How to Import an AWS ElastiCache Subnet Group into Terraform

Import AWS ElastiCache Subnet Group with Terraback (recommended)

Terraback reverse-engineers your live infrastructure: it reads the Amazon ElastiCache resource with read-only credentials, generates the HCL, and produces the exact import block. Two commands take you from a live AWS ElastiCache Subnet Group to managed Terraform.

terraback scan all aws --region us-east-1

terraback aws import --method bulk

The Terraform import block

Terraback emits a Terraform 1.5+ import block like the one below. Because the block lives in your configuration, the import is reviewable in a pull request and repeatable across environments.

import {
  to = aws_elasticache_subnet_group.cache
  id = "app-prod-cache-subnets"
}

Example aws_elasticache_subnet_group configuration

Here is a realistic AWS ElastiCache Subnet Group block. Terraback generates a fuller version from your actual resource attributes; this is a minimal, valid starting point.

resource "aws_elasticache_subnet_group" "cache" {
  name       = "app-prod-cache-subnets"
  subnet_ids = ["subnet-0aa1", "subnet-0bb2"]
}

Gotchas when importing a AWS ElastiCache Subnet Group

• Import by name; the ARN does not work as the import ID.
• AWS lower-cases the subnet group name on creation, so use the lower-case form in the import ID to avoid a not-found error.
• All subnets must belong to the same VPC as the cache cluster that uses this group; mixing VPCs is rejected at apply time.
• If description is omitted, AWS stores the literal string "Managed by Terraform" or a default; set it explicitly to avoid a recurring diff.

Doing it manually with terraform import

The native approach is to write the aws_elasticache_subnet_group block by hand, then run terraform import aws_elasticache_subnet_group.example <import-id> for every resource, one at a time. That works for a handful of resources, but it does not scale: you author all the HCL yourself and repeat the command for each item. Terraback generates the HCL and the import blocks for your whole account in one pass.

Import other AWS resources