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:

Forced server-side encryption at rest for the S3 bucket
S3 bucket versioning to allow for Terraform state recovery in the case of accidental deletions and human errors
State locking and consistency checking via DynamoDB table to prevent concurrent operations
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: hashicorp/terraform-provider-aws#629

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Usage

Create

Follow this procedure just once to create your deployment.

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.

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

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

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

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.
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.
terraform destroy. This deletes all resources in your deployment.
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"
}

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.

Makefile Targets

Available targets:

  help                                Help screen
  help/all                            Display help for all targets
  help/short                          This help short screen
  lint                                Lint terraform code

Requirements

Name	Version
terraform	>= 1.1.0
aws	>= 4.9.0
local	>= 2.0
time	>= 0.7.1

Providers

Name	Version
aws	>= 4.9.0
local	>= 2.0
time	>= 0.7.1

Modules

Name	Source	Version
bucket_label	cloudposse/label/null	0.25.0
dynamodb_table_label	cloudposse/label/null	0.25.0
replication_label	cloudposse/label/null	0.25.0
this	cloudposse/label/null	0.25.0

Resources

Name	Type
aws_dynamodb_table.with_server_side_encryption	resource
aws_iam_policy.replication	resource
aws_iam_role.replication	resource
aws_iam_role_policy_attachment.replication	resource
aws_s3_bucket.default	resource
aws_s3_bucket_acl.default	resource
aws_s3_bucket_logging.default	resource
aws_s3_bucket_ownership_controls.default	resource
aws_s3_bucket_policy.default	resource
aws_s3_bucket_public_access_block.default	resource
aws_s3_bucket_replication_configuration.replication	resource
aws_s3_bucket_server_side_encryption_configuration.default	resource
aws_s3_bucket_versioning.default	resource
local_file.terraform_backend_config	resource
time_sleep.wait_for_aws_s3_bucket_settings	resource
aws_iam_policy_document.aggregated_policy	data source
aws_iam_policy_document.bucket_policy	data source
aws_iam_policy_document.replication	data source
aws_iam_policy_document.replication_sts	data source
aws_region.current	data source

