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 gathers nothing itself. It depends on the collectors below, which the CLI runs once per build before any check, and reads what they found out of GUARDRAIL_FACTS. A collector that collects nothing skips this guardrail rather than failing it.

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. Read out of the files themselves, so it works on a runner with no Terraform installed, and enriched with the versions an initialised root has already resolved when the terraform CLI is there.	none

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

Configuration

{
  "guardrails": {
      "failOn": "error",
      "comment": true,
      "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

Declare locking on the backend. S3 has held the lock itself since Terraform 1.10:

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

Older configurations name a dynamodb_table instead, and both are recognised. Without a lock, two applies that overlap each write a state file describing only what they did, and the resources the other created are then unmanaged and invisible.

More in terraform

• terraform/modules-pinned. Every module a Terraform root takes from a registry or a git URL names the version it takes, so the same commit resolves to the same module twice.
• 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 its backend encrypted, so the state it writes is not readable from the bucket it sits in.

All 6 terraform guardrails