K8s or Kubernetes is an open-source platform, created for deploying automation, administering and scaling containerized applications. Kubernetes are based on the idea of the cluster. A Kubernetes cluster is essential for coordinating containers on multiple machines, ensuring smooth and efficient application performance.What is a Kubernetes Cluster?A Kubernetes cluster consists of nodes that run containerized apps. Containerizing apps encapsulates an app, its dependencies, and some essential services. They are more lightweight and adaptable than virtual machines. Kubernetes clusters facilitate application development, migration, and management.Kubernetes clusters enable containers to run on numerous machines and settings, including virtual, physical, cloud-based, and on-premises. Kubernetes clusters consist of one master node and several worker nodes. These nodes might be actual or virtual machines, depending on the cluster.The master node manages the cluster's state, such as which apps are executing and what container images they use. The master node is the starting point for all task assignments. It coordinates processes including:Scheduling and scaling applicationsMaintaining a cluster's state.Implementing updates.Worker nodes are the components that power these apps. Worker nodes complete duties delegated by the master node. They can be virtual machines or actual computers that all function as part of the same system.A Kubernetes cluster must have at least one master node and one worker node to function properly. For production and staging, the cluster is spread among several worker nodes. For testing, all components can operate on the same physical or virtual.Key Components of a Kubernetes Cluster:To comprehend how a Kubernetes cluster operates internally, we must explore the fundamental elements that comprise the control plane and worker nodes.1. Control Plane:API Server: The API server serves as the main access point for all administrative duties within the Kubernetes cluster. Both users and internal components communicate with Kubernetes through the API server, which manages RESTful API requests and facilitates communication among other components.etcd: It is the key-value store distributed across the cluster, storing all configuration data. It is an essential element that retains the cluster's present condition, informing the system about active nodes, container statuses, and necessary modifications.Controller Manager: Its role is to guarantee that the cluster's current state aligns with the desired state. It monitors the cluster's status via the API server and triggers the required modifications, such as increasing or decreasing the application scale.Scheduler: It is the scheduler's responsibility to determine the worker node on which a container will be assigned. It assesses the available resources on every node and allocates the container to a node that has enough resources to efficiently run it.2. Worker Nodes:The actual workloads are executed in containers on the worker nodes. Every worker node is equipped with these components:Kubelet: The agent present on each worker node that communicates with the control plane. It makes sure that the containers are executing based on the commands provided by the control plane.Kube-proxy: Its role is to handle network routing for services in the Kubernetes cluster. It makes sure that traffic going to and from the containers is directed correctly.Container Runtime: It is the mechanism that executes the containers. Common container runtimes used in Kubernetes are Docker, containerd, and CRI-O.How to create a Kubernetes cluster?A Kubernetes cluster can be created and deployed on both real and virtual machines. It is advised that new users start by constructing a Kubernetes cluster with Minikube. Minikube is an open-source program that works with Linux, Mac, and Windows operating systems. Minikube allows you to design and deploy a tiny, streamlined cluster with only one worker node.You may also use Kubernetes patterns to automate the scaling of your cluster. Kubernetes patterns make it easier to reuse cloud-based designs for containerised apps. While Kubernetes offers a lot of helpful APIs, it does not provide instructions for successfully integrating these technologies into an operating system. Kubernetes patterns provide a standard method for accessing and utilising existing Kubernetes architecturesUseful Kubernetes Cluster commandsCategoryCommandDescriptionCluster Infokubectl cluster-infoDisplays cluster information.Node Managementkubectl get nodesLists all nodes in the cluster. kubectl describe node <node-name>Shows detailed information about a specific node. kubectl cordon <node-name>Marks a node as unschedulable. kubectl drain <node-name>Safely evicts all pods from a node before maintenance. kubectl uncordon <node-name>Marks a node as schedulable again.Pod Managementkubectl get podsLists all pods in the current namespace. kubectl describe pod <pod-name>Shows details of a specific pod. kubectl delete pod <pod-name>Deletes a specific pod.Namespacekubectl get namespacesLists all namespaces in the cluster. kubectl create namespace <namespace>Creates a new namespace. kubectl delete namespace <namespace>Deletes a specific namespace.Service Managementkubectl get svcLists all services in the current namespace. kubectl describe svc <service-name>Provides