Relative paths in Terraform

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}"]
  }
}