Terraform-provider-google: Update workload_metadata_config.node_metadata on node pools without force replacement.

[sho-abe]

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Description

Workload Identity setting of google_container_cluster and google_container_node_pool is available in google-beta. However, enabling the Workload Identity setting on an existing cluster or node pool results in "force replacement" and will be recreated.

If modify Workload Identity setting with gcloud container clusters update and/or gcloud container node-pool update, cluster and node pool will not be re-created, and Pod and Service will remain as they are.

I would prefer not to be force replacement for changing below configurations.

• workload_identity_config.identity_namespace in google_container_cluster
• node_config.workload_metadata_config.node_metadata in google_container_node_pool

New or Affected Resource(s)

• google_container_cluster
• google_container_node_pool

Potential Terraform Configuration

resource "google_container_cluster" "workload_identity" {
  provider = "google-beta"
  name     = "workload-identity"
  location = "asia-northeast1-b"

  network    = google_compute_network.workload_identity.self_link
  subnetwork = google_compute_subnetwork.workload_identity.self_link

  min_master_version = "1.13.6"
  initial_node_count = 1

  ...(snip)...

  # add below config
  workload_identity_config {
    identity_namespace = "workload-identity.svc.id.goog"
  }
}

resource "google_container_node_pool" "workload_identity" {
  provider = "google-beta"
  cluster  = google_container_cluster.workload_identity.name
  name     = "workload-identity-pool"

  location   = google_container_cluster.workload_identity.location
  node_count = 1

  node_config {

  ...(snip)...

   # add below config
    workload_metadata_config {
      node_metadata = "GKE_METADATA_SERVER" 
    }
  }
}

The result of terraform plan is as follows.

...snip...
      + workload_identity_config { # forces replacement
          + identity_namespace = "workload-identity.svc.id.goog" # forces replacement
        }

...snip...
          + workload_metadata_config { # forces replacement
              + node_metadata = "GKE_METADATA_SERVER" # forces replacement
            }

References

• Enable Workload Identity on an existing cluster

[rileykarson]

https://github.com/terraform-providers/terraform-provider-google-beta/pull/896 is tackling this, there's a bit of nuance because changing this value requires modifying certain values in node pools.

[rtoma]

Piggybacking on this issue, because the title covers my finding and the issue is still open. Feel free to ask me to create a separate issue.

--

With terraform-providers/terraform-provider-google-beta#896 (we use v2.13.0) it is possible to update the google_container_cluster.NAME.node_config.workload_metadata_config parameter of a cluster resource. This however only enabled workload identity in new node pools.

When you attempt to upgrade an existing nodepool by changing the config of a google_container_node_pool.NAME.node_config.workload_metadata_config.node_metadata parameter the whole node pool is deleted and recreated:

-/+ resource "google_container_node_pool" "NAME" {
     ~ node_config {
         ~ workload_metadata_config {
             ~ node_metadata = "SECURE" -> "GKE_METADATA_SERVER" # forces replacement
           }
       }
   }

Where as gcloud can do it rolling:

$ cloud beta container node-pools update NODEPOOL --cluster=CLUSTER \
  --project=PROJECT --workload-metadata-from-node=GKE_METADATA_SERVER

A rolling reprovisioning of the nodepool nodes is of course preferred to ensure maximum pod availability.

In the current state we can not use terraform to migrate existing node pools in production without scheduled downtime of all workloads running in the node pool.

[RochesterinNYC]

So if I understand correctly, the purpose of https://github.com/terraform-providers/terraform-provider-google-beta/pull/896 was to change the behavior so that enabling workload identity on GKE clusters via Terraform did not result in a need for GKE cluster recreation, but it didn't change the behavior that enabling workload identity on the GKE node pools causes them to recreate?

[rileykarson]

That's correct @RochesterinNYC. I'll retitle this issue so it's about updating that field now that we support updating the cluster-level one.

[hashibot[bot]]

I'm going to lock this issue because it has been closed for _30 days_ ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 [email protected]. Thanks!