"Attempt to get attribute from null value" error

[fatmcgav]

Description

I am attempting to create a wrapper module around this alb module, and as part of this am defining a listeners var which includes a number of object definitions:

variable "listeners" {
  description = "Listeners to attach to ALB. A http-https-redirect-listener will be created automatically if 'enable_http_https_redirect = true'"
  default     = {}

  type = map(object({
    port     = number
    protocol = optional(string, "HTTP")

    # Default behaviours
    fixed_response = optional(object({
      content_type = optional(string, "text/plain")
      message_body = optional(string)
      status_code  = optional(string)
    }))

    forward = optional(object({
      target_groups = list(object({
        name   = optional(string, null)
        weight = optional(number)
      }))
      stickiness = object({
        duration = optional(number)
        enabled  = optional(bool, false)
      })
    }))

    redirect = optional(object({
      host        = optional(string, "#{host}")
      path        = optional(string, "#{path}")
      port        = optional(string, "#{port}")
      protocol    = optional(string, "#{protocol}")
      query       = optional(string, "#{query}")
      status_code = optional(string, "HTTP_301")
    }))

    # Listener rules
    rules = map(object({
      type = optional(string)
      fixed_response = optional(object({
        content_type = optional(string)
        message_body = optional(string)
        status_code  = optional(string)
      }))

      forward = optional(object({
        target_groups = list(object({
          name   = string
          weight = optional(number)
        }))
        stickiness = object({
          duration = number
          enabled  = optional(bool, false)
        })
      }))

      redirect = optional(object({
        host        = optional(string, "#{host}")
        path        = optional(string, "#{path}")
        port        = optional(string, "#{port}")
        protocol    = optional(string, "#{protocol}")
        query       = optional(string, "#{query}")
        status_code = optional(string, "HTTP_301")
      }))
    }))
  }))

  validation {
    condition = alltrue([
      for listener in var.listeners : contains([80, 443], listener.port)
    ])
    error_message = "listener 'port' value should be '80' or '443'"
  }

  validation {
    condition = alltrue([
      for listener in var.listeners : contains(["HTTP", "HTTPS"], listener.protocol)
    ])
    error_message = "listener 'protocol' value should be 'HTTP' or 'HTTPS'"
  }
}

However the plan is failing with:

╷
│ Error: Attempt to get attribute from null value
│
│   on .terraform/modules/alb/main.tf line 203, in resource "aws_lb_listener" "this":
│  203:         status_code = default_action.value.status_code
│     ├────────────────
│     │ default_action.value is null
│
│ This value is null, so it does not have any attributes.

• ✋ I have searched the open/closed issues and my issue is not listed.

⚠️ Note

Before you submit an issue, please perform the following first:

1. Remove the local .terraform directory (! ONLY if state is stored remotely, which hopefully you are following that best practice!): rm -rf .terraform/
2. Re-initialize the project root to pull down modules: terraform init
3. Re-attempt your terraform plan or apply and check if the issue still persists

Versions

• Module version [Required]: latest

• Terraform version: 1.5.7

• Provider version(s): 5.79.0

Reproduction Code [Required]

https://gist.github.com/fatmcgav/82606b5ceef39b92d08398a0b08ec0a4

Steps to reproduce the behavior:

Expected behavior

ALB should be created

Actual behavior

Terraform plan failed

Terminal Output Screenshot(s)

Additional context

Changes in #389 fix the issue

[bryantbiggs]

Cross posting from linked PR

You should change your variables in your wrapper to make it work with the existing implementation. I would start with not using null and instead default to an empty list.

[rruenroengYahara]

Hi @bryantbiggs,
I'm not totally following your suggestion for @fatmcgav . I am running into the same error when trying to setup this module. I have the following implemented as a first pass at getting things set up.

listeners = {
    http-main-example = {
      port     = 80
      protocol = "HTTP"
      forward = {
        target_group_key = "tg-default"
      }
      rules = {
        auth-rule = {
          priority = 1
          actions = [{
            type             = "forward"
            target_group_key = "auth-tg"
          }]
          conditions = [{
            path_pattern = {
              values = ["/auth/*"]
            }
          }]
        }
        secrets-rule = {
          priority = 2
          actions = [{
            type             = "forward"
            target_group_key = "secrets-tg"
          }]
          conditions = [{
            path_pattern = {
              values = ["/secrets/*"]
            }
          }]
        }
      }
    }
  }

What are you suggesting I provide to the module to get it to work?

[bryantbiggs]

this variable for listeners https://gist.github.com/fatmcgav/82606b5ceef39b92d08398a0b08ec0a4#file-variables-tf-L1-L80

does not match our variable for listeners

terraform-aws-alb/variables.tf

Lines 195 to 199 in 5121d71

	variable "listeners" {
	description = "Map of listener configurations to create"
	type = any
	default = {}
	}

If you are running into an issue, I would suggest opening a separate issue with steps to reproduce and any error messages/details