🪐 Add Terraform config to provision clusters

This is a new provisioning mechanism. Right now, it can
provision clusters on:
- Digital Ocean
- Linode
- Oracle Cloud
- Scaleway

Others should be relatively straightforward to add.
Check the README in the prepare-tf subdirectory for details.

prepare-tf/modules/oraclecloud/generate-tfvars.sh

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+#!/bin/sh
+grep = ~/.oci/config | tr "=" " " | while read key value; do
+  echo $key=\"$value\"
+done > terraform.tfvars

prepare-tf/modules/oraclecloud/main.tf

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+resource "oci_identity_compartment" "_" {
+  name        = var.cluster_name
+  description = var.cluster_name
+}
+
+locals {
+  compartment_id = oci_identity_compartment._.id
+}
+
+data "oci_identity_availability_domains" "_" {
+  compartment_id = local.compartment_id
+}
+
+data "oci_core_images" "_" {
+  for_each                 = local.pools
+  compartment_id           = local.compartment_id
+  operating_system         = "Oracle Linux"
+  operating_system_version = "7.9"
+  shape                    = each.value.shape
+}
+
+resource "oci_containerengine_cluster" "_" {
+  compartment_id     = local.compartment_id
+  kubernetes_version = var.k8s_version
+  name               = "oke-tf"
+  vcn_id             = oci_core_vcn._.id
+  options {
+    service_lb_subnet_ids = [oci_core_subnet.loadbalancers.id]
+  }
+  endpoint_config {
+    is_public_ip_enabled = true
+    subnet_id            = oci_core_subnet.controlplane.id
+  }
+}
+
+resource "oci_containerengine_node_pool" "_" {
+  for_each           = local.pools
+  cluster_id         = oci_containerengine_cluster._.id
+  compartment_id     = local.compartment_id
+  kubernetes_version = var.k8s_version
+  name               = each.key
+  node_shape         = each.value.shape
+  node_shape_config {
+    memory_in_gbs = local.node_type.memory_in_gbs
+    ocpus         = local.node_type.ocpus
+  }
+  node_config_details {
+    size = var.min_nodes_per_pool
+    placement_configs {
+      availability_domain = data.oci_identity_availability_domains._.availability_domains[0].name
+      subnet_id           = oci_core_subnet.nodes.id
+    }
+  }
+  node_source_details {
+    image_id    = data.oci_core_images._[each.key].images[0].id
+    source_type = "image"
+  }
+  ssh_public_key = "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDxLXAXB3CUztORPd+SCEcxhSGakSqecCgtCQTK3owuOKnG9LAYsXFDc7DLGoWzhnYeU9fVkKuMh6aDXYCHJmjSyK5V7f+VVxrH/6kf2VrIK+bGglHbPxNVLS1/UsSEzdZdP0vFwoBoGjAFNFEcn0NXKAvtNlMsyakvjfrpuPIFrb7xkrZHhvezNKrG3Sx6lQ2RaSFFGJSTPOWQg/q8DsCv0D1T7RaR1oHrrb6KKQAWjGYoU75/zNN6x7nD/ITQe7JGNPS3JbqXqXj7WtM4Wm0FHF5CthEKecbyxCFGxhpNBwXN2GzNkItQkeans+pn6/g6lstWIT/ugddoxW3CvQt1 /home/jp/.ssh/id_rsa"
+}

