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KubeStellar Example Scenarios#

This document shows some simple examples of using the release that contains this version of this document. These scenarios can be used to test a KubeStellar installation for proper functionality. These scenarios suppose that you have done "setup". General setup instructions are outlined in the User Guide Overview; a simple example setup is in the Setup section of Getting Started.

Assumptions and variables#

Each scenario supposes that one ITS and one WDS have been created, and that two WECs have been created and registered and also labeled for selection by KubeStellar control objects. These scenarios are written as shell commands (bash or zsh). These commands assume that you have defined the following shell variables to convey the needed information about that ITS and WDS and those WECs. For a concrete example of settings of these variables, see the end of Getting Started.

  • host_context: the name of the kubeconfig context to use when accessing the KubeFlex hosting cluster.
  • its_cp: the name of the KubeFlex control plane that is playing the role of ITS.
  • its_context: the name of the kubeconfig context to use when accessing the ITS.
  • wds_cp: the name of the KubeFlex control plane that is playing the role of WDS.
  • wds_context: the name of the kubeconfig context to use when accessing the WDS.
  • wec1_name, wec2_name: the names of the ManagedCluster objects in the ITS representing the two WECs.
  • wec1_context, wec2_context: the names of the kubeconfig contexts to use when accessing the two WECs.
  • label_query_both: a restricted kubectl label query over ManagedCluster objects in the ITS that matches both WECs. The general form of label query usable here is a comma-separated series of key=value requirements.
  • label_query_one: a restricted kubectl label query over ManagedCluster objects that picks out just one of the WECs.

Each example scenario concludes with instructions on how to undo its effects.

There are also end-to-end (E2E) tests that are based on scenario 4 and an extended variant of scenario 1. These tests normally exercise the copy of the repo containing them (rather than a release). They can alternatively test a release. See the e2e tests (in test/e2e). Contributors can run these tests, and CI includes checking that these E2E tests pass. Some of these tests, and the setup for all of them, are written in bash so that contributors can easily follow them.

Scenario 0 - look around#

The following command will list all the ManagedCluster objects that will be relevant to these scenarios.

kubectl --context "$its_context" get managedclusters -l "$label_query_both"

Expect to get a listing of your two ManagedCluster objects.

Scenario 1 - multi-cluster workload deployment with kubectl#

Create a BindingPolicy to deliver an app to all clusters in the WDS:

kubectl --context "$wds_context" apply -f - <<EOF
apiVersion: control.kubestellar.io/v1alpha1
kind: BindingPolicy
metadata:
  name: nginx-bpolicy
spec:
  clusterSelectors:
  - matchLabels: {$(echo "$label_query_both" | tr , $'\n' | while IFS="=" read key val; do echo -n ", \"$key\": \"$val\""; done | tail -c +3)}
  downsync:
  - objectSelectors:
    - matchLabels: {"app.kubernetes.io/name":"nginx"}
EOF

This BindingPolicy configuration determines where to deploy the workload by using the label selector expressions found in clusterSelectors. It also specifies what to deploy through the downsync.labelSelectors expressions. Each matchLabels expression is a criterion for selecting a set of objects based on their labels. Other criteria can be added to filter objects based on their namespace, api group, resource, and name. If these criteria are not specified, all objects with the matching labels are selected. If an object has multiple labels, it is selected only if it matches all the labels in the matchLabels expression. If there are multiple objectSelectors, an object is selected if it matches any of them.

