d1-infra

Note

This repository is part of the reference architecture for the ControlPlane Enterprise for Flux CD.

The d1 reference architecture comprised of d1-fleet, d1-infra and d1-apps is a set of best practices and production-ready examples for using Flux to manage the continuous delivery of Kubernetes infrastructure and applications on multi-cluster multi-tenant environments.

Scope and Access Control

This repository is managed by the platform team who are responsible for the Kubernetes infrastructure.

This repository is used to define the Kubernetes infrastructure components such as:

• Cluster add-ons (CRD controllers, admission controllers, monitoring, logging, etc.)
• Cluster-wide definitions (Namespaces, Ingress classes, Storage classes, etc.)
• Pod security standards
• Network policies

This repository is reconciled on the cluster fleet by Flux as the cluster admin. Access to this repository is restricted to the platform team and the Flux bot account.

Repository Structure

This repository contains the following directories:

• The components dir contains Flux HelmReleases for cluster addons with custom configuration per environment.
• The update dir contains the Flux configuration for automating the OCI chart updates of the Helm releases.

A cluster component is defined in a directory with the following structure:

component/
├── controllers # CRD definitions and controllers
│   ├── base # common definitions (Namespaces, RBAC, HelmRepositories, HelmReleases)
│   ├── production # production specific HelmRelease values
│   └── staging # staging specific HelmRelease values
└── configs # Custom Resources of controllers
    ├── base # common definitions
    ├── production # production specific values
    └── staging # staging specific values

The CRDs and their controllers are reconciled before the custom resources to ensure that the controllers are ready to process the custom resources.

Continuous Delivery

To prevent reconciliation errors due to malformed YAML manifests or invalid Kubernetes definitions, changes to the main branch should be made through pull requests. On pull requests a GitHub Action runs that downloads the Flux OpenAPI schemas, and validates the custom resources and the kustomize overlays using kubeconform.

Changes to the main branch are automatically reconciled by Flux on the staging cluster.

sequenceDiagram
    actor me
    participant git as Git<br><br>repository
    participant sc as Flux<br><br>source-controller
    participant kc as Flux<br><br>kustomize-controller
    participant kube as Kubernetes<br><br>api-server
    participant nc as Flux<br><br>notification-controller
    me->>git: 1. git push
    sc->>git: 2. git pull
    sc->>sc: 3. build artifact for revision
    sc->>kube: 4. update status for revision
    sc-->>nc: 5. emit events
    kube->>kc: 6. notify about new revision
    kc->>sc: 7. fetch artifact for revision
    kc->>kc: 8. build manifests to objects
    kc->>kube: 9. reconcile objects
    kc-->>kube: 10. wait for readiness
    kc->>kube: 11. update status for revision
    kc-->>nc: 12. emit events
    nc-->>me: 13. send alerts for revision

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After the changes are reconciled on staging, the platform team can promote the changes to the production clusters by merging the main branch into the production branch.

Helm Release Automation

The staging cluster runs the Flux image automation controllers which automatically update the HelmRelease definitions with the latest chart version.

When a new chart version is pushed to the container registry, and if it matches the semver policy, Flux will update the HelmRelease YAML definitions and will push the changes to the main branch.

sequenceDiagram
    participant oci as OCI<br><br>repository
    participant irc as Flux<br><br>image-reflector-controller
    participant iac as Flux<br><br>image-automation-controller
    participant kube as Kubernetes<br><br>api-server
    participant git as Git<br><br>repository
    irc->>oci: 1. list chart versions
    irc->>irc: 2. match versions to policy
    irc->>kube: 3. update status
    kube->>iac: 4. notify about new version
    iac->>git: 5. git checkout main
    iac->>iac: 6. patch HelmRelease with new chart version
    iac->>git: 7. git push origin main
    iac->>kube: 8. update status

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After the changes are pushed to the main branch, the HelmReleases will be upgraded to the new chart versions on the staging cluster.

sequenceDiagram
    participant git as OCI<br><br>repository
    participant sc as Flux<br><br>source-controller
    participant hc as Flux<br><br>helm-controller
    participant kube as Kubernetes<br><br>api-server
    sc->>git: 1. pull new chart version
    sc->>kube: 2. update chart status
    kube->>hc: 3. notify about new version
    hc->>sc: 4. fetch chart
    hc->>kube: 5. get release values
    hc->>kube: 6. upgrade release
    hc-->>kube: 7. run tests
    hc->>kube: 8. wait for readiness
    hc->>kube: 9. update status

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