Kubernetes Architecture

Kubernetes will work as on Master and worker node architecture. In total Kubernetes has 7 components out of which 4 belongs to the Master node and 3 belongs to the worker node

Master Node components:

  1. API Server
  2. Controller Manager
  3. ETCD
  4. Scheduler

Worker Node components:

  1. Kube-proxy
  2. Kubelet
  3. Runtime

Master Node – Since the name suggests it is the master for the cluster and entry point for the administrative tasks that will be in charge of managing the Kubernetes cluster.

There might be one or multiple Master inside a bunch for fault tolerance & high availability. Let’s check every component which are accountable to make a node Master.

API SERVER:

This is the Kubernetes control plane’s front end. All API calls are sent to this server and the server sends commands to the other services.

No component talks together directly, the API server is responsible for the communication.

Etcd:

This is the Key-Value store for the cluster. When an item is established, that object state is stored here.

Etcd acts whilst the reference for the cluster state. If the cluster is different from what is indicated in Etcd, the cluster would change to match the declared state. For e.g 2 Pods supposed to run with certain images or tasks if any pods it gets deleted automatically create one more to match the state.

Scheduler:

Each time a new pod is established scheduler determines which node should run it & this decision is dependant on many factors including hardware, workloads, affinity, etc.

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Controller Manager:

It operates the cluster controllers –

  • Node Controller – In charge of noticing and responding when nodes go down.
  • Replication Controller – in charge of maintaining the proper amount of pods for every replication controller object in the device
  • Endpoints Controller – Populates the joins services and pods
  • Service Accounts & Token Controllers – creates default accounts and API access tokens for new namespaces

kubernetes architecture

Worker Node (minions) – It is a physical server or VM which runs the applications using Pods that will be controlled by the Master node.

“Pods are the littlest working unit of Kubernetes the same as container of Docker” or you can say Kubernetes doesn’t run containers instead it wraps a number of containers right. Pods are utilized as the system of replication in Kubernetes.

Let’s check the aspects of Worker Nodes:

Kube-Proxy:

This runs on the nodes and provides network connectivity for services on the nodes that connect with the pods.

It serves as a network proxy and a load balancer for something about the same worker node and manages the network routing for TCP and UDP packets.

Kube-proxy runs on each node to deal with individual host sub-netting and make certain that the services are available to external parties.

Kubelet:

It is an agent that communicates with the Master node and executes on nodes or the worker nodes. It gets the Pod specifications all the way through the API server and executes the containers associated to the Pod and ensures that the containers described in those Pods are running and healthy.

Container Runtime:

This is the container manager. It can be any container runtime that is compliant with the Open Container inventiveness such as Docker or to run and manage a container’s lifecycle, we need a container runtime on the worker node.

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