terraform-aws-tfstate-backend

Terraform module to provision an S3 bucket to store terraform.tfstate file and a DynamoDB table to lock the state file to prevent concurrent modifications and state corruption.

The module supports the following:

1. Forced server-side encryption at rest for the S3 bucket
2. S3 bucket versioning to allow for Terraform state recovery in the case of accidental deletions and human errors
3. State locking and consistency checking via DynamoDB table to prevent concurrent operations
4. DynamoDB server-side encryption

https://www.terraform.io/docs/backends/types/s3.html

NOTE: The operators of the module (IAM Users) must have permissions to create S3 buckets and DynamoDB tables when performing terraform plan and terraform apply

NOTE: This module cannot be used to apply changes to the mfa_delete feature of the bucket. Changes regarding mfa_delete can only be made manually using the root credentials with MFA of the AWS Account where the bucket resides. Please see: https://github.com/terraform-providers/terraform-provider-aws/issues/629

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Usage

Create

Follow this procedure just once to create your deployment.

1. Add the terraform_state_backend module to your main.tf file. The comment will help you remember to follow this procedure in the future:

   # You cannot create a new backend by simply defining this and then
   # immediately proceeding to "terraform apply". The S3 backend must
   # be bootstrapped according to the simple yet essential procedure in
   # https://github.com/cloudposse/terraform-aws-tfstate-backend#usage
   module "terraform_state_backend" {
     source = "cloudposse/tfstate-backend/aws"
     # Cloud Posse recommends pinning every module to a specific version
     # version     = "x.x.x"
     namespace  = "eg"
     stage      = "test"
     name       = "terraform"
     attributes = ["state"]
   
     terraform_backend_config_file_path = "."
     terraform_backend_config_file_name = "backend.tf"
     force_destroy                      = false
   }
   
   # Your Terraform configuration
   module "another_module" {
     source = "....."
   }
   

   Module inputs terraform_backend_config_file_path and terraform_backend_config_file_name control the name of the backend definition file. Note that when terraform_backend_config_file_path is empty (the default), no file is created.

2. terraform init. This downloads Terraform modules and providers.

3. terraform apply -auto-approve. This creates the state bucket and DynamoDB locking table, along with anything else you have defined in your *.tf file(s). At this point, the Terraform state is still stored locally.

   Module terraform_state_backend also creates a new backend.tf file that defines the S3 state backend. For example:

   backend "s3" {
     region         = "us-east-1"
     bucket         = "< the name of the S3 state bucket >"
     key            = "terraform.tfstate"
     dynamodb_table = "< the name of the DynamoDB locking table >"
     profile        = ""
     role_arn       = ""
     encrypt        = true
   }
   

   Henceforth, Terraform will also read this newly-created backend definition file.

4. terraform init -force-copy. Terraform detects that you want to move your Terraform state to the S3 backend, and it does so per -auto-approve. Now the state is stored in the S3 bucket, and the DynamoDB table will be used to lock the state to prevent concurrent modification.

This concludes the one-time preparation. Now you can extend and modify your Terraform configuration as usual.

Destroy

Follow this procedure to delete your deployment.

1. In main.tf, change the terraform_state_backend module arguments as follows:

    module "terraform_state_backend" {
      # ...
      terraform_backend_config_file_path = ""
      force_destroy                      = true
    }
   

2. terraform apply -target module.terraform_state_backend -auto-approve. This implements the above modifications by deleting the backend.tf file and enabling deletion of the S3 state bucket.
3. terraform init -force-copy. Terraform detects that you want to move your Terraform state from the S3 backend to local files, and it does so per -auto-approve. Now the state is once again stored locally and the S3 state bucket can be safely deleted.
4. terraform destroy. This deletes all resources in your deployment.
5. Examine local state file terraform.tfstate to verify that it contains no resources.

Bucket Replication (Disaster Recovery)

To enable S3 bucket replication in this module, set s3_replication_enabled to true and populate s3_replica_bucket_arn with the ARN of an existing bucket.

module "terraform_state_backend" {
  source = "cloudposse/tfstate-backend/aws"
  # Cloud Posse recommends pinning every module to a specific version
  # version     = "x.x.x"
  namespace  = "eg"
  stage      = "test"
  name       = "terraform"
  attributes = ["state"]

  terraform_backend_config_file_path = "."
  terraform_backend_config_file_name = "backend.tf"
  force_destroy                      = false

  s3_replication_enabled = true
  s3_replica_bucket_arn  = "arn:aws:s3:::eg-test-terraform-tfstate-replica"
}

Lifecycle Rules

This module does not create a lifecycle configuration. A bucket can have only one, so add your own with the s3_bucket_id output.

