Spring Boot Kubernetes Integration

Spring Boot seamlessly integrates with Kubernetes to provide scalable, containerized applications. This guide explores how to deploy and manage Spring Boot applications in a Kubernetes cluster.

✨ Why Use Kubernetes for Spring Boot?

• Scalability: Automatically scale applications based on traffic.
• Self-Healing: Kubernetes restarts failed containers automatically.
• Declarative Configuration: Manage infrastructure with YAML configurations.
• Load Balancing & Service Discovery: Built-in support for routing requests efficiently.
• Efficient Resource Utilization: Optimize CPU and memory usage dynamically.

✨ Prerequisites

Ensure you have the following:

• ☕ Java Development Kit (JDK) 17+
• 📦 Maven or Gradle installed
• 🛠 Docker installed and running
• 🌐 Kubernetes Cluster (Minikube or a cloud provider like AWS EKS, GKE, or AKS)
• 🛠 kubectl installed for managing Kubernetes

🛠 Step 1: Add Dependencies

Add the necessary dependencies for Spring Boot Web and Actuator to expose health endpoints.

Maven Configuration:

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-actuator</artifactId>
    </dependency>
</dependencies>

Gradle Configuration:

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation 'org.springframework.boot:spring-boot-starter-actuator'
}

📖 Step 2: Create a Simple Spring Boot Application

Define a REST endpoint to deploy inside Kubernetes.

• Java
• Kotlin

package com.example.kubernetes;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@RestController
public class KubernetesApplication {

    public static void main(String[] args) {
        SpringApplication.run(KubernetesApplication.class, args);
    }

    @GetMapping("/hello")
    public String hello() {
        return "Hello from Spring Boot running in Kubernetes!";
    }
}

package com.example.kubernetes

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.web.bind.annotation.GetMapping
import org.springframework.web.bind.annotation.RestController

@SpringBootApplication
@RestController
class KubernetesApplication {

    @GetMapping("/hello")
    fun hello(): String = "Hello from Spring Boot running in Kubernetes!"
}

fun main(args: Array<String>) {
    runApplication<KubernetesApplication>(*args)
}

💪 Step 3: Create Kubernetes Deployment and Service

Create a deployment.yaml file:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-boot-app
spec:
  replicas: 2
  selector:
    matchLabels:
      app: spring-boot-app
  template:
    metadata:
      labels:
        app: spring-boot-app
    spec:
      containers:
        - name: spring-boot-app
          image: myproject:0.0.1-SNAPSHOT
          ports:
            - containerPort: 8080

Create a service.yaml file:

apiVersion: v1
kind: Service
metadata:
  name: spring-boot-service
spec:
  type: LoadBalancer
  selector:
    app: spring-boot-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080

Apply the configurations:

kubectl apply -f deployment.yaml
kubectl apply -f service.yaml

▶️ Running the Application

Once deployed, retrieve the service URL:

kubectl get services

Test the endpoint:

curl -X GET http://your-service-ip/hello

Expected Output:

Hello from Spring Boot running in Kubernetes!

Spring Boot provides seamless integration with Kubernetes, enabling scalable and resilient applications. Whether for microservices, load balancing, or orchestration, Kubernetes is the go-to platform for deploying Spring Boot applications efficiently.