Use Flux to support Helm chart propagation
Flux is most useful when used as a deployment tool at the end of a Continuous Delivery Pipeline. Flux will make sure that your new container images and config changes are propagated to the cluster. With Flux, Karmada can easily realize the ability to distribute applications packaged by Helm across clusters. Not only that, with Karmada's OverridePolicy, users can customize applications for specific clusters and manage cross-cluster applications on the unified Karmada Control Plane.
Start up Karmada clusters
To start up Karmada, you can refer to here.
If you just want to try Karmada, we recommend building a development environment by hack/local-up-karmada.sh.
git clone https://github.com/karmada-io/karmada
cd karmada
hack/local-up-karmada.sh
After that, you will start a Kubernetes cluster by kind to run the Karmada Control Plane and create member clusters managed by Karmada.
kubectl get clusters --kubeconfig ~/.kube/karmada.config
You can use the command above to check registered clusters, and you will get similar output as follows:
NAME VERSION MODE READY AGE
member1 v1.23.4 Push True 7m38s
member2 v1.23.4 Push True 7m35s
member3 v1.23.4 Pull True 7m27s
Start up Flux
In the Karmada Control Plane, you need to install Flux CRDs but do not need controllers to reconcile them. They are treated as resource templates, not specific resource instances. Based on the work API here, they will be encapsulated as a work object delivered to member clusters and reconciled by Flux controllers in member clusters, finally.
kubectl --kubeconfig ~/.kube/karmada.config --context karmada-apiserver apply -k https://github.com/fluxcd/flux2/manifests/crds?ref=v2.4.0
For testing purposes, we'll install Flux on member clusters without storing its manifests in a Git repository:
kubectl --kubeconfig ~/.kube/members.config --context member1 apply -f https://github.com/fluxcd/flux2/releases/download/v2.4.0/install.yaml
kubectl --kubeconfig ~/.kube/members.config --context member2 apply -f https://github.com/fluxcd/flux2/releases/download/v2.4.0/install.yaml
Tips:
If you want to manage Helm releases across your fleet of clusters, Flux must be installed on each cluster.
If the Flux toolkit controllers are successfully installed, you should see the following Pods:
$ kubectl --kubeconfig ~/.kube/members.config --context member1 get pods -n flux-system
NAME READY STATUS RESTARTS AGE
helm-controller-79bb868f5d-7cxnx 1/1 Running 0 13m
image-automation-controller-cb5ff5bf9-5vbhg 1/1 Running 0 13m
image-reflector-controller-568fc784cb-t99r7 1/1 Running 0 13m
kustomize-controller-866fbd5855-zrn85 1/1 Running 0 13m
notification-controller-75846575bf-c42m9 1/1 Running 0 13m
source-controller-cc7bd674d-mntb6 1/1 Running 0 13m
Helm release propagation
If you want to propagate Helm releases for your apps to member clusters, you can refer to the guide below.
- Define a Flux
HelmRepositoryand aHelmReleasemanifest in the Karmada Control Plane. They will serve as resource templates.
apiVersion: source.toolkit.fluxcd.io/v1
kind: HelmRepository
metadata:
name: podinfo
spec:
interval: 1m
url: https://stefanprodan.github.io/podinfo
---
apiVersion: helm.toolkit.fluxcd.io/v2
kind: HelmRelease
metadata:
name: podinfo
spec:
interval: 5m
chart:
spec:
chart: podinfo
version: 5.0.3
sourceRef:
kind: HelmRepository
name: podinfo
- Define a Karmada
PropagationPolicythat will propagate them to member clusters:
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: helm-repo
spec:
resourceSelectors:
- apiVersion: source.toolkit.fluxcd.io/v1
kind: HelmRepository
name: podinfo
placement:
clusterAffinity:
clusterNames:
- member1
- member2
---
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: helm-release
spec:
resourceSelectors:
- apiVersion: helm.toolkit.fluxcd.io/v2
kind: HelmRelease
name: podinfo
placement:
clusterAffinity:
clusterNames:
- member1
- member2
The above configuration is for propagating the Flux objects to member1 and member2 clusters.