Remove old state versions (current states are not changed):

resource "aws_s3_bucket_lifecycle_configuration" "tfstate" {
  bucket = module.terraform_state_backend.s3_bucket_id

  rule {
    id     = "prune-noncurrent-versions"
    status = "Enabled"
    filter {}
    noncurrent_version_expiration {
      noncurrent_days           = 30
      newer_noncurrent_versions = 90
    }
  }
}

To also remove the state of destroyed workspaces, add a rule that expires small objects. An empty state is a few hundred bytes. Check the object sizes in your bucket before you set the limit. Versioning keeps the previous version, so you can restore it until the noncurrent rule removes it.

  rule {
    id     = "expire-empty-states"
    status = "Enabled"
    filter {
      object_size_less_than = 512
    }
    expiration {
      days = 30
    }
  }

[!IMPORTANT] In Cloud Posse’s examples, we avoid pinning modules to specific versions to prevent discrepancies between the documentation and the latest released versions. However, for your own projects, we strongly advise pinning each module to the exact version you’re using. This practice ensures the stability of your infrastructure. Additionally, we recommend implementing a systematic approach for updating versions to avoid unexpected changes.

Requirements

Modules

Resources

Inputs

{
  “additional_tag_map”: {},
  “attributes”: [],
  “delimiter”: null,
  “descriptor_formats”: {},
  “enabled”: true,
  “environment”: null,
  “id_length_limit”: null,
  “label_key_case”: null,
  “label_order”: [],
  “label_value_case”: null,
  “labels_as_tags”: [
    “unset”
  ],
  “name”: null,
  “namespace”: null,
  “regex_replace_chars”: null,
  “stage”: null,
  “tags”: {},
  “tenant”: null
}

[
  “default”
]

list(object({
    target_bucket = string
    target_prefix = string
  }))

Outputs

Related Projects

Check out these related projects.

• terraform-aws-dynamodb - Terraform module that implements AWS DynamoDB with support for AutoScaling
• terraform-aws-dynamodb-autoscaler - Terraform module to provision DynamoDB autoscaler

✨ Contributing

This project is under active development, and we encourage contributions from our community.

Many thanks to our outstanding contributors:

For 🐛 bug reports & feature requests, please use the issue tracker.

In general, PRs are welcome. We follow the typical “fork-and-pull” Git workflow.

1. Review our Code of Conduct and Contributor Guidelines.
2. Fork the repo on GitHub
3. Clone the project to your own machine
4. Commit changes to your own branch
5. Push your work back up to your fork
6. Submit a Pull Request so that we can review your changes

NOTE: Be sure to merge the latest changes from “upstream” before making a pull request!

Running Terraform Tests

We use Atmos to streamline how Terraform tests are run. It centralizes configuration and wraps common test workflows with easy-to-use commands.

All tests are located in the test/ folder.

Under the hood, tests are powered by Terratest together with our internal Test Helpers library, providing robust infrastructure validation.

Setup dependencies:

• Install Atmos (installation guide)
• Install Go 1.24+ or newer
• Install Terraform or OpenTofu

To run tests:

• Run all tests:

  atmos test run
  

• Clean up test artifacts:

  atmos test clean
  

• Explore additional test options:

  atmos test --help
  

The configuration for test commands is centrally managed. To review what’s being imported, see the atmos.yaml file.

Learn more about our automated testing in our documentation or implementing custom commands with atmos.

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License

Licensed to the Apache Software Foundation (ASF) under one
or more contributor license agreements.  See the NOTICE file
distributed with this work for additional information
regarding copyright ownership.  The ASF licenses this file
to you under the Apache License, Version 2.0 (the
"License"); you may not use this file except in compliance
with the License.  You may obtain a copy of the License at

  https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing,
software distributed under the License is distributed on an
"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
KIND, either express or implied.  See the License for the
specific language governing permissions and limitations
under the License.

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