Loop over a Map of Objects - terraform

Question

How do I do a for_each loop for the following?
I want to create a tfe_variable node_count & vm_size.
I need both these tfe_variables in both wksp1 and wksp2
variable "custom_variables" {
type = map(object({
node_count = number
vm_size = string
}))
default = {
wksp1 = {
node_count = 2
vm_size = "Standard_D2_v3"
},
wksp2 = {
node_count = 5
vm_size = "Standard_D2_v5"
}
}
}
resource "tfe_variable" "custom" {
for_each = {
# for each workspace & variable in var.custom_variables create a tfe_variable
}
key = each.value.name
value = each.value.value
category = "terraform"
workspace_id = each.value.workspace_id
}

Answer 1

You're really close! Here are a couple of things to consider:
Option 1: Multiple tfe_variable resources
Create a tfe_variable resource for each variable you want to create
Make sure the key in you custom_variables map is the workspace ID.
variable "custom_variables" {
type = map(object({
node_count = number
vm_size = string
}))
default = {
wksp1_id = {
node_count = 2
vm_size = "Standard_D2_v3"
},
wksp2_id = {
node_count = 5
vm_size = "Standard_D2_v5"
}
}
}
resource "tfe_variable" "node_count" {
for_each = var.custom_variables
key = "node_count"
value = each.value.node_count
category = "terraform"
workspace_id = each.key
}
resource "tfe_variable" "vm_size" {
for_each = var.custom_variables
key = "vm_size"
value = each.value.vm_size
category = "terraform"
workspace_id = each.key
}
The drawback to this option is that you'll need an additional resource for each variable.
Option 2: A list of variable objects
Define a list of the keys, values, and workspace IDs of each variable
Use count to iterate the list
variable "custom_variables" {
type = list(object({
key = string
value = string
workspace_id = string
}))
default = [
{
key = "node_count"
value = "2"
workspace_id = "wksp1_id"
},
{
key = "node_count"
value = "5"
workspace_id = "wksp2_id"
},
{
key = "vm_size"
value = "Standard_D2_v3"
workspace_id = "wksp1_id"
},
{
key = "vm_size"
value = "Standard_D2_v5"
workspace_id = "wksp2_id"
}
]
}
resource "tfe_variable" "custom" {
count = length(var.custom_variables)
key = var.custom_variables[count.index].key
value = var.custom_variables[count.index].value
workspace_id = var.custom_variables[count.index].workspace_id
category = "terraform"
}
There are a couple of drawbacks to this approach as well:
There is a fair amount of duplicated code in the variable definition
The value must always be of the same type
If you're struggling with loop concepts in Terraform, this blog post might help you.

Answer 2

The main requirement to keep in mind for for_each is that we always need to create a map that has one element for each instance of the resource we want to create. In this case, that means you need a map with one element per workspace per variable, because tfe_variable describes a single variable on a single workspace.
Our job then is to write an expression to project the map-of-objects value coming in via the variable to a collection that has a separate element per variable. Here's one way to get that done, using the flatten function in a way similar to an example in its documentation:
locals {
workspace_variables = flatten([
for ws_name, ws in var.custom_variables : [
for var_name, value in ws : {
workspace = ws_name
variable = var_name
value = value
}
]
])
}
The above should produce a local.workspace_variables that looks like this:
[
{ workspace = "wksp1", variable = "node_count", value = 2 },
{ workspace = "wksp1", variable = "vm_size", value = "Standard_D2_v3" },
{ workspace = "wksp2", variable = "node_count", value = 5 },
{ workspace = "wksp2", variable = "vm_size", value = "Standard_D2_v5" },
]
This now meets the requirement of having one element per desired tfe_variable instance, so our only remaining job is to project this into a map to provide unique identifiers for each element and describe how to populate the tfe_variable arguments based on these objects:
resource "tfe_variable" "custom" {
for_each = {
for wsv in local.workspace_variables : "${wsv.workspace}.${wsv.variable}" => wsv
}
key = each.value.variable
value = each.value.value
category = "terraform"
workspace_id = each.value.workspace
}
One thing I didn't contend with above, because it wasn't directly you question, is the value of workspace_id in tfe_variable. If I recall correctly, that argument is expecting a workspace id rather than a workspace name, in which case you might need a slightly more complicated expression for the workspace_id argument. If you already have a tfe_workspace resource using the workspace names as keys then something like this might work, for example:
workspace_id = tfe_workspace.example[each.value.workspace].id
If your workspaces are created in a different way then you may have to do something more complicated here, but that's getting far off the topic of your original question so I won't try to dig into that here. I'm happy to try to help with it in a separate question on this site though, if you like.