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Add Seed Cluster for EE

Enterprise Edition

This document describes how a new seed cluster can be added to an existing KKP master cluster.

For smaller scale setups it’s possible to use the existing master cluster as a seed cluster (a “shared” cluster installation). In this case both master and seed components will run on the same cluster and in the same namespace. It is however not possible to use the same cluster for multiple seeds.

Please refer to the architecture diagrams for more information about the cluster relationships.

Install KKP Dependencies

Compared to master clusters, seed clusters are still mostly manually installed. Future versions of KKP will improve the setup experience further.

When using Helm 2, install Tiller into the seed cluster first:

kubectl create namespace kubermatic
kubectl create serviceaccount -n kubermatic tiller
kubectl create clusterrolebinding tiller-cluster-role --clusterrole=cluster-admin --serviceaccount=kubermatic:tiller
helm --service-account tiller --tiller-namespace kubermatic init

Cluster Backups

KKP performs regular backups of user cluster by snapshotting the etcd of each cluster. By default these backups are stored locally inside the seed cluster, but they can be reconfigured to work with any S3-compatible storage. The in-cluster storage is provided by Minio and the accompanying minio Helm chart.

If your cluster has no default storage class, it’s required to configure a class explicitly for Minio. You can check the cluster’s storage classes via:

kubectl get storageclasses
#NAME                 PROVISIONER              AGE
#kubermatic-fast      kubernetes.io/aws-ebs   195d
#kubermatic-backup    kubernetes.io/aws-ebs   195d
#standard (default)   kubernetes.io/aws-ebs   2y43d

As Minio does not require any of the SSD’s advantages, we can use HDDs. It’s recommended to create a separate storage class kubermatic-backup with a different location/security level. For a cluster running on AWS, an example class could look like this:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: kubermatic-backup
provisioner: kubernetes.io/aws-ebs
parameters:
  type: sc1

To configure the storage class and size, extend your values.yaml. For more information about the Minio options, take a look at minio chart values.yaml and the min.io documentation - S3 gateway:

minio:
  storeSize: '200Gi'
  # SC will store the etcd backup of the seed hosted user clusters
  storageClass: kubermatic-backup
  # access key/secret for the exposed minio S3 gateway
  credentials:
    # generated access key length should be at least 3 characters
    accessKey: "YOUR-ACCESS-KEY"
    # generated secret key length should be at least 8 characters
    secretKey: "YOUR-SECRET-KEY"

It’s also advisable to install the s3-exporter Helm chart, as it provides basic metrics about user cluster backups.

Install Charts

With this you can install the charts:

Helm 3

helm --namespace minio upgrade --install --wait --values /path/to/your/helm-values.yaml minio charts/minio/
helm --namespace kube-system upgrade --install --wait --values /path/to/your/helm-values.yaml s3-exporter charts/s3-exporter/

Helm 2

helm --tiller-namespace kubermatic upgrade --install --values /path/to/your/helm-values.yaml --namespace minio minio charts/minio/
helm --tiller-namespace kubermatic upgrade --install --values /path/to/your/helm-values.yaml --namespace kube-system s3-exporter charts/s3-exporter/

Add the Seed Resource

To connect the new seed cluster with the master, you need to create a kubeconfig Secret and a Seed resource. This allows the KKP components in the master cluster to communicate with the seed cluster and reconcile user-cluster control planes.

To make sure that the kubeconfig stays valid forever, it must not contain temporary login tokens. Depending on the cloud provider, the default kubeconfig that is provided may not contain username+password / a client certificate, but instead try to talk to local token helper programs like aws-iam-authenticator for AWS or gcloud for the Google Cloud (GKE). These kubeconfig files will not work for setting up Seeds.

The KKP repository provides a script that can be used to prepare a kubeconfig for usage in KKP. The script will create a ServiceAccount in the seed cluster, bind it to the cluster-admin role and then put the ServiceAccount’s token into the kubeconfig file. Afterwards the file can be used in KKP.

