Get started with cluster registry

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  • Original Author: Tobias Weisserth
  • Original Publish Date: July 26, 2024

Overview

Improve resiliency for cloud native network functions with Azure Operator Service Manager cluster registry. This feature requires the following minimum environment:

  • AOSM ARM API Version: 2023-09-01
  • AOSM CNF Arc for Kubernetes Extension Build Number: 1.0.2711-7

Introduction

Azure Operator Service Manager (AOSM) cluster registry (CR) enables a local copy of container images in the Nexus K8s cluster. When the containerized network function (CNF) is installed with cluster registry enabled, the container images are pulled from the remote AOSM artifact store and saved to a local registry. With cluster register, CNF access to container images survives loss of connectivity to the remote artifact store.

Key use cases

Cloud native network functions (CNF) need access to container images, not only during the initial deployment using AOSM artifact store, but also to keep the network function operational. Some of these scenarios include:

  • Pod restarts: Stopping and starting a pod can result in a cluster node pulling container images from the registry.
  • Kubernetes scheduler operations: During pod to node assignments, according to scheduler profile rules, if the new node does not have the container images locally cached, the node pulls container images from the registry.

In the above scenarios, if there's a temporary issue with accessing the AOSM artifact store, the cluster registry provides the necessary container images to prevent disruption to the running CNF. Also, the AOSM cluster registry feature decreases the number of image pull requests on AOSM artifact store since each Nexus K8s node pulls container images from the cluster registry instead of the AOSM artifact store.

How cluster registry works

AOSM cluster registry is enabled using the Network Function Operator Arc K8s extension. The following CLI shows how cluster registry is enabled on a Nexus K8s cluster.

az k8s-extension create --name networkfunction-operator --cluster-name <CLUSTER_NAME> --resource-group <RESOURCE_GROUP_NAME> --cluster-type connectedClusters --extension-type Microsoft.Azure.HybridNetwork --scope cluster --release-namespace azurehybridnetwork --config Microsoft.CustomLocation.ServiceAccount=azurehybridnetwork-networkfunctionoperator --config global.networkfunctionextension.enableClusterRegistry=true --config global.networkfunctionextension.clusterRegistry.storageSize=100Gi --version 1.0.2711-7 --auto-upgrade-minor-version false --release-train stable

When the cluster registry feature is enabled in the Network Function Operator Arc K8s extension, any container images deployed from AOSM artifact store are accessible locally in the Nexus K8s cluster. The user can choose the persistent storage size for the cluster registry.

Note

If the user doesn't provide any input, a default persistent volume of 100 GB is used.

Frequently Asked Questions

Can I use AOSM cluster registry with a CNF application previously deployed?

If there's a CNF application already deployed without cluster registry, the container images are not available automatically. The cluster registry must be enabled before deploying the network function with AOSM.

Which Nexus K8s storage class is used?

AOSM cluster registry feature uses nexus-volume storage class to store the container images in the Nexus Kubernetes cluster. By default, a 100-GB persistent volume is created if the user doesn't specify the size of the cluster registry.

Can I change the storage size after a deployment?

Storage size can't be modified after the initial deployment. We recommend configuring the volume size by 3x to 4x of the starting size.