Deploying Spring Boot Applications on Kubernetes with Spring Boot Operator

Using Spring Boot Operator to deploy Spring Boot applications to Kubernetes.

Introduction

Deploying Spring Boot apps on Kubernetes can be cumbersome; the Spring Boot Operator simplifies the process by extending the Kubernetes API with Custom Resource Definitions (CRDs).

Packaging Docker Image

Before deployment, the Spring Boot app must be packaged into a Docker image. The article introduces Google’s open‑source Jib plugin for Maven/Gradle, noting that Jib‑built images run the Java process with pid = 1, which the operator resolves by enabling the ShareProcessNamespace flag.

Example command to build the image with Jib:

mvn com.google.cloud.tools:jib-maven-plugin:build \
-Djib.to.auth.username=${{ secrets.MY_USERNAME }} \
-Djib.to.auth.password=${{ secrets.MY_PASSWORD }} \
-Djib.container.jvmFlags=--add-opens,java.base/sun.nio.ch=ALL-UNNAMED \
-Djib.from.image=freemanliu/oprenjre:11.0.5 \
-Dimage=registry.cn-shanghai.aliyuncs.com/qingmuio/operator-demo/operator-demo:v1.0.0

Operator Quick Start

After building the image, install the operator in a Kubernetes cluster (a three‑node cluster is assumed). The quick‑install command is:

kubectl apply -f https://raw.githubusercontent.com/goudai/spring-boot-operator/master/manifests/deployment.yaml

The console output shows the creation of namespaces, CRDs, RBAC resources, services, and the operator deployment.

Verify the installation with:

kubectl get po -n spring-boot-operator-system

Deploying the Demo Application

Create a CRD yaml (Demo.yaml) that defines a SpringBootApplication resource with name and version. Apply it:

kubectl apply -f Demo.yaml

The operator creates the corresponding pods and service. The article demonstrates checking pod status, verifying the ShareProcessNamespace setting, and accessing the service via curl.

Scaling and Cleanup

To scale replicas, add a replicas field to Demo.yaml and re‑apply. Deleting the application is done with:

kubectl delete -f Demo.yaml

Deploying a Private Image

Create a Docker‑registry secret, then reference it in the CRD’s imagePullSecrets field. Provide a full example yaml with image, replicas, resources, health check paths, and node affinity.

Graceful Shutdown

Enable the Spring Boot shutdown endpoint in application.yml and expose it via a custom GET controller.

@RestController
public class ShutdownController {
    @Autowired
    private ShutdownEndpoint shutdownEndpoint;

    @GetMapping("/spring/shutdown")
    public Map
shutdown(HttpServletRequest request) {
        return shutdownEndpoint.shutdown();
    }
}

Node Affinity Example

Label nodes with zones (cn‑i, cn‑h, cn‑g) and configure the CRD’s nodeAffinity to distribute pods across zones.

Custom Operator Installation

Modify the operator Deployment (spring‑boot‑operator‑controller‑manager) to set environment variables such as IMAGE_REPOSITORY, resource requests, health check paths, replica count, and node‑affinity parameters.

Appendix

Provides a table of environment variables used by the operator.