The Seed resource then needs to reference the new kubeconfig Secret like so:

apiVersion: v1
kind: Secret
metadata:
  name: kubeconfig-europe-west3
  namespace: kubermatic
type: Opaque
data:
  # You can use `base64 -w0 my-kubeconfig-file` to encode the
  # kubeconfig properly for inserting into this Secret.
  kubeconfig: <base64 encoded kubeconfig>

---
apiVersion: kubermatic.k8s.io/v1
kind: Seed
metadata:
  name: europe-west3
  namespace: kubermatic
spec:
  # these two fields are only informational
  country: DE
  location: Hamburg

  # list of datacenters where this seed cluster is allowed to create clusters in
  datacenters: []

  # reference to the kubeconfig to use when connecting to this seed cluster
  kubeconfig:
    name: kubeconfig-europe-west3
    namespace: kubermatic

Refer to the Seed CRD documentation for a complete example of the Seed CustomResource and all possible datacenters.

Apply the manifest above in the master cluster and KKP will pick up the new Seed and begin to reconcile it by installing the required Kubermatic components. You can watch the progress by using kubectl and watch:

kubectl apply -f seed-with-secret.yaml
Secret/kubeconfig-europe-west3 created.
Seed/europe-west3 created.

watch kubectl -n kubermatic get pods
#NAME                                                   READY   STATUS    RESTARTS   AGE
#kubermatic-api-55765568f7-br9jl                        1/1     Running   0          5m4s
#kubermatic-api-55765568f7-xbvz2                        1/1     Running   0          5m13s
#kubermatic-dashboard-5d784d586b-f46f8                  1/1     Running   0          35m
#kubermatic-dashboard-5d784d586b-rgl29                  1/1     Running   0          35m
#kubermatic-master-controller-manager-f58d4df59-w7rkz   1/1     Running   0          5m13s
#kubermatic-operator-7f6957869d-89g55                   1/1     Running   0          5m37s
#nodeport-proxy-envoy-6d8bb6fbff-9z57l                  2/2     Running   0          5m6s
#nodeport-proxy-envoy-6d8bb6fbff-dl58l                  2/2     Running   0          4m54s
#nodeport-proxy-envoy-6d8bb6fbff-k4gp8                  2/2     Running   0          4m44s
#nodeport-proxy-updater-7fd55f948-cll8n                 1/1     Running   0          4m44s
#seed-proxy-europe-west3-6dd5cc95cf-r6wvb               1/1     Running   0          80m

Update DNS

The apiservers of all user cluster control planes running in the seed cluster are exposed by the NodePort Proxy. By default each user cluster gets a virtual domain name like [cluster-id].[seed-name].[kubermatic-domain], e.g. hdu328tr.europe-west3.kubermatic.example.com for the Seed from the previous step when kubermatic.example.com is the main domain where the KKP dashboard/API are available.

To facilitate this, a wildcard DNS record *.[seed-name].[kubermatic-domain] must be created. The target of the DNS wildcard record should be the EXTERNAL-IP of the nodeport-proxy service in the kubermatic namespace.

With LoadBalancers

When your cloud provider supports LoadBalancers, you can find the target IP / hostname by looking at the nodeport-proxy Service:

kubectl -n kubermatic get services
#NAME             TYPE           CLUSTER-IP      EXTERNAL-IP    PORT(S)                      AGE
#nodeport-proxy   LoadBalancer   10.47.248.232   8.7.6.5        80:32014/TCP,443:30772/TCP   449d

The EXTERNAL-IP is what we need to put into the DNS record.

Without LoadBalancers

Without a LoadBalancer, you will need to point to one or many of the seed cluster’s nodes. You can get a list of external IPs like so:

kubectl get nodes -o wide
#NAME                        STATUS   ROLES    AGE     VERSION         INTERNAL-IP   EXTERNAL-IP
#worker-node-cbd686cd-50nx   Ready    <none>   3h36m   v1.15.8-gke.3   10.156.0.36   8.7.6.4
#worker-node-cbd686cd-59s2   Ready    <none>   21m     v1.15.8-gke.3   10.156.0.14   8.7.6.3
#worker-node-cbd686cd-90j3   Ready    <none>   45m     v1.15.8-gke.3   10.156.0.22   8.7.6.2

DNS Record

Create an A or CNAME record as needed pointing to the target:

*.europe-west3.kubermatic.example.com.   IN   A   8.7.6.5

or, for a CNAME:

*.europe-west3.kubermatic.example.com.   IN   CNAME   myloadbalancer.example.com.