Terraform中能否通过嵌套count.index实现多AWS API Gateway域名与多路径映射的关联配置？

Absolutely, you can implement this 2D matrix-style mapping where each API Gateway domain name gets paired with all 4 of your API/stage combinations in Terraform. While you can't directly use nested count.index values, we can use Terraform's setproduct function to generate all required domain-API pairs, then create resources based on that list.

Step 1: Generate Domain-API Pairings #

First, create a local value that combines the indices of your domain names and your API/stage resources into a list of pairs. This gives us every possible combination (the Cartesian product) of domains and APIs:

locals {
  # Get indices for all created domain names (0 to count-1)
  domain_indices = range(length(aws_api_gateway_domain_name.apigw_domain_name))
  # Indices for your 4 API/stage resources (0,1,2,3)
  api_indices = range(4)
  # Generate all domain-api index pairs (e.g., [0,0], [0,1], ..., [n-1,3])
  domain_api_pairs = setproduct(local.domain_indices, local.api_indices)
}

Step 2: Create Base Path Mappings for Each Pair #

Now, use the domain_api_pairs list to create your aws_api_gateway_base_path_mapping resources. Each entry in the list corresponds to one domain-api pairing:

resource "aws_api_gateway_base_path_mapping" "api_gateway_base_path_mapping" {
  # One resource per domain-api pair
  count = length(local.domain_api_pairs)

  # Extract the domain index from the current pair
  domain_name = aws_api_gateway_domain_name.apigw_domain_name[local.domain_api_pairs[count.index][0]].domain_name
  # Extract the API index from the current pair
  api_id      = aws_api_gateway_rest_api.apigw[local.domain_api_pairs[count.index][1]].id
  stage_name  = aws_api_gateway_stage.stage[local.domain_api_pairs[count.index][1]].stage_name
}

How This Works #

• When var.api_server_custom_domain_name is non-empty (so aws_api_gateway_domain_name.apigw_domain_name has count=1 or more), local.domain_indices will include all indices for those domains.
• setproduct combines each domain index with each API index, creating a list where every domain is paired with every one of your 4 APIs.
• The count on the base path mapping resource will automatically match the total number of pairs, ensuring each domain gets all 4 mappings.
• If no domains are created (count=0), local.domain_indices will be empty, so local.domain_api_pairs will also be empty, and no base path mappings will be created—perfect for conditional behavior.

Can You Use Nested count.index? #

No, Terraform doesn't support directly nesting count.index values within the same resource block. You can't reference count.index for one resource while also using another count.index for a different list in the same argument. However, the setproduct approach achieves the same goal by precomputing all required pairs, letting you access both indices via the pre-generated list entries.

内容的提问来源于stack exchange，提问作者pankaj_m05