terraform resource s3 upload file is not updated

Question

I am using terraform to upload a file with contents to s3.However, when the content changes, I need to update the s3 file as well. But since the state file stores that the s3 upload was completed, it doesn't upload a new file.

resource "local_file" "timestamp" {
  filename = "timestamp"
  content = "${timestamp()}"
}


resource "aws_s3_bucket_object" "upload" {
 bucket = "bucket"
 key = "date"
 source = "timestamp"
}

expected:

aws_s3_bucket_object change detected aws_s3_bucket_object.timestamp Creating...

result:

aws_s3_bucket_object Refreshing state...

Answer 1

When you give Terraform the path to a file rather than the direct content to upload, it is the name of the file that decides whether the resource needs to be updated, rather than the file's contents.

For a short piece of data as shown in your example, the easiest solution is to specify the data directly in the resource configuration:

resource "aws_s3_bucket_object" "upload" {
 bucket  = "bucket"
 key     = "date"
 content = "${timestamp()}"
}

If your file is actually too large to reasonably load into a string variable, or if it contains raw binary data that cannot be loaded into a string, you can set the etag of the object to an MD5 hash of the content so that the provider can see when the content has changed:

resource "aws_s3_bucket_object" "upload" {
 bucket  = "bucket"
 key     = "date"
 source  = "${path.module}/timestamp"
 etag    = "${filemd5("${path.module}/timestamp")}"
}

By setting the etag, any change to the content of the file will cause this hash result to change and thus allow the provider to detect that the object needs to be updated.