Only run update logic if objects are actually different

pkg/apply/apply.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/pkg/errors"
 
+	"k8s.io/apimachinery/pkg/api/equality"
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	uns "k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/types"
@@ -52,14 +53,12 @@ func ApplyObject(ctx context.Context, client k8sclient.Client, obj *uns.Unstruct
 	if err := MergeObjectForUpdate(existing, obj); err != nil {
 		return errors.Wrapf(err, "could not merge object %s with existing", objDesc)
 	}
-
-	if err := client.Update(ctx, obj); err != nil {
-		return errors.Wrapf(err, "could not update object %s", objDesc)
-	}
-	if existing.GetResourceVersion() == obj.GetResourceVersion() {
-		log.Printf("update was noop")
-	} else {
-		log.Printf("update was successful")
+	if !equality.Semantic.DeepEqual(existing, obj) {
+		if err := client.Update(ctx, obj); err != nil {
+			return errors.Wrapf(err, "could not update object %s", objDesc)
+		} else {
+			log.Printf("update was successful")
+		}
 	}
 
 	return nil

pkg/apply/merge.go

@@ -6,12 +6,26 @@ import (
 	uns "k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 )
 
+// MergeMetadataForUpdate merges the read-only fields of metadata.
+// This is to be able to do a a meaningful comparison in apply,
+// since objects created on runtime do not have these fields populated.
+func MergeMetadataForUpdate(current, updated *uns.Unstructured) error {
+	updated.SetCreationTimestamp(current.GetCreationTimestamp())
+	updated.SetSelfLink(current.GetSelfLink())
+	updated.SetGeneration(current.GetGeneration())
+	updated.SetUID(current.GetUID())
+	updated.SetResourceVersion(current.GetResourceVersion())
+
+	mergeAnnotations(current, updated)
+	mergeLabels(current, updated)
+
+	return nil
+}
+
 // MergeObjectForUpdate prepares a "desired" object to be updated.
 // Some objects, such as Deployments and Services require
 // some semantic-aware updates
 func MergeObjectForUpdate(current, updated *uns.Unstructured) error {
-	updated.SetResourceVersion(current.GetResourceVersion())
-
 	if err := MergeDeploymentForUpdate(current, updated); err != nil {
 		return err
 	}
@@ -24,11 +38,10 @@ func MergeObjectForUpdate(current, updated *uns.Unstructured) error {
 		return err
 	}
 
-	// For all object types, merge annotations.
+	// For all object types, merge metadata.
 	// Run this last, in case any of the more specific merge logic has
 	// changed "updated"
-	mergeAnnotations(current, updated)
-	mergeLabels(current, updated)
+	MergeMetadataForUpdate(current, updated)
 
 	return nil
 }