In this post I will go through how to write a simple terraform module to install a Kubernetes GKE cluster.

pre reqs:

  • A GCP account
  • Terraform v0.11.11
  • gcloud CLI
  • kubectl 

Set up GCP project and service account:

In the GCP console create a new google project. Login with the cloud CLI 

gcloud auth login

Switch to your newly created project

gcloud config set project your-gcp-project

Create a service account 

gcloud iam service-accounts create your-gcp-project-sa

Link this service account to your project

gcloud projects add-iam-policy-binding your-terraform-project \ 
  --member “serviceAccount:your-gcp-project-sa@your-gcp-project.iam.gserviceaccount.com" \ 
  --role "roles/owner"

Create and download a private key for this service account (Terraform will use this to authenticate to your gcp project) 

gcloud iam service-accounts keys create “/path/you/choose/your-terraform-project-sa.json" \ 
   --iam-account "your-gcp-project-sa@your-gcp-project.iam.gserviceaccount.com"

Set up backend for remote terraform state 

Create a bucket to store terraform state 

gsutil mb -l eu gs://your-gcp-project-remote-state

Create a file named backend.tf and add the following to set up the google terraform provider 

terraform { 
  backend "gcs" { 
    bucket                    = "your-gcp-project-remote-state" 
    prefix                    = "terraform" 
    project                   = "your-gcp-project" 
    credentials               = "/path/you/choose/your-gcp-project-sa.json" 
  } 
}

Initialise the backend

 terraform init

This should result in something similar to the following:

Check that the remote state has been initialised (note - we’re not using workspaces yet therefore we’re working in the default workspace) 

gsutil cat gs://your-gcp-project-remote-state/terraform/default.tfstate

This resulting display should be something similar to:

{ 
    "version": 3, 
    "serial": 1, 
    "lineage": "2c1eae35-87b7-8d2a-556a-09ab57d0bff7", 
    "modules": [ 
        { 
            "path": [ 
                "root" 
            ], 
            "outputs": {}, 
            "resources": {}, 
            "depends_on": [] 
        } 
    ] 
}

Set up the Google provider:

Create a file named providers.tf with the following contents: 

provider "google" { 
  project                     = “your-gap-project" 
  region                      = "europe-west2" 
  zone                        = "europe-west2-a" 
  credentials                 = "${file(“/path/you/choose/your-gcp-project-sa.json")}" 
}

Initialise the provider:

terraform init

This should result in something similar to the following output:

Enable the container.googleapis.com API Service:

gcloud services enable container.googleapis.com

We’re now ready to start building stuff - let’s use terraform modules to do this as they are pretty cool 

Create your first Terraform module:

Create a directory called modules and under here create a directory called kubernetes_cluster (yes - we’re going to write a module to deploy a k8s cluster 🙂) cd to modules/kubernetes_cluster and create a file named k8s_main.tf 

mkdir -p modules/kubernetes_cluster 
cd modules/kubernetes_cluster 
touch k8s_main.tf

Add the following contents to  k8s_main.tf (Notice we’re not using any variables at the moment, this will come later) 

resource "google_container_cluster" "k8s_cluster" { 
  count              = "1" 
  name               = "terraform-from-scratch-k8s-cluster" 
  zone               = "europe-west2-a" 
  initial_node_count = "3" 
  project            = "terraform-from-scratch" 




  node_config { 
    oauth_scopes = [ 
      "https://www.googleapis.com/auth/compute", 
      "https://www.googleapis.com/auth/devstorage.read_only", 
      "https://www.googleapis.com/auth/logging.write", 
      "https://www.googleapis.com/auth/monitoring", 
    ] 
  } 
}

Now we need to call this module. To do this cd back up to your top level directory (where backend.tf and providers.tf reside) and create main.tf with the following contents. 

module "kubernetes-cluster" { 
  source = "modules/kubernetes_cluster" 
}

Initialise the new module: 

terraform init

Plan the build

terraform plan

If all looks well, run the build  

terraform apply -auto-approve

Update ~/.kube/config and set context to your new kubernetes cluster  

gcloud container clusters get-credentials your-gcp-project-k8s-cluster

Check connectivity  

kubectl get pods -n kube-system