> If this topic does not interest you, you can safely skip ahead! While we use what we built in the following parts, you can still understand what is going on without reading this article.
Terraform is an Infrastructure-as-Code tool. It allows us to define our infrastructure in a declarative way and then apply the changes to our cloud provider. If you have never used it before, I would recommend checking out some of their [tutorials](https://developer.hashicorp.com/terraform/tutorials) to get you started.
I will only `apply` our configuration at the end, to keep this post short. If you are developing this, I would recommend running `terraform plan`&`terraform apply` in between the steps to make sure everything so far works as expected.
Let us create our main terraform file:
```hcl
# dev-env.tf
terraform {
# In this block we will later define all providers we use.
required_providers {}
}
```
#### SSH Key
As we try to keep the development environment mostly self-contained, we start by creating an SSH Key that we can use to connect to our servers:
```hcl
terraform {
required_providers {
tls = {
source = "hashicorp/tls"
version = "4.0.4"
}
local = {
source = "hashicorp/local"
version = "2.4.0"
}
}
}
# This will generate a new random private key and save it to the Terraform state
resource "tls_private_key" "ssh" {
algorithm = "ED25519"
}
# This writes out the private key to a file in the current directory.
# We can use this to connect to our servers through SSH later.
resource "local_sensitive_file" "ssh" {
content = tls_private_key.ssh.private_key_openssh
filename = "${path.module}/.dev-env.ssh"
}
```
Now is a good time to add some Terraform specific files to our `.gitignore`:
```gitignore
# .gitignore
# Directory created by terraform for caches & internal state
.terraform
# The terraform state
terraform.tfstate
# Terraform makes a backup of the state before any operation
terraform.tfstate.backup
# Our private key we wrote in local_sensitive_file.ssh
.dev-env.ssh
# We will use this file in the next step to load credentials for the hcloud provider
credentials.auto.tfvars
# We will save the kubeconfig to this path in a later step
kubeconfig.yaml
```
#### Hetzner Cloud Resources
We will need:
- An SSH Key
- A Network & Subnet (for the `Routes` controller)
- A Control Plane Server
- 0 to X Worker Servers
To access the Hetzner Cloud API, we need to configure the provider with a token:
```hcl
terraform {
required_providers {
# Add to the others
hcloud = {
source = "hetznercloud/hcloud"
version = "1.42.1"
}
}
}
variable "hcloud_token" {
type = string
sensitive = true
}
# Configure the Hetzner Cloud Provider
provider "hcloud" {
token = var.hcloud_token
}
```
Now we can create create a new project in the [Clound Console](https://console.hetzner.cloud) and [generate a new API Token](https://docs.hetzner.com/cloud/api/getting-started/generating-api-token). This token will be saved in `credentials.auto.tfvars`. Because the file has the suffix `auto.tfvars`, Terraform will automatically use it.
```terraform
# credentials.auto.tfvars
hcloud_token = "YOUR_TOKEN"
```
Next, create the SSH Key:
```terraform
resource "hcloud_ssh_key" "default" {
name = "ccm-from-scratch dev env"
# Using the public key from the SSH Key we generated earlier
# This makes sure that the server is fully initialized before we install the Kubernetes cluster
provisioner "remote-exec" {
inline = ["cloud-init status --wait"]
}
}
resource "hcloud_server_network" "control" {
server_id = hcloud_server.control.id
subnet_id = hcloud_network_subnet.cluster.id
}
```
As we want to be able to scale the number of worker nodes, we will use a `count` to create multiple servers, besides that and the name prefix, the configuration are the same:
```terraform
variable "worker_count" {
type = number
default = 0
}
resource "hcloud_server" "worker" {
count = var.worker_count
name = "ccm-from-scratch-worker-${count.index}"
server_type = "cpx11"
location = "fsn1"
image = "ubuntu-22.04"
ssh_keys = [hcloud_ssh_key.default.id]
}
resource "hcloud_server_network" "control" {
for_each = hcloud_server.worker
server_id = each.id
subnet_id = hcloud_network_subnet.cluster.id
}
```
#### Kubernetes Cluster
As mentioned earlier, we will use `k3sup` to install `k3s` and other dependencies on the servers and join them to the Cluster.
We will use the `null_resource` and a local provisioner to run these commands locally as soon as the servers are ready. The control plane server needs a different command from the worker nodes, so we will use two resources.
```terraform
terraform {
required_providers {
null = {
source = "hashicorp/null"
version = "3.2.1"
}
}
}
# We need to define some additional configuration values for the Kubernetes cluster
locals {
# The CIDR range for the Pods, must be included in the range of the
# network (10.0.0.0/8) but must not overlap with the Subnet (10.0.0.0/24)
cluster_cidr = "10.244.0.0/16"
# Path to write the kubeconfig to, should be the same as the path in our gitignore from earlier.
# path.module is the directory the `dev-env.tf` file is in.
Nice! We now have a working Kubernetes Cluster, so let's deploy our CNI solution Cilium to it. We are going to use the Cilium Helm Chart & and the `helm` Provider for Terraform to install it.
As with the hcloud provider, we need to configure Helm and tell it how to connect to the cluster.
`k3sup` wrote the config to a local file, and luckily the provider supports reading this _but_ we need to make sure that the file is actually written / the Cluster is initialized _before_ we can use it.
Terraform has the `depends_on` meta-argument, but this does not work on `providers`.
Instead we will create an intermediary `local_sensitive_file` resource that has `depends_on` specified, and use its output `filename` in the Helm provider config.
With the provider configured, we can install Cilium:
```terraform
resource "helm_release" "cilium" {
name = "cilium"
chart = "cilium"
repository = "https://helm.cilium.io"
namespace = "kube-system"
version = "1.13.1"
set {
name = "ipam.mode"
value = "kubernetes"
}
}
```
For our own purposes, we will need to create one more resource: a `Secret` containing the Hetzner Cloud API Token. We will use this later in the `cloud-controller-manager` to access the API.
We will use the `kubernetes` provider this time, which is configured similar to the `helm` provider:
Skaffold requires a configuration file. We need to specify which image to build & how our application should be deployed.
For Image building we will use [ko](https://ko.build/).
It produces very small images very quickly, and we do not need to write an _artisanal_ Dockerfile.
The `ko` builder by default builds & containerizes the `main.go` in the project root.
For deployment we use the `kubectl` deployer and point it at the `deploy.yaml` from the last section.
```yaml
# skaffold.yaml
apiVersion: skaffold/v4beta7
kind: Config
metadata:
name: ccm-from-scratch
build:
artifacts:
# Must match the image you used in deploy.yaml
- image: apricote/ccm-from-scratch
ko: {}
deploy:
kubectl:
manifests:
- deploy.yaml
```
TODO: SKAFFOLD_DEFAULT_REPO?
#### Babies first deploy
Lets try to deploy our application:
```shell
$ export KUBECONFIG=kubeconfig.yaml
$ export SKAFFOLD_DEFAULT_REPO? TODO
$ skaffold run
... TODO Output
```
> If you are using Docker Hub the first deployment will probably fail, Docker Hub sets new images to "private" by default.
> You need to configure an `ImagePullSecret` or make the image public in the Docker Hub settings.
> Afterward you can retry the `skaffold run` step and it should work.
If everything worked, you should now have a running `ccm-from-scratch` deployment in the `kube-system` namespace and `skaffold` should show some logs from the application.
```shell
$ kubectl get pods -n kube-system -l app=ccm-from-scratch
