Guardrails / terraform

Terraform state is locked

terraform/state-locking@v1

Every live Terraform root declares state locking, so two applies cannot write the same state at once.

Id	terraform/state-locking
Version	v1
Category	terraform
Default severity	error
Interpreter	python3
Timeout	30 seconds
Violations tolerated	0
Collects	terraform

Collectors

This guardrail doesn't gather anything itself. It relies on the collectors below, which the CLI runs once per build before any check, and reads what they found from GUARDRAIL_FACTS. If a collector collects nothing, this guardrail is skipped, not failed.

Collector	Gathers	Inputs it is given
terraform	The Terraform configuration in the checkout: every root directory holding .tf files, the backend it stores state in, the providers and modules it takes on and how tightly they are pinned, the resources it declares, the variables it takes, the lock file that resolves it, and any state file left in the tree. Everything is read from the files themselves, so it works on a runner with no Terraform installed. When the terraform CLI is there, the versions an initialised root has already resolved are added.	none

The inputs above are this guardrail's own inputs, passed straight through to the collector. Setting one in buildnote.json changes what is collected, and two guardrails configured the same way share a single collection.

Configuration

{
  "guardrails": {
      "failOn": "error",
      "checks": [
          {
              "use": "terraform/state-locking@v1",
              "severity": "error",
              "with": {
                  "modulePaths": "modules/*,*/modules/*"
              },
              "exemptions": []
          }
      ]
  }
}

Inputs

Input	Description	Default	Environment variable
modulePaths	Comma separated globs naming directories that hold reusable modules rather than live roots. A module declares no backend and pins nothing, so it is not judged here. A directory another root takes on with a local source is recognised as a module whether or not it matches.	modules/*,*/modules/*	GUARDRAIL_INPUT_MODULEPATHS

How to fix

Enable locking on the backend. Since Terraform 1.10, S3 can hold the lock itself:

terraform {
  backend "s3" {
    bucket       = "company-terraform-state"
    key          = "live/main/terraform.tfstate"
    region       = "eu-west-1"
    use_lockfile = true
  }
}

Older configurations use a dynamodb_table instead, and both are recognised. Without a lock, two overlapping applies each write a state file that describes only their own changes, and the resources the other one created become unmanaged and invisible.

More in terraform

• terraform/modules-pinned. Every module a Terraform root pulls from a registry or a git URL names a version, so the same commit always resolves to the same module code.
• terraform/no-plaintext-secrets. Every Terraform variable named like a credential declares sensitive = true.
• terraform/providers-pinned. Every provider a live Terraform root requires is pinned to one exact version, and the lock file that resolves them is committed.
• terraform/remote-state. Every live Terraform root stores its state in a remote backend, and no state file is left in the checkout.
• terraform/state-encrypted. Every live Terraform root declares an encrypted backend, so its state isn't stored in the clear in its bucket.

All 6 terraform guardrails