How to for_each through a list(objects) in Terraform 0.12

Question

I need to deploy a list of GCP compute instances. How do I loop for_each through the "vms" in a list of objects like this:

    "gcp_zone": &q         


        

Answer 1

Using the for_each block is pretty new and there's not too much documentation. Some of the best info comes from their announcement blog post: https://www.hashicorp.com/blog/hashicorp-terraform-0-12-preview-for-and-for-each/

Also make sure to check out the Dynamic Blocks section of their documentation: https://www.terraform.io/docs/configuration/expressions.html#dynamic-blocks

From what your example looks like you need to have a set of values for each instance that is created so you'll have a map of maps:

Below is an example I created using Terraform 0.12.12:

variable "hostnames" {
    default = {
        "one" = {
            "name" = "one",
            "machine" = "n1-standard-1",
            "os" = "projects/coreos-cloud/global/images/coreos-stable-2247-5-0-v20191016",
            "zone" = "us-central1-a"
        },
        "two" = {
            "name" = "two",
            "machine" = "n1-standard-2",
            "os" = "projects/centos-cloud/global/images/centos-8-v20191018",
            "zone" = "us-central1-b"
        }
    }
}

resource "google_compute_instance" "default" {
    for_each = var.hostnames
    name         = each.value.name
    machine_type = each.value.machine
    zone         = each.value.zone

    boot_disk {
        initialize_params {
            image = each.value.os
        }
    }

    scratch_disk {
    }

    network_interface {
        network = "default"
    }
}

Terraform plan output:

Terraform will perform the following actions:

  # google_compute_instance.default["one"] will be created
  + resource "google_compute_instance" "default" {
      + can_ip_forward       = false
      + cpu_platform         = (known after apply)
      + deletion_protection  = false
      + guest_accelerator    = (known after apply)
      + id                   = (known after apply)
      + instance_id          = (known after apply)
      + label_fingerprint    = (known after apply)
      + machine_type         = "n1-standard-1"
      + metadata_fingerprint = (known after apply)
      + name                 = "one"
      + project              = (known after apply)
      + self_link            = (known after apply)
      + tags_fingerprint     = (known after apply)
      + zone                 = "us-central1-a"

      + boot_disk {
          + auto_delete                = true
          + device_name                = (known after apply)
          + disk_encryption_key_sha256 = (known after apply)
          + kms_key_self_link          = (known after apply)
          + mode                       = "READ_WRITE"
          + source                     = (known after apply)

          + initialize_params {
              + image  = "projects/coreos-cloud/global/images/coreos-stable-2247-5-0-v20191016"
              + labels = (known after apply)
              + size   = (known after apply)
              + type   = (known after apply)
            }
        }

      + network_interface {
          + address            = (known after apply)
          + name               = (known after apply)
          + network            = "default"
          + network_ip         = (known after apply)
          + subnetwork         = (known after apply)
          + subnetwork_project = (known after apply)
        }

      + scheduling {
          + automatic_restart   = (known after apply)
          + on_host_maintenance = (known after apply)
          + preemptible         = (known after apply)

          + node_affinities {
              + key      = (known after apply)
              + operator = (known after apply)
              + values   = (known after apply)
            }
        }

      + scratch_disk {
          + interface = "SCSI"
        }
    }

  # google_compute_instance.default["two"] will be created
  + resource "google_compute_instance" "default" {
      + can_ip_forward       = false
      + cpu_platform         = (known after apply)
      + deletion_protection  = false
      + guest_accelerator    = (known after apply)
      + id                   = (known after apply)
      + instance_id          = (known after apply)
      + label_fingerprint    = (known after apply)
      + machine_type         = "n1-standard-2"
      + metadata_fingerprint = (known after apply)
      + name                 = "two"
      + project              = (known after apply)
      + self_link            = (known after apply)
      + tags_fingerprint     = (known after apply)
      + zone                 = "us-central1-b"

      + boot_disk {
          + auto_delete                = true
          + device_name                = (known after apply)
          + disk_encryption_key_sha256 = (known after apply)
          + kms_key_self_link          = (known after apply)
          + mode                       = "READ_WRITE"
          + source                     = (known after apply)

          + initialize_params {
              + image  = "projects/centos-cloud/global/images/centos-8-v20191018"
              + labels = (known after apply)
              + size   = (known after apply)
              + type   = (known after apply)
            }
        }

      + network_interface {
          + address            = (known after apply)
          + name               = (known after apply)
          + network            = "default"
          + network_ip         = (known after apply)
          + subnetwork         = (known after apply)
          + subnetwork_project = (known after apply)
        }

      + scheduling {
          + automatic_restart   = (known after apply)
          + on_host_maintenance = (known after apply)
          + preemptible         = (known after apply)

          + node_affinities {
              + key      = (known after apply)
              + operator = (known after apply)
              + values   = (known after apply)
            }
        }

      + scratch_disk {
          + interface = "SCSI"
        }
    }

Plan: 2 to add, 0 to change, 0 to destroy.