ocm-controller

README

ocm-controller

This is the main repository for ocm-controller. The ocm-controller is designed to enable the automated deployment of software using the Open Component Model and Flux.

It has the following features:

• Resolves ComponentDescriptor metadata for a particular component version
• Performs authentication with OCM repositories
• Retrieves artifacts from OCM repositories
• Verifies components
• Makes individual resources from components available within the cluster
• Performs localization and configuration of component resources

Quick Start

Pre-requisites

• Create a kind cluster: kind create cluster
• Make sure flux is installed in your cluster using: flux install
• Install the controller using: ocm controller install

---

In this tutorial, we'll deploy the ocm.software/podinfo component which contains a Kubernetes Deployment manifest for the podinfo application.

To get started, save the following ComponentVersion to a file named component_version.yaml:

# component_version.yaml
apiVersion: delivery.ocm.software/v1alpha1
kind: ComponentVersion
metadata:
  name: podinfo
  namespace: ocm-system
spec:
  interval: 10m0s
  component: ocm.software/podinfo
  version:
    semver: ">=v6.2.3"
  repository:
    url: ghcr.io/open-component-model

Apply the ComponentVersion:

kubectl apply -f component_version.yaml

Create a Resource for the deployment resource:

# resource.yaml
apiVersion: delivery.ocm.software/v1alpha1
kind: Resource
metadata:
  name: podinfo-deployment
  namespace: ocm-system
spec:
  interval: 10m0s
  sourceRef:
    apiVersion: delivery.ocm.software/v1alpha1
    kind: ComponentVersion
    name: podinfo
    namespace: ocm-system
    resourceRef:
      name: deployment

Apply the Resource:

kubectl apply -f resource.yaml

Create a FluxDeployer to apply the Resource and save it to a file named deployer.yaml:

# deployer.yaml
apiVersion: delivery.ocm.software/v1alpha1
kind: FluxDeployer
metadata:
  name: podinfo
  namespace: ocm-system
spec:
  interval: 10m0s
  sourceRef:
    apiVersion: delivery.ocm.software/v1alpha1
    kind: Resource
    name: podinfo-deployment
  kustomizationTemplate:
    path: ./
    prune: true
    targetNamespace: default

Apply the FluxDeployer:

kubectl apply -f deployer.yaml

View the deployment spinning up:

kubectl get po -n default

What just happened?

We used ComponentVersion to retrieve the ocm.software/podinfo component from a remote OCM repository (ghcr.io/open-component-model). We then fetched a resource from this component using the Resource CRD.

The ocm-controller fetched this resource and created a Snapshot containing the contents of the OCM resource. This snapshot is a Flux compatible OCI image which is stored in a registry managed by ocm-controller.

Because the snapshot is Flux compatible we asked the ocm-controller to create a corresponding Flux source for it. This means that we can then use a Flux Kustomization resource to apply content of it to the cluster.

The following diagram illustrates the flow:

  graph TD;
      ComponentVersion --> Resource --> Snapshot;
      OCIRepository --> Snapshot;
      subgraph "Flux Deployer";
          OCIRepository --> Kustomization --> Deployment;
    end

Elements

ComponentVersion

Retrieves a ComponentVersion from an OCM repository. Handles authentication with the repository and optionally verifies the component using provided signatures.

Resource

Makes a resource available within the cluster as a snapshot.

HelmChart type Resource

In order to identify a Resource as a HelmChart an extra identify needs to be added. The key is helmChart and the value is the name of the chart. For example:

apiVersion: delivery.ocm.software/v1alpha1
kind: Resource
metadata:
  name: ocm-with-helm-deployment
  namespace: ocm-system
spec:
  interval: 10m
  sourceRef:
    kind: ComponentVersion
    name: ocm-with-helm
    namespace: ocm-system
    resourceRef:
      name: charts
      version: 6.3.5
      extraIdentity:
        helmChart: podinfo # name of the chart

This extra information is needed, because it cannot be inferred from the resource's information.

Localization

This Localization represents a way to configure resources to use local references once a transfer occurs. To understand more, please take a look at OCM Localization reference.

Let's take a look at a simple Localization object:

apiVersion: delivery.ocm.software/v1alpha1
kind: Localization
metadata:
  name: podinfo-localization
  namespace: mpas-ocm-applications
spec:
  configRef:
    kind: ComponentVersion
    name: podinfocomponent-version
    namespace: mpas-ocm-applications
    resourceRef:
      name: config
      version: 1.0.0
  interval: 10m0s
  sourceRef:
    kind: ComponentVersion
    name: podinfocomponent-version
    namespace: mpas-ocm-applications
    resourceRef:
      name: manifests
      version: 1.0.0

The two most essential pieces are the sourceRef and the configRef. The sourceRef contains the resource to localize while the configRef points to the resource containing the localization values. In this case, an image reference:

localization:
- resource:
    name: image
  file: deploy.yaml
  image: spec.template.spec.containers[0].image

These are OCM's localization rules.