Now deploy the app:

kubectl --context "$wds_context" apply -f - <<EOF
apiVersion: v1
kind: Namespace
metadata:
  labels:
    app.kubernetes.io/name: nginx
  name: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  namespace: nginx
  labels:
    app.kubernetes.io/name: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: public.ecr.aws/nginx/nginx:latest
        ports:
        - containerPort: 80
EOF

Verify that manifestworks wrapping the objects have been created in the mailbox namespaces with the following command. Expect to see a ManifestWork object named "nginx-bpolicy-wds1" in each namespace.

kubectl --context "$its_context" get manifestworks -n "$wec1_name"
kubectl --context "$its_context" get manifestworks -n "$wec2_name"

Verify that the deployment has been created in both clusters

kubectl --context "$wec1_context" get deployments -n nginx
kubectl --context "$wec2_context" get deployments -n nginx

Please note, in line with Kubernetes’ best practices, the order in which you apply a BindingPolicy and the objects doesn’t affect the outcome. You can apply the BindingPolicy first followed by the objects, or vice versa. The result remains consistent because the binding controller identifies any changes in either the BindingPolicy or the objects, triggering the start of the reconciliation loop.

[Optional] Teardown Scenario 1#

kubectl --context "$wds_context" delete ns nginx
kubectl --context "$wds_context" delete bindingpolicies nginx-bpolicy

Scenario 2 - Out-of-tree workload#

This scenario is like the previous one but involves a workload whose kind of objects is not built into Kubernetes. Instead, the workload object kind is defined by a CustomResourceDefinition object. While KubeStellar can handle the case where the CRD is part of the workload, this example concerns the case where the CRD is established in the WECs by some other means.

In order to run this scenario using the post-create-hook method you need the raise the permissions for the kubeflex controller manager (TODO 1: move this material and its undo to the doc on WDS; TODO 2: why is this needed? Is it needed for the core chart too? can we remove the need for this?):

kubectl --context "$host_context" apply -f - <<EOF
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: kubeflex-manager-cluster-admin-rolebinding
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: cluster-admin
subjects:
- kind: ServiceAccount
  name: kubeflex-controller-manager
  namespace: kubeflex-system
EOF

For this example, we use the AppWrapper custom resource defined in the multi cluster app dispatcher project.

Install the AppWrapper CRD in the WDS and the WECs.

clusters=("$wds_context" "$wec1_context" "$wec2_context");
  for cluster in "${clusters[@]}"; do
  kubectl --context ${cluster} apply -f https://raw.githubusercontent.com/project-codeflare/multi-cluster-app-dispatcher/v1.39.0/config/crd/bases/workload.codeflare.dev_appwrappers.yaml
done

If desired, you may remove the kubeflex-manager-cluster-admin-rolebinding after the kubestellar-controller-manager is started, with the command kubectl --context "$host_context" delete clusterrolebinding kubeflex-manager-cluster-admin-rolebinding

Run the following command to give permission for the klusterlet to operate on the appwrapper cluster resource.

clusters=("$wec1_context" "$wec2_context");
for cluster in "${clusters[@]}"; do
kubectl --context ${cluster} apply -f - <<EOF
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: appwrappers-access
rules:
- apiGroups: ["workload.codeflare.dev"]
  resources: ["appwrappers"]
  verbs: ["get", "list", "watch", "create", "update", "patch"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: klusterlet-appwrappers-access
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: appwrappers-access
subjects:
- kind: ServiceAccount
  name: klusterlet-work-sa
  namespace: open-cluster-management-agent
EOF
done

This step will be eventually automated, see this issue for more details.

Next, apply an appwrapper object to the WDS:

kubectl --context "$wds_context" apply -f  https://raw.githubusercontent.com/project-codeflare/multi-cluster-app-dispatcher/v1.39.0/test/yaml/0008-aw-default.yaml

Label the appwrapper to match the binding policy:

kubectl --context "$wds_context" label appwrappers.workload.codeflare.dev defaultaw-schd-spec-with-timeout-1 app.kubernetes.io/part-of=my-appwrapper-app

