kubectl diff fails to detect differences in Service objects

[jrcast]

What happened:
kubectl diff is not detecting diffs between a service's manifest file and the modified service object in Kubernetes. I tried both client-side or server-side mode without success.

What you expected to happen:
kubectl diff identifies the diff

How to reproduce:

1. Create a K8s service using a manifest kubectl create -f my-svc.yaml. Where my-svc.yaml is:

   apiVersion: v1
   kind: Service
   metadata:
     name: example
     namespace: default
   spec:
     ports:
       - name: service-port
         port: 80
         protocol: TCP
         targetPort: service-port
     selector:
       app.kubernetes.io/instance: example
     type: ClusterIP

2. Using kubectl edit, modify the K8s service. i.e. Add an extra port.

   apiVersion: v1
   kind: Service
   metadata:
     name: example
     namespace: default
   spec:
     ports:
       - name: service-port
         port: 80
         protocol: TCP
         targetPort: service-port
       - name: shouldntbehere    # <<<< THIS 
         port: 8080
         protocol: TCP
         targetPort: service-port
     selector:
       app.kubernetes.io/instance: example
     type: ClusterIP

3. Run:

   kubectl diff -f my-svc.yaml
   # or
   kubectl diff -f my-svc.yaml --server-side --force-conflicts

4. No diff shows up.

Anything else we need to know?:

Environment:

• Kubernetes client and server versions (use kubectl version): 1.27 on both server/client. Also tried 1.30 with same results.
• Cloud provider or hardware configuration: AWS EKS
• OS (e.g: cat /etc/os-release): Ubuntu 22.04.4 LTS

[ardaguclu]

Have you verified that the kubectl edit actually updated your service?

[kundan2707]

@jrcast have you checked if kubectl command executed successfully without error ?

[kundan2707]

/remove-kind bug

[kundan2707]

/kind support

[brianpursley]

Can confirm this happens when you make changes using kubectl edit, and it does seem to have something to do with server side apply.

If you use the --save-config flag with edit, then kubectl diff will work:

kubectl edit service example --save-config

$ kubectl diff -f my-svc.yaml 
diff -u -N /tmp/LIVE-3530718821/v1.Service.default.example /tmp/MERGED-1768176721/v1.Service.default.example
--- /tmp/LIVE-3530718821/v1.Service.default.example	2024-05-28 11:44:49.052930430 -0400
+++ /tmp/MERGED-1768176721/v1.Service.default.example	2024-05-28 11:44:49.056930322 -0400
@@ -22,10 +22,6 @@
     port: 80
     protocol: TCP
     targetPort: service-port
-  - name: shouldntbehere
-    port: 8080
-    protocol: TCP
-    targetPort: service-port
   selector:
     app.kubernetes.io/instance: example
   sessionAffinity: None

But if you use that flag, it's going to add the kubectl.kubernetes.io/last-applied-configuration annotation, which shouldn't be a requirement for diff.

/remove-kind support
/kind bug

[ardaguclu]

/triage accepted
/priority backlog