Configuration

Use configuration rules to apply custom settings to objects. These could be manifest files, like a Deployment for which we configure the replica count. Or a setting for a Redis database, etc.

It's much the same as Localization in design:

apiVersion: delivery.ocm.software/v1alpha1
kind: Configuration
metadata:
  name: podinfo-configuration
  namespace: mpas-ocm-applications
spec:
  configRef:
    kind: ComponentVersion
    name: podinfocomponent-version
    namespace: mpas-ocm-applications
    resourceRef:
      name: config
      version: 1.0.0
  interval: 10m0s
  sourceRef:
    apiVersion: delivery.ocm.software/v1alpha1
    kind: Localization
    name: podinfo-localization
    namespace: mpas-ocm-applications
  valuesFrom:
    configMapSource:
      key: values.yaml
      sourceRef:
        name: podinfo-values-500b59e1
      subPath: podinfo

However, it's much more complex. It uses cue-lang to achieve a flexibility in configuring and defining user-friendly default values.

For example:

// | Parameter | Type | Default | Description                          |
// |-----------|------|---------|--------------------------------------|
// | replicas  | int  | 1       | The number of replicas for the cache |
#SchemaVersion: "v1.0.0"
redis: replicas: 1

This is a basic CUE config that will be used to set the Redis deployment's replica count.

Flux Deployer

Creates a Flux Kustomization object and points it to a snapshot. This resource represents a connection with Flux to be used to deploy a resource that might contain a set of manifest files. Other deployers can later be implemented if requested.

Snapshot

A Kubernetes resource that manages a Flux compatible single-layer OCI image. Enables interoperability between OCM and Flux.

A snapshot might look something like this:

apiVersion: delivery.ocm.software/v1alpha1
kind: Snapshot
metadata:
  name: podinfo-localization-6t34w4w
  namespace: mpas-ocm-applications
spec:
  digest: sha256:1ecc4af8574082e411b9c90903c73befbf5c8aefb98eae835ddbcd3d60ee1795
  identity:
    component-name: ocm.software-demos-podinfo-v1.0.0-15225012871519309609
    component-version: v1.0.0
    resource-name: config
    resource-version: 1.0.0
  tag: "7833"
status:
  conditions:
  - lastTransitionTime: "2024-04-04T11:20:38Z"
    message: Snapshot with name 'podinfo-localization-6t34w4w' is ready
    observedGeneration: 2
    reason: Succeeded
    status: "True"
    type: Ready
  digest: sha256:1ecc4af8574082e411b9c90903c73befbf5c8aefb98eae835ddbcd3d60ee1795
  observedGeneration: 2
  repositoryURL: https://registry.ocm-system.svc.cluster.local:5000/sha-3967392847701103634
  tag: "7833"

These are never created by hand. They are always an end-result of some in-cluster process.

The important bits are the digest, repository URL and the tag. These three signify and identify of what has been created. The URL will always point to the in-cluster managed registry.

Registry

This project also creates an in-cluster HTTPS based OCI registry. This registry is used as a sync-point between the ocm-controller and the Flux eco-system. It also serves as a cache. All three sync objects, Resource, Localization and Configuration will put the end result into this cache.

This means that fetching a remote resource happens only once at the begin of a sync chain. Then that resource will exist in the local registry and any further operations will take it from there.

Testing

To run the test suite use make test.

Tinygo is used to compile the test suite to a single binary. This binary is then used to run the tests.

In order to install tinygo visit the installation instructions.

Local Testing

ocm-controller has a Tiltfile that can be used for rapid development. tilt is a convenient little tool to spin up a controller and do some extra setup in the process conditionally. It will also keep updating the environment via a process that is called control loop; it's similar to a controller's reconcile loop.

To use tilt, we'll have to first prime a test cluster. ocm-controller requires certificates to be present for the in-cluster registry that's running using https. To prime a test cluster simply execute make prime-test-cluster. This will spin up a local KinD cluster, download the generated certificates and add them to the local trust-store using mkcert.

This project also requires Flux to be installed in the cluster. For testing purposes, there is no need to configure a Flux Source. Simply, run flux install to install the controllers and the CRDs.

Once that is done, we are ready to start up the controller. Run tilt up, then hit <space> to enter tilt's ui. You should see ocm-controller starting up.

Licensing

Copyright 2022 SAP SE or an SAP affiliate company and Open Component Model contributors. Please see our LICENSE for copyright and license information. Detailed information including third-party components and their licensing/copyright information is available via the REUSE tool.