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Introduction

Hosted control planes for Red Hat OpenShift with the KubeVirt provider makes it possible to host OpenShift tenant clusters on bare metal machines at scale. It can be installed on an existing bare metal OpenShift cluster (OCP) environment allowing you to quickly provision multiple guest clusters using KubeVirt virtual machines. The current model allows running hosted control planes and KubeVirt virtual machines on the same underlying base OCP cluster. Unlike the standalone OpenShift cluster where some of the Kubernetes services in the control plane are running as systemd services, the control planes that HyperShift deploys are just another workload which can be scheduled on any available nodes placed in their dedicated namespaces. This post will show the detailed steps of installing HyperShift with the KubeVirt provider on an existing bare metal cluster and configuring the necessary components to launch guest clusters in a matter of minutes.

Please note that the support status of this provider is still in dev preview and it will be officially supported in a future release.

Diagram of Hypershift Architecture

Benefits

The list below highlights the benefits of using HyperShift KubeVirt provider:

  • Enhance resource utilization by packing multiple hosted control planes and hosted clusters in the same underlying bare metal infrastructure.
  • Strong isolation by separating hosted control planes and guest clusters.
  • Reduce cluster provision time by eliminating baremetal node bootstrapping process.
  • Manage multiple different releases under the same base OCP cluster

Cluster Preparation

OCP 4.12.0 is running as the underlying base OCP cluster on top of 6 bare metal nodes (3 masters + 3 workers). Required operators and controllers are listed as follows:

  • OpenShift Data Foundation (ODF)  using local storage devices
  • OpenShift Virtualization 
  • MetalLB
  • Multicluster Engine
  • Cluster Manager
  • HyperShift

The list of required operators might vary depending on your specific environment. The following sections cover the detailed configuration and some explanation of each operator and controller, the corresponding installation link is inserted in each section.

OpenShift Data Foundation

In our case, OpenShift Data Foundation (ODF) with local storage devices is used as the default software defined storage to persist the guest cluster etcd pods and VM workers.

After completing the installation guide and creating the corresponding storage system, you should be able to examine the operators installed and the storage classes managed by ODF:

[root@e24-h21-740xd ~]# oc get csv -n openshift-storage
NAME                              DISPLAY                       VERSION   REPLACES   PHASE
mcg-operator.v4.12.0              NooBaa Operator               4.12.0               Succeeded
ocs-operator.v4.12.0              OpenShift Container Storage   4.12.0               Succeeded
odf-csi-addons-operator.v4.12.0   CSI Addons                    4.12.0               Succeeded
odf-operator.v4.12.0              OpenShift Data Foundation     4.12.0               Succeeded

 

[root@e24-h21-740xd ~]# oc get sc
NAME                          PROVISIONER                             RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
lvset                         kubernetes.io/no-provisioner            Delete          WaitForFirstConsumer   false                  23m
ocs-storagecluster-ceph-rbd   openshift-storage.rbd.csi.ceph.com      Delete          Immediate              true                   17m
ocs-storagecluster-ceph-rgw   openshift-storage.ceph.rook.io/bucket   Delete          Immediate              false                  21m
ocs-storagecluster-cephfs     openshift-storage.cephfs.csi.ceph.com   Delete          Immediate              true                   17m
openshift-storage.noobaa.io   openshift-storage.noobaa.io/obc         Delete          Immediate              false                  14m

 

Once ODF is setup, annotate a default storage class for HyperShift to persist VM workers and guest cluster etcd pods:

oc patch storageclass ocs-storagecluster-ceph-rbd -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'

 

Check if the storage class is labeled as default:

[root@e24-h21-740xd ~]# oc get sc | grep ocs-storagecluster-ceph-rbd
ocs-storagecluster-ceph-rbd (default)   openshift-storage.rbd.csi.ceph.com      Delete          Immediate              true                   20m

 

OpenShift Virtualization

OpenShift Virtualization Operator is an add-on to OCP that allows you to run and manage virtual machines alongside pods. HyperShift with the KubeVirt provider allows you to run guest cluster components using KubeVirt virtual machines. Once you installed the operator and created HyperConverged Object, you should be able to see the following output:

[root@e24-h21-740xd ~]# oc get csv -n openshift-cnv
NAME                                       DISPLAY                    VERSION   REPLACES                                   PHASE
kubevirt-hyperconverged-operator.v4.12.0   OpenShift Virtualization   4.12.0    kubevirt-hyperconverged-operator.v4.11.1   Succeeded

 

MetalLB

Metallb is recommended as the network load balancer for bare-metal clusters. Once installation is complete, create the MetalLB instance using the following yaml:

oc create -f - <<EOF
apiVersion: metallb.io/v1beta1
kind: MetalLB
metadata:
name: metallb
namespace: metallb-system
EOF

 

An address pool needs to be allocated. In our case, dnsmasq is used, you should be able to see the allocated IP range at /etc/dnsmasq.d/ocp4-lab.conf, please choose a free range and apply the following yaml:

oc create -f - <<EOF
apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
name: metallb
namespace: metallb-system
spec:
addresses:
- 192.168.216.32-192.168.216.122
EOF

