Lambda s3_object_version is not updated with new S3 etag

[gthole]

Terraform Version

Terraform v0.6.16

Affected Resource(s)

• aws_lambda_function
• aws_s3_bucket_object

Terraform Configuration Files

resource "aws_s3_bucket" "artifacts" {
    bucket = "test-terraform-issue-artifacts"
    acl = "private"
    versioning {
        enabled = true
    }
}

resource "aws_s3_bucket_object" "lambda_zip" {
    bucket = "${aws_s3_bucket.artifacts.bucket}"
    key = "lambda_function.zip"
    source = "./lambda_function.zip"
    etag = "${md5(file("./lambda_function.zip"))}"
}

resource "aws_lambda_function" "lambda_function" {
    s3_bucket = "${aws_s3_bucket_object.lambda_zip.bucket}"
    s3_key = "${aws_s3_bucket_object.lambda_zip.key}"
    s3_object_version = "${aws_s3_bucket_object.lambda_zip.version_id}"
    function_name = "test-lambda-function"
    description = "Example lambda to reproduce S3 version lag"
    role = "arn:aws:iam::1234567890:role/lambda_function_role"
    runtime = "java8"
    timeout = 15
    memory_size = 1024
    handler = "com.package.name.LambdaHandler::handle"
}

Expected Behavior

Modifying the S3 upload zip file with terraform apply should update the s3_object_version of the lambda function with the S3 bucket object's version_id.

Actual Behavior

The version_id on the S3 bucket object is updated after pushing the updated file, but the s3_object_version is not updated on the lambda.

Steps to Reproduce

1. terraform apply with the manifests listed above.
2. Modify the content of the zip file uploaded so that it forces a new S3 etag
3. terraform apply - note the S3 bucket object updates the etag, but Lambda does not get the new s3_object_version.
4. terraform apply again, the Lambda gets the new s3_object_version.

[gthole]

I also note that adding an explicit depends_on = ["aws_s3_bucket_object.lambda_zip"] to the Lambda function does not help.

[radeksimko]

Hi @gthole ,
this is unfortunately a known issue, specifically a missing schema feature - ComputedWhen.

In the current implementation all Computed fields are recognized correctly for re-computation at the time of (re)creation of the whole resource, but not at the time of update - hence it requires two apply steps.

See WIP in #4846.
The specific issue with Lambda function & S3 is actually being addressed/tested in #5330

---

Probably the best workaround for now is to either run two terraform apply or have S3 upload in a separate context/directory or deal with S3 upload outside of terraform.

[gthole]

Thanks for the prompt reply @radeksimko - happy to close this since the issue is well known.

[hollsteinm]

Is this still the only workaround or has there been a fix? I am assuming not as I am running into this issue as well and there is no linked fix.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.