05-terraform-functions

Terraform Functions

Module Overview

Terraform functions allow us to transform, manipulate, and combine strings of text. This is useful for instance when wanting to control the CASING of a resource name.

Use the Terraform console

Terraform includes a built-in console for testing Terraform function syntax. Start the console with the terraform console command.

terraform console

Enter the following to run the lower function on the string HELLO).

lower("HELLO")

Enter the following to run the substr function on the long string.

substr("ThisIsALongStfunctions-demongThatWouldFailAsAnAzureStorageAccountName", 0, 6)

The following example combines both the lower and substr functions.

lower(substr("ThisIsALongStfunctions-demongThatWouldFailAsAnAzureStorageAccountName", 0, 6))

Exit the Terraform console with the exit command.

exit

Update container name

Open the main.tf file created in the last module and update the name of the Azure Container Instance to use the lower function.

resource "azurerm_resource_group" "hello-world" {
  name     = var.resource_group
  location = var.location
}

resource "random_integer" "ri" {
  min = 10000
  max = 99999
}

resource "azurerm_container_group" "hello-world" {
  name                = lower(var.container-name)
  location            = azurerm_resource_group.hello-world.location
  resource_group_name = azurerm_resource_group.hello-world.name
  ip_address_type     = "public"
  dns_name_label      = "${var.dns-prefix}-${random_integer.ri.result}"
  os_type             = "linux"

  container {
    name   = "hello-world"
    image  = var.container-image
    cpu    = "0.5"
    memory = "1.5"
    ports {
      port      = 80
      protocol  = "TCP"
    }
  }
}

Create the deployment plan.

terraform plan --out plan.out

If you have been following along, the container instance name should have changed from HelloWorld to helloworld which should be noted in the plan (output below).

# azurerm_container_group.hello-world must be replaced
-/+ resource "azurerm_container_group" "hello-world" {
        dns_name_label      = "hello-world-71849"
      ~ fqdn                = "hello-world-71849.eastus.azurecontainer.io" -> (known after apply)
      ~ id                  = "/subscriptions/3762d87c-ddb8-425f-b2fc-29e5e859edaf/resourceGroups/hello-world/providers/Microsoft.ContainerInstance/containerGroups/HelloWorld" -> (known after apply)
      ~ ip_address          = "52.224.150.48" -> (known after apply)
      ~ ip_address_type     = "Public" -> "public"
        location            = "eastus"
      ~ name                = "HelloWorld" -> "helloworld" # forces replacement
      ~ os_type             = "Linux" -> "linux"
        resource_group_name = "hello-world"
        restart_policy      = "Always"
      ~ tags                = {} -> (known after apply)

      ~ container {
          + command                      = (known after apply)
          ~ commands                     = [] -> (known after apply)
            cpu                          = 0.5
          - environment_variables        = {} -> null
            image                        = "microsoft/aci-helloworld"
            memory                       = 1.5
            name                         = "hello-world"
          ~ port                         = 80 -> (known after apply)
          ~ protocol                     = "TCP" -> (known after apply)
          - secure_environment_variables = (sensitive value)

            ports {
                port     = 80
                protocol = "TCP"
            }
        }

      + identity {
          + identity_ids = (known after apply)
          + principal_id = (known after apply)
          + type         = (known after apply)
        }
    }

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

Use terraform apply plan.out to apply the plan.

terraform apply plan.out

The containers FQDN can be used to see the running application.

Next Module

In the next module, you will learn about Terraform state.

Module 6: Terraform State