RDE (Runtime Defined Entities) framework support with Runtime Defined Entity Interfaces resource and data source (1/3)

[adambarreiro]

Overview

This PR depends on vmware/go-vcloud-director#527

This PR adds a new resource and data source vcd_rde_interface to be able to create, read, update and delete Defined Interfaces, and also to import existing ones into Terraform state.

Design details

To define a Defined Interface unequivocally, one needs vendor, nss and version:

• Same 3-tuple of (vendor, nss,version) can't have a different name. Otherwise it fails with RDE_INTERFACE_ALREADY_EXISTS.
• Different 3-tuples of (vendor, nss,version) can have the same name.

An example of a valid scenario:

{
  "name": "sameName",
  "nss": "nss1",
  "version": "1.0.0",
  "vendor": "vendor1"
}
{
  "name": "sameName",
  "nss": "nss2",
  "version": "1.0.0",
  "vendor": "vendor2"
}

Because the 3-tuple (vendor, nss,version) is different.

An example of a wrong scenario:

{
  "name": "someName",
  "nss": "nss1",
  "version": "1.0.0",
  "vendor": "vendor1"
}
{
  "name": "differentName",
  "nss": "ns11", // Wrong: same nss
  "version": "1.0.0", // Wrong: same version
  "vendor": "vendor1" // Wrong: same vendor
}

Creation of differentName will fail as the 3-tuple is being reused.

• Because of the constraint above, the data source requires only the vendor, nss and version. In other words, we can't use name to fetch Defined Interfaces for the data source because it can be non-unique.

• In the resource, all attributes except name have ForceNew: true, this is because the PUT endpoint in VCD API ignores all changes in fields except for name. Also, if name is not sent during the PUT, API fails with a very ugly error.

• To import an existing Defined Interface from VCD into Terraform state, one needs to build an URN like vendor.nss.version. As version follows SemVer, the identifier results in something like vmware.kubernetes.1.0.0 which can be visually odd. The usage of . as separator can be changed with VCD_IMPORT_SEPARATOR, but as with the data source, one requires the version to unequivocally identify the Defined Interface.

Disclaimer

The new resource vcd_rde_interface does NOT add behaviors support in this PR. A "behavior" is an extension of the capabilities of the Defined Interfaces that would require an extra resource (something like vcd_rde_interface_behavior). These behaviors can be mapped in the Runtime Defined Entity types hooks map[string]string property, where this map supports PRE_CREATED, POST_CREATION, etc as keys and behavior IDs coming from Defined Interfaces as values.

RDE saga:

• RDE types PR: RDE (Runtime Defined Entities) framework support with RDE Type resource and data source (2/3) #973
• RDEs PR: RDE (Runtime Defined Entities) framework support with RDE resource and data source (3/3) #977

[lvirbalas]

My only reservation is whether nss (field name coming from the API) is not too cryptic for the new users.