Kubernetes Architecture
What is Kubernetes?
- Kubernetes is a portable, extensible, opensource platform for managing containerized workloads and services
Architecture:
- Components of kubernetes (k8s) cluster
- Control Plane Components
- The control plane components make decissions about the cluster
- Control plane can be run on any machine in the cluster
- We can create a highly available cluster by using multiple machines for control plane components
- The components are:
- kube-apiserver
- etcd
- kube-scheduler
- kube-controller-manager
- kube-cloud-controller-manager
- Node Components:
- Thy run on every node, maintianing running pods and providing k8s runtime environment.
- Our applications will be running on nodes
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The Node Components are
- kubelet
- kube-proxy
- Container runtime
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kube-apiserver:
- The API server is a component of k8s control plane that exposes k8s API (Front-end of k8s)
- All the communication between control plane and nodes is also handled by api server
- To make k8s HA (highly Available), we can horizontal scale api-server
- As a user of k8s cluster we can interact with kube-api server using API with json or a tool called a kubectl which is a command line tool
- etcd: Refer Here
- This is distribute key-value store.
- k8s uses etc to store all the cluster data
- kube-scheduler:
- Control plane component that creates Pods on the nodes by selecting them
- kube-controller-manager:
- Control plane component runs controller proceses. Each controller is a seperate process, but to reduce complexity they run in single process
- Some major types of controller are
- Node Controller: Responsible for noticing and responding when node goes down
- Job Controller
- Endpoints controller
- Cloud-controller-manager:
- This component embeds cloud-specific logic
- Kubelet:
- This is an agent that runs on each node in the cluster.
- Kubelet recieves requests/orders to create new Pods
- kube-proxy:
- This is a network proxy that runs on each node in k8s
- This maintains network rules on the nodes
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Container runtime:
- Kubernetes suppors container run times such as containerd, CRI-O and any implementation of Kubernetes CRI (Container Runtime instance)
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Basic Workflow
- Note: JSON and YAML Tutorial Refer Here
