We'll declare a Kubernetes cluster using the Typhoon Terraform module. Then apply the changes to create a resource group, virtual network, subnets, security groups, controller availability set, worker scale set, load balancer, and TLS assets.
Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and `calico` (or `flannel`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
## Requirements
* Azure account
* Azure DNS Zone (registered Domain Name or delegated subdomain)
* Terraform v0.12.6+ and [terraform-provider-ct](https://github.com/poseidon/terraform-provider-ct) installed locally
## Terraform Setup
Install [Terraform](https://www.terraform.io/downloads.html) v0.12.6+ on your system.
```sh
$ terraform version
Terraform v0.12.21
```
Add the [terraform-provider-ct](https://github.com/poseidon/terraform-provider-ct) plugin binary for your system to `~/.terraform.d/plugins/`, noting the final name.
Read [concepts](/architecture/concepts/) to learn about Terraform, modules, and organizing resources. Change to your infrastructure repository (e.g. `infra`).
```
cd infra/clusters
```
## Provider
[Install](https://docs.microsoft.com/en-us/cli/azure/install-azure-cli?view=azure-cli-latest) the Azure `az` command line tool to [authenticate with Azure](https://www.terraform.io/docs/providers/azurerm/authenticating_via_azure_cli.html).
```
az login
```
Configure the Azure provider in a `providers.tf` file.
Additional configuration options are described in the `azurerm` provider [docs](https://www.terraform.io/docs/providers/azurerm/).
## Fedora CoreOS Images
Fedora CoreOS publishes images for Azure, but does not yet upload them. Azure allows custom images to be uploaded to a storage account bucket and imported.
[Download](https://getfedora.org/en/coreos/download?tab=cloud_operators&stream=stable) a Fedora CoreOS Azure VHD image and upload it to an Azure storage account container (i.e. bucket) via the UI (quite slow).
az disk create --name fedora-coreos-31.20200323.3.2 -g GROUP --source https://BUCKET.blob.core.windows.net/fedora-coreos/fedora-coreos-31.20200323.3.2-azure.x86_64.vhd
az image create --name fedora-coreos-31.20200323.3.2 -g GROUP --os-type=linux --source /subscriptions/some/path/providers/Microsoft.Compute/disks/fedora-coreos-31.20200323.3.2
```
Set the [os_image](#variables) in the next step.
## Cluster
Define a Kubernetes cluster using the module `azure/fedora-coreos/kubernetes`.
Reference the [variables docs](#variables) or the [variables.tf](https://github.com/poseidon/typhoon/blob/master/azure/fedora-coreos/kubernetes/variables.tf) source.
## ssh-agent
Initial bootstrapping requires `bootstrap.service` be started on one controller node. Terraform uses `ssh-agent` to automate this step. Add your SSH private key to `ssh-agent`.
```sh
ssh-add ~/.ssh/id_rsa
ssh-add -L
```
## Apply
Initialize the config directory if this is the first use with Terraform.
```sh
terraform init
```
Plan the resources to be created.
```sh
$ terraform plan
Plan: 86 to add, 0 to change, 0 to destroy.
```
Apply the changes to create the cluster.
```sh
$ terraform apply
...
module.ramius.null_resource.bootstrap: Still creating... (6m50s elapsed)
module.ramius.null_resource.bootstrap: Still creating... (7m0s elapsed)
module.ramius.null_resource.bootstrap: Creation complete after 7m8s (ID: 3961816482286168143)
In 4-8 minutes, the Kubernetes cluster will be ready.
## Verify
[Install kubectl](https://kubernetes.io/docs/tasks/tools/install-kubectl/) on your system. Obtain the generated cluster `kubeconfig` from module outputs (e.g. write to a local file).
| ssh_authorized_key | SSH public key for user 'core' | "ssh-rsa AAAAB3NZ..." |
!!! tip
Regions are shown in [docs](https://azure.microsoft.com/en-us/global-infrastructure/regions/) or with `az account list-locations --output table`.
#### DNS Zone
Clusters create a DNS A record `${cluster_name}.${dns_zone}` to resolve a load balancer backed by controller instances. This FQDN is used by workers and `kubectl` to access the apiserver(s). In this example, the cluster's apiserver would be accessible at `ramius.azure.example.com`.
You'll need a registered domain name or delegated subdomain on Azure DNS. You can set this up once and create many clusters with unique names.
Reference the DNS zone with `azurerm_dns_zone.clusters.name` and its resource group with `"azurerm_resource_group.global.name`.
!!! tip ""
If you have an existing domain name with a zone file elsewhere, just delegate a subdomain that can be managed on Azure DNS (e.g. azure.mydomain.com) and [update nameservers](https://docs.microsoft.com/en-us/azure/dns/dns-delegate-domain-azure-dns).
### Optional
| Name | Description | Default | Example |
|:-----|:------------|:--------|:--------|
| controller_count | Number of controllers (i.e. masters) | 1 | 1 |
| worker_count | Number of workers | 1 | 3 |
| controller_type | Machine type for controllers | "Standard_B2s" | See below |
| worker_type | Machine type for workers | "Standard_DS1_v2" | See below |
| disk_size | Size of the disk in GB | 40 | 100 |
| worker_priority | Set priority to Spot to use reduced cost surplus capacity, with the tradeoff that instances can be deallocated at any time | Regular | Spot |
| host_cidr | CIDR IPv4 range to assign to instances | "10.0.0.0/16" | "10.0.0.0/20" |
| pod_cidr | CIDR IPv4 range to assign to Kubernetes pods | "10.2.0.0/16" | "10.22.0.0/16" |
| service_cidr | CIDR IPv4 range to assign to Kubernetes services | "10.3.0.0/16" | "10.3.0.0/24" |
| worker_node_labels | List of initial worker node labels | [] | ["worker-pool=default"] |
Check the list of valid [machine types](https://azure.microsoft.com/en-us/pricing/details/virtual-machines/linux/) and their [specs](https://docs.microsoft.com/en-us/azure/virtual-machines/linux/sizes-general). Use `az vm list-skus` to get the identifier.
!!! warning
Unlike AWS and GCP, Azure requires its *virtual* networks to have non-overlapping IPv4 CIDRs (yeah, go figure). Instead of each cluster just using `10.0.0.0/16` for instances, each Azure cluster's `host_cidr` must be non-overlapping (e.g. 10.0.0.0/20 for the 1st cluster, 10.0.16.0/20 for the 2nd cluster, etc).
!!! warning
Do not choose a `controller_type` smaller than `Standard_B2s`. Smaller instances are not sufficient for running a controller.
#### Spot Priority
Add `worker_priority=Spot` to use [Spot Priority](https://docs.microsoft.com/en-us/azure/virtual-machines/linux/spot-vms) workers that run on Azure's surplus capacity at lower cost, but with the tradeoff that they can be deallocated at random. Spot priority VMs are Azure's analog to AWS spot instances or GCP premptible instances.
