cert-manager
Terraform module for Kubernetes platforms

TL;DR:

• Use kbst add service cert-manager to add cert-manager to your platform
• The kbst CLI scaffolds the Terraform module boilerplate for you
• Kubestack platform service modules bundle upstream manifests and are fully customizable

Use the module

The kbst CLI helps you scaffold the Terraform code to provision cert-manager on your platform. It takes care of calling the module once per cluster, and sets the correct source and latest version for the module. And it also makes sure the module's configuration and configuration_base_key match your platform.

# add cert-manager service to all platform clusters
kbst add service cert-manager

# or optionally only add cert-manager to a single cluster
# 1. list existing platform modules
kbst list
aks_gc0_westeurope
eks_gc0_eu-west-1
gke_gc0_europe-west1

# 2. add cert-manager to a single cluster
kbst add service cert-manager --cluster-name aks_gc0_westeurope

Scaffolding the boilerplate is convenient, but platform service modules are fully documented, standard Terraform modules. They can also be used standalone without the Kubestack framework.

Customize resources

All Kubestack platform service modules support the same module attributes and configuration as all Kubestack modules. The module configuration is a Kustomization set in the per environment configuration map following Kubestack's inheritance model.

The example below shows some options to customize the resources provisioned by the cert-manager module.

module "example_cert_manager" {
  providers = {
    kustomization = kustomization.example
  }
  source  = "kbst.xyz/catalog/cert-manager/kustomization"
  version = "1.14.3-kbst.0"
  configuration = {
    apps = {
+     # change the namespace of all resources
+     namespace = var.example_cert_manager_namespace
+
+     # or add an annotation
+     common_annotations = {
+       "terraform-workspace" = terraform.workspace
+     }
+
+     # use images to pull from an internal proxy
+     # and avoid being rate limited
+     images = [{
+       # refers to the 'pod.spec.container.name' to modify the 'image' attribute of
+       name     = "container-name"
+       
+       # customize the 'registry/name' part of the image
+       new_name = "reg.example.com/nginx"
+     }]
    }
    ops = {
+     # scale down replicas in ops
+     replicas = [{
+       # refers to the 'metadata.name' of the resource to scale
+       name = "example"
+       
+       # sets the desired number of replicas
+       count = 1
+     }]
    }
  }
}

In addition to the example attributes shown above, modules also support secret_generator, config_map_generator, patches and many other Kustomization attributes.

Provision ClusterIssuer

A common requirement is to install cert-manager and a ClusterIssuer. The Kubestack cert-manager module supports this using the additional_resources attribute. First create a YAML file in manifests/cluster-issuer.yaml with the ClusterIssuer configurations. This example is for Let's Encrypt.

apiVersion: cert-manager.io/v1
kind: ClusterIssuer
metadata:
  name: letsencrypt
spec:
  acme:
    # You must replace this email address with your own.
    # Let's Encrypt will use this to contact you about expiring
    # certificates, and issues related to your account.
    email: user@example.com
    server: https://acme-v02.api.letsencrypt.org/directory
    privateKeySecretRef:
      # Secret resource that will be used to store the account's private key.
      name: letsencrypt-account-key
    # Add a single challenge solver, HTTP01 using nginx
    solvers:
    - http01:
        ingress:
          class: nginx

Then we add additional_resources to all cert-manager modules to provision the ClusterIssuer manifest with the bundled upstream resources.

module "example_cert_manager" {
  providers = {
    kustomization = kustomization.example
  }
  source  = "kbst.xyz/catalog/cert-manager/kustomization"
  version = "1.11.0-kbst.0"
  configuration = {
    apps = {
+     additional_resources = ["${path.root}/manifests/cluster-issuer.yaml"]
    }
    ops = {}
  }
}

Optionally, you can also patch the ClusterIssuer to use Let's Encrypt staging for ops.

module "example_cert_manager" {
  providers = {
    kustomization = kustomization.example
  }
  source  = "kbst.xyz/catalog/cert-manager/kustomization"
  version = "1.11.0-kbst.0"
  configuration = {
    apps = {
      additional_resources = ["${path.root}/manifests/cluster-issuer.yaml"]
    }
    ops = {
+     patches = [
+       {
+         patch = <<-EOF
+           - op: replace
+             path: /spec/acme/server
+             value: https://acme-staging-v02.api.letsencrypt.org/directory
+         EOF
+            
+         target = {
+           group   = "cert-manager.io"
+           version = "v1"
+           kind    = "ClusterIssuer"
+           name    = "letsencrypt"
+         }
+       }
+     ]
    }
  }
}