Add Seed Cluster for EE

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

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

Install Kubermatic Dependencies

Cluster Backups

Kubermatic performs regular backups of user cluster by snapshotting the etcd of each cluster. By default these backups are stored locally inside the 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 explicitely for Minio. You can check the cluster’s storage classes via:

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

As Minio does not require any of the SSD’s advantages, we can use HDDs. For a cluster running on AWS, an example class could look like this:

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

To configure the storage class and size, extend your values.yaml like so:

minio:
  storeSize: '500Gi'
  storageClass: minio-hdd

Install Charts

With this you can install the chart:

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 s3-exporter s3-exporter charts/s3-exporter/

It’s also advisable to install the s3-exporter Helm chart, as it provides basic metrics about user cluster backups. This will need the creation of a secret named s3-credentials in the s3-exporter namespace. You can use the following command:

kubectl create secret -n s3-exporter generic s3-credentials --from-literal=ACCESS_KEY_ID=<aws_access_key_id> --from-literal=SECRET_ACCESS_KEY=<aws_secret_access_key>

Add the Seed Resource

To connect the new seed cluster with the master, you need to create a Secret containing the kubeconfig and a Seed resource.

You will add the master cluster as the seed cluster

Make sure the kubeconfig contains static, long-lived credentials. Some cloud providers use custom authentication providers (like GKE using gcloud and EKS using aws-iam-authenticator). Those will not work in Kubermatic’s usecase because the required tools are not installed inside the cluster environment.

You can follow the template below or use the yaml file inside the examples folder of the tarball.

apiVersion: v1
kind: Secret
metadata:
  name: kubeconfig-europe-west1
  namespace: kubermatic
type: Opaque
data:
  kubeconfig: <base64 encoded kubeconfig>

---
apiVersion: kubermatic.k8s.io/v1
kind: Seed
metadata:
  name: kubermatic
  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-west1
    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 Kubermatic will pick up the new Seed and begin to reconcile it by installing the required Kubermatic components.

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-west1.kubermatic.example.com for the Seed from the previous step when kubermatic.example.com is the main domain where the Kubermatic 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 Load Balancers, 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 Load Balancers

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-west1.kubermatic.example.com.   IN   A   8.7.6.5

or, for a CNAME:

*.europe-west1.kubermatic.example.com.   IN   CNAME   myloadbalancer.example.com.