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Links: 110 Kubernetes Index

FOR BETTER VERSION REFER: Cluster Architecture

  • Architecture diagram for reference
    • attachments/Pasted image 20230515144649.jpg

Components

  • api-server is responsible for managing everything.
    • It talks to the UI, API and the CLI.
    • api-server or kube-apiserver is how we talk and interact with the cluster (entry point to the k8s cluster).
  • etcd is a highly available key value store.
    • It is only accessible via the api server for security reasons.
    • It has all the configuration and status data of kubernetes.
  • A scheduler identifies the right node to place a pod on based on different requirements and available resources.
    • It is also known as the control plane.
    • It ensures pod placement.
  • A kubelet is an agent that runs on each worker node in a cluster.
    • It listens for instructions from the kubeapi-server or api-server and deploys and destroys containers on the node as required.
  • Controllers/controller-manager is the brain behind orchestration they are responsible for noticing and responding when pods go down. ^9d5e63
    • It consists of several controllers like the deployment controller, replicas set controller etc.
    • In Kubernetes, controllers are control loops that watch the state of your cluster, then make or request changes where needed.
  • Container runtime is the underlying software used to run containers.
    • Some container runtimes are containerd, docker, rocket, etc.
  • Suppose you have a database server running on a pod on one of the worker nodes and the application server running on a pod in some other worker node.
    • Communication between worker nodes is facilitated using kube-proxy.
We can have multiple pods on a single worker node.
  • So it is possible to have 3 worker nodes and 20 pods.
  • It is Kubernetes job (scheduler) to take care of resources and decide which pod should go to which worker.

Last updated: 2023-05-15