Virtual Clusters
vClusters (i.e. virtual clusters) are lightweight, namespace-scoped virtual Kubernetes clusters that allow you to create isolated Kubernetes clusters within a larger “host” Kubernetes cluster.
vClusters behave like a full-fledged Kubernetes cluster for users and applications but is backed by the resources and API of the host cluster. vClusters run their own Kubernetes API server within a namespace of the host cluster.
Key Characteristics¶
Here’s how vClusters help achieve isolation
Control Plane Isolation¶
Each vCluster is isolated within a namespace on the host cluster. The virtual cluster has its own API server and control plane components, separate from the host cluster. Users interact with the vCluster as if it were an independent Kubernetes cluster.
Workload Placement¶
Workloads scheduled in the vCluster are translated into pods in the host cluster’s namespace.
Networking & RBAC Isolation¶
The vCluster has its own Kubernetes networking, RBAC, and policies, distinct from the host cluster.
Lightweight¶
Because vClusters are virtual, they are faster to spin up and require fewer resources than creating dedicated Kubernetes clusters.
Why is it needed?¶
Let's review the use cases and challenges addressed by vClusters.
Multi-Tenancy¶
In a multi-tenant environment, tenants often need isolated clusters. Creating dedicated clusters for each tenant is resource-intensive and operationally complex. vClusters provide tenant isolation within a single host cluster, reducing overhead while maintaining independence.
Dev/Test Environments¶
Developers need isolated environments for testing, debugging, and prototyping. Provisioning dedicated clusters is time-consuming and expensive. Developers can spin up lightweight vClusters quickly, test changes, and discard them when done.
Multiple Kubernetes Versions¶
Users may need specific Kubernetes versions for their applications which may require setting up clusters with specific versions. Since each vCluster has its own API server, you can run different Kubernetes versions in parallel on the same host cluster.
Cost Optimization¶
Running multiple dedicated Kubernetes clusters for isolated workloads increases costs for infrastructure and management. vClusters leverage a single host cluster’s resources, reducing infrastructure and operational expenses.
Avoid Namespace Collisions¶
Using namespaces for multi-tenancy in Kubernetes can lead to conflicts in resource names, RBAC policies, and network configurations. Each vCluster operates independently and avoids namespace-level conflicts.
Isolation for Third-Party Applications¶
Third-party applications may require specific configurations or elevated permissions, which can conflict with other workloads in the host cluster. vClusters isolate the application and provide a separate control plane for configuration.