Fix Terraform updating dependency layer object when content hasn't changed

[reweeden]

While doing Cumulus upgrades, I noticed that on every update Terraform was adding something like this to the plan:

 # module.thin_egress_app.aws_s3_bucket_object.lambda_code_dependency_archive will be updated in-place
  ~ resource "aws_s3_bucket_object" "lambda_code_dependency_archive" {
      ~ etag                          = "661d0e0eb0bc955857a7a71087a4208a-2" -> "96bac3b47b39d00107729959bc6689d3"
        id                            = "96bac3b47b39d00107729959bc6689d3.zip"
        tags                          = {}
      + version_id                    = (known after apply)
        # (20 unchanged attributes hidden)
    }

The etag attribute has a warning about using it for files larger than 16MB as it can cause this behavior where the etag after uploading with a multipart upload does not match the full source code hash causing Terraform to needlessly update the object.

While I was at it I also applied the tags variable to the bucket objects as well.

[mattp0]

"Triggers updates when the value changes."

Won't this cause updates not to occur when the content changes ?

[reweeden]

"Triggers updates when the value changes."

Won't this cause updates not to occur when the content changes ?

That's what source_hash is for. Also the key is the hash of the content, so that will change also triggering an update.