Finally, apply the BindingPolicy:

kubectl --context "$wds_context" apply -f - <<EOF
apiVersion: control.kubestellar.io/v1alpha1
kind: BindingPolicy
metadata:
  name: aw-bpolicy
spec:
  clusterSelectors:
  - matchLabels: {$(echo "$label_query_both" | tr , $'\n' | while IFS="=" read key val; do echo -n ", \"$key\": \"$val\""; done | tail -c +3)}
  downsync:
  - objectSelectors:
    - matchLabels: {"app.kubernetes.io/part-of":"my-appwrapper-app"}
EOF

Check that the app wrapper has been delivered to both clusters:

kubectl --context "$wec1_context" get appwrappers
kubectl --context "$wec2_context" get appwrappers

[Optional] Teardown Scenario 2#

kubectl --context "$wds_context" delete bindingpolicies aw-bpolicy
kubectl --context "$wds_context" delete appwrappers --all

Wait until the following commands show no appwrappers in the two WECs.

kubectl --context "$wec1_context" get appwrappers -A
kubectl --context "$wec2_context" get appwrappers -A

Then continue.

for cluster in "$wec1_context" "$wec2_context"; do
  kubectl --context $cluster delete clusterroles appwrappers-access
  kubectl --context $cluster delete clusterrolebindings klusterlet-appwrappers-access
done

If you have not already done so, then do the following command.

kubectl --context "$host_context" delete clusterrolebinding kubeflex-manager-cluster-admin-rolebinding

Delete the CRD from the WDS and the WECs.

clusters=("$wds_context" "$wec1_context" "$wec2_context");
  for cluster in "${clusters[@]}"; do
  kubectl --context ${cluster} delete -f https://raw.githubusercontent.com/project-codeflare/multi-cluster-app-dispatcher/v1.39.0/config/crd/bases/workload.codeflare.dev_appwrappers.yaml
done

Scenario 3 - multi-cluster workload deployment with helm#

Create a BindingPolicy for the helm chart app:

kubectl --context "$wds_context" apply -f - <<EOF
apiVersion: control.kubestellar.io/v1alpha1
kind: BindingPolicy
metadata:
  name: postgres-bpolicy
spec:
  clusterSelectors:
  - matchLabels: {$(echo "$label_query_both" | tr , $'\n' | while IFS="=" read key val; do echo -n ", \"$key\": \"$val\""; done | tail -c +3)}
  downsync:
  - objectSelectors:
    - matchLabels: {
      "app.kubernetes.io/managed-by": Helm,
      "app.kubernetes.io/instance": postgres}
EOF

Note that helm sets app.kubernetes.io/instance to the name of the installed release.

Create and label the namespace and install the chart:

kubectl --context "$wds_context" create ns postgres-system
kubectl --context "$wds_context" label ns postgres-system app.kubernetes.io/managed-by=Helm app.kubernetes.io/instance=postgres
helm --kube-context "$wds_context" install -n postgres-system postgres oci://registry-1.docker.io/bitnamicharts/postgresql

Verify that StatefulSet has been created in both clusters

kubectl --context "$wec1_context" get statefulsets -n postgres-system
kubectl --context "$wec2_context" get statefulsets -n postgres-system

[Optional] Propagate helm metadata Secret to managed clusters#

Run "helm list" on the WDS:

helm --kube-context "$wds_context" list -n postgres-system

and expect to see output like the following.

NAME            NAMESPACE       REVISION        UPDATED                                 STATUS       CHART                    APP VERSION
postgres        postgres-system 1               2023-10-31 13:39:52.550071 -0400 EDT    deployed     postgresql-13.2.0        16.0.0

And try that on the managed clusters; you will get empty output.

helm list --kube-context "$wec1_context" -n postgres-system
helm list --kube-context "$wec2_context" -n postgres-system

This is because Helm creates a Secret object to hold its metadata about a "release" (chart instance) but Helm does not apply the usual labels to that object, so it is not selected by the BindingPolicy above and thus does not get delivered. The workload is functioning in the WECs, but helm list does not recognize its handiwork there. That labeling could be done for example with:

kubectl --context "$wds_context" label secret -n postgres-system $(kubectl --context "$wds_context" get secrets -n postgres-system -l name=postgres -l owner=helm  -o jsonpath='{.items[0].metadata.name}') app.kubernetes.io/managed-by=Helm app.kubernetes.io/instance=postgres

Verify that the chart shows up on the managed clusters:

helm list --kube-context "$wec1_context" -n postgres-system
helm list --kube-context "$wec2_context" -n postgres-system

Implementing this in a controller for automated propagation of helm metadata is tracked in this issue.

