Building CI/CD Pipeline for Scala Application on Kubernetes

Overview of Scala Application

Scala is an object-oriented programming language. It provides support to functional programming. It also helps to remove bugs in complex applications. In this article, you get to know about Scala and Scala Applications on Kubernetes. Running Containers at any real-world scale requires container orchestration, and scheduling platform like Docker Swarm, Apache Mesos, AWS ECS but the most popular out of it is Kubernetes. Kubernetes is an open-source system for automating deployment and management of containerised applications. Continuous delivery is a branch of continuous integration. It concentrates on automating the software delivery process so that teams can quickly and confidently deploy their code to production at any point.

CI/CD Pipeline is a crucial part of the modern DevOps environment. Click to explore about, Continuous Integration and Continuous Delivery

What are the basics terminology for Scala Application?

To follow this guide you need -

• Kubernetes
• Kubectl
• Scala Application Source Code
• Dockerfile
• Container-Registry

Kubernetes

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

Kubectl

Kubectl is a command-line interface to manage Kubernetes cluster either remotely or locally. To configure kubectl on 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 when container dies. We will be using GlusterFS as the persistent data store for Kubernetes container applications.

Scala Application Source Code

It's source code will be run inside a Kubernetes container.

DockerFile

Dockerfile contains a bunch of commands to build PHP Laravel application.

Container Registry

The 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

Continuous delivery is a branch of continuous integration. It concentrates on automating the software delivery process. Source- Continuous Delivery Pipeline with Jenkins

How to write a Dockerfile for Scala Application?

FROM openjdk: 8
RUN apt - get update\ && apt - get install apt - transport - https - y
RUN echo "deb https://dl.bintray.com/sbt/debian /" | tee - a / etc / apt / sources.list.d / sbt.list\ && apt - key adv--keyserver hkp: //keyserver.ubuntu.com:80 --recv 2EE0EA64E40A89B84B2DF73499E82A75642AC823 \
 && apt - get update\ && apt - get install sbt - y\ && rm - rf /
 var / lib / apt / lists /*

Building Scala Base Image

$ docker build -t scala-sbt:0.13

Dockerfile (Application)

FROM scala - sbt: 0.13

MAINTAINER XenonStack

# Creating Home Directory in container
RUN mkdir - p / usr / src / app

# Setting Home Directory
WORKDIR / usr / src / app

# Copying src code to Container
COPY. / usr / src / app

# Compiling Scala Code
RUN sbt compile

# Exposing Port
EXPOSE 3000

# Running Scala Application
CMD["sbt", "run"]

Building Scala Application Image

$ docker build -t <name application="" of="" scala="" your="">:<version application="" of="">

Publishing Scala Application Container Image

• Login to Container Registry

$ docker login < dns link of private container registry >
 Username: xxxx
Password: xxxxx

• Retag Container Images

$ docker tag <name application="" of="" your="">:<version application="" of="" your=""> <privater name="" registry="">/<name of="" repository="" your="">:<version application="" of="" your="">

• Push Application container Images

$ docker push < privater registry name > /<name of="" repository="" your="">:<version application="" of="" your="">

Creating Deployment files in Scala Application for Kubernetes

apiVersion: extensions / v1beta1
kind: Deployment
metadata:
 name: < name of application >
 namespace: < namespace of Kubernetes >
 spec:
 replicas: < number of application pods >
 template:
 metadata:
 labels:
 k8s - app: < name of application >
 spec:
 containers:
 -name: < name of application >
 image: < image name > : < version tag >
 imagePullPolicy: "IfNotPresent"
ports:
 -containerPort: 9000

apiVersion: v1
kind: Service
metadata:
 labels:
 k8s - app: < name of application >
 name: < name of application >
 namespace: < namespace of Kubernetes >
 spec:
 type: NodePort
ports:
 -port: 9000
selector:
 k8s - app: < name of application >
 

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

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

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

• Read here about CI/CD Pipeline Tools and its Use Cases
• Explore here about Deploying Java Microservices Application on Kubernetes