Don't reconcile delete events for GatewayClasses that do not reference NGF

[kate-osborn]

Describe the bug
NGF ignores create and update events for GatewayClasses that have a controller name that doesn't match NGF. However, NGF reconciles delete events for these GatewayClasses.

To Reproduce
Steps to reproduce the behavior:

1. Create a GatewayClass with a controller name that does not match NGF's controller name
2. Delete this GatewayClass
3. View logs on NGF pod and search for "Reconciling" and "GatewayClass" and you will see a log for the delete event.

{"level":"info","ts":"2024-01-17T16:46:22Z","msg":"Reconciling the resource","controller":"gatewayclass","controllerGroup":"gateway.networking.k8s.io","controllerKind":"GatewayClass","GatewayClass":{"name":"not-nginx"},"namespace":"","name":"not-nginx","reconcileID":"60f42506-e703-44ec-81da-60d932e93788"}
{"level":"info","ts":"2024-01-17T16:46:22Z","msg":"Deleted the resource","controller":"gatewayclass","controllerGroup":"gateway.networking.k8s.io","controllerKind":"GatewayClass","GatewayClass":{"name":"not-nginx"},"namespace":"","name":"not-nginx","reconcileID":"60f42506-e703-44ec-81da-60d932e93788"}
{"level":"info","ts":"2024-01-17T16:46:22Z","logger":"eventLoop","msg":"added an event to the next batch","type":"*events.DeleteEvent","total":1}
{"level":"info","ts":"2024-01-17T16:46:22Z","logger":"eventLoop.eventHandler","msg":"Handling events from the batch","batchID":5,"total":1}
{"level":"info","ts":"2024-01-17T16:46:22Z","logger":"eventLoop.eventHandler","msg":"Handling events didn't result into NGINX configuration changes","batchID":5}
{"level":"info","ts":"2024-01-17T16:46:22Z","logger":"eventLoop.eventHandler","msg":"Finished handling the batch","batchID":5}

Expected behavior
NGF should ignore delete events for GatewayClasses with a controller name that does not match NGF.

Your environment

• Version of the NGINX Gateway Fabric - edge (b2d078b)
• Version of Kubernetes 1.27
• Kubernetes platform (e.g. Mini-kube or GCP): Kind

Additional context
Add any other context about the problem here. Any log files you want to share.

[hckuo]

I can take at look at this.

[hckuo]

should the behavior be eventLoop ignores the incoming delete event that does not match the name or the reconciler does not fire the event?

[mpstefan]

Hey @hckuo!

I can assign this to you, thanks for taking a look!

@ciarams87 Any advice on how to tackle this?

[ciarams87]

Hi @hckuo!

For this bug, the easiest thing to do would be to implement a default DeleteEvent filter for validating a GatewayClass controllerName in the GatewayClass predicate. This will prevent the event being queued for reconciliation at all. We have filters for Create and Update but not Delete, hence the Delete event reconciliation 😄

Let me know if you need anything else!

Ciara