Switching to OpenTofu

[gtirloni]

I want to start a discussion about how teams can switch to OpenTofu in a progressive way.

In the past, certain pre-1.0 versions of Terraform would taint the state file and not allow earlier versions to be used anymore.

Do we expect that simply running an opentofu plan command on an otherwise Terraform-managed environment would taint the state file in such a way that Hashicorp's Terraform would refuse to work afterwards? We can always restore the state file but I'm thinking from a least surprise perspective.

Are the other things that teams should worry about when planning a switch to OpenTofu?

[davidjeddy]

taint the state file in such a way that Hashicorp's Terraform would refuse to work afterwards?

I think this would make migrating a very scary one-way migration. When evaluating if a new tool is worth the effort to onboard the ability to not negatively impact existing configurations and resources is a high value consideration.

IMO OpenTofu should stay as close to binary and operationally compatible with Terraform for the foreseeable future. Like how MariaDB was a drop in binary replacement for MySQL for many years.

OR, worse case, an additional tool to convert the state file between OTF and TF.

[gtirloni]

Agreed. I meant the opposite: Hashicorp implements the logic to refuse states that were touched by OpenTofu. So OpenTofu would need to be stealth in this case, I hope that doesn't cause any issues with Hashicorp.

[Jake-Mok-Nelson]

@gtirloni , where is this logic? I find this really surprising and wasn't able to find anything about opentf or opentofu in Terraform.

[gtirloni]

That's because this is conjecture.

[sftim]

We can use CI to validate that Terraform 1.0 to 1.5 (MPL) do not balk at opening a state file that OpenTofu has worked on. We can't tell what Hashicorp intend for later releases that aren't open source; however, validating compatibility with 1.0.x sounds like a useful thing to ensure.