 

Once IP address pool is created, we can advertise the address pool using L2 protocol:

oc create -f - <<EOF
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
name: l2advertisement
namespace: metallb-system
spec:
ipAddressPools:
 - metallb
EOF

 

Multicluster Engine

Multicluster engine (MCE) is one of the core components of HyperShift. Make sure to install 2.2.0+ in order to launch 4.12 guest clusters. Once the installation completes, you should be able to see the following output:

[root@e24-h21-740xd hypershift]# oc get csv -n multicluster-engine
NAME                                   DISPLAY                              VERSION               REPLACES   PHASE
multicluster-engine.v2.2.0             multicluster engine for Kubernetes   2.2.0                            Succeeded

 

Apply the following yaml to create a MulticlusterEngine instance:

oc apply -f - <<EOF
apiVersion: multicluster.openshift.io/v1
kind: MultiClusterEngine
metadata:
name: multiclusterengine-sample
spec: {}
EOF

 

Since HyperShift with the KubeVirt provider is in dev preview, the functionality is not enabled by default. Apply the following patch to allow the hypershift addon to be installed in a subsequent step:

oc patch mce multiclusterengine-sample --type=merge -p '{"spec":{"overrides":{"components":[{"name":"hypershift-preview","enabled": true}]}}}'

 

Cluster Manager

The local-cluster ManagedCluster allows the MCE components to treat the cluster it runs on as a host for guest clusters. Note that the creation of this object might fail initially. This failure occurs if the MultiClusterEngine is still being initialized and hasn’t registered the “ManagedCluster” CRD yet. It might take a few minutes of retrying this command before it succeeds.

oc apply -f - <<EOF
apiVersion: cluster.open-cluster-management.io/v1
kind: ManagedCluster
metadata:
labels:
  local-cluster: "true"
name: local-cluster
spec:
hubAcceptsClient: true
leaseDurationSeconds: 60
EOF

 

HyperShift

Apply the following yaml to enable HyperShift operator within the local cluster:

oc apply -f - <<EOF
apiVersion: addon.open-cluster-management.io/v1alpha1
kind: ManagedClusterAddOn
metadata:
name: hypershift-addon
namespace: local-cluster
spec:
installNamespace: open-cluster-management-agent-addon
EOF

 

The hypershift operator pods can be viewed within the “hypershift” namespace. To verify the operator pod in running in this namespace:

[root@e24-h21-740xd ~]# oc get pods -n hypershift | grep "operator.*Running"
operator-78c8bc5898-c47rm   1/1     Running   0          3m54s

 

Ingress wildcard routes are required since the guest cluster's base domain will be a subdomain of the infra cluster's `*apps` A record:

oc patch ingresscontroller -n openshift-ingress-operator default --type=json -p '[{ "op": "add", "path": "/spec/routeAdmission", "value": {wildcardPolicy: "WildcardsAllowed"}}]'

 

Demo

The following sections will take you through the steps of:

  • Build HyperShift Client
  • Configure Environment Variables
  • Create HyperShift KubeVirt Hosted Cluster
  • Create Ingress Service
  • Create Ingress Route
  • Examine Hosted Cluster

Build HyperShift Client

To build the HyperShift client binary. Use the following command to build the CLI tool within a pod:

podman run --rm --privileged -it -v \
$PWD:/output docker.io/library/golang:1.18 /bin/bash -c \
'git clone https://github.com/openshift/hypershift.git && \
cd hypershift/ && \
make hypershift && \
mv bin/hypershift /output/hypershift'

 

The binary will be placed under the $PWD directory, move the binary to /usr/local/bin which should be included in the $PATH environment variable:

sudo mv $PWD/hypershift /usr/local/bin

 

Configure Environment Variables

The pull secret is needed for pods accessing images from the registry. Make sure to replace the PULL_SECRET variable with a path to your pull secret file:

export KUBEVIRT_CLUSTER_NAME=kv-00
export PULL_SECRET="/path/to/pull-secret"

 

Create HyperShift KubeVirt Hosted Cluster

Use the following command to create a node pool of 2 workers and the guest cluster playload version can be specified by `--release-image`. Starting from 4.12.2, a default ingress passthrough feature is added, we no longer need to create ingress services and routes manually.

hypershift create cluster \
kubevirt \
--name $KUBEVIRT_CLUSTER_NAME \
--node-pool-replicas=2 \
--memory '8Gi' \
--pull-secret $PULL_SECRET \
--release-image=quay.io/openshift-release-dev/ocp-release@sha256:382f271581b9b907484d552bd145e9a5678e9366330059d31b007f4445d99e36

 

It takes some time for the VMs to be provisioned, you can use the following command to wait until the VM workers reach ready state:

oc wait --for=condition=Ready --namespace $KUBEVIRT_CLUSTER_NAMESPACE vm --all --timeout=600s

 

