Fix waiting on StatefulSet scale down

changelogs/fragments/391-fix-statefulset-wait.yaml

@@ -0,0 +1,2 @@
+bugfixes:
+  - k8s_scale - fix waiting on statefulset when scaled down to 0 replicas (https://github.com/ansible-collections/kubernetes.core/issues/203).

plugins/module_utils/common.py

@@ -633,15 +633,19 @@ def _daemonset_ready(daemonset):
             )
 
         def _statefulset_ready(statefulset):
+            # These may be None
+            updated_replicas = statefulset.status.updatedReplicas or 0
+            ready_replicas = statefulset.status.readyReplicas or 0
+
             return (
                 statefulset.status
                 and statefulset.spec.updateStrategy.type == "RollingUpdate"
                 and statefulset.status.observedGeneration
                 == (statefulset.metadata.generation or 0)
                 and statefulset.status.updateRevision
                 == statefulset.status.currentRevision
-                and statefulset.status.updatedReplicas == statefulset.spec.replicas
-                and statefulset.status.readyReplicas == statefulset.spec.replicas
+                and updated_replicas == statefulset.spec.replicas
+                and ready_replicas == statefulset.spec.replicas
                 and statefulset.status.replicas == statefulset.spec.replicas
             )
 

tests/integration/targets/k8s_scale/tasks/main.yml

@@ -341,6 +341,54 @@
           - scale_out.changed
           - scale_out.results | map(attribute='result.status.replicas') | list | unique == [2]
 
+    - name: Create a StatefulSet
+      kubernetes.core.k8s:
+        wait: yes
+        wait_timeout: "{{ k8s_wait_timeout | default(omit) }}"
+        definition:
+          apiVersion: apps/v1
+          kind: StatefulSet
+          metadata:
+            namespace: "{{ scale_namespace }}"
+            name: scale-set
+          spec:
+            replicas: 2
+            selector:
+              matchLabels:
+                app: foo
+            template:
+              metadata:
+                labels:
+                  app: foo
+              spec:
+                terminationGracePeriodSeconds: 10
+                containers:
+                  - image: busybox
+                    name: busybox
+                    command:
+                      - sleep
+                      - "600"
+      register: output
+
+    - assert:
+        that:
+          - output.result.status.replicas == 2
+
+    - name: Wait for StatefulSet to scale down to 0
+      kubernetes.core.k8s_scale:
+        kind: StatefulSet
+        api_version: apps/v1
+        name: scale-set
+        namespace: "{{ scale_namespace }}"
+        replicas: 0
+        wait: yes
+        wait_timeout: "{{ k8s_wait_timeout | default(omit) }}"
+      register: output
+
+    - assert:
+        that:
+          - output.result.status.replicas == 0
+
   always:
     - name: Remove namespace
       k8s: