.name, s.labels, s.value) for s in result]
             
                         self.assertEqual(result, expected)
             
                 def test_get_balena_fleets(self):
                     with mock.patch("main.requests.get") as mock_get:
                         mock_get.return_value.ok = True
                         mock_get.return_value.json.return_value = {"d": [{"id": "fleet1"}, {"id": "fleet2"}]}
                         result = list(self.collector.get_balena_fleets())
                         expected = ["fleet1", "fleet2"]
                         self.assertEqual(result, expected)
             
             
                 def test_get_fleet_metrics(self):
                     with mock.patch("main.requests.get") as mock_get:
                         mock_get.return_value.ok = True
                         mock_get.return_value.json.return_value = {"d": [{"owns__device": 3, "app_name": "test_fleet"}]}
                         result = self.collector.get_fleet_metrics("fleet1")
                         expected = ("test_fleet", 3)
                         self.assertEqual(result, expected)
             
             unittest.main()
             

3. Deploy: The README.md demonstrates a basic Docker run command for local deployment.

   $ docker build -t balena-exporter .
             $ docker run -d \
             --name balena-exporter \
             -p 8000:8000 \
             -e BALENA_TOKEN= \
             balena-exporter
             

CI/CD Implementation:

GitHub Actions:

• GitHub Actions is a popular choice for CI/CD pipelines within GitHub repositories.
• A workflow could be defined to automatically build the Docker image, run tests, and deploy to a container registry or directly to a Balena cloud application.
• https://docs.github.com/en/actions/using-workflows
• https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions

Jenkins:

• Jenkins is a widely used CI/CD server that can be integrated with the project.
• Jenkins pipelines can be created to automate the build, test, and deployment processes.
• https://www.jenkins.io/

Balena Cloud:

• Balena Cloud offers a built-in CI/CD system.
• It provides a workflow for building Docker images, running tests, and deploying them to devices.
• https://www.balena.io/docs/

Considerations:

• Security: Securely store the BALENA_TOKEN and other sensitive credentials.
• Testing: Expand the test suite to cover more code paths and edge cases.
• Monitoring: Integrate with monitoring tools to track the performance and health of the exporter.
• Deployment Strategy: Choose the appropriate deployment strategy, considering factors like blue-green deployments or canary releases.

Example CI/CD Pipeline (GitHub Actions):

name: CI/CD
          on:
            push:
              branches:
                - main
          
          jobs:
            build:
              runs-on: ubuntu-latest
              steps:
                - uses: actions/checkout@v3
                - name: Build Docker Image
                  run: docker build -t balena-exporter .
                - name: Run Tests
                  run: pytest tests/test_exporter.py
                - name: Push Image to Registry
                  run: docker push balena-exporter
            deploy:
              runs-on: ubuntu-latest
              needs: build
              steps:
                - uses: actions/checkout@v3
                - name: Deploy to Balena Cloud
                  uses: balena-io/[email protected]
                  with:
                    balenaToken: ${{ secrets.BALENA_TOKEN }}
                    applicationId: ${{ secrets.APPLICATION_ID }}
                    release: balena-exporter
          

Top-Level Directory Explanations

tests/ - This directory contains all the unit and integration tests for the project. It includes the __init__.py file which makes it a package, and specific test files like test_exporter.py.