Quickstart: Edit a Game Server

The following guide is for developers without Docker or Kubernetes experience, that want to use the simple-udp example as a starting point for a custom game server.

This guide addresses Google Kubernetes Engine and Minikube. We would welcome a Pull Request to expand this to include other platforms as well.

Prerequisites

  1. A Go environment
  2. Docker
  3. Agones installed on GKE or Minikube
  4. kubectl properly configured

To install on GKE, follow the install instructions (if you haven’t already) at Setting up a Google Kubernetes Engine (GKE) cluster. Also complete the “Enabling creation of RBAC resources” and “Installing Agones” sets of instructions on the same page.

To install locally on Minikube, read Setting up a Minikube cluster. Also complete the “Enabling creation of RBAC resources” and “Installing Agones” sets of instructions on the same page.

Modify the code and push another new image

Modify the simple-udp example source code

Modify the main.go file. For example:

Change main.go line 92:

From:

ack := "ACK: " + txt + "\n"

To:

ack := "ACK: Echo says " + txt + "\n"

Build Server

Since Docker image is using Alpine Linux, the “go build” command has to include few more environment variables.

>> go get agones.dev/agones/pkg/sdk
>> GOOS=linux GOARCH=amd64 CGO_ENABLED=0 go build -o bin/server -a -v main.go

Using Docker File

Create a new docker image

>> docker build -t gcr.io/[PROJECT_ID]/agones-udp-server:modified .

Note: you can change the image name “agones-udp-server” to something else.

If using GKE, push the image to GCP Registry

>> docker push gcr.io/[PROJECT_ID]/agones-udp-server:modified

Note: Review Authentication Methods for additional information regarding use of gcloud as a Docker credential helper and advanced authentication methods to the Google Container Registry.

If using Minikube, load the image into Minikube

>> docker save gcr.io/[PROJECT_ID]/agones-udp-server:modified | (eval $(minikube docker-env) && docker load)

Modify gameserver.yaml

Modify the following line from gameserver.yaml to use the new configuration.

    spec:
      containers:
      - name: agones-simple-udp
        image: gcr.io/[PROJECT_ID]/agones-udp-server:modified

If using GKE, deploy Server to GKE

Apply the latest settings to kubernetes container.

>> gcloud config set container/cluster [CLUSTER_NAME]
>> gcloud container clusters get-credentials [CLUSTER_NAME]
>> kubectl apply -f gameserver.yaml

If using Minikube, deploy the Server to Minikube

>> kubectl apply -f gameserver.yaml

Check the GameServer Status

>> kubectl describe gameserver

Verify

Let’s retrieve the IP address and the allocated port of your Game Server:

kubectl get gs simple-udp -o jsonpath='{.status.address}:{.status.ports[0].port}'

You can now communicate with the Game Server :

NOTE: if you do not have netcat installed (i.e. you get a response of nc: command not found), you can install netcat by running sudo apt install netcat.

nc -u {IP} {PORT}
Hello World!
ACK:  Echo says  Hello World!
EXIT

You can finally type EXIT which tells the SDK to run the Shutdown command, and therefore shuts down the GameServer.

If you run kubectl describe gameserver again - either the GameServer will be gone completely, or it will be in Shutdown state, on the way to being deleted.

Next Steps

If you want to perform rolling updates of modified game servers, see Quickstart Create a Game Server Fleet.