For loop in terraform - amazon-web-services

Question

I am trying to get the value of function name from local.tf but I am not able to get it. I have terraform,tfvars in which I am giving the function name then it is passed to variable.tf. From varibale.tf I pass it to local.tf then to main.tf. I am not able to get the function name in main.tf. Any help would be appreciated.
terraform.tfvars
config = {
s3= {
//s3 configurations
}
s3_notifications = {
function_name = "test-lambda-mary"
}
}
variable.tf
variable "config" {
type = any
description = "S3 configuration block"
}
local.tf
function_name = {
for k, v in var.config :
k => lookup(v, "function_name", "")
}
module "all_notifications" {
source = "terraform-aws-modules/s3-bucket/aws//modules/notification"
for_each = var.config
bucket = module.s3_bucket[each.key].this_s3_bucket_id
lambda_notifications = {
lambda = {
function_name = local.function_name[each.key]
function_arn = "arn:aws:lambda:${data.aws_region.current.name}:${data.aws_caller_identity.current.account_id}:function:${local.function_name[each.key]}"
events = ["s3:ObjectCreated:*"]
}
}
}
error
"function_name" doesn't comply with restrictions ("^(arn:[\\w-]+:lambda:)?([a-z]{2}-(?:[a-z]+-){1,2}\\d{1}:)?(\\d{12}:)?(function:)?([a-zA-Z0-9-_]+)(:(\\$LATEST|[a-zA-Z0-9-_]+))?$"): ""
│
│ with module.all_notifications["s3"].aws_lambda_permission.allow["lambda"],
│ on .terraform/modules/all_notifications/modules/notification/main.tf line 63, in resource "aws_lambda_permission" "allow":
│ 63: function_name = each.value.function_name

Answer 1

If I put the function_name inside s3 braces it works absolutely fine but I need to have the fucntion name in s3_notification
That looks like a great hint. You're iterating over var.config which has 2 keys and only 1 of them has function_name defined. So when module is requested with s3 as a key, the function_value for that key will be empty string and AWS will fail the request as expected.
You can filter for_each = var.config to exclude such case, something like:
for_each = { for k, v in var.config: k => v if local.function_name[each.key] != ""}
Little nitpick: seems like the source of the module could be incorrectly written. Instead of terraform-aws-modules/s3-bucket/aws//modules/notification potentially it should be terraform-aws-modules/terraform-aws-s3-bucket//modules/notification. See https://github.com/terraform-aws-modules/terraform-aws-s3-bucket

Answer 2

A stab in the dark as I haven't used that module before.
But by looking at your error message:
"function_name" doesn't comply with restrictions ("^(arn:[\\w-]+:lambda:)?
it looks like for function_name you should pass Lambda's ARN, not name (contrary to what the variable name says).
BTW, is function_arn even a parameter here?

Answer 3

This error is coming since terraform module is expecting a valid and mandatory function name to create [aws_lambda_permission][1] resource using terraform-aws-modules/s3-bucket/aws//modules/notification module.
In your case you are looping the module on var.config which consist s3 and s3_notifications part and while first iteration its getting function name as null therefore its throwing this error.
"function_name" doesn't comply with restrictions ("^(arn:[\\w-]+:lambda:)?([a-z]{2}-(?:[a-z]+-){1,2}\\d{1}:)?(\\d{12}:)?(function:)?([a-zA-Z0-9-_]+)(:(\\$LATEST|[a-zA-Z0-9-_]+))?$"): ""
Better split the variable specific to s3_notification as list and iterate the module as below using count.
variable "s3_config" {
type = any
default = {
s3 = {
}
}
}
variable "s3_notify_lambda_func" {
type = list
default = ["test-lambda-mary","test"]. #N Numbers of functions
}
data "aws_region" "current" {}
data "aws_caller_identity" "current" {}
module "all_notifications" {
source = "terraform-aws-modules/s3-bucket/aws//modules/notification"
count = length(var.s3_notify_lambda_func) > 0 ? length(var.s3_notify_lambda_func) : 0
bucket = module.s3_bucket[count.index].this_s3_bucket_id
lambda_notifications = {
lambda = {
function_name = var.s3_notify_lambda_func[count.index]
function_arn = "arn:aws:lambda:${data.aws_region.current.name}:${data.aws_caller_identity.current.account_id}:function:${var.s3_notify_lambda_func[count.index]}"
events = ["s3:ObjectCreated:*"]
}
}
}