Important changes to the oVirt Terraform Provider

[ghost]

We are making sweeping and backwards-incompatible changes to the oVirt Terraform provider. We want your feedback before we make these changes.

Here’s the short list what we would like to change, please read the details below.

1. The current master branch will be renamed to legacyv0. The usage of this provider will be phased out within Red Hat around the end / beginning of next year. If you want to create a fork, we are happy to add a link to your fork to the readme.
2. A new main branch will be created and a new Terraform provider written from scratch on the basis of go-ovirt-client. (Preview here) This provider will only have limited functionality in its first release.
3. This new provider will be released to the Terraform registry, and will have full test coverage and documentation. This provider will be released as version v2.0.0 when ready to signal that it is built on the Terraform SDK v2.
4. A copy of this new Terraform provider will be kept in the v1 branch and backported to the Terraform SDK v1 for the benefit of the OpenShift Installer. We will not tag any releases, and we will not release this backported version in binary form.
5. We are hosting a community call on the 14th of October at 13:00 UTC on this link. Please join to provide feedback and suggest changes to this plan.

Why are we doing this?

The original Terraform provider for oVirt was written four years ago by @Maigard at EMSL-MSC. The oVirt fork of this provider is about 2 years old and went through rapid expansion, adding a large number of features.

Unfortunately, this continuous rapid growth came at a price: the original test infrastructure deteriorated and certain resources, especially the virtual machine creation ballooned to a size we feel has become unmaintainable.

If you tried to contribute to the Terraform provider recently, you may have noticed that our review process has become extremely slow. We can no longer run the original tests, and our end to end test suite is not integrated outside of the OpenShift CI system. Every change to the provider requires one of only 3 people to review the code and also run a manual test suite that is currently only runable on one computer.

We also noticed an increasing number of bugs reported on OpenShift on oVirt/RHV related to the Terraform provider.

Our original plan was that we would fix the test infrastructure and then subsequently slowly transition API calls to go-ovirt-client, but that resulted in a PR that is over 5000 lines in code and cannot in good conscience be merged in a single piece. Splitting it up is difficult, and would likely result in broken functionality where test coverage is not present.

What are we changing for you, the users?

First of all, documentation. You can already preview the documentation here. You will notice that the provider currently only supports a small set of features. You can find the full list of features we are planning for the first release on GitHub. However, if you are using resources like cluster creation, etc. these will currently not work and we recommend sticking to the old provider for the time being.

The second big change will be how resources are treated. Instead of creating large resources that need to call several of the oVirt APIs to create, we will create resources that are only calling one API. This will lead to fewer bugs. For example:

• ovirt_vm will create the VM, but not attach any disks or network interfaces to it.
• ovirt_disk_attachment or ovirt_disk_attachments will attach a disk to the VM.
• ovirt_nic will create a network interface.
• ovirt_vm_start will start the virtual machine when provisioned, stop it when deprovisioned.

You can use the depends_on meta-argument to make sure disks and network interfaces are attached before you start the VM. Alternatively, you can hot-plug network interfaces later. For example:

resource "ovirt_vm" "test" {
  cluster_id  = "some-cluster-id"
  template_id = "some-template-id"
}

resource "ovirt_disk" "test" {
  storagedomain_id = "some-storage-domain-id"
  format           = "cow"
  size             = 512
  alias            = "test"
  sparse           = true
}

resource "ovirt_disk_attachment" "test" {
  vm_id          = ovirt_vm.test.id
  disk_id        = ovirt_disk.test.id
  disk_interface = "virtio_scsi"
}

resource "ovirt_vm_start" "test" {
  vm_id      = ovirt_vm.test.id
  depends_on = [ovirt_disk_attachment.test]
}

The next change is the availability of the provider on the Terraform Registry. You will no longer have to download the binary. Instead, you will be able to simply pull in the provider like this:

terraform {
  required_providers {
    ovirt = {
      source = "ovirt/ovirt"
      version = "..."
    }
  }
}

provider "ovirt" {
  # Configuration options
}

The configuration options for the provider itself have also been greatly expanded, see the preliminary documentation for details.

What’s changing behind the scenes?

The new Terraform provider is a complete rewrite based on the go-ovirt-client library. The single biggest advantage of this library is that it has built-in mocks for all resources it supports. Having mocks allows us to run tests without needing to spin up an oVirt instance. We have already configured GitHub Actions on the new provider and all changes are automatically checked against these mocks.

We may decide to add an end-to-end test later, but for the foreseeable future we will trust the correctness of the mocks to test community contributions. This means that we will be able to merge changes much quicker.

On the OpenShift side we will also switch to using the new provider, since this is the primary motivation for the change. The OpenShift Installer uses the legacy version 1 of the Terraform SDK, so we will maintain a version 1-compatible copy in the v1 branch, which the installer can pull in. It is important to note, however, that the v1 branch will be a pure backport, we will not develop it separately. Development will be focused on the version in main that is being released to the Terraform Registry.

What does this mean to you, the contributors?

The current Terraform provider has several pull requests open. Unfortunately, we currently do not have the capacity to properly vet and and run our internal test suite against these changes. In contrast to the new Terraform provider, we do not have working tests, linting, and the code structure that make merging changes easier.

We are very sorry to say that these patches are unlikely to be merged. We know that this is a terrible thing, you have put in effort into writing them. Unfortunately, we do not see an alternative as there already numerous bugs on our radar and adding more code would not make the problem go away.

We want to hear your opinion

As the owners of the original Terraform provider we haven’t been keeping up with reviewing your contributions and issues. Some are several months old and haven’t received answers for a long time. We want to change that, we want to hear from you. Please join our community round table around the Terraform provider on the 14th of October at 13:00 UTC on this link.

We want to know: Which resources are the most important to you? How does this change impact you? Can we make the transition smoother for you? Would you do anything differently in the light of the issues described above?