Inputs

Name	Description	Type	Default	Required
acl	The canned ACL to apply to the S3 bucket	`string`	`"private"`	no
additional_tag_map	Additional key-value pairs to add to each map in `tags_as_list_of_maps`. Not added to `tags` or `id`. This is for some rare cases where resources want additional configuration of tags and therefore take a list of maps with tag key, value, and additional configuration.	`map(string)`	`{}`	no
arn_format	ARN format to be used. May be changed to support deployment in GovCloud/China regions.	`string`	`"arn:aws"`	no
attributes	ID element. Additional attributes (e.g. `workers` or `cluster`) to add to `id`, in the order they appear in the list. New attributes are appended to the end of the list. The elements of the list are joined by the `delimiter` and treated as a single ID element.	`list(string)`	`[]`	no
billing_mode	DynamoDB billing mode	`string`	`"PAY_PER_REQUEST"`	no
block_public_acls	Whether Amazon S3 should block public ACLs for this bucket	`bool`	`true`	no
block_public_policy	Whether Amazon S3 should block public bucket policies for this bucket	`bool`	`true`	no
bucket_enabled	Whether to create the S3 bucket.	`bool`	`true`	no
bucket_ownership_enforced_enabled	Set bucket object ownership to "BucketOwnerEnforced". Disables ACLs.	`bool`	`true`	no
context	Single object for setting entire context at once. See description of individual variables for details. Leave string and numeric variables as `null` to use default value. Individual variable settings (non-null) override settings in context object, except for attributes, tags, and additional_tag_map, which are merged.	`any`	{ "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 }	no
deletion_protection_enabled	A boolean that enables deletion protection for DynamoDB table	`bool`	`false`	no
delimiter	Delimiter to be used between ID elements. Defaults to `-` (hyphen). Set to `""` to use no delimiter at all.	`string`	`null`	no
descriptor_formats	Describe additional descriptors to be output in the `descriptors` output map. Map of maps. Keys are names of descriptors. Values are maps of the form `{<br> format = string<br> labels = list(string)<br>}` (Type is `any` so the map values can later be enhanced to provide additional options.) `format` is a Terraform format string to be passed to the `format()` function. `labels` is a list of labels, in order, to pass to `format()` function. Label values will be normalized before being passed to `format()` so they will be identical to how they appear in `id`. Default is `{}` (`descriptors` output will be empty).	`any`	`{}`	no
dynamodb_enabled	Whether to create the DynamoDB table.	`bool`	`true`	no
dynamodb_table_name	Override the name of the DynamoDB table which defaults to using `module.dynamodb_table_label.id`	`string`	`null`	no
enable_point_in_time_recovery	Enable DynamoDB point-in-time recovery	`bool`	`true`	no
enable_public_access_block	Enable Bucket Public Access Block	`bool`	`true`	no
enabled	Set to false to prevent the module from creating any resources	`bool`	`null`	no
environment	ID element. Usually used for region e.g. 'uw2', 'us-west-2', OR role 'prod', 'staging', 'dev', 'UAT'	`string`	`null`	no
force_destroy	A boolean that indicates the S3 bucket can be destroyed even if it contains objects. These objects are not recoverable	`bool`	`false`	no
id_length_limit	Limit `id` to this many characters (minimum 6). Set to `0` for unlimited length. Set to `null` for keep the existing setting, which defaults to `0`. Does not affect `id_full`.	`number`	`null`	no
ignore_public_acls	Whether Amazon S3 should ignore public ACLs for this bucket	`bool`	`true`	no
label_key_case	Controls the letter case of the `tags` keys (label names) for tags generated by this module. Does not affect keys of tags passed in via the `tags` input. Possible values: `lower`, `title`, `upper`. Default value: `title`.	`string`	`null`	no
label_order	The order in which the labels (ID elements) appear in the `id`. Defaults to ["namespace", "environment", "stage", "name", "attributes"]. You can omit any of the 6 labels ("tenant" is the 6th), but at least one must be present.	`list(string)`	`null`	no
label_value_case	Controls the letter case of ID elements (labels) as included in `id`, set as tag values, and output by this module individually. Does not affect values of tags passed in via the `tags` input. Possible values: `lower`, `title`, `upper` and `none` (no transformation). Set this to `title` and set `delimiter` to `""` to yield Pascal Case IDs. Default value: `lower`.	`string`	`null`	no
labels_as_tags	Set of labels (ID elements) to include as tags in the `tags` output. Default is to include all labels. Tags with empty values will not be included in the `tags` output. Set to `[]` to suppress all generated tags. Notes: The value of the `name` tag, if included, will be the `id`, not the `name`. Unlike other `null-label` inputs, the initial setting of `labels_as_tags` cannot be changed in later chained modules. Attempts to change it will be silently ignored.	`set(string)`	[ "default" ]	no
logging	Destination (S3 bucket name and prefix) for S3 Server Access Logs for the S3 bucket.	list(object({ target_bucket = string target_prefix = string }))	`[]`	no
mfa_delete	A boolean that indicates that versions of S3 objects can only be deleted with MFA. ( Terraform cannot apply changes of this value; hashicorp/terraform-provider-aws#629 )	`bool`	`false`	no
name	ID element. Usually the component or solution name, e.g. 'app' or 'jenkins'. This is the only ID element not also included as a `tag`. The "name" tag is set to the full `id` string. There is no tag with the value of the `name` input.	`string`	`null`	no
namespace	ID element. Usually an abbreviation of your organization name, e.g. 'eg' or 'cp', to help ensure generated IDs are globally unique	`string`	`null`	no
permissions_boundary	ARN of the policy that is used to set the permissions boundary for the IAM replication role	`string`	`""`	no
prevent_unencrypted_uploads	Prevent uploads of unencrypted objects to S3	`bool`	`true`	no
profile	AWS profile name as set in the shared credentials file	`string`	`""`	no
read_capacity	DynamoDB read capacity units when using provisioned mode	`number`	`5`	no
regex_replace_chars	Terraform regular expression (regex) string. Characters matching the regex will be removed from the ID elements. If not set, `"/[^a-zA-Z0-9-]/"` is used to remove all characters other than hyphens, letters and digits.	`string`	`null`	no
restrict_public_buckets	Whether Amazon S3 should restrict public bucket policies for this bucket	`bool`	`true`	no
role_arn	The role to be assumed	`string`	`""`	no
s3_bucket_name	S3 bucket name. If not provided, the name will be generated from the context by the label module.	`string`	`""`	no
s3_replica_bucket_arn	The ARN of the S3 replica bucket (destination)	`string`	`""`	no
s3_replication_enabled	Set this to true and specify `s3_replica_bucket_arn` to enable replication	`bool`	`false`	no
source_policy_documents	List of IAM policy documents (in JSON format) that are merged together into the generated S3 bucket policy. Statements must have unique SIDs. Statement having SIDs that match policy SIDs generated by this module will override them.	`list(string)`	`[]`	no
stage	ID element. Usually used to indicate role, e.g. 'prod', 'staging', 'source', 'build', 'test', 'deploy', 'release'	`string`	`null`	no
tags	Additional tags (e.g. `{'BusinessUnit': 'XYZ'}`). Neither the tag keys nor the tag values will be modified by this module.	`map(string)`	`{}`	no
tenant	ID element _(Rarely used, not included by default)_. A customer identifier, indicating who this instance of a resource is for	`string`	`null`	no
terraform_backend_config_file_name	(Deprecated) Name of terraform backend config file to generate	`string`	`"terraform.tf"`	no
terraform_backend_config_file_path	(Deprecated) Directory for the terraform backend config file, usually `.`. The default is to create no file.	`string`	`""`	no
terraform_backend_config_template_file	(Deprecated) The path to the template used to generate the config file	`string`	`""`	no
terraform_state_file	The path to the state file inside the bucket	`string`	`"terraform.tfstate"`	no
terraform_version	The minimum required terraform version	`string`	`"1.0.0"`	no
write_capacity	DynamoDB write capacity units when using provisioned mode	`number`	`5`	no

Outputs

Name	Description
dynamodb_table_arn	DynamoDB table ARN
dynamodb_table_id	DynamoDB table ID
dynamodb_table_name	DynamoDB table name
s3_bucket_arn	S3 bucket ARN
s3_bucket_domain_name	S3 bucket domain name
s3_bucket_id	S3 bucket ID
s3_replication_role_arn	The ARN of the IAM Role created for replication, if enabled.
terraform_backend_config	Rendered Terraform backend config file

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

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License

Preamble to the Apache License, Version 2.0

Complete license is available in the LICENSE file.

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cloudposse / terraform-aws-tfstate-backend