[Enhancement]: ECS Task Definitions now supports deletion

[andrewradamis-paay]

Description

I haven't found the official AWS announcement yet, but it appears ECS rolled out a Delete Task Definitions API for ECS (finally). The AWS ECS Console has also been updated.

Per the documentation, deletion requires the task definition to be deregistered first.

I don't think this feature has hit the aws-go-sdk yet, but I believe it will require some discussion before implementing as it could introduce a breaking change. I've listed a few ways in the Potential Terraform Configuration section that would be both opt-in and useful to me.

Affected Resource(s) and/or Data Source(s)

aws_ecs_task_definition

Potential Terraform Configuration

// Deletes task definition after de-registering
resource "aws_ecs_task_definition" "service" {
  ...
  delete_on_deregister = true
}

// Delete all old task definition iterations except the last 3
resource "aws_ecs_task_definition" "service" {
  family = "service"
  ...
  delete_old_versions_except = 3
}

// Delete all iterations on delete
resource "aws_ecs_task_definition" "service" {
  family = "service"
  ...
  delete_all_iterations_on_dispose = true
}

References

https://docs.aws.amazon.com/AmazonECS/latest/APIReference/API_DeleteTaskDefinitions.html
aws/containers-roadmap#685 (comment)

Would you like to implement a fix?

Yes

[github-actions]

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[ewbankkit]

Announcement.
Blog post.

[wedge-jarrad]

Here's my thoughts. I'm nobody, so take them for what they're worth :D

delete_on_deregister - probably the easiest to implement though I have a hard time imagining that I would use this. I currently use skip_destroy = true in order to keep the old versions active to facilitate rollbacks.

delete_all_iterations_on_dispose - Seems useful as a 1-time cleanup task if you've built up a large number of task definition versions over the years while waiting for the ability to delete them to be implemented. But, in the extreme case where you have thousands of versions, this may take a very long time. A user might be more wise to manage the 1-time cleanup outside of Terraform.

delete_old_versions_except - To me this would be the most useful option by far. The first time you add it on an existing task def with many old versions you'll have the same issue as I mentioned for delete_all_iterations_on_dispose so user beware, but it would be useful going forward. My only argument against it is that it will be obsoleted (hopefully soon but who knows) by official lifecycle management aws/containers-roadmap#1967. Would also need to figure out how this would interact with skip_destroy = true since I want to keep the old version active until I'm sure I won't want to roll back to it, at which point it can be both deregistered and deleted.

[david-hodgson-at-sky]

This feature would be a partial mitigation to #11526 Terraform forcing replacement of ECS task definition