fix: repair a drifted pool label when the pool releases a used member

Change-Id: I12ec1a3bb4be216f5884862537716ae328764254
Signed-off-by: Thomas Kosiewski <tk@coder.com>

Author: ThomasK33

internal/controller/coderworkspacepool_controller.go

@@ -257,7 +257,8 @@ func (r *CoderWorkspacePoolReconciler) deleteFailedMembers(
 // unclaimed members that someone used (plan 6.3 step 4, decision D6). A
 // used member then never counts as unclaimed again, and neither the pool
 // nor its deletion deletes it. It keeps the pool label for
-// status.usedReplicas. The update carries the listed resourceVersion, and
+// status.usedReplicas, set again if it drifted. The update carries the
+// listed resourceVersion, and
 // the listed members stay as they were, so the later steps decide on the
 // list.
 func (r *CoderWorkspacePoolReconciler) releaseUsedMembers(
@@ -272,6 +273,11 @@ func (r *CoderWorkspacePoolReconciler) releaseUsedMembers(
 		}
 		released := m.DeepCopy()
 		released.OwnerReferences = slices.DeleteFunc(released.OwnerReferences, func(o metav1.OwnerReference) bool { return o.UID == pool.UID })
+		// The label is the only link left, so repair a drifted one.
+		if released.Labels == nil {
+			released.Labels = map[string]string{}
+		}
+		released.Labels[coderv1alpha1.CoderWorkspacePoolSelectorLabel] = string(pool.UID)
 		if err := r.Update(ctx, released); err != nil {
 			return fmt.Errorf("release used pool member %s/%s: %w", m.Namespace, m.Name, err)
 		}

internal/controller/coderworkspacepool_delete_test.go

@@ -114,7 +114,9 @@ func TestPoolReleasesUsedMember(t *testing.T) {
 	t.Parallel()
 	e := newPoolMemberEnv(t)
 	e.editPool(t, func(s *coderv1alpha1.CoderWorkspacePoolSpec) { s.Replicas = new(int32(2)) })
-	used := e.createMember(t, nil)
+	// The label drifted: the release sets it again, because it is the only
+	// link to the pool after the release.
+	used := e.createMember(t, func(m *coderv1alpha1.CoderWorkspacePoolMember) { m.Labels = nil })
 	e.setMemberStatus(t, used, withWorkspace(usedStatus))
 	ready := e.createMember(t, nil)
 	e.setMemberStatus(t, ready, withWorkspace(readyStatus))
@@ -128,6 +130,7 @@ func TestPoolReleasesUsedMember(t *testing.T) {
 	require.Equal(t, string(pool.UID), released.Labels[coderv1alpha1.CoderWorkspacePoolSelectorLabel])
 	require.Equal(t, int32(1), pool.Status.UsedReplicas)
 	require.Zero(t, pool.Status.Replicas)
+	require.Equal(t, int32(1), e.reconcilePool(t, 1).Status.UsedReplicas, "found again through the repaired label")
 
 	// The member reconciler marks the member used between the list and the
 	// delete: the resourceVersion precondition refuses the delete.