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CH1 - Introducing Kubernetes

From Kubernetes in Action

Control Plane

Runs on Kubernetes master node (or nodes, for HA)

Components

  • API Server
  • Scheduler - schedules your pods
  • Controller Manager - Performs cluster-level functions, like replicating components, tracking worker nodes, handling node failures, etc
  • Etcd - Distributed data store

Nodes

Machines that run your containerized applications

Components

  • Container runtime - Docker, rkt, etc
  • Kubelet - talks to API server and manages containers on its node
  • Kubernetes Service Proxy (kube-proxy) - load balances network traffic between application components

Running an application in Kubernetes

  1. Create container images for your application
  2. Push images to an image registry
  3. Send a description of your app to the Kubernetes API server

Pods

  • A pod is a group of containers. You can have different (but usually closely related) containers in a pod
  • A pod’s containers are always run on the same host
  • You can replicate a pod on multiple nodes, if you need more of a container