Relative paths in Terraform - amazon-web-services

Question

I am trying to create an AWS lambda Function using terraform.
My terraform directory looks like
terraform
iam-policies
main.tf
lambda
files/
main.tf
main.tf
I have my lambda function stored inside /terraform/lambda/files/lambda_function.py.
Whenever I terraform apply, I have a "null_resource" that executes some commands in local machine that will zip the python file
variable "pythonfile" {
description = "lambda function python filename"
type = "string"
}
resource "null_resource" "lambda_preconditions" {
triggers {
always_run = "${uuid()}"
}
provisioner "local-exec" {
command = "rm -rf ${path.module}/files/zips"
}
provisioner "local-exec" {
command = "mkdir -p ${path.module}/files/zips"
}
provisioner "local-exec" {
command = "cp -R ${path.module}/files/${var.pythonfile} ${path.module}/files/zips/lambda_function.py"
}
provisioner "local-exec" {
command = "cd ${path.module}/files/zips && zip -r lambda.zip ."
}
}
My "aws_lambda_function" resource looks like this.
resource "aws_lambda_function" "lambda_function" {
filename = "${path.module}/files/zips/lambda.zip"
function_name = "${format("%s-%s-%s-lambda-function", var.name, var.environment, var.function_name)}"
role = "${aws_iam_role.iam_for_lambda.arn}"
handler = "lambda_function.lambda_handler"
source_code_hash = "${base64sha256(format("%s/files/zips/lambda.zip", path.module))}", length(path.cwd) + 1, -1)}")}"
runtime = "${var.function_runtime}"
timeout = "${var.function_timeout}"
memory_size = "${var.function_memory}"
environment {
variables = {
region = "${var.region}"
name = "${var.name}"
environment = "${var.environment}"
}
}
vpc_config {
subnet_ids = ["${var.subnet_ids}"]
security_group_ids = ["${aws_security_group.lambda_sg.id}"]
}
depends_on = [
"null_resource.lambda_preconditions"
]
}
Problem:
Whenever I change the lambda_function.py file and terraform apply again, everything works fine but the actual code in the lambda function do not change.
Also if I delete all the terraform state files and apply again, the new change is propagated without any problem.
What could be the possible reason for this?

Answer 1

Instead of using null_resource, I used the archive_file data source that creates the zip file automatically if new changes are detected. Next I took a reference from the archive_file data in the lambda resource source_code_hash attribute.
archive_file data source
data "archive_file" "lambda_zip" {
type = "zip"
output_path = "${path.module}/files/zips/lambda.zip"
source {
content = "${file("${path.module}/files/ebs_cleanup_lambda.py")}"
filename = "lambda_function.py"
}
}
The lambda resource
resource "aws_lambda_function" "lambda_function" {
filename = "${path.module}/files/zips/lambda.zip"
function_name = "${format("%s-%s-%s-lambda-function", var.name, var.environment, var.function_name)}"
role = "${aws_iam_role.iam_for_lambda.arn}"
handler = "lambda_function.lambda_handler"
source_code_hash = "${data.archive_file.lambda_zip.output_base64sha256}"
runtime = "${var.function_runtime}"
timeout = "${var.function_timeout}"
memory_size = "${var.function_memory}"
environment {
variables = {
region = "${var.region}"
name = "${var.name}"
environment = "${var.environment}"
}
}
vpc_config {
subnet_ids = ["${var.subnet_ids}"]
security_group_ids = ["${aws_security_group.lambda_sg.id}"]
}
}