Allow further customization of Terraform Lock table for S3 Remote State

STATUS: In proposal

Background

When Terragrunt creates a DynamoDB table, it sets the throughput to the default, PROVISIONED. Provisioned is good for stable throughput, but Terraform largely works with variable workloads, often going unused.

AWS also offers a PAY_PER_REQUEST billing mode that charges based on the number of requests to the lock table. The pricing is dirt cheap, and it will further reduce the costs associated with using Terragrunt to manage Terraform’s base requirements.

Terraform has solved this problem: It involves creating and managing the resource manually. But, if Terragrunt is going to be managing the table, it should allow for additional configuration to be layered on top of it via Terragrunt.

Proposed solution

dynamodb_table_config block in remote_state.config

Because our company has a need for it, I’ve implemented a solution in my own fork that accomplishes this.

https://github.com/ThatGerber/terragrunt/tree/add-dynamodb-billing-mode

The dynamodb_table_config block accepts several arguments that are forwarded through to the DynamoTableInput object, pulling in additional values from the parent config as defaults.

To receive the full values, I had to write a few interfaces for the methods being called (like GetLockTableName) and change the function calls to accept the interfaces instead of strings.

dynamodb_table_config block that populates dynamodb.CreateTableInput struct

Another option is to create a config attribute that accepts any arguments that would be sent to CreateTable or UpdateTable map the values through to the methods when they’re being applied.

References

• DynamoDB Pricing
• DynamoDB Billing Mods