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Deploy docker image using kubernetes

Introduction

This is a Continuation of this article related to Docker. Kubernetes is a Container Orchestration Tool. It is used when our Application is distributed in Multiple Containers. Kubernetes Job is to Monitor, Scale, Restart Containers automatically even if containers are spread across multiple nodes.

This Article targets the below areas in explaining how to use Kubernetes to Deploy the docker image with simple Steps. To create Docker image, refer this link,

  1. What is Kubernetes
  2. Features of Kubernetes
  3. Kubernetes Functions
  4. How Kubernetes Works
  5. Kubernetes (Service & POD Interaction)
  6. Ingress (High Level)
  7. To Set up Kubernetes Dashboard
  8. To Set up the Metric Server
  9. Kubernetes Commands

Prerequisites

1.       Should have knowledge in developing Service API using .Net Core (or) .Net Framework. I have used .Net core to create the service.

2.       Should have knowledge in Docker and its Commands.

3.       Docker and Kubernetes should be Installed and Running on Your Machine.


Before learning Kubernetes, checkout the below topics for better understanding on the need of Docker and Kubernetes.

1.       Limitations of Monolithic Application, refer here.

2.       Why Micro Service and its Limitation, refer here.

3.       Why Docker and Kubernetes is needed, refer here.


Below are few challenges in using Docker Deployment,
  • Monitoring - Each Service’s Monitoring is difficult. Monitoring is needed to ensure there is 100% availability of Service.
  • Scaling - With Docker Deployment we can’t scale the deployment automatically. Auto Scaling is needed if the container (i.e Service) is getting more load on it.
  • Manual Intervention - If Kubernetes is not present, we need to manage it manually and it is difficult & challenging Process.
  • Managing Containers - Managing Container on multiple Servers become difficult.

1. What is Kubernetes

AboutKubernetes.png


Kubernetes is a Container Orchestration Tool. It is used when our Application is distributed in Multiple Containers. Kubernetes Job is to Monitor, Scale, Restart Containers automatically even if containers are spread across multiple nodes.

2. Features of Kubernetes

Features Of Kubernetes.png



3. Kubernetes Functions

KubernetesArchitecture_One.png
4. How Kubernetes Works

Kubernetes is a Cluster. Master have several nodes inside it.

How_Kubernetes_Works.png
K - Master
  • Schedule container on the nodes.
  • Monitor the Nodes
  • Monitor the Container Running inside the Nodes.
  • It keeps the Track of the Logs of what operation is performed on each container.

K – Nodes (Worker Node)
  • Processing the Request
  • Sending API Calls 
Kubernetes will run both on the Master and the Node and interacting with each other as its one System. It’s easy to add more nodes to the existing Cluster

4. Kubernetes (Service & POD Interaction)

Kubernetes_Service_POD.png
Deployment will handle the POD deployment by specifying an image and number for replicas Image specified during the deployment will be present in the each POD.

Service is an internal Load balancer for all the PODs which is running inside the cluster. It caters the user request to the PODs

5. Ingress (High Level)

Kubernetes_Ingress_Service_POD.png
Ingress - If an Application is deployed in Multiple Services, Ingress will direct to the Service based on the Configuration done inside it.

7. To Set up Kubernetes Dashboard

Use the below command to setup the Dashboard,

kubectl apply –f https://raw.githubusercontent.com/kubernetes/dashboard/v1.10.1/src/deploy/recommended/kubernetes-dashboard.yaml

To deploy and View Dashboard.

Kubectl proxy

Above command will deploy the dashboard on your system and will be able to access the link like given below.

http://127.0.0.1:8001/api/v1/namespaces/kube-system/services/https:kubernetes-dashboard:/proxy/#!/login

There are two ways to login into the Dashboard,

1.       Using Config

2.       Using Token

Use the below commands to log in into the above Link.

PS C:\WINDOWS\system32> $TOKEN=((kubectl -n kube-system describe secret default | Select-String "token:") -split " +")[1]

PS C:\WINDOWS\system32> kubectl config set-credentials docker-for-desktop --token="${TOKEN}"

User "docker-for-desktop" set. à Response of the above Commands

Above command will update the .config file with the Token Information which is present in the .kube Folder. You can either upload the “Config” file (or) Token to enter into the Kubernetes Dashboard.


8. To Set up the Metric Server

git clone https://github.com/kubernetes-incubator/metrics-server.git
cd metrics-server
kubectl apply -f deploy/1.8+/

Refer this Article for brief understanding on the Metric Server

Once it is installed, use the below command to get the metrics of the deployment.

kubectl top node

NAME                

CPU(cores)  

CPU%     

MEMORY(bytes)  

MEMORY%

docker-for-desktop

292m

14%      

1265Mi

67%

 

9.  Kubernetes Commands

Mycurrentserviceapi à Consider this is a Service API image Name

·         Using the below command, we can deploy docker image using Kubernetes Command.

kubectl run mycurrentserviceapikube --image=mycurrentserviceapi --port=80 --requests=cpu=200m --image-pull-policy=IfNotPresent

·         To expose the deployment, use the below command to expose the Service.

kubectl expose deployment mycurrentserviceapikube --type=NodePort

·         To get the details of the Service, use the below command.

kubectl get svc mycurrentserviceapikube

·         To describe the Service Deployment, use the below command.

 kubectl describe services mycurrentserviceapikube

·         To enable Auto Scale on the Deployment

kubectl autoscale deployment mycurrentserviceapikube --cpu-percent=50 --min=1 --max=10

Below are the Main Commands which will be used to manage the deployment of Docker Image using Kubernetes Commands.

          To view all nodes running on a System

                kubectl get nodes

          To view container PODs

                 kubectl get pods

          To view container PODs

                kubectl get pods -o wide

          To View all PODs running on a System

                kubectl get pods --all-namespaces

          To View where PODs are running

                kubectl get pods --all-namespaces -o wide

          To Run Service

                 kubectl run mycurrentserviceapikube --image=mycurrentserviceapi --port=80 --requests=cpu=200m --image-pull-policy=IfNotPresent

          To expose Service

                kubectl expose deployment mycurrentserviceapikube --type=NodePort

          To get HPA

                kubectl get hpa

          To view all Services

                kubectl get svc

          To get Service Information

                 kubectl get svc mycurrentserviceapikube

          To describe Service

                kubectl describe services mycurrentserviceapikube

          To get Deployment

                kubectl get deployments

          To Scale Container

                 kubectl scale deploy mycurrentserviceapikube --replicas=2

          To Auto Scale

                kubectl autoscale deployment mycurrentserviceapikube --cpu-percent=50 --min=1 --max=10

          To Delete AutoScale HPA

                kubectl delete hpa mycurrentserviceapikube

          To Delete Deployment

                kubectl delete deployment mycurrentserviceapikube --namespace=default

          To Delete Service

                kubectl delete svc mycurrentserviceapikube


That's it! Hope this article given an overview of Kubernetes and its uses. To become Proficient in Docker & Kubernetes, it needs Practical Implementation using Docker, converting Application code into Docker Image and Deploy it using Kubernetes. Happy Learning!

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Raj Kumar
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sivasankari
Good Post. Thanks for giving detailed knowledge on Kubernetes. The pictorial representation gives better understanding.
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