WORKER NODES: Worker nodes will have an instance of kubelet, kube-proxy and a certain container runtime (such as Docker, containerd) running on each node, and are used to run user defined containers.There are two distinct classifications of a node within Kubernetes: Master and Worker nodes. Each node will contain the components necessary to run pods. Depending on your environment, a node can represent a virtual or physical machine. Kubernetes runs workloads by placing your pods into nodes. The scheduler will use information such as compute requests and limits defined within your workload (if any), as well as finding the right node candidate based on its available resources to appropriately assign your workload to a particular node. Running as part of the control plane, the kube-scheduler’s responsibility is to assign pods to nodes within your cluster. This means that any access and authentication such as deployments of pods and other Kubernetes API objects via kubectl are handled by this API server. The API Server provides the frontend to the cluster’s shared state, which is where all of the other components interact. The Kube-API server, a component within the control plane, validates and configures data for API objects, including pods and services. Service account and token controllers: Responsible the management of service accounts within each namespace, as well as API access tokens ENDPOINT CONTROLLER: Responsible for provisioning of endpoints (such as service endpoints).REPLICATION CONTROLLER: Responsible for maintaining replications of objects in the cluster (such as replicasets).NODE CONTROLLER: Responsible for identifying changes in nodes within the cluster.The following controllers are present within this manager: The Kubernetes controller manager is a collection of controllers bundled within a single binary and run in a single process. Kube-proxy is used to reach kubernetes services in addition to load balancing of services.
It maintains network rules, which allow for network communication to Pods from network sessions inside or outside of a cluster. Kube-proxy is a network proxy that runs on each node. Its functionality is watching for new or changed pod specifications from master nodes and ensuring that pods within the node that it resides in are healthy, and the state of pods matches the pod specification. The kubelet functions as an agent within nodes and is responsible for the runnings of pod cycles within each node. If you don’t already have a Kubernetes cluster, follow our tutorial to play around with Kubernetes and create one. To run etcd, you first need to have a Kubernetes cluster and the command-line tool configured to communicate with said cluster. It stores and replicates the Kubernetes cluster state. Just note: If you’re running Kubernetes on-prem, your cluster won’t have a cloud-controller-manager.Įtcd is a distributed key-value store and the primary datastore of Kubernetes. The cloud-controller-manager is what allows you to connect your clusters with the cloud provider’s API and only runs controllers specific to the cloud provider you’re using. The cloud-controller-manager runs in the control plane as a replicated set of processes (typically, these would be containers in Pods). Kube proxies and kubelets live on each node, talking to the API and managing the workload of each node.Īs the control plane handles most of Kubernetes’ ‘decision making’, nodes which have these components running generally don’t have any user containers running – these are normally named as master nodes. The Control plane is made up of the kube-api server, kube scheduler, cloud-controller-manager and kube-controller-manager. The nodes are at the centre of a Kubernetes cluster and are often referred to as the ‘powerhouses’ or ‘workhorses’.īelow is a deeper dive into not only nodes, but each of the various components that you’ll need to have a complete and working Kubernetes cluster. The master is there to expose the API and manage the general running of the cluster. At a base level, a Kubernetes cluster is made up of a control plane (master), distributed storage system for keeping the cluster state (etcd) consistent and a group of cluster nodes (workers).
When you’re just getting started with Kubernetes, the first step is to understand the foundations of the functionality and how clusters are set up.
0 kommentar(er)
