Use tuple output as string input for terraform submodule

Question

We have a module that creates a redis instance in GCP. I'm calling that from the example folder where I define the variables. This works fine. This redis instance will output a tuple of IPs that I want to use to create consul service via a submodule. The submodule requires the IP as a string, so I'd need to somehow iterate through either with the output from the module / terraform state or data resource that grabs the info with a for each to the submodule but I'm a bit lost!

main.tf
output.tf
variables.tf
submodule.tf
└── example
   ├── main.tf
   └── output.tf

example/main.tf

module "create_redis_instance_example" {
  source  = "../."
  stage   = "eng"
  redis_instances = {
    test1 = {
      memory_size_gb = 1
      tier           = "BASIC"
      redis_config = {
        maxmemory-policy = "allkeys-lru"
      }
    }
  }
  register_consul = true
  consul_servicenames = [
    "test1",
  ]
}

example/output.tf

output "redis_instances" {
  value     = module.create_redis_instance_example.redis_instances
}

main.tf

resource "google_redis_instance" "cache" {
  provider = google-beta
  for_each = var.redis_instances

  name               = "${var.stage}-${each.key}"
  display_name       = "${var.stage}-${each.key}"
  memory_size_gb     = each.value["memory_size_gb"]
  auth_enabled       = true
  authorized_network = test
  connect_mode       = "PRIVATE_SERVICE_ACCESS"
  redis_configs           = each.value["redis_config"]
  tier                    = each.value["tier"]
}

output.tf

output "redis_instances" {
  value = toset([
    for i in google_redis_instance.cache : i.host
  ])
}

variables.tf

variable "stage" {
  description = "Stage of the redis instance"
  type        = string
}

variable "redis_instances" {
  description = "A list of bucket-suffixes with optional information"
  type = map(object({
    memory_size_gb = number
    tier           = string
    redis_config   = map(any)
  }))
}

etc. etc.

submodule.tf

module "terraform_consul_dns" {
  for_each = var.redis_instances
  depends_on = [google_redis_instance.cache]
 
  #ipaddress = "${google_redis_instance.cache[host]}"
  #ipaddress = "${google_redis_instance.cache[each.value].host}"
  #ipaddress = "${var.google_redis_instances[each.value.host]}"
  ipaddress = "1.1.1.1"
  nodename  = "test1-${var.stage}-${each.key}"
  services_with_ports = [
    {
      servicename = "test1-${var.stage}-${each.key}"
      port        = "1234"
    },
  ]
}

So when we specify the IP:

ipaddress = "1.1.1.1"

This works fine but as mentioned we'd like to create this either with the output, terraform state or data source dynamically. Tried a few things as you can see above but nothing really works :-( any hints, much welcomed!

lema · Accepted Answer · 2022-01-07 14:19:44Z

1

There is no need to gather this from the output/tf state as I can directly get this from the module that is creating the resource and than call the submodule, so all that needed to be changed was:

submodule.tf

module "terraform_consul_dns" {
  for_each = google_redis_instance.cache
  depends_on = [google_redis_instance.cache]

  ipaddress = google_redis_instance.cache[each.KEY].host
}

So we made the mistake to grab value instead of key. As value had no host attribute but key has.

answered Jan 7, 2022 at 14:19

lema

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