High-Performance Kubernetes

High-Performance Kubernetes (HPK), allows HPC users to run their own private "mini Clouds" on a typical HPC cluster. HPK uses a single container to run the Kubernetes control plane and a Virtual Kubelet Provider implementation to translate container lifecycle management commands from Kubernetes-native to Slurm/Apptainer.

To allow users to run HPK, the HPC environment should have Apptainer configured so that:

• It allows users to run containers with --fakeroot.
• It uses a CNI plug-in that hands over private IPs to containers, which are routable across cluster hosts (we use flannel and the flannel CNI plug-in).

In contrast to a typical Kubernetes installation at the Cloud:

• HPK uses a pass-through scheduler, which assigns all pods to the single hpk-kubelet that represents the cluster. In practice, this means that all scheduling is delegated to Slurm.
• All Kubernetes services are converted to headless. This avoids the need for internal, virtual cluster IPs that would need special handling at the network level. As a side effect, HPK services that map to multiple pods are load-balanced at the DNS level if clients support it.

HPK is a continuation of the KNoC project, a Virtual Kubelet Provider implementation that can be used to bridge Kubernetes and HPC environments.

Trying it out

First you need to configure Apptainer for HPK. The install-environment.sh script showcases how we implement the requirements in a single node for testing.

Once setup, compile the hpk-kubelet using make.

make build

Then you need to start the Kubernetes Master and hpk-kubelet seperately.

To run the Kubernetes Master:

make run-kubemaster

Once the master is up and running, you can start the hpk-kubelet:

make run-kubelet

Now you can configure and use kubectl:

export KUBE_PATH=~/.k8sfs/kubernetes/
export KUBECONFIG=${KUBE_PATH}/admin.conf
kubectl get nodes

In case that you experience DNS issues, you should retry starting the Kubernetes Master with:

export EXTERNAL_DNS=<your dns server>
make run-kubemaster

The above command will set CoreDNS to forward requests for external names to your DNS server.

Acknowledgements

We thankfully acknowledge the support of the European Commission and the Greek General Secretariat for Research and Innovation under the EuroHPC Programme through projects EUPEX (GA-101033975) and DEEP-SEA (GA-955606). National contributions from the involved state members (including the Greek General Secretariat for Research and Innovation) match the EuroHPC funding.