[Bug]: aws_lambda_function try to update qualified_arn every time

[eduardocque]

Terraform Core Version

1.5.5

AWS Provider Version

5.16.1

Affected Resource(s)

aws_lambda_function

Expected Behavior

after do plan or apply if i havent do any change to my lambda function code or environment variables, this should not try to deploy it again over and over

Actual Behavior

each time that i do plan or apply this try to update qualified_arn and qualified_invoke_arn even if i havent change the code or environment variables or environment variables is empty

Relevant Error/Panic Output Snippet

# module.lambda_deployment_security.aws_lambda_function.lambda_function will be updated in-place
  ~ resource "aws_lambda_function" "lambda_function" {
        id                             = "DeploymentSecurity-test"
      ~ qualified_arn                  = "arn:aws:lambda:us-east-1:xxxxxxxxxxxxx:function:DeploymentSecurity-test:5" -> (known after apply)
      ~ qualified_invoke_arn           = "arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/arn:aws:lambda:us-east-1:xxxxxxxxxxxxxx:function:DeploymentSecurity-test:5/invocations" -> (known after apply)
        tags                           = {}
      ~ version                        = "5" -> (known after apply)
        # (20 unchanged attributes hidden)

        # (2 unchanged blocks hidden)
    }

Terraform Configuration Files

data "archive_file" "lambda" {
  type        = "zip"
  source_file = var.source_path
  output_path = "./builds/${var.name}.zip"
}

resource "aws_iam_role" "lambda_role" {
  name = "lambda-${var.project_name}-${var.name}-LambdaRole"
  path = "/"
  assume_role_policy = jsonencode({
    "Version" : "2012-10-17",
    "Statement" : [
      {
        "Action" : "sts:AssumeRole",
        "Principal" : {
          "Service" : [
            "lambda.amazonaws.com",
            "edgelambda.amazonaws.com"
          ]
        },
        "Effect" : "Allow",
        "Sid" : ""
      }
    ]
  })
}

resource "aws_iam_role_policy_attachment" "lambda_inst_role_attc_execution" {
  role       = aws_iam_role.lambda_role.name
  policy_arn = "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
}

resource "aws_iam_role_policy_attachment" "lambda_inst_role_attc_cloud_watch" {
  role       = aws_iam_role.lambda_role.name
  policy_arn = "arn:aws:iam::aws:policy/CloudWatchLogsFullAccess"
}

locals {
  environment_map = var.environment[*]
}

resource "aws_lambda_function" "lambda_function" {
  filename         = data.archive_file.lambda.output_path
  function_name    = var.name
  description      = var.description
  role             = aws_iam_role.lambda_role.arn
  handler          = "index.handler"
  source_code_hash = data.archive_file.lambda.output_base64sha256
  runtime          = var.runtime
  publish          = true

  dynamic "environment" {
    for_each = local.environment_map
    content {
      variables = environment.value
    }
  }
}

Steps to Reproduce

im just running terraform plan and each time that i do that, the previous output happens

if is the first time its fine because we have to apply the changes, but after that you do again terraform plan you will notice the previous output

Debug Output

No response

Panic Output

No response

Important Factoids

No response

References

No response

Would you like to implement a fix?

None

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[justinretzolk]

Hey @eduardocque 👋 Thank you for taking the time to raise this! I noticed that in your configuration, this resource is within a module. Is that module dependent on any other changes in the configuration? If so, that might be delaying the data source reads until apply time, which might explain this behavior. If you can supply them, debug logs (redacted as needed) might help us look into this a bit more too.

[eduardocque]

Hi @justinretzolk well the module is very simple and is completely independent, basically is just to group a few resources and be able to reuse it

full main.tf (module)

terraform {
  required_providers {
    aws = {
      source = "hashicorp/aws"
    }
  }
}

data "archive_file" "lambda" {
  type        = "zip"
  source_file = var.source_path
  output_path = "./builds/${var.name}.zip"
}

resource "aws_iam_role" "lambda_role" {
  name = "lambda-${var.project_name}-${var.name}-LambdaRole"
  path = "/"
  assume_role_policy = jsonencode({
    "Version" : "2012-10-17",
    "Statement" : [
      {
        "Action" : "sts:AssumeRole",
        "Principal" : {
          "Service" : [
            "lambda.amazonaws.com",
            "edgelambda.amazonaws.com"
          ]
        },
        "Effect" : "Allow",
        "Sid" : ""
      }
    ]
  })
}

