How to Import an Google Cloud Spanner Instance into Terraform

Import Google Cloud Spanner Instance with Terraback (recommended)

Terraback reverse-engineers your live infrastructure: it reads the Cloud Spanner resource with read-only credentials, generates the HCL, and produces the exact import block. Two commands take you from a live Google Cloud Spanner Instance to managed Terraform.

terraback scan all gcp --project my-gcp-project

terraback gcp 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 = google_spanner_instance.prod
  id = "projects/my-project/instances/prod-spanner"
}

Example google_spanner_instance configuration

Here is a realistic Google Cloud Spanner Instance block. Terraback generates a fuller version from your actual resource attributes; this is a minimal, valid starting point.

resource "google_spanner_instance" "prod" {
  name         = "prod-spanner"
  config       = "regional-us-central1"
  display_name = "Production Spanner"
  num_nodes    = 1
}

Gotchas when importing a Google Cloud Spanner Instance

• config is the instance configuration name such as regional-us-central1 or nam3 (a multi-region) and is immutable.
• Capacity is set with either num_nodes or processing_units, not both; match whichever the live instance uses.
• Databases inside the instance are separate google_spanner_database resources and are not imported with the instance.
• force_destroy defaults to false, so Terraform cannot delete an instance that still contains databases.

Doing it manually with terraform import

The native approach is to write the google_spanner_instance block by hand, then run terraform import google_spanner_instance.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 Google Cloud resources