Terraform: Create multiple Kubernetes manifests using templates - kubernetes

Question

I have a requirement to execute multiple Kubernetes manifests of the same kind. Just names, action, and port changes
my networkpolicy.yaml.tpl
${yamlencode(
apiVersion: projectcalico.org/v3
kind: GlobalNetworkPolicy
metadata:
name: ${name}-policy
spec:
action: ${action}
rules:
- to:
- operation:
ports: [for port in ports : "${port}"]
)}
values that need to be populated for each microservice
| -------- | -------- | --------------| --------------|
| name | frontend | backend | middleware |
| action | allow | allow | allow |
| ports | 8080,443 | 4731 | 8751,7542 |
Example networkpolicy.yaml after generation
apiVersion: projectcalico.org/v3
kind: GlobalNetworkPolicy
metadata:
name: frontend-policy
spec:
action: allow
rules:
- to:
- operation:
ports: ["8080", "443"]
how can I achieve this? I am not clear as how-to write main.tf
resource "kubernetes_manifest" "istio-config" {
manifest = yamldecode(templatefile("${path.module}/networkpolicy.yaml.tpl", {
name =
action =
port =
}))
}

Answer 1

What you are looking for is for_each. You can declare a local values block and then loop over that block, replacing what you need. f.e.:
locals {
services = {
frontend = {
action = "allow"
ports = [8080,433]
}
backend = {
...
}
middleware = {
...
}
}
}
resource "kubernetes_manifest" "istio-config" {
for_each = local.services
manifest = yamldecode(templatefile("${path.module}/networkpolicy.yaml.tpl", each.value)
}

Answer 2

You can use the loop
Example
menifest = yamldecode(templatefile("${path.module}/networkpolicy.yaml.tpl", {
name = var.name
})
update the networkpolicy.yaml.tpl file
%{ for s in nameservers ~}
name ${s}
%{ endfor ~}
If you don't want to edit the tpl file you can edit the main.tf directly
name = <<-EOT
%{ for s in var.name ~}
name ${s}
%{ endfor ~}
EOT
Ref : https://www.terraform.io/language/functions/templatefile
Read more about simple loop : https://blog.gruntwork.io/terraform-tips-tricks-loops-if-statements-and-gotchas-f739bbae55f9
You can use the count or for_each loop to simple make it possible.