How do I use s3 lifeycle rules in Terraform in a modular form, i.e. referenced in separate JSON? - json

Question

Currently, I'm specifying lifecycle_rule under my s3 resource:
resource "aws_s3_bucket" "bucket-name" {
bucket = "bucket-name"
lifecycle_rule {
id = "Expiration Rule"
enabled = true
prefix = "reports/"
expiration {
days = 30
}
}
}
...but I imagine there must be a way to make this more modular, like putting the lifecycle rule into a separate JSON so I can reference it for multiple s3 buckets and reduce the need to edit each resource. I know how to do this in general and have done this with other resources as seen here:
resource "aws_iam_policy" "devops-admin-write" {
name = "devops-admin-s3"
description = "Devops-Admin group s3 policy."
policy = file("iam_policies/devops-admin-write.json")
}
...the difference is that "lifecycle_rule" is an argument and not an attribute - and it's not clear to me how to make it work. Google-Fu has not yielded any clear answers either.

Answer 1

You can use dynamic blocks that you execute with a generic local variable.
So you just need to change the local variable and changes will reflect in all places where this variable is used.
To make it more maintainable I would suggest building a module and reusing the module or using an exiting module.
But the locals + dynamic implementation could look like this:
locals {
lifecycle_rules = [
{
id = "Expiration Rule"
enabled = true
prefix = "reports/"
expiration = {
days = 30
}
}
]
}
resource "aws_s3_bucket" "bucket-name" {
bucket = "bucket-name"
dynamic "lifecycle_rule" {
for_each = local.lifecycle_rules
content {
id = lifecycle_rule.each.id
enabled = lifecycle_rule.each.enabled
prefix = lifecycle_rule.each.prefix
expiration {
days = lifecycle_rule.each.expiration.days
}
}
}
}
This does not check for errors and is not complete of course - it just implements your example.
See a more complete generic example in our terraform s3-bucket module: find code here