Terraform by Example

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Dynamics

The dynamics expression is used to produce nested blocks inside the resource it is defined. The dynamics expression acts as a for expression but produces nested blocks instead.

It is important to note that a dynamic block can not be used to generate the meta-argument blocks such as lifecycle and provisioner blocks, since Terraform needs to process the meta-arguments before evaluating expressions.

Creating a Firewall rule defining multiple allow blocks #

resource "google_compute_firewall" "default" {
  name    = "example-firewall"
  network = google_compute_network.default.name

  allow {
    protocol = "tcp"
    ports    = ["80", "8080", "1000-2000"]
  }

  allow {
    protocol = "udp"
    ports    = ["3000-4000"]
  }

  source_tags = ["example"]
}

Creating Firewall rule using the dynamics expression #

resource "google_compute_firewall" "default" {
  name    = "example-firewall"
  network = google_compute_network.default.name

  dynamic "allow" {
    for_each = {
      tcp = ["80", "8080", "1000-2000"]
      udp = ["3000-4000"]
    }
    content {
      protocol = allow.key
      ports    = allow.value
    }
  }
  source_tags = ["example"]
}

The label of the dynamic block, "allow" in the example above, corresponds to an argument of the resource.

The iterator object #

The iterator object, allow in the example above has 2 attributes:

• key - Map key or set member corresponding to the current iteration.
• value - Map value corresponding to the current iteration. (If a set was provided, it would have the same value as the each.key has).

Want to learn more about the Dynamics expression? Check out the docs.

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