prepare-tf/modules/oraclecloud/network.tf

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+resource "oci_core_vcn" "_" {
+  compartment_id = local.compartment_id
+  cidr_block     = "10.0.0.0/16"
+  display_name   = "tf-vcn-${var.cluster_name}"
+}
+
+#
+# On OCI, you can have either "public" or "private" subnets.
+# In both cases, instances get addresses in the VCN CIDR block;
+# but instances in "public" subnets also get a public address.
+#
+# Then, to enable communication to the outside world, you need:
+# - for public subnets, an "internet gateway"
+#   (will allow inbound and outbound traffic)
+# - for private subnets, a "NAT gateway"
+#   (will only allow outbound traffic)
+# - optionally, for private subnets, a "service gateway"
+#   (to access other OCI services, e.g. object store)
+#
+# In this configuration, we use public subnets, and since we
+# need outside access, we add an internet gateway.
+#
+# Note that the default routing table in a VCN is empty, so we
+# add the internet gateway to the default routing table.
+# Similarly, the default security group in a VCN blocks almost
+# everything, so we add a blanket rule in that security group.
+#
+
+resource "oci_core_internet_gateway" "_" {
+  compartment_id = local.compartment_id
+  display_name   = "tf-igw"
+  vcn_id         = oci_core_vcn._.id
+}
+
+resource "oci_core_default_route_table" "_" {
+  manage_default_resource_id = oci_core_vcn._.default_route_table_id
+  route_rules {
+    destination       = "0.0.0.0/0"
+    destination_type  = "CIDR_BLOCK"
+    network_entity_id = oci_core_internet_gateway._.id
+  }
+}
+
+resource "oci_core_default_security_list" "_" {
+  manage_default_resource_id = oci_core_vcn._.default_security_list_id
+  ingress_security_rules {
+    protocol = "all"
+    source   = "0.0.0.0/0"
+  }
+  egress_security_rules {
+    protocol    = "all"
+    destination = "0.0.0.0/0"
+  }
+}
+
+resource "oci_core_subnet" "controlplane" {
+  compartment_id    = local.compartment_id
+  cidr_block        = "10.0.254.0/24"
+  vcn_id            = oci_core_vcn._.id
+  display_name      = "tf-subnet-controlplane"
+  route_table_id    = oci_core_default_route_table._.id
+  security_list_ids = [oci_core_default_security_list._.id]
+}
+
+resource "oci_core_subnet" "nodes" {
+  compartment_id    = local.compartment_id
+  cidr_block        = "10.0.0.0/20"
+  vcn_id            = oci_core_vcn._.id
+  display_name      = "tf-subnet-nodes"
+  route_table_id    = oci_core_default_route_table._.id
+  security_list_ids = [oci_core_default_security_list._.id]
+}
+
+resource "oci_core_subnet" "loadbalancers" {
+  compartment_id    = local.compartment_id
+  cidr_block        = "10.0.96.0/20"
+  vcn_id            = oci_core_vcn._.id
+  display_name      = "tf-subnet-loadbalancers"
+  route_table_id    = oci_core_default_route_table._.id
+  security_list_ids = [oci_core_default_security_list._.id]
+}

prepare-tf/modules/oraclecloud/outputs.tf

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+data "oci_containerengine_cluster_kube_config" "_" {
+  cluster_id = oci_containerengine_cluster._.id
+}
+
+output "kubeconfig" {
+  value = data.oci_containerengine_cluster_kube_config._.content
+}
+
+output "cluster_id" {
+  value = oci_containerengine_cluster._.id
+}

prepare-tf/modules/oraclecloud/provider.tf

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+terraform {
+  required_providers {
+    oci = {
+      source  = "hashicorp/oci"
+      version = "4.48.0"
+    }
+  }
+}

prepare-tf/modules/oraclecloud/variables.tf

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+variable "cluster_name" {
+  type    = string
+  default = "deployed-with-terraform"
+}
+
+variable "common_tags" {
+  type    = list(string)
+  default = []
+}
+
+variable "node_size" {
+  type    = string
+  default = "M"
+}
+
+variable "min_nodes_per_pool" {
+  type    = number
+  default = 2
+}
+
+variable "max_nodes_per_pool" {
+  type    = number
+  default = 5
+}
+
+variable "enable_arm_pool" {
+  type    = bool
+  default = true
+}
+
+locals {
+  arm_pool = {
+    shape = "VM.Standard.A1.Flex"
+  }
+  x86_pool = {
+    shape = "VM.Standard.E4.Flex"
+  }
+  pools = var.enable_arm_pool ? {
+    "oke-arm" = local.arm_pool
+    "oke-x86" = local.x86_pool
+    } : {
+    "oke-x86" = local.x86_pool
+  }
+}
+
+output "pool" {
+  value = local.pools
+}
+
+variable "node_types" {
+  # FIXME put better typing here
+  type = map(map(number))
+  default = {
+    "S" = {
+      memory_in_gbs = 2
+      ocpus         = 1
+    }
+    "M" = {
+      memory_in_gbs = 4
+      ocpus         = 1
+    }
+    "L" = {
+      memory_in_gbs = 8
+      ocpus         = 2
+    }
+  }
+}
+
+locals {
+  node_type = var.node_types[var.node_size]
+}
+
+# To view supported versions, run:
+# oci ce cluster-options get --cluster-option-id all | jq -r '.data["kubernetes-versions"][]'
+variable "k8s_version" {
+  type    = string
+  default = "v1.20.11"
+}