Introduction to Kubernetes

Introduction to Kubernetes Kubernetes is an orchestration engine and open-source platform for managing containerized application services and workloads that facilitates both configuration and automation. Kubernetes can be commonly referred as K8s.

Kubernetes can be considered as a replacement for Docker Swarm and far more complex than Swarm and requires more work to deploy.

Benefits of Kubernetes Kubernetes can increase the development process by making easy, automated deployments, updates (rolling-update) and by managing our apps and services with almost zero downtime. In addition, it provides self-healing. Kubernetes is originally developed by Google, it's open-sourced since its launch and managed by a large community of contributors. It makes better usage of hardware to maximise resources needed to operate your enterprise apps. It can be utilized to Scale containerized applications and their resources on the fly. With basic Docker knowledge any developer can package up applications and deploy them on Kubernetes.

Kubernetes Architecture

Kubernetes Components Web UI (Dashboard) Dashboard is just a web-based Kubernetes user interface. Dashboard can be used to deploy containerized applications to a Kubernetes cluster, troubleshoot application, and manage the cluster itself along using its attendant resources.

Kubectl Kubectl is just a command line configuration tool (CLI) for Kubernetes used to communicate with master node of kubernetes. Kubectl includes a config file called kubeconfig, this file has the information about server and authentication information to gain access to the API Server.

Kubernetes Master Kubernetes Master is just a main node in charge of managing the entire kubernetes clusters. It handles the orchestration of the worker nodes. It's three primary elements that look after communication, scheduling and controllers.

• • •

API Server - Kube API Server interacts with API, Its a frontend of the kubernetes control plane.

Scheduler - Scheduler watches the pods and assigns the pods to operate on specific hosts.

Kube Controller Manager - Controller manager runs the controllers in background that runs different tasks in Kubernetes cluster.

Some of the controllers are, • • • • • • • •

Node controller - Its in charge of noticing and responding when nodes go down.

Replication controllers - It maintains how many pods. It controls how many identical copies of a pod ought to be running somewhere on the cluster.

Endpoint controllers joins services and pods together.

Services account and Token controllers handles access managements.

Replicaset controllers ensure quantity of replication of pods running at all time.

Daemonsets controller ensure all nodes run a copy of specific pods.

Jobs controller may be the supervisor process for pods carrying out batch jobs Services enable the communication.

Etcd etcd is just a simple distribute key value store. kubernetes uses etcd as its database to store all cluster datas. some of the data stored in etcd is job scheduling information, pods, state information and etc.

Worker Nodes Worker nodes will be the nodes where the application form actually running in kubernetes cluster, it can be know as minion.

Container Platform should be running on each worker nodes and it works as well as kubelet to operate the containers, This is why we use Docker engine and protects managing images and containers. We are able to also use other container platforms like CoreOS, Rocket.

Requirements of Worker Nodes: • • • •

kubelet should be running Docker container platform kube-proxy should be running supervisord

Kubelet Kubelet is the primary node agent that runs on each nodes and reads the container manifests, ensures that containers are running and healthy.

Kube-proxy Kube-proxy is a process helps us to own network proxy and loadbalancer for the services in one worker node. It performs network routing for tcp and udp packets, and performs connection folding. Worker nodes can come in contact with internet via kubeproxy.

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