akka-sample-cluster-kubernetes-scala

akka sample cluster with kubernetes discovery in scala

This is an example SBT project showing how to create an Akka Cluster on Kubernetes.

It is not always necessary to use Akka Cluster when deploying an Akka application to Kubernetes: if your application can be designed as independent stateless services that do not need coordination, deploying them on Kubernetes as individual Akka application without Akka Cluster can be a good fit. When coordination between nodes is necessary, this is where the Akka Cluster features become interesting and it is worth consider making the nodes form an Akka Cluster.

Kubernetes Instructions

Docker Desktop for Kubernetes

For Windows and Mac users, may be handier to use a Kubernetes cluster on Docker-Desktop. If you use Kubernetes on Docker Desktop, after turning it on, you should first issue:

export KUBECONFIG=~/.kube/config
kubectl config set-context docker-desktop

A script that comprises all steps involved is scripts/test_docker_desktop.sh. To run it, do:

cd akka-sample-cluster-kubernetes-java
scripts/test_docker_desktop.sh

Minikube

If you are using minikube for Kubernetes, please run the included scripts in the scripts directory.

Starting

First, package the application and make it available locally as a docker image:

sbt docker:publishLocal

Then akka-cluster.yml should be sufficient to deploy a 2-node Akka Cluster, after creating a namespace for it:

kubectl apply -f namespace.json
kubectl config set-context --current --namespace=appka-1
kubectl apply -f kubernetes/akka-cluster.yml

Finally, create a service so that you can then test http://127.0.0.1:8080 for 'hello world':

kubectl expose deployment appka --type=LoadBalancer --name=appka-service

To check what you have done in Kubernetes so far, you can do:

kubectl get deployments
kubectl get pods
kubectl get replicasets
kubectl cluster-info dump
kubectl logs appka-79c98cf745-abcdee   # pod name

To wipe everything clean and start over, do:

kubectl delete namespaces appka-1

How it works