[Optional] Teardown Scenario 3#

helm --kube-context "$wds_context" uninstall -n postgres-system postgres
kubectl --context "$wds_context" delete ns postgres-system
kubectl --context "$wds_context" delete bindingpolicies postgres-bpolicy

Scenario 4 - Singleton status#

This scenario shows how to get the full status updated when setting wantSingletonReportedState in the BindingPolicy. This still an experimental feature.

Apply a BindingPolicy with the wantSingletonReportedState flag set:

kubectl --context "$wds_context" apply -f - <<EOF
apiVersion: control.kubestellar.io/v1alpha1
kind: BindingPolicy
metadata:
  name: nginx-singleton-bpolicy
spec:
  wantSingletonReportedState: true
  clusterSelectors:
  - matchLabels: {"name":"cluster1"}
  downsync:
  - objectSelectors:
    - matchLabels: {"app.kubernetes.io/name":"nginx-singleton"}
EOF

Apply a new deployment for the singleton BindingPolicy:

kubectl --context "$wds_context" apply -f - <<EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-singleton-deployment
  labels:
    app.kubernetes.io/name: nginx-singleton
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: public.ecr.aws/nginx/nginx:latest
        ports:
        - containerPort: 80
EOF

Verify that the status is available in the WDS for the deployment by running the command:

kubectl --context "$wds_context" get deployments nginx-singleton-deployment -o yaml

Finally, scale the deployment from 1 to 2 replicas in the WDS:

kubectl --context "$wds_context" scale deployment nginx-singleton-deployment --replicas=2

and verify that replicas has been updated in the WEC and the WDS:

kubectl --context "$wec1_context" get deployment nginx-singleton-deployment
kubectl --context "$wds_context" get deployment nginx-singleton-deployment

[Optional] Teardown Scenario 4#

kubectl --context "$wds_context" delete bindingpolicies nginx-singleton-bpolicy
kubectl --context "$wds_context" delete deployments nginx-singleton-deployment

Scenario 5 - Resiliency testing#

This is a test that you can do after finishing Scenario 1.

TODO: rewrite this so that it makes sense after Scenario 4.

Bring down the control plane: stop and restart the ITS and WDS API servers, KubeFlex and KubeStellar controllers:

First stop all:

kubectl --context "$host_context" scale deployment -n "$wds_cp"-system kube-apiserver --replicas=0
kubectl --context "$host_context" scale statefulset -n "$its_cp"-system vcluster --replicas=0
kubectl --context "$host_context" scale deployment -n kubeflex-system kubeflex-controller-manager --replicas=0
kubectl --context "$host_context" scale deployment -n "$wds_cp"-system kubestellar-controller-manager --replicas=0
kubectl --context "$host_context" scale deployment -n "$wds_cp"-system transport-controller --replicas=0

Then restart all:

kubectl --context "$host_context" scale deployment -n "$wds_cp"-system kube-apiserver --replicas=1
kubectl --context "$host_context" scale statefulset -n "$its_cp"-system vcluster --replicas=1
kubectl --context "$host_context" scale deployment -n kubeflex-system kubeflex-controller-manager --replicas=1
kubectl --context "$host_context" scale deployment -n "$wds_cp"-system kubestellar-controller-manager --replicas=1
kubectl --context "$host_context" scale deployment -n "$wds_cp"-system transport-controller --replicas=1

