Common resource patterns #

Singletons #

Singletons are resources – often config or settings objects – that can only exist once. In some cases, it may be possible to create and delete the resource (but only one can exist at a time); in other cases the resource always exists and can only be read and updated.

Implementing resources like this may require some or all of the following:

1. If there isn’t a create endpoint, set the create_url to point to the update endpoint.
2. If there is a create endpoint, add pre-create custom code that implements “acquire-on-create” logic. The custom code should check whether the resource already exists with a read request, and if it does, run the update logic and return early. For example, see mmv1/templates/terraform/pre_create/firebasehosting_site.go.tmpl.
   • Note: The main disadvantage of “acquire-on-create” logic is that users will not be presented with a diff between the resource’s old and new states – because from the terraform perspective, the resource is only being created. Please upvote https://github.com/hashicorp/terraform/issues/19017 to request better support for this workflow.
3. If there is no delete endpoint, set exclude_delete: true at the top level of the resource.