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Terraform Tips & Tricks

S3 Bucket Lifecycle Rules​

Example: S3 Bucket Lifecycle Rules
module "assets_bucket_label" {
  source    = "git::https://github.com/cloudposse/terraform-null-label.git?ref=tags/0.3.3"
  namespace = "eg"
  stage     = "dev"
  name      = "assets"
}

resource "aws_s3_bucket" "assets" {
  bucket        = "${module.assets_bucket_label.id}"
  tags          = "${module.assets_bucket_label.tags}"
  acl           = "private"
  region        = "us-west-2"
  force_destroy = false

  lifecycle_rule {
    id      = "${module.assets_bucket_label.id}"
    enabled = true

    prefix = ""
    tags   = "${module.assets_bucket_label.tags}"

    noncurrent_version_expiration {
      days = "90"
    }

    noncurrent_version_transition {
      days          = "60"
      storage_class = "GLACIER"
    }

    transition {
      days          = "30"
      storage_class = "STANDARD_IA"
    }

    transition {
      days          = "60"
      storage_class = "GLACIER"
    }

    expiration {
      days = "180"
    }
  }
}

For an example of how we use it, check out our terraform-aws-s3-log-storage module.

info

Encrypted S3 Buckets​

Example: Encrypted S3 Bucket
module "assets_bucket_label" {
  source    = "git::https://github.com/cloudposse/terraform-null-label.git?ref=tags/0.3.3"
  namespace = "eg"
  stage     = "dev"
  name      = "assets"
}

resource "aws_s3_bucket" "assets" {
  bucket        = "${module.assets_bucket_label.id}"
  tags          = "${module.assets_bucket_label.tags}"
  acl           = "private"
  region        = "us-west-2"
  force_destroy = false

  server_side_encryption_configuration {
    rule {
      apply_server_side_encryption_by_default {
        sse_algorithm = "AES256"
      }
    }
  }
}

For an example of how we use it, check out our terraform-aws-s3-log-storage module.

Use Pre Commit Hooks for Linting​

We strongly urge that all code be linted prior to checking into Git. Running terraform fmt on the codebase before committing will accomplish this.

To set this up so that it happens automatically prior to any commit, configure git pre-commit hooks using the pre-commit utility.

OSX Installation​

brew install pre-commit

Then run pre-commit install in a given terraform repo to configure the hooks.

.pre-commit-config.yaml​

- repo: git://github.com/antonbabenko/pre-commit-terraform
  sha: v1.45.0
  hooks:
    - id: terraform_fmt
    - id: terraform_validate

After setting this up, every time you commit, the terraform fmt command will be run to canonicalize your files and a basic smoke test to validate all configurations without requiring required variables to be set.

Any time your commit affects any *.tf files, the validator will ensure well-formed terraform code.