Once the VM workers are ready, we can generate the guest cluster kubeconfig file which is useful when we want to examine the guest cluster.

hypershift create kubeconfig --name="$KUBEVIRT_CLUSTER_NAME" > "${KUBEVIRT_CLUSTER_NAME}-kubeconfig"

 

Examine The Hosted Cluster

Once all the guest cluster operators are deployed successfully, the status of the Available column should be True and the PROGRESS column should be changed to Completed. We created three guest clusters with different releases just to show that it is possible to manage multi-version hosted clusters in HyperShift with the KubeVirt provider:

[root@e24-h21-740xd hypershift]# oc get hc -A
NAMESPACE   NAME    VERSION   KUBECONFIG               PROGRESS    AVAILABLE   PROGRESSING   MESSAGE
clusters    kv-00   4.12.2    kv-00-admin-kubeconfig   Completed   True        False         The hosted control plane is available
clusters    kv-04   4.12.3    kv-04-admin-kubeconfig   Completed   True        False         The hosted control plane is available
clusters    kv-05   4.12.4    kv-05-admin-kubeconfig   Completed   True        False         The hosted control plane is available

 

If we take a closer look, there is a dedicated namespace `clusters-kv-00` being created for the hosted control plane. Under this namespace, we should be able see control plane pods such as etcd and  kube-api-server are running:

[root@e24-h21-740xd ~]# oc get pod -n clusters-kv-00 | grep 'kube-api\|etcd'
etcd-0                                                2/2     Running     0          47h
kube-apiserver-864764b74b-t2tcl                       3/3     Running     0          47h

 

There are two virt-launcher pods for the KubeVirt virtual machines since we specified `node-pool-replicas=2`:

[root@e24-h21-740xd ~]# oc get pod -n clusters-kv-00 | grep 'virt-launcher'
virt-launcher-kv-00-j45fr-mt5lc                       1/1     Running     0          2d1h
virt-launcher-kv-00-l7f27-fk9tj                       1/1     Running     0          2d1h

 

To check the status of those two VMs:

[root@e24-h21-740xd ~]# oc get vm -n clusters-kv-00
NAME          AGE    STATUS    READY
kv-00-j45fr   2d1h   Running   True
kv-00-l7f27   2d1h   Running   True

 

To examine our guest clusters, we need to have the oc tool pointing to the guest kubeconfig. From OCP’s perspective, these two virtual machines will be the worker nodes:

[root@e24-h21-740xd hypershift]# oc --kubeconfig kv-00-kubeconfig get nodes
NAME          STATUS   ROLES    AGE    VERSION
kv-00-j45fr   Ready    worker   2d1h   v1.25.4+77bec7a
kv-00-l7f27   Ready    worker   2d1h   v1.25.4+77bec7a

 

We should also be able to see that there is a dedicated monitoring and networking stack for each guest cluster:

[root@e24-h21-740xd hypershift]# oc --kubeconfig kv-00-kubeconfig get pod -A | grep 'prometh\|ovn\|ingress'
openshift-ingress-canary                           ingress-canary-j4lq4                                     1/1     Running     0              2d1h
openshift-ingress-canary                           ingress-canary-zd28w                                     1/1     Running     0              2d1h
openshift-ingress                                  router-default-68df75f88d-dszb2                          1/1     Running     0              2d1h
openshift-monitoring                               prometheus-adapter-6fd546d669-c2dw6                      1/1     Running     0              2d1h
openshift-monitoring                               prometheus-k8s-0                                         6/6     Running     0              2d1h
openshift-monitoring                               prometheus-operator-688459b4f4-45775                     2/2     Running     0              2d1h
openshift-monitoring                               prometheus-operator-admission-webhook-849b6cd6bf-52rpq   1/1     Running     0              2d1h
openshift-ovn-kubernetes                           ovnkube-node-4hmgz                                       5/5     Running     4 (2d1h ago)   2d1h
openshift-ovn-kubernetes                           ovnkube-node-87nk7                                       5/5     Running     0              2d1h

 

Summary

We went through the detailed steps of installing and configuring necessary operators and controllers to set up HyperShift with the KubeVirt provider in an existing bare metal OCP cluster environment. We also demonstrated how to launch a hosted cluster using the HyperShift command line tool, examined where the hosted control planes pods are running and what components are being placed inside of guest clusters.

Future Work

Future work will cover the topics of:

  • Persistent storage for pod running in the guest cluster.
  • Different storage configurations for guest etcd pods.
  • Isolate hosted control planes from nodes that are running worker VMs.
  • Hosted cluster density scale testing.

執筆者紹介

I mainly focus on HyperShift/KubeVirt project, a multi-cluster Kubernetes engine that uses KubeVirt, enabling the running of KVM virtual machines alongside containers. The goal is to identify limitations and improve performance and scalability. My responsibilities include deploying large-scale on-premise clusters, contributing to the CI/CD pipeline, developing automation tools, and conducting performance analyses on ETCD, OVN networking, and ODF storage.

Read full bio

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