enable force_update instead of destroy and then recreate for CRD

[cytar]

Description

Hello, we are using terraform to deploy a kafka cluster handled by strimzi operator (this request can be useful for many other cases) through a Custom Resource Definition handled by the operator itself. The problem is that, modifying a simple config on the crd through kubernetes_manifest module, destroys completely (causing service to be down) and then recreate the kafka object, while if applying the same yaml with kubectl, the strimzi operator will do a blue/green deployment of the new configuration.

Saying it differently: we need a way to only update some terraform resources, so that an operator handles itself if it should be destroyed/recreated/updated_only...

Potential Terraform Configuration

resource "kubernetes_manifest" "xxx" {
  manifest = yamldecode(file("kube_manifests/kafka/strimzi-kafka-cluster2.yaml"))
}

with: kube_manifests/kafka/strimzi-kafka-cluster2.yaml =>

apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  name: xxx
  namespace: yyy
spec:
  kafka:
    config:
      default.replication.factor: 4
      ...

if i change "default.replication.factor" using kubernetes_manifest:

Actual behavior

terraform plan -target=kubernetes_manifest.xxx
...
Plan: 1 to add, 0 to change, 1 to destroy.

and then the whole kafka cluster is destroyed an the recreated:

kubectl -n yyy get kafka, pods    
No resources found in yyy namespace.

What we want

terraform plan -target=kubernetes_manifest.xxx
...
Plan: 0 to add, 1 to change, 0 to destroy.

so that the strimzi operator (like any other operator), handles it (like it does if we update its definition through kubectl):

kubectl -n yyy get kafka,pods
NAME                               DESIRED KAFKA REPLICAS   DESIRED ZK REPLICAS   READY   WARNINGS
kafka.kafka.strimzi.io/xxx.               3                        3                        
NAME                                            READY   STATUS     RESTARTS   AGE
pod/xxx-kafka-0                           1/1     Running    0          12m
pod/xxx-kafka-1                           0/1     Init:0/1   0          5s
pod/xxx-kafka-2                           1/1     Running    0          12m
...

Proposal

adding a parameter like: force_update_only at resource level in kubernetes_manifest

resource "kubernetes_manifest" "xxx" {
  manifest = yamldecode(file("kube_manifests/kafka/strimzi-kafka-cluster2.yaml"))
  force_update_only = true
}

References

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[fabio-s-franco]

@cytar I know this won't address the issue with this particular resource type directly, but I had a much better time using kubectl_manifest.

It does what you need already (and doesn't require a special flag as changes are tracked) and instead has a "force_new" flag when that is desired.

[BBBmau]

Similar Issue to #2375