Deploying Kotlin Application on Docker & Kubernetes

 

Overview

 In this post, We’ll show how you can launch Kotlin Application in Kubernetes. 

Kotlin is a new programming language from JetBrains. It first appeared in 2011 when JetBrains unveiled their project named “Kotlin”. Kotlin is an Open-Source Language.

Basically like Java, C and C++ - Kotlin is also “statically typed programming language”. Statically typed programming languages are those languages in which variables need not be defined before they are used.

Prerequisites

To follow this guide you need

• Kubernetes - Kubernetes is an open source platform that automates container operations and Minikube is best for testing Kubernetes.

• Kubectl - Kubectl is command line interface to manage Kubernetes cluster either remotely or locally. To configure kubectl in your machine follow this link.

• Shared Persistent Storage - Shared Persistent Storage is permanent storage that we can attach to the Kubernetes container so that we don`t lose our data even container died. We will be using GlusterFS as a persistent data store for Kubernetes container applications.

• Kotlin Application Source Code - Application Source Code is source code that we want to run inside a kubernetes container.

• Dockerfile - Dockerfile contains a bunch of commands to build Kotlin application.

• Container-Registry - The Container Registry is an online image store for container images.

Below mentioned options are few most popular registries.

• Private Docker Hub
• AWS ECR
• Docker Store
• Google Container Registry

Create a Dockerfile

The below mentioned code is sample dockerfile for Kotlin applications. In which we are using maven 3 as a builder for Kotlin applications and OpenJDK 8 as a base development environment. Alpine Linux is used due to its very compact size.

	FROM maven:3-alpine
	MAINTAINER XenonStack
	# Creating Application Source Code Directory
	RUN mkdir -p /usr/src/app
	# Setting Home Directory for containers
	WORKDIR /usr/src/app
	# Copying src code to Container
	COPY . /usr/src/app
	# Building From Source Code
	RUN mvn clean package
	# Setting Persistent drive
	VOLUME ["/kotlin-data"]
	# Exposing Port
	EXPOSE 8082
	# Running Kotlin Application
	CMD ["java", "-jar", "target/<name of your kotlin jar>.jar"]

view rawCreating a Docker File For Deploying Kotlin on Kubernetes hosted with ❤ by GitHub

Building Kotlin Application Image

The below mentioned command will build your application container image.

$ docker build -t <name of your Kotlin application>:<version of application>

view rawBuilding Kotlin Application Image For Deploying Kotlin on Kubernetes hosted with ❤ by GitHub

Publishing Container Image

 

Now we publish our Kotlin application container images to any container registry like Docker Hub, AWS ECR, Google Container Registry, Private Docker Registry.

I am using Docker Hub registry to publish images to the Kubernetes cluster.

Create an account on Docker Hub and create a Public/Private Repository of you application name.

To login to your docker hub account, Execute below-mentioned command.

$ docker login

view rawLogging into Docker Hub for Deploying Kotlin on Kubernetes hosted with ❤ by GitHub

Now we need to retag Kotlin application image and push them to docker hub container registry.

To Retag application container image

$ docker tag <name of your application>:<version of your application> <your docker hub account >/<name of your repository >:<version of your application>

view rawRetagging Application Container Image for Deploying Kotlin On Kubernetes hosted with ❤ by GitHub

To Push application container Images

$ docker push <your docker account >/<name of your repository >:<version of your application>

view rawPushing Application Container Image for Deploying Kotlin on Kubernetes hosted with ❤ by GitHub

Similarly, we can push images to any of above-mentioned container registry like Docker Hub, AWS ECR, Google Container Registry, Private Docker Registry etc.

Creating Deployment files for Kubernetes

Deploying application on kubernetes with ease using deployment and service files either in JSON or YAML format.

• Deployment File

Following Content is for “<name of application>.deployment.yml” file of python container application.

	apiVersion: extensions/v1beta1
	kind: Deployment
	metadata:
	name: <name of application>
	namespace: <namespace of Kubernetes>
	spec:
	replicas: 1
	template:
	metadata:
	labels:
	k8s-app: <name of application>
	spec:
	containers:
	- name: <name of application>
	image: <image name >:<version tag>
	imagePullPolicy: "IfNotPresent"
	ports:
	- containerPort: 8082
	volumeMounts:
	- mountPath: /kotlin-data
	name: <name of application>
	volumes:
	- name: <name of application>
	emptyDir: {}

view rawCreating Deployment File For kubernetes for Deploying Kotlin on Kubernetes hosted with ❤ by GitHub

• Service File

Following Content is for “<name of application>.service.yml” file of python container application.

	apiVersion: v1
	kind: Service
	metadata:
	labels:
	k8s-app: <name of application>
	name: <name of application>
	namespace: <namespace of Kubernetes>
	spec:
	type: NodePort
	ports:
	- port: 7102
	selector:
	k8s-app: <name of application>

view rawService File For Deploying Kotlin on Kubernetes hosted with ❤ by GitHub

Running Kotlin Application on Kubernetes

Kotlin Application Container can be deployed either by kubernetes Dashboard or Kubectl (Command line).

I`m explaining command line that you can use in production Kubernetes cluster.

	$ kubectl create -f <name of application>.deployment.yml
	$ kubectl create -f <name of application>.service.yml

view rawRunning Kotlin Application on Kubernetes for Deploying Kotlin on Kubernetes hosted with ❤ by GitHub

Now we have successfully deployed Kotlin Application on Kubernetes.

Verification

We can verify application deployment either by using Kubectl or Kubernetes Dashboard.

 The below-mentioned command will show you running pods of your application with status running/terminated/stop/created.

  

$ kubectl get po --namespace=<namespace of kubernetes> | grep <application name>

view rawVerificiation on Deploying Kotlin on Kubernetes hosted with ❤ by GitHub

Result of above command

< name of your application >-1349584344-uah2u 1/1 Running 0 22d 10.233.84.18 k8-master

view rawResult of Verification Process for Deploying Kotlin on Kubernetes hosted with ❤ by GitHub

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