GlossaryCluster

Cluster

A Kubernetes cluster is a group of machines, called nodes, that work together under a control plane to run and manage containerized applications.

Table of Contents

Table of Contents

What Does Cluster Mean?

In Kubernetes, a cluster is a group of machines that work together to run containerized applications. Worker nodes run the workloads, and a control plane manages scheduling, networking, and orchestration.

Clusters abstract the underlying infrastructure. Applications deploy the same way whether the cluster runs in the cloud, on-premises, or both.

Core Components of a Kubernetes Cluster

  • Control plane: API server, scheduler, controller manager, and etcd
  • Worker nodes: machines that run application pods
  • Kubelet: the agent on each node that runs containers
  • Pods: the smallest deployable units, holding one or more containers
  • Networking: services and ingress that connect workloads

Node vs. Cluster

Aspect Node Cluster
What it is One machine, physical or virtual A managed group of nodes
Role Runs pods Schedules and manages all workloads
Failure impact Workloads move to other nodes Whole environment affected
Example A single cloud VM A production cluster on EKS

Why Clusters Matter in Kubernetes

  • Scalability: workloads spread across many nodes
  • High availability: applications recover from node failures
  • Consistency: the same deployment model across cloud, on-prem, and hybrid
  • Flexibility: microservices, batch jobs, and machine learning on one platform

Common Challenges with Clusters

  • Upgrades and config: keeping versions and settings aligned across environments
  • Resource balance: avoiding bottlenecks and noisy neighbors
  • Security: protecting node and service communication
  • Multi-cluster setups: managing global or hybrid deployments
  • Observability: monitoring distributed workloads

Real-World Examples

  • B2B SaaS: a SaaS company keeps separate staging and production clusters to isolate testing from customers
  • E-commerce: a retailer runs its stack across several clusters for availability and disaster recovery
  • Financial services: a firm runs clusters in different regions to meet data sovereignty rules

How Clusters Work with Testkube

Testkube uses your Kubernetes clusters as the test environment. Test workflows run as pods inside the cluster, so:

  • Tests match production: same networking, config, and resources
  • Drift disappears: no gap between test and deployment infrastructure
  • Scale is built in: load and integration tests use cluster capacity
  • Multi-cluster is central: runs across clusters are managed from one platform

Best Practices for Testing in Clusters

  • Use namespaces: separate test workloads from applications
  • Set resource limits: keep tests from starving production pods
  • Validate after upgrades: run cluster validation tests after changes
  • Mirror production: keep staging clusters close to production config
  • Centralize results: track tests across every cluster in one view

Frequently Asked Questions (FAQs)

What is the difference between a node and a cluster?

A node is a single machine that runs workloads. A cluster is a collection of nodes managed together by Kubernetes.

Can you run multiple clusters?

Yes. Many organizations use separate clusters for staging, production, or regions, often managed with GitOps tools.

Do clusters have to run in the cloud?

No. Clusters can run on bare metal, virtual machines, or cloud services like AWS, GCP, and Azure.

How does Testkube use clusters for testing?

Testkube runs test pods inside Kubernetes clusters. Testing becomes Kubernetes-native and environment drift goes away.

What tools help manage clusters?

Common options include kubeadm, Rancher, OpenShift, and managed services like Amazon EKS, Google GKE, and Azure AKS.

Related Terms and Concepts

Kubernetes

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications across clusters of machines.
Read more

Multi-Cluster

Multi-cluster is a Kubernetes architecture where workloads and services are deployed, managed, and tested across two or more clusters instead of a single cluster.
Read more

Kubernetes-native Testing

Kubernetes-native testing is an approach that runs tests directly inside Kubernetes clusters, using pods, Jobs, and native APIs, instead of on external machines or hosted testing services.
Read more