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Build Process For Project Operators

As a type of Project Operator, Prometheus Federator is primarily composed of three components:

  • The Underlying Helm Chart (Build Dependency)
  • The Project Operator Image (Build Dependency)
  • The Project Operator Helm Chart (What A User Actually Deploys)

Underlying Helm Chart

The underlying Helm Chart whose releases are deployed on behalf of every registered ProjectHelmChart CR is found in rancher-project-monitoring.

While the source of this chart is found in the packages/ directory, which is a construct of any rancher/charts-build-scripts repository (see the docs on Packages for more information), it is expected that a developer who files a PR with changes will run the make charts command to ensure that the package is read by the rancher/charts-build-scripts binary to produce / auto-generate the Helm Charts and manage the assets/+charts/ directories as well as the index.yaml entries to introduce this package in a standard Helm repository fashion.

Once make charts has been run and the chart is built from packages/rancher-project-monitoring/ -> charts/rancher-project-monitoring/${VERSION} (part of the make charts command), the built chart is then converted into a .tgz.base64 version of itself in scripts/build-chart and left in bin/rancher-project-monitoring/rancher-project-monitoring.tgz.base64.

helm package charts/${CHART}/${VERSION} --destination bin/${CHART}
base64 bin/${CHART}/${CHART}-${VERSION}.tgz > bin/${CHART}/${CHART}.tgz.base64
rm bin/${CHART}/${CHART}-${VERSION}.tgz

The Project Operator Image

To implement a Project Operator, Helm Project Operator expects a user to run the operator.Init command, which appears in Prometheus Federator's main.go as follows:

operator.Init(ctx, f.Namespace, cfg, common.Options{
    OperatorOptions: common.OperatorOptions{
        HelmAPIVersion:   HelmAPIVersion,
        ReleaseName:      ReleaseName,
        SystemNamespaces: SystemNamespaces,
        ChartContent:     base64TgzChart,
        Singleton:        true, // indicates only one HelmChart can be registered per project defined
    },
    RuntimeOptions: f.RuntimeOptions,
})

While the HelmAPIVersion, ReleaseName, and SystemNamespaces supplied are hard-coded into the main.go and the RuntimeOptions are taken from the CLI arguments provided, the only additional value that is needed to build this chart is the .tgz.base64 version of the chart that is passed in as a string to the operator.

This is precisely what we build in the prior step at bin/rancher-project-monitoring/rancher-project-monitoring.tgz.base64, which is why that path is found as a go embed directive on building the main.go:

//go:embed bin/rancher-project-monitoring/rancher-project-monitoring.tgz.base64
base64TgzChart string

Once your main.go is ready to be built, you can run ./scripts/build, which will run the underlying go build command and place the created binary in bin/prometheus-federator.

Once the binary has been created, it is then packaged into a container image in the scripts/package step, where we build the Dockerfile found in packages/Dockerfile to produce the final image.

The Project Operator Helm Chart

This is the component that the average user is actually expected to directly deploy; it is also maintained in the packages/ directory, like the Underlying Helm Chart.

As explained above, packages are a construct of any rancher/charts-build-scripts repository (see the docs on Packages for more information), so just like with the Underlying Helm Chart, it is expected that a developer who files a PR with changes will run the make charts command to ensure that the package is read by the rancher/charts-build-scripts binary to produce / auto-generate the Helm Charts and manage the assets/+charts/ directories as well as the index.yaml entries to introduce this package in a standard Helm repository fashion.

Once make charts has been run and the chart is built from packages/prometheus-federator -> charts/prometheus-federator/${VERSION} (part of the make charts command), the chart is now visible on the Helm repository maintained within your fork!

TLDR; Putting It All Together

Therefore, as a whole, the build process of Underlying Helm Chart looks as follows:

  • By a developer on making a PR to change the Underlying Helm Chart:
    • Run make charts to produce the Underlying Helm Chart in charts/rancher-project-monitoring/${VERSION} from packages/rancher-project-monitoring/
  • By running make (which runs rancher/dapper on the Dockerfile.dapper, which in turn runs ./scripts/ci that runs the following commands in an container image):
    • Run ./scripts/build-chart to produce bin/rancher-project-monitoring/rancher-project-monitoring.tgz.base64 from the Underlying Helm Chart
    • Run ./scripts/build to produce the Project Operator Binary bin/prometheus-federator; this will work since bin/rancher-project-monitoring/rancher-project-monitoring.tgz.base64 exists from the previous step
    • Run ./scripts/package to produce the Project Operator Image
  • By a developer on making a PR to change the Project Operator Helm Chart:
    • Make changes in packages/rancher-project-monitoring/ (such as updating the values.yaml or Chart.yaml to point to the latest Project Operator Image on a change that has been made)
    • Run make charts to produce charts/rancher-project-monitoring/${VERSION} from packages/rancher-project-monitoring/
    • Run ./scripts/build-chart to produce bin/rancher-project-monitoring/rancher-project-monitoring.tgz.base64 from charts/rancher-project-monitoring/${VERSION}