Kotlin is a JVM language that is gaining popularity for its Concurrency and Coroutines support. Kubernetes is a container orchestration platform that is widely used for deploying, managing, and scaling containerized applications.
In this article, we will see how to use Kotlin and Kubernetes to deploy and scale your applications. We will also learn about some of the best practices for using these technologies together.
The first step in deploying applications on Kubernetes is to containerize them. We can use any containerization technology like Docker, rkt, or LXD. In this article, we will use Docker.
Docker is a containerization platform that makes it easy to package and deploy applications. It uses Linux containers to create isolated environments for your applications.
To containerize our Kotlin application, we will first need to create a Dockerfile
. A Dockerfile
is a text file that contains instructions for docker on how to build a docker image.
The following is a simple Dockerfile
for a Kotlin application:
FROM openjdk:8-jdk-alpine
VOLUME /tmp
ARG JAR_FILE
COPY ${JAR_FILE} app.jar
ENTRYPOINT ["java","-jar","/app.jar"]
This Dockerfile
uses the openjdk:8-jdk-alpine
docker image as the base image. It then creates a volume at /tmp
and copies the app.jar
file to the container. The ENTRYPOINT
instruction is used to specify the command that will be run when the container is started.
Now that we have our Dockerfile
, we can build a docker image using the docker build
command. The following is the command to build a docker image from our Dockerfile
:
docker build -t kotlin-app:latest .
This command will build a docker image with the tag kotlin-app:latest
. We can now run our application in a docker container using the docker run
command.
docker run -d -p 8080:8080 kotlin-app:latest
This command will start our container in detached mode and expose port 8080
of the container to port 8080
on the host. We can now access our application at http://localhost:8080
.
Now that we have our application containerized, we can deploy it on Kubernetes. Kubernetes is a container orchestration platform that can be used to deploy, manage, and scale containerized applications.
There are many ways to deploy applications on Kubernetes. In this article, we will use the kubectl
command-line tool.
The kubectl
tool can be used to create and manage Kubernetes resources. We will use it to create a Deployment
resource. A Deployment
resource is used to manage the deployment of applications on Kubernetes.
The following is the kubectl
command to create a Deployment
resource for our application:
kubectl create deployment kotlin-app --image=kotlin-app:latest
This command will create a Deployment
resource with the name kotlin-app
. It will use the kotlin-app:latest
docker image for the deployment.
Once the Deployment
resource is created, Kubernetes will create a Pod
to run our application. A Pod
is a group of one or more containers that are deployed together on Kubernetes.
The Pod
for our application will be created in the default
namespace. We can view the Pod
using the kubectl get pods
command.
kubectl get pods
NAME READY STATUS RESTARTS AGE
kotlin-app-7567cf6b7f-x8b8j 1/1 Running 0 2m9s
We can see that the Pod
is up and running. We can now access our application at http://localhost:8080
.
Kubernetes makes it easy to scale your applications. We can use the kubectl
tool to scale our application.
The following is the command to scale our application to 10 replicas:
kubectl scale deployment kotlin-app --replicas=10
This command will scale our Deployment
resource to 10 replicas. Kubernetes will create additional Pods
to run the additional replicas. We can view the Pods
using the kubectl get pods
command.
kubectl get pods
NAME READY STATUS RESTARTS AGE
kotlin-app-7567cf6b7f-x8b8j 1/1 Running 0 9m
kotlin-app-7567cf6b7f-b4vh2 1/1 Running 0 9m
kotlin-app-7567cf6b7f-4xb4p 1/1 Running 0 9m
kotlin-app-7567cf6b7f-c66r8 1/1 Running 0 9m
kotlin-app-7567cf6b7f-f8j8k 1/1 Running 0 9m
kotlin-app-7567cf6b7f-hbk8r 1/1 Running 0 9m
kotlin-app-7567cf6b7f-kxw6k 1/1 Running 0 9m
kotlin-app-7567cf6b7f-mjsjl 1/1 Running 0 9m
kotlin-app-7567cf6b7f-nlx89 1/1 Running 0 9m
kotlin-app-7567cf6b7f-snx4x 1/1 Running 0 9m
We can see that Kubernetes has created 10 Pods
to run our 10 replicas. We can now access our application at http://localhost:8080
.
Here are some best practices for using Kotlin and Kubernetes:
Use a JVM language like Kotlin for developing applications that will be deployed on Kubernetes. This will allow you to use the Concurrency and Coroutines features of Kotlin to write efficient and scalable applications.
Use Kubernetes resources like Deployment
and Service
to manage the deployment and scaling of your applications.
Use the kubectl
tool to interact with Kubernetes resources.
Use Docker
to containerize your applications.
Use the kubectl
tool to scale your applications.