Deploying a simple SpringBoot app to Docker for Mac Kubernetes

Several months back I spent some time playing with Kubernetes but it’s been a while so I need to retrace my steps to get back up to speed.

I’ve already have my Docker for Mac single Kubernetes node running (see here)

Next, I need to run a local Docker repository where I can push my Docker images for testing. I walked through these steps here.

I have a Docker image called examplespringboot that I want to deploy to my local single node Kubernetes cluster, so first up, tag it:

docker tag examplespringboot [ip of your docker machine]:5000/examplespringboot

And then push it:

docker push [ip of your docker machine]:5000/examplespringboot

With my local Kubernetes cluster up:

$ kubectl cluster-info
Kubernetes master is running at https://localhost:6443
KubeDNS is running at https://localhost:6443/api/v1/namespaces/kube-system/services/kube-dns/proxy

I created a deployment.yml for my Docker container using the example here:

apiVersion: apps/v1
kind: Deployment
metadata:
name: exampleservice
labels:
app: exampleservice
spec:
replicas: 1
selector:
matchLabels:
app: exampleservice
template:
metadata:
labels:
app: exampleservice
spec:
containers:
- name: exampleservice
image: 192.168.0.126:5000/examplespringboot
ports:
- containerPort: 8080

This references the Docker image from my local Docker repo.

To create the deployment:

$ kubectl create -f exampleservice-deployment.yml

Now you can describe the pod and the deployment and watch them come up:

$ kubectl get pods
NAME READY STATUS RESTARTS AGE
exampleservice-7b9b4b7db9-c7hx6 1/1 Running 0 9m

At this point the running pod is not exposed outside of the cluster. Following the steps here to expose as a service and assign an external ip:

$ kubectl expose deployment exampleservice --type=LoadBalancer --name=exampleservice

If you describe the service you now see it has a LoadBalancer Ingress assigned on localhost:

$ kubectl describe service exampleservice
Name: exampleservice
Namespace: default
Labels: app=exampleservice
Annotations:
Selector: app=exampleservice
Type: LoadBalancer
IP: 10.98.115.137
LoadBalancer Ingress: localhost
Port: 8080/TCP
TargetPort: 8080/TCP
NodePort: 30718/TCP
Endpoints: 10.1.0.16:8080
Session Affinity: None
External Traffic Policy: Cluster
Events:

Calling localhost:8080/example/hello on my service, now it’s up and responding:

{"message":"hello!"}

Done!

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