Terraform create map(any) and fill with values from variables

Question

I do have this vms variable (cannot change this):

variable vms {
  description = "Individual VM settings, like ip address and master/worker"
  type        = map(any)
  default     = null
}

I want to fill it with values from other (list)variables with ipaddresses and a calculated master = true/false.

I want to create the following map:

vms = {
  m1 = {
    ip_address = "172.16.201.1"
    master     = true
  w1 = {
    ip_address = "172.16.201.2"
    master     = false

How do I create this in Terraform? If this is possible, next to create, how do I add a m3 for example to the just created map?

Thanks!

Answer 1

Instead of declaring your variable as a generic map:

variable vms {
  description = "Individual VM settings, like ip address and master/worker"
  type        = map(any)
  default     = null
}

Consider declaring your variable as a map of objects, as following:

variable "vms" {
  description = "Individual VM settings, like ip address and master/worker"

  type = map(object({
    ip_address = string
    master     = bool
  }))

  default = {}
}

This will ensure that you don't declare variables with invalid properties (e.g. foo) or values (e.g. master = 123456).

You can then set your variable as follows:

vms = {
  "m1" = {
    ip_address = "172.16.201.1"
    master     = true
  }
  "w1" = {
    ip_address = "172.16.201.2"
    master     = false
  }
  "m3" = {
    ip_address = "172.16.201.3"
    master     = false
  }
}

Example

Full working example:

# main.tf

variable "vms" {
  description = "Individual VM settings, like ip address and master/worker"

  type = map(object({
    ip_address = string
    master     = bool
  }))

  default = {
    "m1" = {
      ip_address = "172.16.201.1"
      master     = true
    }
    "w1" = {
      ip_address = "172.16.201.2"
      master     = false
    }
    "m3" = {
      ip_address = "172.16.201.3"
      master     = false
    }
  }
}

output "m1" {
  value       = var.vms["m1"]
  description = "m1 VM settings"
}

output "w1" {
  value       = var.vms["w1"]
  description = "w1 VM settings"
}

output "m3" {
  value       = var.vms["m3"]
  description = "m3 VM settings"
}

Running terraform plan:

Changes to Outputs:
  + m1 = {
      + ip_address = "172.16.201.1"
      + master     = true
    }
  + m3 = {
      + ip_address = "172.16.201.3"
      + master     = false
    }
  + w1 = {
      + ip_address = "172.16.201.2"
      + master     = false
    }