- Apply those manifests to the Karmada-apiserver:
kubectl --kubeconfig ~/.kube/karmada.config --context karmada-apiserver apply -f <file-contains-configuration-above>
The output is similar to:
helmrepository.source.toolkit.fluxcd.io/podinfo created
helmrelease.helm.toolkit.fluxcd.io/podinfo created
propagationpolicy.policy.karmada.io/helm-repo created
propagationpolicy.policy.karmada.io/helm-release created
- Switch to the distributed cluster and verify:
helm --kubeconfig ~/.kube/members.config --kube-context member1 list
The output is similar to:
NAME NAMESPACE REVISION UPDATED STATUS CHART APP VERSION
podinfo default 1 2024-12-11 09:38:55.3331234 +0000 UTC deployed podinfo-5.0.3 5.0.3
Based on Karmada's propagation policy, you can schedule Helm releases to your desired cluster flexibly, just like Kubernetes schedules Pods to the desired node.
Customize the Helm release for specific clusters
The example above shows how to propagate the same Helm release to multiple clusters in Karmada. Besides, you can use Karmada's OverridePolicy to customize applications for specific clusters. For example, if you just want to change replicas in member1, you can refer to the overridePolicy below.
- Define a Karmada
OverridePolicy:
apiVersion: policy.karmada.io/v1alpha1
kind: OverridePolicy
metadata:
name: example-override
namespace: default
spec:
resourceSelectors:
- apiVersion: helm.toolkit.fluxcd.io/v2
kind: HelmRelease
name: podinfo
overrideRules:
- targetCluster:
clusterNames:
- member1
overriders:
plaintext:
- path: "/spec/values"
operator: add
value:
replicaCount: 2
- Apply the manifest to the Karmada-apiserver:
kubectl --kubeconfig ~/.kube/karmada.config --context karmada-apiserver apply -f <file-contains-configuration-above>
The output is similar to:
overridepolicy.policy.karmada.io/example-override created
- After applying the above policy in the Karmada Control Plane, you will find that replicas in member1 have changed to 2, but those in member2 keep the same.
kubectl --kubeconfig ~/.kube/members.config --context member1 get pods
The output is similar to:
NAME READY STATUS RESTARTS AGE
podinfo-77b795cc54-hk9pg 1/1 Running 0 5m39s
podinfo-77b795cc54-mk75j 1/1 Running 0 16s
Kustomize propagation
Kustomize propagation is basically the same as helm chart propagation above. You can refer to the guide below.
- Define a Flux
GitRepositoryand aKustomizationmanifest in the Karmada Control Plane:
apiVersion: source.toolkit.fluxcd.io/v1
kind: GitRepository
metadata:
name: podinfo
spec:
interval: 1m
url: https://github.com/stefanprodan/podinfo
ref:
branch: master
---
apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
metadata:
name: podinfo-dev
spec:
interval: 5m
path: "./deploy/overlays/dev/"
prune: true
sourceRef:
kind: GitRepository
name: podinfo
timeout: 80s
- Define a Karmada
PropagationPolicythat will propagate them to member clusters:
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: kust-release
spec:
resourceSelectors:
- apiVersion: kustomize.toolkit.fluxcd.io/v1
kind: Kustomization
name: podinfo-dev
placement:
clusterAffinity:
clusterNames:
- member1
- member2
---
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: kust-git
spec:
resourceSelectors:
- apiVersion: source.toolkit.fluxcd.io/v1
kind: GitRepository
name: podinfo
placement:
clusterAffinity:
clusterNames:
- member1
- member2
- Apply those YAMLs to the karmada-apiserver:
kubectl --kubeconfig ~/.kube/karmada.config --context karmada-apiserver apply -f <file-contains-configuration-above>
The output is similar to:
gitrepository.source.toolkit.fluxcd.io/podinfo created
kustomization.kustomize.toolkit.fluxcd.io/podinfo-dev created
propagationpolicy.policy.karmada.io/kust-release created
propagationpolicy.policy.karmada.io/kust-git created
- Switch to the distributed cluster and verify:
kubectl --kubeconfig ~/.kube/members.config --context member1 get pods -n dev
The output is similar to:
NAME READY STATUS RESTARTS AGE
backend-69c7655cb-rbtrq 1/1 Running 0 15s
cache-bdff5c8dc-mmnbm 1/1 Running 0 15s
frontend-7f98bf6f85-dw4vq 1/1 Running 0 15s