Terraform 0.12.19在Cloud中配置list(string)变量触发报错求助

Hey there, let's break down and fix those two Terraform errors you're hitting with v0.12.19 in Terraform Cloud:

Error 1: Root module variable "mq-c" is not set and has no default value #

This happens because Terraform can't locate a valid value for the mq-c variable you declared in inputs.tf. Even though you defined the value in dev.tfvars, you need to ensure Terraform Cloud is actually loading that configuration for your workspace.

Fixes: #

• In Terraform Cloud Workspace:
  1. Navigate to your workspace's Variables tab.
  2. Under the Terraform Variables section, add the entire mq-c object as a variable (paste the JSON-like structure from dev.tfvars), or
  3. Create a Variable Set containing the dev.tfvars content and attach it to your dev workspace, or
  4. If your dev.tfvars is stored in your linked VCS repo, configure your workspace to use this file for variable inputs (check the "Terraform Variables" settings for file inclusion options).
• Optional Fallback: Add a default value to the mq-c variable in inputs.tf (useful for testing baseline configurations):

  variable "mq-c" {
    type = object({
      node_name = string
      lt = object({
        instance_type = string
        disable_api_termination = bool
      })
      asg = object({
        desired_capacity = number
        max_size = number
        min_size = number
        protect_from_scale_in = bool
        target_group_arns = list(string)
      })
    })
    # Example default configuration
    default = {
      node_name = "default-mq-c"
      lt = {
        instance_type = "t2.micro"
        disable_api_termination = false
      }
      asg = {
        desired_capacity = 1
        max_size = 2
        min_size = 0
        protect_from_scale_in = false
        target_group_arns = []
      }
    }
  }
  

Error 2: Using ${aws_lb_target_group._1416.arn} in dev.tfvars is not allowed #

This is intentional Terraform behavior: .tfvars files are designed for static values only (like strings, numbers, or lists of static text). You can't reference dynamic Terraform resource attributes (like aws_lb_target_group._1416.arn) here because resource ARNs are generated during Terraform's execution phase, while .tfvars files are parsed much earlier (during variable loading).

Fixes: #

Choose an option based on how flexible your configuration needs to be:

Option 1: Directly reference the target group ARN in asg.tf (simplest) #

Since you confirmed this works, replace the variable reference with the actual resource ARN in your autoscaling group:

resource "aws_autoscaling_group" "asg_2" {
  # ... your existing configuration ...
  target_group_arns = [aws_lb_target_group._1416.arn] # Replace var.mq-c.asg.target_group_arns
  # ... rest of your config ...
}

Option 2: Keep variable flexibility with dynamic data lookup (multi-environment friendly) #

If you need different target groups per environment, pass static target group names in .tfvars instead of ARNs, then use a data source to fetch the dynamic ARNs:

1. Update inputs.tf to accept target group names:

   variable "mq-c" {
     type = object({
       node_name = string
       lt = object({
         instance_type = string
         disable_api_termination = bool
       })
       asg = object({
         desired_capacity = number
         max_size = number
         min_size = number
         protect_from_scale_in = bool
         target_group_names = list(string) # Renamed from target_group_arns
       })
     })
   }
   

2. Update dev.tfvars to pass static target group names:

   mq-c = {
     "node_name" = "mq-c"
     "lt" = {
       "instance_type" = "m5.large"
       "disable_api_termination" = false
     }
     "asg" = {
       "desired_capacity" = 1
       "max_size" = 1
       "min_size" = 1
       "protect_from_scale_in" = false
       "target_group_names" = ["1416"] # Static name, not dynamic ARN
     }
   }
   

3. Add a data source in asg.tf to fetch ARNs from names:

   # Fetch target group ARNs by name
   data "aws_lb_target_group" "mq_target_groups" {
     for_each = toset(var.mq-c.asg.target_group_names)
     name     = each.value
     vpc_id   = data.aws_vpc.self.id
   }
   
   resource "aws_autoscaling_group" "asg_2" {
     # ... your existing configuration ...
     target_group_arns = values(data.aws_lb_target_group.mq_target_groups)[*].arn # Map names to ARNs
     # ... rest of your config ...
   }
   

Option 3: Use modules for reusable components #

For larger setups, wrap your load balancer and target groups in a Terraform module that outputs target group ARNs. Then reference the module's output in your ASG configuration to keep your code clean and reusable across environments.

内容的提问来源于stack exchange，提问作者user393