resource "aws_iam_role_policy_attachment" "lambda_inst_role_attc_execution" {
  role       = aws_iam_role.lambda_role.name
  policy_arn = "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole"
}

resource "aws_iam_role_policy_attachment" "lambda_inst_role_attc_cloud_watch" {
  role       = aws_iam_role.lambda_role.name
  policy_arn = "arn:aws:iam::aws:policy/CloudWatchLogsFullAccess"
}

resource "aws_iam_role_policy_attachment" "lambda_inst_role_attc_dynamodb" {
  count      = var.hasDynamoDB ? 1 : 0
  role       = aws_iam_role.lambda_role.name
  policy_arn = "arn:aws:iam::aws:policy/AmazonDynamoDBFullAccess"
}

# locals {
#   environment_map = var.environment[*]
# }

resource "aws_lambda_function" "lambda_function" {
  filename         = data.archive_file.lambda.output_path
  function_name    = var.name
  description      = var.description
  role             = aws_iam_role.lambda_role.arn
  handler          = "index.handler"
  source_code_hash = data.archive_file.lambda.output_base64sha256
  runtime          = var.runtime
  publish          = true

  # dynamic "environment" {
  #   for_each = local.environment_map
  #   content {
  #     variables = environment.value
  #   }
  # }
}

variables.tf

variable "project_name" {
  description = "Plitzi Project Name"
  type        = string
  default     = "plitzi"
}

variable "name" {
  description = "Lambda Name"
  type        = string
  default     = ""
}

variable "description" {
  description = "Lambda Description"
  type        = string
  default     = ""
}

variable "runtime" {
  description = "Lambda Runtime"
  type        = string
  default     = "nodejs18.x"
}

variable "source_path" {
  description = "Lambda Source Path"
  type        = string
  default     = ""
}

variable "environment" {
  description = "Lambda Environment Variables"
  type        = map(string)
  default     = {}
}

variable "hasDynamoDB" {
  description = "Lambda has DynamoDB"
  type        = bool
  default     = false
}

this is how was called

module "lambda_deployment_redirect" {
  source       = "./modules/lambda"
  source_path  = "./functions/deployment-redirect/index.mjs"
  name         = "DeploymentRedirect"
  description  = "Lambda function to redirect the deployments"
  project_name = var.project_name
  hasDynamoDB  = true

  providers = {
    aws = aws.global
  }
}

If you notice, the environment code is commented, this way it works fine, if I uncomment it, that's when the problem starts to occur

if u have more question feels free to ask thx

[datfinesoul]

See @antonbabenko PR for a fix that needs to be made in the provider. The fields are marked optional in the docs, but leaving them out makes future applies end up in a constant state of drift.

[alexaandru]

Thank you @datfinesoul - that helped! (that is, setting all the optional logging_config fields (apart from log_group) made the "forever updates" go away).

[aidenvaines-bjss]

I am experiencing this issue too, like @eduardocque I to have this problem triggered from an aws_lambda_function in a module, all 4 logging_config attributes are configured per @antonbabenko.

Terraform 1.9.2 & hashicorp/aws v5.61.0

My 'workaround' is just to have a lifecycle policy in place ignoring these changes. Its ok for now but long term i'm not super happy with it, ive been through the debug logs and couldnt identify what was triggering the calculation of the resource information.

  lifecycle {
    ignore_changes = [
      qualified_arn,
      qualified_invoke_arn,
      version
    ]
  }

You also now get this in the output from terraform <action>

Warning: Redundant ignore_changes element
│ 
│   on ../../modules/lambda/lambda_function.tf line 1, in resource "aws_lambda_function" "main":
│    1: resource "aws_lambda_function" "main" {
│ 
│ Adding an attribute name to ignore_changes tells Terraform to ignore future changes to the argument in configuration after the object has been created,
│ retaining the value originally configured.
│ 
│ The attribute qualified_arn is decided by the provider alone and therefore there can be no configured value to compare with. Including this attribute in
│ ignore_changes has no effect. Remove the attribute from ignore_changes to quiet this warning.
│ 
│ (and 2 more similar warnings elsewhere)