Skip writing propagated version to the API when unchanged

CHANGELOG.md

@@ -1,4 +1,6 @@
 # Unreleased
+-  [#1098](https://github.com/kubernetes-sigs/kubefed/pull/1098)
+   Propagated version is now only updated when changed.
 -  [#1087](https://github.com/kubernetes-sigs/kubefed/issues/1087)
    The ReplicaScheduling controller now correctly updates existing
    overrides of `/spec/replicas`. Previously the controller was able

pkg/controller/sync/version/manager.go

@@ -175,8 +175,12 @@ func (m *VersionManager) Update(resource VersionedResource,
 	}
 
 	if oldStatus != nil && util.PropagatedVersionStatusEquivalent(oldStatus, status) {
+		m.Unlock()
 		klog.V(4).Infof("No update necessary for %s %q", m.adapter.TypeName(), qualifiedName)
-	} else if obj == nil {
+		return nil
+	}
+
+	if obj == nil {
 		ownerReference := ownerReferenceForUnstructured(resource.Object())
 		obj = m.adapter.NewVersion(qualifiedName, ownerReference, status)
 		m.versions[key] = obj
@@ -186,6 +190,9 @@ func (m *VersionManager) Update(resource VersionedResource,
 
 	m.Unlock()
 
+	// Since writeVersion calls the Kube API, the manager should be
+	// unlocked to avoid blocking on calls across the network.
+
 	return m.writeVersion(obj, qualifiedName)
 }