Add support to filter/taint expired deployments to trigger recreation

[azrdev]

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Description

Our vRA imposes a lifetime on all deployments, i.e. they expire after 30 days. Afterwards the deployed VMs are powered off and not useable anymore until being deleted some time after.
For terraform, however, they still exist "in good state" -- attributes like last_request and lease_expire_at tell it has been expired and allow failing such a VM early using a postcondition, but I'm looking for a way to re-create such expired deployments.
Context is a scheduled CI pipeline which runs terraform followed by config management to ensure certain infrastructure (VM + application) is always present. Currently it fails in config management due to the expired VM being powered off, requiring manual destruction of the VM to recreate the setup.

This is a follow-up to #436 since even with it solved in #462 (thank you!) a workaround seems not to be possible (see hashicorp/terraform#31702).

Possible solutions

Adding a parameter to the resource (or provider?) recreate_expired: bool is probably the best way to go

Describe alternatives you've considered

1. workaround using postcondition with self.last_request.action_id != "Deployment.Expire" -- works, but only fails plan/apply and requires manual action to trigger recreation
2. replace_triggered_by: cannot be applied to self, see linked terraform issue above
3. replace_triggered_by → data "vra_resource" { (same ID as the resource) } (full example see linked tf issue above): data source fails when resource not yet exists

References

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[azrdev]

I'm trying to implement a fix for this one:

• setting "tainted" seems infeasible as per https://stackoverflow.com/a/57829163/

• the docs for Schema.ForceNew tell that this boolean flag can be set on any field, to make any change in the field trigger a replacement of the resource. Enabling this on the "lease_expire_at" attribute would wrongly affect resources who are prolonged (or whose expiration date is otherwise changed)

• SetId(""):

  • the docs for Resource.Read state "Managed resources can signal to Terraform that the managed resource instance no longer exists and potentially should be recreated by calling the SetId method with an empty string ("") parameter and without returning an error."
  • I tried to insert in vra/resource_deployment.go#resourceDeploymentRead() after d.Set("lease_expire_at" ...) the code if time.Time(deployment.LeaseExpireAt).Before(time.Now()) { d.SetId("") }
  • the result is that a vra_deployment already in tfstate is terraform planned to be created but there's no reference that the old deployment is removed. this solves the problem , but IMHO could dangerously hide a situation one would want to recognize

• as proposed in the stackoverflow answer, I implemented CustomizeDiff and call ForceNew conditionally: in vra/resource_deployment.go#resourceDeployment() I add

  	CustomizeDiff: customdiff.ForceNewIf(
  		"lease_expire_at",
  		func(ctx context.Context, d *schema.ResourceDiff, meta interface{}) bool {
  			expiration, err := strfmt.ParseDateTime(d.Get("lease_expire_at").(string))
  			log.Printf("checking expiration: %s %s vs %s", expiration, err, time.Now())
  			return err == nil && time.Time(expiration).Before(time.Now())
  		}),

  but that results in an empty plan on an expired deployment. TF_LOG=1 reveals provider.terraform-provider-vra: unable to require attribute replacement: error="ForceNew: No changes for lease_expire_at" tf_attribute_path=lease_expire_at tf_req_id=<uuid> @caller=/home/x/go/pkg/mod/github.com/hashicorp/terraform-plugin-sdk/[email protected]/helper/customdiff/force_new.go:29 @module=sdk.helper_schema tf_provider_addr=provider tf_resource_type=vra_deployment tf_rpc=PlanResourceChange

  ForceNewIf requiring an attribute works as documented

• implement a new attribute that changes exactly when the deployment is expired (and has ForceNew = true: just adding a boolean attribute and setting it with d.Set("is_expired", time.Time(deployment.LeaseExpireAt).Before(time.Now())) doesn't suffice, because ForceNew triggers on changes of that attribute, so if at planning time it's already expired it remains (false negative), and if a resource is resurrected/un-expired, ForceNew will recreate it (false positive)

• implement a new attribute into which the .tf config sets plantimestamp(), and ForceNew is set to true, when expired_at < plantimestamp. This works as expected, but when the attribute is used, it shows a diff on every plan: see fix: add vra_deployment.recreate_if_expired_at attribute #514
  I tried to hide/suppress that diff with the following addition to the PR (in the CustomizeDiff func, just above the Before() comparison), but that will suppress the recreation also:

    			old, new := d.GetChange("recreate_if_expired_at")
    			log.Printf("Hiding recreate_if_expired_at from diff: overwriting new %#v with old %#v", new, old)
    			if err = d.SetNew("recreate_if_expired_at", old); err != nil {
    				log.Printf("[DEBUG] Failed to hide recreate_if_expired_at from diff:", err)
    			}

[azrdev]

So given what I've tried above, I see two solutions:

1. implement the third bulletpoint d.SetId("") (maybe behind a boolean user-input flag):
   an expired vra_deployment already in tfstate is planned to be created but there's no reference that the old deployment is removed.
   plan output:

   attribute (TODO: implement flag)	recreate_if_expired = false	recreate_if_expired = true
   is expired	nothing	create (expired deployment is ignored)
   is not expired	nothing	nothing

2. merge my PR fix: add vra_deployment.recreate_if_expired_at attribute #514 which will yield these plans:

   attribute	recreate_if_expired_at = null	recreate_if_expired_at = plantimestamp()
   is expired	nothing	destroy+create
   is not expired	nothing	diff on the attribute in every plan

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