How to deploy using Terraform

Terraform is an infrastructure automation tool to provision and manage resources in clouds or data centers. To deploy Charmed PostgreSQL K8s using Terraform and Juju, you can use the Juju Terraform Provider.

The easiest way is to start from these examples of terraform modules prepared by Canonical. This page will guide you through a deployment using an example module for PostgreSQL on Kubernetes.

For an in-depth introduction to the Juju Terraform Provider, read this Discourse post.

Summary

• Install Terraform tooling
• Verify the deployment
• Apply the deployment
• Check deployment status
• Clean up

Install Terraform tooling

This guide assumes Juju is installed and you have a K8s controller already bootstrapped. For more information, check the Set up the environment tutorial page.

Let’s install Terraform Provider and example modules:

sudo snap install terraform --classic

Switch to the K8s provider and create a new model:

juju switch microk8s
juju add-model my-model

Clone examples and navigate to the PostgreSQL machine module:

git clone https://github.com/canonical/terraform-modules.git
cd terraform-modules/modules/k8s/postgresql

Initialise the Juju Terraform Provider:

terraform init

Verify the deployment

Open the main.tf file to see the brief contents of the Terraform module:

resource "juju_application" "k8s_postgresql" {
  name  = var.postgresql_application_name
  model = var.juju_model_name
  trust = true

  charm {
    name    = "postgresql-k8s"
    channel = var.postgresql_charm_channel
  }

  units = 1
}

Run terraform plan to get a preview of the changes that will be made:

terraform plan -var "juju_model_name=my-model"

Apply the deployment

If everything looks correct, deploy the resources (skip the approval):

terraform apply -auto-approve -var "juju_model_name=my-model"

Check deployment status

Check the deployment status with

juju status --model k8s:my-model --watch 1s

Sample output:

Model     Controller  Cloud/Region        Version  SLA          Timestamp
my-model  k8s         microk8s/localhost  3.5.3    unsupported  12:09:38Z

App             Version  Status  Scale  Charm           Channel    Rev  Address         Exposed  Message     
postgresql-k8s  14.11    active      1  postgresql-k8s  14/stable  281  10.152.183.137  no                                     

Unit               Workload  Agent  Address     Ports  Message       
postgresql-k8s/0*  active    idle   10.1.77.74         Primary                                           

Continue to operate the charm as usual from here or apply further Terraform changes.

Clean up

To keep the house clean, remove the newly deployed Charmed PostgreSQL by running

terraform destroy -var "juju_model_name=my-model"

Sample output:

juju_application.k8s_postgresql: Refreshing state... [id=my-model:postgresql-k8s]

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
  - destroy

Terraform will perform the following actions:

  # juju_application.k8s_postgresql will be destroyed
  - resource "juju_application" "k8s_postgresql" {
      - constraints = "arch=amd64" -> null
      - id          = "my-model:postgresql-k8s" -> null
      - model       = "my-model" -> null
      - name        = "postgresql-k8s" -> null
      - placement   = "" -> null
      - storage     = [
          - {
              - count = 1 -> null
              - label = "pgdata" -> null
              - pool  = "kubernetes" -> null
              - size  = "1G" -> null
            },
        ] -> null
      - trust       = true -> null
      - units       = 1 -> null

      - charm {
          - base     = "[email protected]" -> null
          - channel  = "14/stable" -> null
          - name     = "postgresql-k8s" -> null
          - revision = 281 -> null
          - series   = "jammy" -> null
        }
    }

Plan: 0 to add, 0 to change, 1 to destroy.

Changes to Outputs:
  - application_name = "postgresql-k8s" -> null

Do you really want to destroy all resources?
  Terraform will destroy all your managed infrastructure, as shown above.
  There is no undo. Only 'yes' will be accepted to confirm.

  Enter a value: yes

juju_application.k8s_postgresql: Destroying... [id=my-model:postgresql-k8s]
juju_application.k8s_postgresql: Destruction complete after 0s

Destroy complete! Resources: 1 destroyed.

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