Terraform Error: Invalid value for module argument when running tf plan for cloudfront module

Question

I have a module which creates submodules and each submodule have a custom_error_response that land to a different response_page_path.

In the main module I have added;

 custom_error_response = [
    {
      error_code            = "403"
      error_caching_min_ttl = "30"
      response_code         = "200"
      response_page_path    = "/${var.default_root_object}"
    },
  ]

and the variable default_root_object is:

variable "default_root_object" {
  description = "Default root object at origin for CloudFront distribution"
}

In the submodules I have added the following in the variables.tf:

variable "custom_error_response" {
  description = "(Optional) - List of one or more custom error response element maps"
  type        = "list"
  default     = []
}

In the main.tf of each sub-module I have also defined the custom_error_response like this:

    dynamic "custom_error_response" {
    for_each = var.custom_error_response
    content {
      error_caching_min_ttl = lookup(custom_error_response.value, "error_caching_min_ttl", null)
      error_code            = custom_error_response.value.error_code
      response_code         = lookup(custom_error_response.value, "response_code", null)
      response_page_path    = lookup(custom_error_response.value, "response_page_path", null)
    }
  } 

When I am running terraform init it is okay, but when I run terraform plan it gives me the same error 8 times for the 8 sub modules I have made.

Error: Invalid value for module argument

  on portal_distribution/main.tf line 32, in module "**mainmodule**":
  32:   custom_error_response = [
  33:     {
  34:       error_code            = "403"
  35:       error_caching_min_ttl = "30"
  36:       response_code         = "200"
  37:       response_page_path    = "/${var.default_root_object}"
  38:     },
  39:   ]

The given value is not suitable for child module variable
"custom_error_response" defined at
.terraform/modules/**submodule**_portal.**mainmodule**/modules/aws-terraform-cloudfront_s3_origin/variables.tf:302,1-33:
element 0: string required.

How do I fix the error?

Answer 1

The type of your variable is a list. The fact that you're doing map lookups suggest you're trying to use a map or something. What I'd recommend: use a map of objects.

If you need it to be a var:

variable myinput {
  type = map(list(object({
    error_caching_min_ttl = string
    error_code = number
    response_code = number
    response_page_path = string
  })))
}

In the code I used to prove this on my machine, I didnt' use a var. So where the for_each is, just put the var there instead and populate the var with your values. The solution is to use a map of objects. I like maps over lists because you can give each item in the collection a descriptive title. This helps with giving names in the state that are meaningul.

dynamic "custom_error_response" {
    for_each = map(
        "descriptiveTitleForThis", {
            error_caching_min_ttl = "60"
            error_code = 403
            response_code = 11
            response_page_path = "page1"
        },
        "551directToPage2", {
            error_caching_min_ttl = "60"
            error_code = 551
            response_code = 10
            response_page_path = "page2"
        }
    )
    content {
      error_caching_min_ttl = custom_error_response.value.error_caching_min_ttl
      error_code            = custom_error_response.value.error_code
      response_code         = custom_error_response.value.response_code
      response_page_path    = custom_error_response.value.response_page_path
    }
  }

My full code below if you want it:

provider aws {
  profile = "myprofile"
  region  = "us-west-2"
}

resource "aws_s3_bucket" "b" {
  bucket = "mybucket"
  acl    = "private"

  tags = {
    Name = "My bucket"
  }
}

locals {
  s3_origin_id = "myS3Origin"
}

resource "aws_cloudfront_distribution" "s3_distribution" {
  enabled = true

  origin {
    domain_name = aws_s3_bucket.b.bucket_regional_domain_name
    origin_id   = local.s3_origin_id
  }

  default_cache_behavior {
    allowed_methods  = ["DELETE", "GET", "HEAD", "OPTIONS", "PATCH", "POST", "PUT"]
    cached_methods   = ["GET", "HEAD"]
    target_origin_id = local.s3_origin_id

    forwarded_values {
      query_string = false

      cookies {
        forward = "none"
      }
    }

    viewer_protocol_policy = "allow-all"
    min_ttl                = 0
    default_ttl            = 3600
    max_ttl                = 86400
  }

  restrictions {
    geo_restriction {
      restriction_type = "whitelist"
      locations        = ["US", "CA", "GB", "DE"]
    }
  }

  viewer_certificate {
    cloudfront_default_certificate = true
  }

  dynamic "custom_error_response" {
    for_each = map(
        "descriptiveTitleForThis", {
            error_caching_min_ttl = "60"
            error_code = 403
            response_code = 11
            response_page_path = "page1"
        },
        "551directToPage2", {
            error_caching_min_ttl = "60"
            error_code = 551
            response_code = 10
            response_page_path = "page2"
        },
        "552directToPage3", {
            error_caching_min_ttl = "60"
            error_code = 552
            response_code = 12
            response_page_path = "page3"
        },
        "553directToPage4", {
            error_caching_min_ttl = "60"
            error_code = 553
            response_code = 13
            response_page_path = "page4"
        },
    )
    content {
      error_caching_min_ttl = custom_error_response.value.error_caching_min_ttl
      error_code            = custom_error_response.value.error_code
      response_code         = custom_error_response.value.response_code
      response_page_path    = custom_error_response.value.response_page_path
    }
  }

}

Edit: I forgot to print the plan

Terraform will perform the following actions:

  # aws_cloudfront_distribution.s3_distribution will be created
  + resource "aws_cloudfront_distribution" "s3_distribution" {
      <..ommitted for brevity...>

      + custom_error_response {
          + error_caching_min_ttl = 60
          + error_code            = 403
          + response_code         = 11
          + response_page_path    = "page1"
        }
      + custom_error_response {
          + error_caching_min_ttl = 60
          + error_code            = 551
          + response_code         = 10
          + response_page_path    = "page2"
        }
      + custom_error_response {
          + error_caching_min_ttl = 60
          + error_code            = 552
          + response_code         = 12
          + response_page_path    = "page3"
        }
      + custom_error_response {
          + error_caching_min_ttl = 60
          + error_code            = 553
          + response_code         = 13
          + response_page_path    = "page4"
        }

      <..ommitted for brevity...>
    }

  # aws_s3_bucket.b will be created
  + resource "aws_s3_bucket" "b" {
      <..ommitted for brevity...>
    }

Plan: 2 to add, 0 to change, 0 to destroy.

terraform version

Terraform v0.12.20

• provider.aws v3.9.0