This guide walks you through writing a simple Ballerina service, building it, and deploying it on Kubernetes.

Code to Cloud is a compiler extension, which is packed with Ballerina. It eases generating the artifacts required for the cloud from your Ballerina code. Currently, you could generate Docker and Kubernetes artifacts from the Ballerina code. This process encourages you to write cloud-ready code from day one without any additional effort.

Set up the prerequisites

To complete this tutorial, you need:

1. Ballerina 2201.0.0 (Swan Lake) or greater
2. A text editor

   Tip: Preferably, Visual Studio Code with the Ballerina extension installed.

3. A command terminal
4. Docker installed and configured in your machine
5. A Docker Hub account
6. Kubectl installed and configured in a Kubernetes cluster

Create the service package

Ballerina uses packages to group code. You need to create a Ballerina package and write the business logic in it. In the terminal, execute the command below to create the Ballerina package for the API implementation.

Info: For more information on Ballerina packages, see Organize Ballerina code.

$ bal new greeter

You view the output below.

Created new package 'greeter' at greeter.

This creates a directory named covid19 with the default module along with a sample code for the service as shown below.

.
greeter/
├── Ballerina.toml
└── main.bal

Create the Ballerina service

To write a Ballerina program that returns a Hello, World! string upon invoking the resource, replace the main.bal content with the code below.

import ballerina/http;

listener http:Listener httpListener = new (8080);
service / on httpListener {
    resource function get greeting() returns string { 
        return "Hello, World!"; 
    }
}

Set the Code to Cloud configurations

Update the Ballerina.toml file

To enable the code to cloud functionality in the Ballerina package, add the cloud="k8s" property below to the build-options in the Ballerina.toml file.

[build-options]
cloud = "k8s"

Note: If you want to deploy your Ballerina service only on Docker, add the cloud="docker" property to the build-options in the Ballerina.toml file.

Create the Cloud.toml file

Create a file named Cloud.toml in the package directory and add the content below.

Info: Make sure to replace the value of the repository field with your Docker hub repository name.

[container.image]
repository="wso2inc" # Docker hub repository name.
name="greeter" # container name
tag="latest"

Build the package

Execute the code below to build the Ballerina package.

$ bal build

You view the output below.

Compiling source
        example/greeter:0.1.0

Generating executable

Generating artifacts...

        @kubernetes:Service                      - complete 1/1
        @kubernetes:Deployment                   - complete 1/1
        @kubernetes:HPA                          - complete 1/1
        @kubernetes:Docker                       - complete 2/2 

        Execute the below command to deploy the Kubernetes artifacts: 
        kubectl apply -f /home/example/greeter/target/kubernetes/greeter

        Execute the below command to access service via NodePort: 
        kubectl expose deployment greeter-deployment --type=NodePort --name=greeter-svc-local

Info: This generates the cloud artifacts inside the target/ directory.

Push the Docker image

Execute the command below to push the created Docker image into Docker Hub for the cluster to get access to the previously built container.

Info: Replace wso2inc with your repository name.

$ docker push wso2inc/greeter:latest

You view the output below.

The push refers to repository [docker.io/wso2inc/greeter]
latest: digest: sha256:c1acf5165848d70c347a970d6b5c32f63669cdbb0d4c1daca2c91cfbe32f61b2 size: 13718

Deploy on Kubernetes

Execute the command below to deploy the Ballerina application into the Kubernetes cluster.

$ kubectl apply -f /home/example/greeter/target/kubernetes/greeter

You view the output below.

service/greeter-svc created
deployment.apps/greeter-deployment created
horizontalpodautoscaler.autoscaling/greeter-hpa created

Learn more

For in-depth information about executing these deployed applications and the supported customizations in code to cloud, see Code to Cloud deployment.