Wait for about a minute for all pods to restart, then apply a new BindingPolicy:

kubectl --context "$wds_context" apply -f - <<EOF
apiVersion: control.kubestellar.io/v1alpha1
kind: BindingPolicy
metadata:
  name: nginx-res-bpolicy
spec:
  clusterSelectors:
  - matchLabels: {$(echo "$label_query_both" | tr , $'\n' | while IFS="=" read key val; do echo -n ", \"$key\": \"$val\""; done | tail -c +3)}
  downsync:
  - objectSelectors:
    - matchLabels: {"app.kubernetes.io/name":"nginx-res"}
EOF

and a new workload:

kubectl --context "$wds_context" apply -f - <<EOF
apiVersion: v1
kind: Namespace
metadata:
  labels:
    app.kubernetes.io/name: nginx-res
  name: nginx-res
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-res-deployment
  namespace: nginx-res
  labels:
    app.kubernetes.io/name: nginx-res
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx-res
  template:
    metadata:
      labels:
        app: nginx-res
    spec:
      containers:
      - name: nginx-res
        image: public.ecr.aws/nginx/nginx:latest
        ports:
        - containerPort: 80
EOF

Verify that deployment has been created in both clusters

kubectl --context "$wec1_context" get deployments -n nginx-res
kubectl --context "$wec2_context" get deployments -n nginx-res

[Optional] Teardown Scenario 5#

kubectl --context "$wds_context" delete ns nginx-res
kubectl --context "$wds_context" delete bindingpolicies nginx-res-bpolicy

Scenario 6 - multi-cluster workload deployment of app with ServiceAccount with ArgoCD#

Before running this scenario, install ArgoCD on the hosting cluster and configure it work with the WDS as outlined here.

Including a ServiceAccount tests whether there will be a controller fight over a token Secret for that ServiceAccount, which was observed in some situations with older code.

Apply the following BindingPolicy to the WDS:

kubectl --context "$wds_context" apply -f - <<EOF
apiVersion: control.kubestellar.io/v1alpha1
kind: BindingPolicy
metadata:
  name: argocd-sa-bpolicy
spec:
  clusterSelectors:
  - matchLabels: {$(echo "$label_query_both" | tr , $'\n' | while IFS="=" read key val; do echo -n ", \"$key\": \"$val\""; done | tail -c +3)}
  downsync:
  - objectSelectors:
    - matchLabels: {"argocd.argoproj.io/instance":"nginx-sa"}
EOF

Switch context to hosting cluster and argocd namespace (this is required by argo to create an app with the CLI)

kubectl config use-context "$host_context"
kubectl config set-context --current --namespace=argocd

Create a new application in ArgoCD:

argocd app create nginx-sa --repo https://github.com/pdettori/sample-apps.git --path nginx --dest-server https://"${wds_cp}.${wds_cp}-system" --dest-namespace nginx-sa

Open browser to Argo UI:

open https://argocd.localtest.me:9443

Open the app nginx-sa and sync it by clicking the "sync" button and then "synchronize".

Alternatively, use the CLI to sync the app:

argocd app sync nginx-sa

Finally, check if the app has been deployed to the two clusters.

kubectl --context "$wec1_context" -n nginx-sa get deployments,sa,secrets
kubectl --context "$wec2_context" -n nginx-sa get deployments,sa,secrets

Repeat multiple syncing on Argo and verify that extra secrets for the service account are not created in the WDS and both clusters:

kubectl --context "$wds_context" -n nginx-sa get secrets
kubectl --context "$wec1_context" -n nginx-sa get secrets
kubectl --context "$wec2_context" -n nginx-sa get secrets

[Optional] Teardown Scenario 6#

(Assuming that kubectl is still using the context for the hosting cluster and namespace argocd.)

argocd app delete nginx-sa --cascade
kubectl --context "$wds_context" delete bindingpolicies argocd-sa-bpolicy