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This is a multiplayer online tank game originally written by Daniel Azuma, Greg Hill, Kyle Rippey, and Ben Stephens during a study group covering Programming Elixir. It is a Phoenix umbrella application with a Javascript front-end.

Running a development server

This procedure will get the server running on your local workstation.


Generally, you should know how to run Phoenix applications. See the Phoenix guides for more details.

  1. Install elixir:
  2. Install hex: mix local.hex
  3. Install node.js:

Running a development server

  1. Install dependencies with mix deps.get
  2. Start Phoenix endpoint with mix phx.server

Now you can visit localhost:4000 from your browser.

Production deployment with Google Kubernetes Engine

This procedure will guide you through building the tanx server as an OTP release in a Docker image, and deploying that image to Kubernetes via Google Kubernetes Engine.


  1. Set up a project on Google Cloud Console if you don't have one, and enable billing.

    Optional: Set the PROJECT_ID environment variable in your shell, to the ID of the project you created. Some commands below will use this variable substitution. (Or you can just substitue the value yourself.)

  2. Install the Google Cloud SDK on your workstation if you don't have it. This includes:

    1. Install gcloud. See the quickstarts if you need instructions.

    2. Install kubectl, the command line for controlling Kubernetes:

      gcloud components install kubectl
    3. Log in using gcloud so it can access your cloud account and resources.

      gcloud auth login
  3. Configure gcloud for your project.

    1. Set the default project. (Substitute your project ID.)

      gcloud config set project ${PROJECT_ID}
    2. Set a default zone (i.e. data center location). I think "us-central1-c" is generally a good one for much of the US, but you may choose one closer to your location.

      gcloud config set compute/zone us-central1-c
  4. Enable the Kubernetes Engine API and Container Builder API, using the following commands:

    gcloud services enable
    gcloud services enable
  5. Optional: if you want to do local builds, install Docker. This is not needed if you just want to deploy.


Tanx builds are done in two stages. First, you build base images that include precompiled dependencies, and build tools such as webpack. This build can take several minutes to complete. Then, a normal application build uses those base images and just builds the app itself, which is usually pretty quick. Generally, you must perform a base build once at the beginning, and then any time your dependencies change. Otherwise, you can perform normal builds.

Tanx uses Google's Cloud Build service to build Docker images in the cloud. The builds are based on bitwalker's Alpine-Erlang image, and use Distillery to produce an OTP release that can be run by Kubernetes or any other container orchestration system.

To perform a base build:

gcloud builds submit --config deploy/built-base.yml .

The period at the end is required; it is the root directory for the application you are building. This builds the base images (including precompiling the hex dependencies and node module tools) and uploads them to your project.

Once that is done, you can perform an application build using the base images:

gcloud builds submit --config deploy/build-tanx.yml .

This builds the application image itself and uploads it to your project. The image is uploaded as${PROJECT_ID}/tanx:latest.

Thereafter, you can rebuild the application by just performing application builds. Another base build is required whenever the dependencies change.

Local builds (optional)

You may also build images locally using Docker. To build the base images:

docker build -f deploy/Dockerfile-builder-base -t tanx-builder-base .
docker build -f deploy/Dockerfile-runtime-base -t tanx-runtime-base .

Note that Docker 17.05 or later is required.

Then, to perform an application build using those base images:

docker build -f deploy/Dockerfile-tanx -t tanx .

You may run a local build using:

docker run --rm -p 8080:8080 tanx

This will run on port 8080. You may need to use docker kill to stop the container.

Create a cluster

Now we'll set up Google Kubernetes Engine to host an online tanx server.

  1. Choose a cluster name. For the rest of these instructions, I'll assume that name is "tanx-cluster-1".

  2. Create the cluster.

    gcloud container clusters create tanx-cluster-1 --num-nodes=2

    You can of course replace the cluster name with a name of your choosing, as well as change the number of nodes in the cluster and the machine type. For now, the defaults will get you started.

  3. Configure gcloud to use your cluster as default so you don't have to specify it every time for the remaining gcloud commands.

    gcloud container clusters get-credentials tanx-cluster-1
    gcloud config set container/cluster tanx-cluster-1

    Replace the name if you named your cluster differently.

  4. Check the cloud console at to make sure your cluster is running. Note that once the cluster is running, you will be charged for the VM usage.

  5. The app will need to access the kubernetes API so it can configure the OTP cluster. To set up that access, first give yourself the ability to edit your cluster's role bindings.

    kubectl create clusterrolebinding my-admin-binding \
      --clusterrole cluster-admin \
      --user $(gcloud config get-value account)
  6. Now give the necessary access to the cluster default service account. The necessary role and binding objects are provided in a config file:

    kubectl create -f deploy/cluster-roles.yml

Deploy to the cluster

A production deployment comprises two parts: a cluster of running containers managed by a Kubernetes deployment, and a front-end load balancer.

We'll assume that you've built the image and created the Kubernetes cluster as described above.

First we'll create the deployment and load balancer:

kubectl create -f deploy/tanx-deployment.yml

This will create the Kubernetes resources and start up containers in pods. The initial deployment, however, just runs nginx in a container (rather than your app). So next you'll need to set the image:

kubectl set image deployment/tanx${PROJECT_ID}/tanx:latest

You may view the running pods using:

kubectl get pods

And the load balancer using:

kubectl get service

Initially, the "external IP" for the service will be pending while Kubernetes Engine works to procure an IP address for you. If you rerun the get service command, eventually the IP address will appear. You can then point your browser at that URL to view the running application.

Updating the app

To update the tanx app to reflect changes you have made, rebuild with a new version tag. To supply a version tag, pass a _BUILD_ID substitution into the build command. For example, to tag a build as v2, do this:

gcloud builds submit --config deploy/build-tanx.yml \
  --substitutions _BUILD_ID=v2 .

Now the new image${PROJECT_ID}/tanx:v2 will be available in your project's container registry. You may deploy it by setting the pod's image to the new image:

kubectl set image deployment/tanx${PROJECT_ID}/tanx:v2

This performs a "rolling" update for zero downtime deploys.

If you do not provide a _BUILD_ID, then the tag will default to latest. For example, in the initial application build we did previously, we did not provide a _BUILD_ID, so that image was tagged as${PROJECT_ID}/tanx:latest.

Remember that if dependencies have been updated, you need to perform a base build first, to prebuild the dependencies and update your base images. Do not pass a _BUILD_ID to the base build. Just perform the base build as described earlier, then perform an application build setting _BUILD_ID.

Cleanup and tearing down a deployment

To clean up a deployment of tanx and stop incurring hosting costs, do the following.

  1. Delete the service

    kubectl delete service tanx
  2. Wait for the load balancer to go away. This may take a few minutes. You may watch the output of the following command to see when this is complete.

    gcloud compute forwarding-rules list
  3. Delete the cluster. This will delete the resources making up the cluster, including the VMs provisioned.

    gcloud container clusters delete tanx-cluster-1


Tank game created by the Programming Elixir study group




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