Terraform module source updater

A simple tool to update host, module path or revision of a module.

Disclaimer

This tool is under heavy development, so no part of it may be considered as stable.
Any commit may break the things so be sure to pin version to particular commit (releases are coming).

NOTE: Only git-over-https is well tested supported at the moment. More schemes and use cases might be added in the future

Assume, there are a lot of blocks like these in your Terraform setup:

main.tf

module "vpc" {
  source = "git::https://github.com/example-corp/terraform-modules.git//src/vpc?ref=v1.2.3"
}

module "rds" {
  source = "git::https://github.com/example-corp/terraform-modules.git//src/rds?ref=v1.2.9"
}

app/backend/main.tf

module "queue" {
  source = "git::https://github.com/example-corp/terraform-modules.git//src/sqs?ref=v1.1.3"
}

module "lambda" {
  source = "git::https://github.com/example-corp/terraform-modules.git//src/lambda?ref=v1.1.3"
}

mobile/backend/main.tf

module "api-gw" {
  source = "git::https://github.com/example-corp/terraform-modules.git//src/apigw?ref=v1.8.3"
}

so you end up with bunch of versions of the same repository.

This tool allows you to update desired module to a defined version in seconds.

Or have it as part of CI to be more declarative.

Usage

As CLI binary

$ tf-module-update -from.url='git::https://github.com/example-corp/terraform-modules.git//src/apigw?ref=v1.8.3' -to.revision='v2.1.1' /path/to/terraform/files /another/path/goes/here

CLI flags

There are 2 main flag sets for module source filtering and manipulation:

• '-from.*' performs filtering of modules in *.tf files that will be considered for updating
• '-to.*' builds patches to apply to source URL of filtered module

Flag	Meaning	Example
*.url	The full url of module source	https://github.com/example-org/tf-modules.git//aws/vpc/multizone?ref=v1.0.0
*.scheme	Source scheme	https, http
*.host	Host part	github.com
*.module	Module part	/example-org/tf-modules/aws/vpc
*.submodule	Submodule, if source scheme supports it	//src/subfolder/azure
*.revision	Revision, usually a tag in form of vX.Y.Z	v2.0.5
-write	Boolean flag to perform actual update on original files. Default (not set) is false
-log.level	Level of logging for application. Default is info	-log.level=debug

Both, from.* and to.* flag sets have only one rule for ordering: *.url, if present, builds the initial object and specific flags like *.submodule update it.

In this example:

$ tf-module-update -from.url='https://github.com/example-org/tf-modules.git//aws/vpc/multizone?ref=v1.0.0' -from.submodule='//aws/vpc/subnets' -to.revision='v1.2.1'

initial object to filter module sources will be built using full -from.url string but submodule is changed to //aws/vpc/subnets.

It is equivalent to this call:

$ tf-module-update -from.scheme='https' -from.host='github.com' -from.module='/example-org/tf-modules.git' -from.submodule='//aws/vpc/subnets' -from.revision='v1.0.0' -to.revision='v1.2.1'

but the previous example is less verbose.

The resulting logic would be: replace all occurrences of https://github.com/example-org/tf-modules.git//aws/vpc/subnets?ref=v1.0.0 with https://github.com/example-org/tf-modules.git//aws/vpc/subnets?ref=v1.2.1

As package in another project

TBD: pull the code out of internal folder

Examples

You can find a few .tf files to play with under examples/fixture directory

TBD

TBDs

• add Development section
• add Docker environment
• add Github Actions
  • deploy Docker images
• make code available as package