morey-tech/argocd-v2.9-examples

Argo CD v2.9.0 Examples

Bootstrapping Argo CD

kind create cluster --config kind-cluster.yaml
kubectl apply -k argocd
kubectl apply -f apps.yaml

This example includes a devcontainer configuration, allowing you to automatically create an environment for testing using the VSCode Dev Containers extension or GitHub Codespaces.

Accessing the UI

Navigate to https://localhost:8080/ on the machine with the kind cluster running.

Get the generated admin password.

argocd admin initial-password -n argocd

Clean Up

kind delete cluster --name argocd-v2-9-0-examples

Examples

Dynamically Re-Balance Clusters Across Shards

The Argo CD application controller can become overloaded when managing multiple remote clusters with many resources. The solution is to run multiple shards of the application controller, where each is responsible for one or more clusters (and each cluster can only belongs to one shard). However, adding new shards requires increasing the number of replicas on the application-controller StatefulSet. Previously, the shard count was set via the ARGOCD_CONTROLLER_REPLICAS environment variable, and changing it forced a restart of all application-controller pods. In 2.9, this alpha feature updates the application-controller to be a Deployment (instead of a StatefulSet). The replicas field is now used for the shard count, and when replicas are added or removed, the sharding algorithm is re-run to ensure that the clusters are distributed accordingly.

In this example, I take advantage of Kustomize components to patch the StatefulSet to 0 replicas and create the application-controller Deployment with 2 replicas. The ARGOCD_ENABLE_DYNAMIC_CLUSTER_DISTRIBUTION environment variable must be set to true on the Pod for the application-controller to enable the cluster shard re-balancing functionality (currently, this breaks the pod due to #16349).

The application-controller Deployment relies on a config map to track the mapping of replica (pod) to shard number, and the heartbeat from each shard. If the argocd-app-controller-shard-cm does not exist in the same namespace as the application-controller, it will create it. Then a shard number (ShardNumber) is associated with a Pod name (the ControllerName). Each shard will update it's heartbeat time (HeartbeatTime) when the readinessProbe on the Pod is called, which is every 10 seconds be default.

% k get cm -n argocd argocd-app-controller-shard-cm -o "jsonpath={.data['shardControllerMapping']}" | jq
[
  {
    "ShardNumber": 0,
    "ControllerName": "argocd-application-controller-c5964bb48-4t7t4",
    "HeartbeatTime": "2023-11-15T16:04:58Z"
  },
  {
    "ShardNumber": 1,
    "ControllerName": "argocd-application-controller-c5964bb48-ss49f",
    "HeartbeatTime": "2023-11-15T16:04:58Z"
  }
]

Users of the default hash-based sharding algorithm won't see any improvements as clusters be roughly-balanced between shards. For users of the round-robin or other custom algorithms, a static assignment can lead to unbalanced shards when replicas are added or removed. So, the dynamic shard re-balancing functionality benefits users of custom shard assignment strategies the most.

Thanks, Ishita Sequeira (Red Hat), for writing the initial proposal and implementing the whole feature!

https://argo-cd.readthedocs.io/en/latest/operator-manual/dynamic-cluster-distribution/

Open issues:

• argoproj/argo-cd#16349

Ignore ApplicationSet Differences

The ApplicationSet is a powerful feature that renders Argo CD Applications dynamically based on generators. However, there are situations where another process revises certain fields of an Application after the ApplicationSet creates it.

A common example is when using the Argo CD Image Updater with Applications managed by an ApplicationSet. When using the imperative write-back method, Image Updater changes the image tag using a parameter override (argocd app set --parameter …), which, if not ignored, would be overwritten by the ApplicationSet.

Or if you simply want to use ApplicationSets to create apps, but allow users to modify those Applications (e.g. disable auto-sync temporarily) without having their changes overwritten by the ApplicationSet.

apiVersion: argoproj.io/v1alpha1
kind: ApplicationSet
metadata:
  name: example
spec:
  ...
  ignoreApplicationDifferences:
  - jsonPointers:
    - /spec/source/targetRevision
  - name: guestbook-dev
    jqPathExpressions:
    - .spec.syncPolicy

This was one of the most voted proposals included in the v2.9.0 release. Thank you to Michael Crenshaw (Intuit) for all your interaction with the community on the issue, and for making this feature happen!

https://argo-cd.readthedocs.io/en/stable/operator-manual/applicationset/Controlling-Resource-Modification/#ignore-certain-changes-to-applications

Support for Inline Kustomize Patches

Argo CD now supports the addition of in-line Kustomize patches in the source.kustomize.pathces field of Applications.

spec:
  ...
  source:
    path: kustomize-guestbook
    repoURL: https://github.com/argoproj/argocd-example-apps.git
    targetRevision: master
    kustomize:
      patches:
        - target:
            kind: Deployment
            name: guestbook-ui
          patch: |-
            - op: replace
              path: /spec/template/spec/containers/0/ports/0/containerPort
              value: 443

The inline kustomize patches work well with ApplicationSets, too. Instead of maintaining a patch or overlay for each cluster, patches can now be done in the Application template and utilize attributes from the generators. For example, with external-dns to set the txt-owner-id to the cluster name.

In an ideal world, the guestbook path contains only plain Kubernetes manifests (no kustomization.yaml) but through the use of the patches field in the Application, you can use Kustomize to alter the Deployment manifest to use port 443. However, a kustomization.yaml is still required (#16352)

With a kustomization.yaml file in the source, the patches from the Application will be merged with any existing patches.

Ref:

• https://argo-cd.readthedocs.io/en/stable/user-guide/kustomize/#patches
• argoproj/argo-cd#14648