To play with these examples, you can install locally Kubernetes & Docker using Minikube within a Virtual Machine managed by a hypervisor (Xhyve, Virtualbox or KVM) if your machine is not a native Unix operating system.

When the Minikube is installed on your machine, you can start kubernetes using this command:

minikube start

You also probably want to configure your docker client to point the Minikube docker daemon with:

eval $(minikube docker-env)

This will make sure that the docker images that you build are available to the Minikube environment.

Kubernetes Reload Example

This example demonstrate how to use the reload feature to change the configuration of a spring-boot application at runtime.

The application consists of a timed bean that periodically prints a message to the console. The message can be changed using a config map.

Running the example

Once you have your environment set up, you can deploy the application using the fabric8 maven plugin:

mvn clean install fabric8:build fabric8:deploy -Pintegration

Changing the configuration

Create a yaml file with the following contents:

apiVersion: v1
kind: ConfigMap
metadata:
  name: reload-example
data:
  application.properties: |-
    bean.message=Hello World!
    another.property=value

A sample config map is provided with this example in the config-map.yml file.

To deploy the config map, just run the following command on Kubernetes:

kubectl create -f config-map.yml

As soon as the config map is deployed, the output of the application changes accordingly. The config map can be now edited with the following command:

kubectl edit configmap reload-example

Changes are applied immediately when using the event reload mode.

The name of the config map ("reload-example") matches the name of the application as declared in the application.properties file.

Note: If you are running in a Kubernetes environment where RBAC is enabled, you need to make sure that your pod has the right level of authorizations to access the K8s APIs or resources. To help you get started, a sample ServiceAccount and RoleBinding configuration is provided in src/k8s directory. These configuration needs to be applied to your K8s cluster and the newly created ServiceAccount needs to be attached to your pod spec like this:

      spec:
        containers:
          image: <image_loc>
          imagePullPolicy: IfNotPresent
          livenessProbe:
            failureThreshold: 3
            httpGet:
              path: /actuator/health
              port: 8080
              scheme: HTTP
            initialDelaySeconds: 180
            successThreshold: 1
          name: spring-boot
          ports:
          - containerPort: 8080
            name: http
            protocol: TCP
          - containerPort: 9779
            name: prometheus
            protocol: TCP
          readinessProbe:
            failureThreshold: 3
            httpGet:
              path: /actuator/health
              port: 8080
              scheme: HTTP
            initialDelaySeconds: 10
            successThreshold: 1
          securityContext:
            privileged: false
        serviceAccountName: <service_account_name>