[General] K8s / EKS 101 (작성 중)

https://kubernetes.io/docs/concepts/overview/components/

🌳 K8s components

1. Control plane

• Master node
• node(s) 관리
• Scheduling과 같은 Global cluster 관리
• Cluster에서 발생하는 모든 이벤트 감지
• 일반적으로 하나의 Machine에서 돌아감 (User container는 별도로 위치시킴)

2. Kube-api server

• Control panel의 FrontEnd
• K8s의 API를 외부에 노출시키는 역할
• 관리자는 다수의 API instances를 동작시켜서 트래픽을 분산시킬수 있다.

3. Kubelet

🌳 K8s networking

(1) Node 👉 control plane

(2) Control plane 👉 node

• API server to kubelet
• API server to proxy

🌳 K8s terms

👉 Cluster

namespace

• Namespaces are a way to divide cluster resources between multiple users (via resource quota).
• namespace: Virtual Sub-cluster를 구분하는/organize하는 방법
• kube-system: System processes
• kube-public: Publicly accessible data (Configmap)
• kube-node-lease: Heartbeats of nodes
• default: Resources you create are located here

👉 Workloads

ReplicaSets

• 동작되고 있는 Pods 갯수 조정 (To maintain a stable set of replica Pods running at any given time.)
• Deployment가 ReplicaSets를 관리하는 higher-level인만큼 Deployment를 통한 replicasets 관리를 권고함. (즉, 직접적인 ReplicaSets 관리 🙅‍♀️)

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Deployment

• A Deployment provides declarative updates for Pods and ReplicaSets.
• Rollback 가능

StatefulSet

• StatefulSet is the workload API object used to manage stateful applications.

DaemonSet

• A Daemonset will not run more than one replica per node. Another advantage of using a Daemonset is that, if you add a node to the cluster, then the Daemonset will automatically spawn a pod on that node, which a deployment will not do.
• Rollback 불가능

(상황에 따라 Deployment, StatefulSet, DaemonSet 중 하나 선택)

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👉 Config and Secret

Configmap

• External configuration of oneself’s application

👀 참고사이트

• https://medium.com/stakater/k8s-deployments-vs-statefulsets-vs-daemonsets-60582f0c62d4
• https://kubernetes.io/docs/concepts/overview/components/