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1 line
8.8 KiB
JavaScript
1 line
8.8 KiB
JavaScript
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Nodes in Kubernetes"},sidebar:"tutorialSidebar",previous:{title:"Recommended Cluster Architecture",permalink:"/v2.0-v2.4/how-to-guides/new-user-guides/kubernetes-clusters-in-rancher-setup/checklist-for-production-ready-clusters/recommended-cluster-architecture"},next:{title:"Setting up Clusters from Hosted Kubernetes Providers",permalink:"/v2.0-v2.4/pages-for-subheaders/set-up-clusters-from-hosted-kubernetes-providers"}},i={},u=[{value:"etcd",id:"etcd",level:2},{value:"controlplane",id:"controlplane",level:2},{value:"kube-apiserver",id:"kube-apiserver",level:3},{value:"kube-controller-manager",id:"kube-controller-manager",level:3},{value:"kube-scheduler",id:"kube-scheduler",level:3},{value:"worker",id:"worker",level:2},{value:"References",id:"references",level:2}],c={toc:u};function d(e){let{components:t,...s}=e;return(0,o.kt)("wrapper",(0,n.Z)({},c,s,{components:t,mdxType:"MDXLayout"}),(0,o.kt)("p",null,"This section describes the roles for etcd nodes, controlplane nodes, and worker nodes in Kubernetes, and how the roles work together in a cluster."),(0,o.kt)("p",null,"This diagram is applicable to Kubernetes clusters ",(0,o.kt)("a",{parentName:"p",href:"/v2.0-v2.4/pages-for-subheaders/launch-kubernetes-with-rancher"},"launched with Rancher using RKE."),"."),(0,o.kt)("p",null,(0,o.kt)("img",{alt:"Cluster diagram",src:r(56492).Z,width:"772",height:"1145"}),(0,o.kt)("br",null)),(0,o.kt)("sup",null,"Lines show the traffic flow between components. Colors are used purely for visual aid"),(0,o.kt)("h2",{id:"etcd"},"etcd"),(0,o.kt)("p",null,"Nodes with the ",(0,o.kt)("inlineCode",{parentName:"p"},"etcd")," role run etcd, which is a consistent and highly available key value store used as Kubernetes\u2019 backing store for all cluster data. etcd replicates the data to each node."),(0,o.kt)("blockquote",null,(0,o.kt)("p",{parentName:"blockquote"},(0,o.kt)("strong",{parentName:"p"},"Note:")," Nodes with the ",(0,o.kt)("inlineCode",{parentName:"p"},"etcd")," role are shown as ",(0,o.kt)("inlineCode",{parentName:"p"},"Unschedulable")," in the UI, meaning no pods will be scheduled to these nodes by default.")),(0,o.kt)("h2",{id:"controlplane"},"controlplane"),(0,o.kt)("p",null,"Nodes with the ",(0,o.kt)("inlineCode",{parentName:"p"},"controlplane")," role run the Kubernetes master components (excluding ",(0,o.kt)("inlineCode",{parentName:"p"},"etcd"),", as it's a separate role). See ",(0,o.kt)("a",{parentName:"p",href:"https://kubernetes.io/docs/concepts/overview/components/#master-components"},"Kubernetes: Master Components")," for a detailed list of components."),(0,o.kt)("blockquote",null,(0,o.kt)("p",{parentName:"blockquote"},(0,o.kt)("strong",{parentName:"p"},"Note:")," Nodes with the ",(0,o.kt)("inlineCode",{parentName:"p"},"controlplane")," role are shown as ",(0,o.kt)("inlineCode",{parentName:"p"},"Unschedulable")," in the UI, meaning no pods will be scheduled to these nodes by default.")),(0,o.kt)("h3",{id:"kube-apiserver"},"kube-apiserver"),(0,o.kt)("p",null,"The Kubernetes API server (",(0,o.kt)("inlineCode",{parentName:"p"},"kube-apiserver"),") scales horizontally. Each node with the role ",(0,o.kt)("inlineCode",{parentName:"p"},"controlplane")," will be added to the NGINX proxy on the nodes with components that need to access the Kubernetes API server. This means that if a node becomes unreachable, the local NGINX proxy on the node will forward the request to another Kubernetes API server in the list."),(0,o.kt)("h3",{id:"kube-controller-manager"},"kube-controller-manager"),(0,o.kt)("p",null,"The Kubernetes controller manager uses leader election using an endpoint in Kubernetes. One instance of the ",(0,o.kt)("inlineCode",{parentName:"p"},"kube-controller-manager")," will create an entry in the Kubernetes endpoints and updates that entry in a configured interval. Other instances will see an active leader and wait for that entry to expire (for example, when a node is unresponsive)."),(0,o.kt)("h3",{id:"kube-scheduler"},"kube-scheduler"),(0,o.kt)("p",null,"The Kubernetes scheduler uses leader election using an endpoint in Kubernetes. One instance of the ",(0,o.kt)("inlineCode",{parentName:"p"},"kube-scheduler")," will create an entry in the Kubernetes endpoints and updates that entry in a configured interval. Other instances will see an active leader and wait for that entry to expire (for example, when a node is unresponsive)."),(0,o.kt)("h2",{id:"worker"},"worker"),(0,o.kt)("p",null,"Nodes with the ",(0,o.kt)("inlineCode",{parentName:"p"},"worker")," role run the Kubernetes node components. See ",(0,o.kt)("a",{parentName:"p",href:"https://kubernetes.io/docs/concepts/overview/components/#node-components"},"Kubernetes: Node Components")," for a detailed list of components."),(0,o.kt)("h2",{id:"references"},"References"),(0,o.kt)("ul",null,(0,o.kt)("li",{parentName:"ul"},(0,o.kt)("a",{parentName:"li",href:"https://kubernetes.io/docs/concepts/overview/components/#node-components"},"Kubernetes: Node Components"))))}d.isMDXComponent=!0},56492:(e,t,r)=>{r.d(t,{Z:()=>n});const n=r.p+"assets/images/clusterdiagram-2b66ee124fed594265b3bc07fa1f145d.svg"}}]); |