Merge more than 2 tfvars file contents - amazon-web-services

Question

I have usecase where I have 3 tfvars files
1.tfvars
api_stages=[
{
api_id= "xxxx"
stage="play"
}
]
2.tfvars
api_stages=[
{
api_id= "yyy"
stage="play"
}
]
3.tfvars
api_stages=[
{
api_id= "zzz"
stage="play"
}
]
and I am creating 1 single usage plan using this
resource "aws_api_gateway_usage_plan" "usage_plan" {
name = var.usage_plan_name
throttle_settings {
burst_limit = var.burst_limit
rate_limit = var.rate_limit
}
dynamic "api_stages" {
for_each = var.api_stages
content {
api_id = api_stages.value.api_id
stage = api_stages.value.stage
}
}
}
And this tfvars files will be created by different users.
Question: How can I merge this different tfvars file and attach all api_id and stages to single usage plan?
right now when I am doing plan, it's only taking last file's value.

Answer 1

.tfvars file processing happens before any configuration expressions are evaluated, so there is no way to do exactly what you asked about here: the rule for .tfvars files is always that the last definition of a particular variable "wins", as you've seen.
The some options that are close to what you want here would be:
Define three different variables, perhaps named to indicate the three different sources that are providing these values, and then concatenate the three of them together in a local value:
locals {
all_api_stages = concat(
var.a_api_stages,
var.b_api_stages,
var.c_api_stages,
)
}
This approach would be appropriate only if there being exactly three sets of variables is a meaningful constraint for your system.
Declare the actual stage objects inside your configuration and make the variable instead be a list of keys for them:
variable "api_stages" {
type = set(string)
}
locals {
api_stages = {
x = {
api_id = "xxxx"
stage = "play"
}
y = {
api_id = "yyyy"
stage = "play"
}
z = {
api_id = "zzzz"
stage = "play"
}
}
}
You can then use -var when running Terraform to choose the appropriate settings, instead of using -var-file:
terraform apply -var='api_stages=["x", "y"]'