Atlantis

https://www.runatlantis.io/

Terraform pull request automation on GitHub using GitHub Actions.

• interaction is through pull request comments
• Atlantis comments on the PR with command prompts of what to type in comments (and even corrects you if you comment terraform instead of atlantis command)
• runs the Terraform / Terragrunt plan automatically upon creation / commit changes to the PR including GitHub update from trunk
• prints the plan output in PR comment
• comment atlantis apply to respond for Atlantis to apply the changes
• requires PR to be mergeable before it will honor atlantis apply comments
  • so your other PR checks must pass first
• Terragrunt becomes more useful in this context to modularize code base to reduce blast radius of changes and have Atlantis do shorter plan and apply runs

• Usage
• Do Not Merge Pull Requests Early
• Back up Atlantis.db from StatefulSet pod
• Troubleshooting
  • Stale Error not picking up Terraform Module fix
  • Checksum Mismatch in .terraform.lock.hcl

Usage

atlantis plan # -d path/to/terragrunt/module/directory

atlantis apply

Do Not Merge Pull Requests Early

If you merge a pull request, Atlantis will refuse to operate and apply it.

You will then need to revert the PR and raise it again.

Back up Atlantis.db from StatefulSet pod

Take a copy to your local machine:

kubectl cp atlantis/atlantis-0:/atlantis-data/atlantis.db atlantis.db -c atlantis

Troubleshooting

Stale Error not picking up Terraform Module fix

You'll need to clear the state from the Atlantis kubernetes pod.

Exec into the pod:

kubectl exec -ti -n atlantis atlantis-0 -c atlantis -- /bin/bash

Go to the data directory:

cd /atlantis-data/

cd into the <owner>/<repo> GitHub subdirectory.

Delete the numbered subdirectory matching the GitHub pull request number.

Checksum Mismatch in .terraform.lock.hcl

If you get an error like this when running Terraform or Terragrunt:

Error: Required plugins are not installed

The installed provider plugins are not consistent with the packages selected
in the dependency lock file:
  - registry.terraform.io/hashicorp/aws: the cached package for registry.terraform.io/hashicorp/aws 5.80.0 (in .terraform/providers) does not match any of the checksums recorded in the dependency lock file

See the Terraform or Terragrunt docs for the explanation and solution.