capacityScaler can't be set to zero for global load balancer

[darkstarmv]

Issue:

• When capacityScaler is set to 0 Google sets it to 100% instead
• When capacityScaler is set to between 0 and 100 everything works as expected

How to recreate

Set up Kubernetes service in two regions:

• region1:

apiVersion: v1
kind: Service
metadata:
  annotations:
    cloud.google.com/neg: '{"exposed_ports": {"80":{"name": "region1-sampleapp"}}}'
    controller.autoneg.dev/neg: '{"backend_services":{"80":[{"name":"sampleapp-backend-global","max_rate_per_endpoint":10,"initial_capacity":10}]}}'

  name: sampleapp-external
  namespace: sampleapp
spec:
  ports:
  - name: http
    port: 80
    protocol: TCP
    targetPort: 8080
  selector:
    app.kubernetes.io/instance: sample

• region2:

apiVersion: v1
kind: Service
metadata:
  annotations:
    cloud.google.com/neg: '{"exposed_ports": {"80":{"name": "region2-sampleapp"}}}'
    controller.autoneg.dev/neg: '{"backend_services":{"80":[{"name":"sampleapp-backend-global","max_rate_per_endpoint":10,"initial_capacity":0}]}}'

  name: sampleapp-external
  namespace: sampleapp
spec:
  ports:
  - name: http
    port: 80
    protocol: TCP
    targetPort: 8080
  selector:
    app.kubernetes.io/instance: sample

• log:

2023-11-15T13:59:04-06:00       INFO    Applying intended status        {"controller": "service", "controllerGroup": "", "controllerKind": "Service", "Service": {"name":"sampleapp-external","namespace":"sampleapp"}, "namespace": "sampleapp", "name": "sampleapp-external", "reconcileID": "c087632a-7860", "service": {"name":"sampleapp-external","namespace":"sampleapp"}, "status": {"backend_services":{"80":{"sampleapp-backend-global":{"name":"sampleapp-backend-global","max_rate_per_endpoint":10,"initial_capacity":0}}},"network_endpoint_groups":{"80":"gcp-central1-hermes1-lab-sampleapp-sampleapp-external"},"zones":["region2-b","region2-c","region2-f"]}}
2023-11-15T13:59:25-06:00       DEBUG   events  Synced NEGs for "sampleapp/sampleapp-external" as backends to backend service "sampleapp-backend-global" (port 80)   {"type": "Normal", "object": {"kind":"Service","namespace":"sampleapp","name":"sampleapp-external","uid":"e80e34435-123213","apiVersion":"v1","resourceVersion":"123453"}, "reason": "Sync"}

• result:

gcloud compute backend-services list --flatten="backends[]" --format "csv(name,backends.group,backends.balancingMode,backends.capacityScaler)" | grep sampleapp
sampleapp-backend-global,https://www.googleapis.com/compute/v1/projects/projectname/zones/region1-b/networkEndpointGroups/region1-sampleapp,RATE,0.1
sampleapp-backend-global,https://www.googleapis.com/compute/v1/projects/projectname/zones/region1-c/networkEndpointGroups/region1-sampleapp,RATE,0.1
sampleapp-backend-global,https://www.googleapis.com/compute/v1/projects/projectname/zones/region1-d/networkEndpointGroups/region1-sampleapp,RATE,0.1
sampleapp-backend-global,https://www.googleapis.com/compute/v1/projects/projectname/zones/region2-b/networkEndpointGroups/region2-sampleapp,RATE,1
sampleapp-backend-global,https://www.googleapis.com/compute/v1/projects/projectname/zones/region2-c/networkEndpointGroups/region2-sampleapp,RATE,1
sampleapp-backend-global,https://www.googleapis.com/compute/v1/projects/projectname/zones/region2-f/networkEndpointGroups/region2-sampleapp,RATE,1

Additional information

• I can set capacityScaler to zero in google console with no issue
• I ran code through debugger and I can see 0 in capacityScaler before it makes a call, so for some reason GCE decides it is not set and takes default instead
• I tried to add NullFields = []string{"CapacityScaler"} and ForceSendFields = []string{"CapacityScaler"} to backend update API call, but it did not help