Creating Terraform Conditional resource based on mapped key.

Let’s create a conditional resource in Terraform based on a mapped key. Following post used for reference:

https://medium.com/@business_99069/terraform-conditional-resources-based-on-a-map-key-a37fd329d3a1

Start with a map data structure in our variable.tfvars:

docker_swarm = {
    az-ds-man-tst1 = {
        ip_address           = "172.19.100.82"
        environment          = "test"
        application          = "docker"
        docker_role          = "swarm-manager"
        vm_size              = "Standard_B2s"
        storage_account_type = "Standard_LRS"
        os_disk_storage_account_type = "Standard_LRS"
        },
    az-ds-man-tst2 = {
        ip_address  = "172.19.100.83"
        environment       = "test"
        application       = "docker"
        docker_role       = "swarm-manager"
        vm_size           = "Standard_B2s"
        storage_account_type = "Standard_LRS"
        os_disk_storage_account_type = "Standard_LRS"
        },
    az-ds-man-tst3 = {
        ip_address = "172.19.100.84"
        environment       = "test"
        application       = "docker"
        docker_role       = "swarm-manager"
        vm_size           = "Standard_B2s"
        storage_account_type = "Standard_LRS"
        os_disk_storage_account_type = "Standard_LRS"
        },
    az-ds-wrk-tst1 = {
        ip_address   = "172.19.100.85"
        environment       = "test"
        application       = "docker"
        docker_role       = "swarm-worker"
        vm_size           = "Standard_A2_v2"
        storage_account_type = "StandardSSD_LRS"
        os_disk_storage_account_type = "Standard_LRS"
        },
    az-ds-wrk-tst2 = {
        ip_address = "172.19.100.86"
        environment       = "test"
        application       = "docker"
        docker_role       = "swarm-worker"
        vm_size           = "Standard_A2_v2"
        storage_account_type = "StandardSSD_LRS"
        os_disk_storage_account_type = "Standard_LRS"
        }
    az-ds-wrk-tst3 = {
        ip_address = "172.19.100.87"
        environment       = "test"
        application       = "docker"
        docker_role       = "swarm-worker"
        vm_size           = "Standard_A2_v2"
        storage_account_type = "StandardSSD_LRS"
        os_disk_storage_account_type = "Standard_LRS"
        }
    az-ds-wrk-tst4 = {
        ip_address = "172.19.100.88"
        environment       = "test"
        application       = "docker"
        docker_role       = "swarm-worker"
        vm_size           = "Standard_A2_v2"
        storage_account_type = "StandardSSD_LRS"
        os_disk_storage_account_type = "Standard_LRS"
        }
    }

Create a conditional azurerm_network_interface_backend_address_pool_assocation resource based on the value of the “docker_role” key in the above map. The lookup used in the logic below will only return true if the value is “swam-worker”. This resource block can be placed in any terraform file within the project.

  resource "azurerm_network_interface_backend_address_pool_association" "ds-swarm-workers" {
  for_each                = {
  for k in keys(var.docker_swarm) : //loop over each object in docker_swarm map
    k => var.docker_swarm[k] //assign value of k to docker_swarm object with key value
    if lookup(var.docker_swarm[k], "docker_role", "swarm-worker") == "swarm-worker" //if docker_role attirbute is set to swarm worker, return true
  }
  network_interface_id    = azurerm_network_interface.dswarm[each.key].id
  ip_configuration_name   = "internal"
  backend_address_pool_id = azurerm_lb_backend_address_pool.ds-swarm-workers.id
  }