README.md

This example demonstrates a basic usage of this module.

On your system,

• you have a root module tfstate-s3-manager which includes terraform-aws-multi-stack-backends
• you have (in this example) 4 root modules, each in their own folder
• two of those root modules belong to one stack, the other two belong to the other stack
• the tfstate-s3-manager/main.tf defines the stacks to manage:

  stacks_map = {
    stack-1 = {
      network = {
        path = "../stack1-network"
      }
      cluster = {
        path = "../stack1-cluster"
      }
    },
    stack-2 = {
      network = {
        path = "../stack2-network"
      }
      cluster = {
        path = "../stack2-cluster"
      }
    },
  }

• the names are arbitrary (stack-1, network, etc)

See the left green box in following diagram:

Step 1

Assume you have already run terraform apply in each root module of each stack. The order does not matter. This step can be done after step 2 as well.

Then terraform apply in the tfstate-s3-manager root module, which will create the common bucket, its replica, dynamodb lock table, IAM policy etc, as well as all the backend.tf files (one for each root module of each stack, specified in the main.tf). See the following diagram.

Step 2

Then you should (although this is optional) move the tfstate-s3-manager tfstate to s3, by running terraform init for that root module. This can be done before or after step 3.

Step 3

Finally you can go to each stack's root module's and terraform init. This will move each stack's root module's tfstate from local host to s3, using the backend.tf generated by the tfstate-s3-manager. See the following diagram.

Subsequently

From then on, whenever you terraform apply in one of the root modules associated with a stack, the whole stack will get locked. See the following diagram.

To delete a root module from a stack, if the stack has other root modules in main.tf

• terraform destroy for the root module you no longer need

• edit the tfstate-s3-manager/main.tf by removing the entry; ATTENTION: if there are no modules left for that stack in main.tf, leave the stack's empty map so that the dynamodb table does not get destroyed yet, eg

  stacks_map = {
    stack-3 = {}, // no longer needed
  }

• depending on your situation:

  • just delete the module folder, OR
  • terraform apply to remove the corresponding backend.tf then terraform init

Once a stack's module have all been removed, you can delete the empty stack map from stacks_map, and terraform apply to remove the dynamodb table for that stack.