details of a specific service. kubectl delete svc <service-name>Deletes a specific service.Deploymentkubectl get deploymentsLists all deployments in the current namespace. kubectl describe deployment <name>Shows detailed information about a deployment. kubectl scale deployment <name> --replicas=<count>Scales a deployment to the specified number of replicas. kubectl delete deployment <name>Deletes a specific deployment.Config Managementkubectl get configmapsLists all ConfigMaps in the current namespace. kubectl describe configmap <name>Shows details of a specific ConfigMap. kubectl create configmap <name> --from-literal=<key>=<value>Creates a ConfigMap from literal key-value pairs.Logs and Debuggingkubectl logs <pod-name>Displays logs of a specific pod. kubectl exec -it <pod-name> -- /bin/bashStarts an interactive shell session inside a pod.Resource Managementkubectl get allLists all resources in the current namespace (pods, services, etc.). kubectl apply -f <filename>.yamlApplies changes from a YAML file to the cluster. kubectl delete -f <filename>.yamlDeletes resources defined in a YAML file.Version and Helpkubectl versionShows the Kubernetes client and server version. kubectl get --helpDisplays help for the kubectl get command.How Kubernetes Clusters Work?The Kubernetes cluster’s control plane oversees the smallest deployable entities called worker nodes and pods for executing tasks. While deploying any application in Kubernetes, certain steps can be considered:Configuration: The user defines the application's desired state using YAML or JSON files. This configuration specifies the number of replicas (instances) of a service, the CPU and memory restrictions, and how the service should be provided (via a load balancer, for example).Scheduling: Based on the resource’s availability and work node, the application’s pods are distributed.Deployment: After the allocation of pods into the worker nodes, the execution of the designated nodes will be benign by the containers. On every node, proper functioning would be ensured by the Kubelet.Scaling and Repairing: Kubernetes consistently checks the well-being of the pods. If a pod malfunctions, Kubernetes will generate a new pod to take its place automatically. Pricing factors for Kubernetes clusters across major cloud providersProviderCluster Pricing ComponentsAdditional NotesGoogle Kubernetes Engine (GKE) Cluster Management Fee$0.10 per cluster per hour (standard mode, excluding Autopilot).No fee for the first zonal cluster in a project.Node PricingBased on the size and type of the machine (e.g., n1-standard-4, custom nodes).Standard Google Cloud Compute Engine pricing applies.Persistent Storage$0.04 per GB per month.Includes SSD and HDD options.Network CostsBased on Google Cloud’s network egress pricing. Amazon Elastic Kubernetes Service (EKS) Cluster Management Fee$0.10 per cluster per hour. Node PricingBased on EC2 instance types used for worker nodes.Pay-as-you-go or reserved instance options available.Persistent StorageBased on EBS volumes (e.g., $0.10 per GB for General Purpose SSD). Network CostsBased on AWS network transfer pricing. Microsoft Azure Kubernetes Service (AKS) Cluster Management FeeNo fee for standard Kubernetes clusters. Node PricingBased on Azure VM pricing for the chosen instance types.Spot instances are available for cost optimization.Persistent Storage$0.10 per GB per month (standard storage). Network CostsBased on Azure outbound data transfer pricing. IBM Kubernetes Service Cluster Management FeeNo fee for clusters with free worker nodes. Node PricingBased on virtual or bare-metal machine pricing. Persistent StorageBased on IBM Cloud block or file storage pricing. Network CostsBased on IBM Cloud data transfer rates. Key Advantages of Kubernetes Clusters in Modern Cloud Infrastructure:Kubernetes clusters are now the foundation of contemporary cloud-native infrastructure due to various factors.Scalability: Kubernetes can automatically adjust application scaling depending on factors like CPU and memory usage. This is especially useful in environments with changing workloads, where applications must be able to adjust in scale.Optimizing resources: Kubernetes efficiently allocates hardware resources by scheduling containers across nodes in an optimal manner. This results in improved use of computational power and lower expenses.Portability: Kubernetes removes the need to directly deal with the underlying infrastructure, enabling applications to be deployed in different environments such as on-premises data centres, public clouds, and hybrid cloud configurations.ConclusionA Kubernetes cluster forms the basis for Kubernetes' capability to automate, scale, and effectively manage containerized applications. Clusters enable developers to concentrate on building applications rather than being concerned about managing the underlying infrastructure by coordinating containers on worker nodes and automating deployment, scaling, and healing procedures.Kubernetes clusters are now indispensable for cloud-native applications, offering a dependable, adaptable, and scalable solution for modern software development due to their capacity to handle intricate workloads, scale dynamically, and ensure high availability.Read Morehttps://devopsden.io/article/what-is-a-pod-in-kubernetesFollow us onhttps://www.linkedin.com/company/devopsden/
