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Red Hat OpenShift GitOps provides Argo CD and other tooling used to implement GitOps workflows for cluster configuration and application delivery. OpenShift GitOps is a Red Hat OpenShift add-on, available as an operator in the OperatorHub. Once you've installed the OpenShift GitOps operator, you can deploy Argo CD instances using Kubernetes custom resources.

OpenShift GitOps deployment modes

OpenShift GitOps supports flexible Argo CD configurations to satisfy diverse user needs in the world of GitOps, as shown in Figure 1.

Argo CD configurations supported by Red Hat OpenShift GitOps.
Figure 1: Argo CD configurations supported by Red Hat OpenShift GitOps.

Cluster-scoped Argo CD

OpenShift GitOps provides single-click enablement of GitOps for OpenShift cluster configuration. When the OpenShift GitOps operator is installed, an Argo CD instance is set up for users out of the box. It comes with the configuration required to configure a cluster in the openshift-gitops namespace, which acts as the GitOps control plane for cluster configuration. Typical cluster configuration activities include configuring control plane operators, setting up developer namespaces, installing Operator Lifecycle Manager (OLM) operators, and managing storage.

Application-scoped Argo CD

You can create additional Argo CD instances to satisfy the needs of software development organizations sharing the same cluster. In this article, we’ll discuss how developers can create independent Argo CD instances for one or more application delivery teams using OpenShift GitOps 1.2.

Application delivery with OpenShift GitOps

To achieve absolute isolation and multitenancy, OpenShift GitOps 1.2 supports the installation of namespace-scoped Argo CD instances for one or more application delivery teams in an organization, as shown in Figure 2.

Diagram of an application-scoped Argo CD pulling application deployment and configurations into application namespaces.
Figure 2: An application-scoped Argo CD pulls application deployment and configurations into application namespaces.

Setting up a control plane

A GitOps control plane is a namespace where Argo CD is installed. You can express an intent to deploy and sync Kubernetes manifests from Git by creating one or more application custom resources in the GitOps control plane.

To initialize a namespace-scoped Argo CD instance, you can create an Argo CD custom resource (CR) in a new namespace designated to be a GitOps control plane, as shown in the following example. This creates a minimalistic Argo CD instance with privileges to manage the contents of the namespace:

apiVersion: argoproj.io/v1alpha1
kind: ArgoCD
metadata:
 name: argocd #name of the Argo CD instance
 namespace: foo #namespace where you want to deploy argocd instance
spec:
 server:
   route:
     enabled: true #creates an openshift route to access Argo CD UI

Deploying an application from Git

The following code example shows how you would deploy an application from Git (also see Figure 3):

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: sample-app #app CR name
  namespace: foo #argocd instance namespace
spec:
  destination:
    namespace: foo #namespace where app is deployed
    server: 'https://kubernetes.default.svc'
  source:
    path: app
    repoURL: 'https://github.com/redhat-developer/openshift-gitops-getting-started'
    targetRevision: HEAD
  project: default
Screenshot of the application deployed in the namespace-scoped Argo CD control plane in the Red Hat OpenShift Container Platform web console.
Figure 3: An application deployed in the namespace-scoped Argo CD control plane managed by OpenShift GitOps.

Adding projects to the control plane

Create a namespace, bar, and try deploying an application in this namespace, which is managed by the Argo CD instance deployed in the namespace foo.

First, create the namespace bar as follows:

apiVersion: v1
kind: Namespace
metadata:
  name: bar
spec:
  finalizers:
  - kubernetes

Then, create an application custom resource in the namespace foo:

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: sample-app-2
  namespace: foo #namespace where Argo CD instance is installed
spec:
  destination:
    namespace: bar #target namespace where app is deployed
    server: 'https://kubernetes.default.svc'
  source:
    path: app
    repoURL: 'https://github.com/redhat-developer/openshift-gitops-getting-started'
    targetRevision: HEAD
  project: default

Authorizing the GitOps control plane

The GitOps control plane will try to deploy the application in the namespace bar. As you can see in Figure 4, the sync fails because the GitOps control plane is not authorized to deploy managed resources in the namespace bar.

Screenshot showing an application sync error in Argo CD.
Figure 4: By default, a namespace-scoped Argo CD control plane is not allowed to manage workloads in other namespaces.

To authorize the GitOps control plane to deploy managed workloads in a namespace, the namespace owner needs to decorate the namespace resource with a label containing the reference to the namespace where the GitOps control plane resides.

The OpenShift GitOps operator reads this expression of intent to have the namespace managed by a specific GitOps control plane and configures the appropriate Argo CD secrets and Kubernetes role-based access control (RBAC).

Label the namespace as follows:

apiVersion: v1
kind: Namespace
metadata:
  labels:
     argocd.argoproj.io/managed-by: foo #argocd instance ns
  name: bar
spec:
  finalizers:
  - kubernetes

This configures the existing namespace bar with the label recognized by the OpenShift GitOps operator.

After configuring the namespace, trigger the sync from the Argo CD UI. The application will sync successfully, as shown in Figure 5.

Screenshot of an application that has been successfully synced in Argo CD.
Figure 5: Argo CD reports the successful reconciliation of the application deployed in the Kubernetes namespace bar.

Figure 6 shows the developer perspective after the user workload in the namespace bar has been successfully deployed.

Screenshot of the developer perspective in OpenShift console showing the user workload in the namespace "bar" has successfully deployed.
Figure 6: The developer perspective in the OpenShift web console displays the successful deployment of the user workload in the namespace bar.

Argo CD configuration in Red Hat OpenShift GitOps

In OpenShift GitOps 1.1.1, a security issue was reported with Argo CD instances configured for application delivery. Handling the vulnerability required significantly curtailing the privileges of Argo CD instances in OpenShift GitOps 1.1.2. This led to upgrading issues and potentially arduous manual configuration of Argo CD instances installed in developer namespaces. These issues showed up in two scenarios:

  • When configuring the Argo CD cluster secret.
  • When creating a rolebinding in participating namespaces with the Argo CD application controller service account.

While the change was necessary, it became a hurdle to the frictionless operation of Argo CD instances and potentially violated the principles of declarative configuration, while also exposing users to Argo CD's underlying deployment details.

As an enhancement, we fast-tracked the development of a new feature that allows users to authorize the management of OpenShift projects seamlessly:

  1. A team lead sets up a GitOps control plane for the team in the namespace my-team.
  2. Members of the team label their own namespaces referring to the my-team namespace indicating that they authorize the GitOps control plane in my-team to manage their namespaces.

Conclusion

OpenShift GitOps strives to make it easy for developer teams to manage, configure, and use Argo CD securely for application delivery on OpenShift. As this article demonstrates, application delivery teams can create multiple isolated Argo CD instances on a Red Hat OpenShift cluster. This provides users and administrators with full control over what an Argo CD instance is empowered to do. Optionally, the cluster administrator can use the Argo CD instance in the openshift-gitops namespace to declaratively manage Argo CD instances across multiple developer namespaces.

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