Introduce Comparator interface (#88016)

* Introduce Comparator interface

* Add compare implementation everywhere

* Add comment explaining what Compare should do

* Lint

pkg/apiserver/rest/dualwriter.go

@@ -35,6 +35,8 @@ type Storage interface {
 	rest.CreaterUpdater
 	rest.GracefulDeleter
 	rest.CollectionDeleter
+	// Compare asserts on the equality of objects returned from both stores	(object storage and legacy storage)
+	Compare(storageObj, legacyObj runtime.Object) bool
 }
 
 // LegacyStorage is a storage implementation that writes to the Grafana SQL database.
@@ -91,18 +93,18 @@ func NewDualWriter(mode DualWriterMode, legacy LegacyStorage, storage Storage) D
 	switch mode {
 	case Mode1:
 		// read and write only from legacy storage
-		return NewDualWriterMode1(legacy, storage)
+		return newDualWriterMode1(legacy, storage)
 	case Mode2:
 		// write to both, read from storage but use legacy as backup
-		return NewDualWriterMode2(legacy, storage)
+		return newDualWriterMode2(legacy, storage)
 	case Mode3:
 		// write to both, read from storage only
-		return NewDualWriterMode3(legacy, storage)
+		return newDualWriterMode3(legacy, storage)
 	case Mode4:
 		// read and write only from storage
-		return NewDualWriterMode4(legacy, storage)
+		return newDualWriterMode4(legacy, storage)
 	default:
-		return NewDualWriterMode1(legacy, storage)
+		return newDualWriterMode1(legacy, storage)
 	}
 }
 

pkg/apiserver/rest/dualwriter_mode1.go

@@ -23,7 +23,7 @@ const mode1Str = "1"
 
 // NewDualWriterMode1 returns a new DualWriter in mode 1.
 // Mode 1 represents writing to and reading from LegacyStorage.
-func NewDualWriterMode1(legacy LegacyStorage, storage Storage) *DualWriterMode1 {
+func newDualWriterMode1(legacy LegacyStorage, storage Storage) *DualWriterMode1 {
 	metrics := &dualWriterMetrics{}
 	metrics.init()
 	return &DualWriterMode1{Legacy: legacy, Storage: storage, Log: klog.NewKlogr().WithName("DualWriterMode1"), dualWriterMetrics: metrics}
@@ -236,3 +236,7 @@ func (d *DualWriterMode1) NewList() runtime.Object {
 func (d *DualWriterMode1) ConvertToTable(ctx context.Context, object runtime.Object, tableOptions runtime.Object) (*metav1.Table, error) {
 	return d.Legacy.ConvertToTable(ctx, object, tableOptions)
 }
+
+func (d *DualWriterMode1) Compare(storageObj, legacyObj runtime.Object) bool {
+	return d.Storage.Compare(storageObj, legacyObj)
+}

pkg/apiserver/rest/dualwriter_mode2.go

@@ -27,7 +27,7 @@ const mode2Str = "2"
 
 // NewDualWriterMode2 returns a new DualWriter in mode 2.
 // Mode 2 represents writing to LegacyStorage and Storage and reading from LegacyStorage.
-func NewDualWriterMode2(legacy LegacyStorage, storage Storage) *DualWriterMode2 {
+func newDualWriterMode2(legacy LegacyStorage, storage Storage) *DualWriterMode2 {
 	metrics := &dualWriterMetrics{}
 	metrics.init()
 	return &DualWriterMode2{Legacy: legacy, Storage: storage, Log: klog.NewKlogr().WithName("DualWriterMode2"), dualWriterMetrics: metrics}
@@ -310,6 +310,10 @@ func (d *DualWriterMode2) ConvertToTable(ctx context.Context, object runtime.Obj
 	return d.Storage.ConvertToTable(ctx, object, tableOptions)
 }
 
+func (d *DualWriterMode2) Compare(storageObj, legacyObj runtime.Object) bool {
+	return d.Storage.Compare(storageObj, legacyObj)
+}
+
 func parseList(legacyList []runtime.Object) (metainternalversion.ListOptions, map[string]int, error) {
 	options := metainternalversion.ListOptions{}
 	originKeys := []string{}

pkg/apiserver/rest/dualwriter_mode3.go

@@ -18,9 +18,9 @@ type DualWriterMode3 struct {
 	Log klog.Logger
 }
 
-// NewDualWriterMode3 returns a new DualWriter in mode 3.
+// newDualWriterMode3 returns a new DualWriter in mode 3.
 // Mode 3 represents writing to LegacyStorage and Storage and reading from Storage.
-func NewDualWriterMode3(legacy LegacyStorage, storage Storage) *DualWriterMode3 {
+func newDualWriterMode3(legacy LegacyStorage, storage Storage) *DualWriterMode3 {
 	metrics := &dualWriterMetrics{}
 	metrics.init()
 	return &DualWriterMode3{Legacy: legacy, Storage: storage, Log: klog.NewKlogr().WithName("DualWriterMode3"), dualWriterMetrics: metrics}
@@ -157,3 +157,7 @@ func (d *DualWriterMode3) NewList() runtime.Object {
 func (d *DualWriterMode3) ConvertToTable(ctx context.Context, object runtime.Object, tableOptions runtime.Object) (*metav1.Table, error) {
 	return d.Storage.ConvertToTable(ctx, object, tableOptions)
 }
+
+func (d *DualWriterMode3) Compare(storageObj, legacyObj runtime.Object) bool {
+	return d.Storage.Compare(storageObj, legacyObj)
+}

pkg/apiserver/rest/dualwriter_mode4.go

@@ -17,9 +17,9 @@ type DualWriterMode4 struct {
 	Log klog.Logger
 }
 
-// NewDualWriterMode4 returns a new DualWriter in mode 4.
+// newDualWriterMode4 returns a new DualWriter in mode 4.
 // Mode 4 represents writing and reading from Storage.
-func NewDualWriterMode4(legacy LegacyStorage, storage Storage) *DualWriterMode4 {
+func newDualWriterMode4(legacy LegacyStorage, storage Storage) *DualWriterMode4 {
 	metrics := &dualWriterMetrics{}
 	metrics.init()
 	return &DualWriterMode4{Legacy: legacy, Storage: storage, Log: klog.NewKlogr().WithName("DualWriterMode4"), dualWriterMetrics: metrics}
@@ -85,3 +85,7 @@ func (d *DualWriterMode4) NewList() runtime.Object {
 func (d *DualWriterMode4) ConvertToTable(ctx context.Context, object runtime.Object, tableOptions runtime.Object) (*metav1.Table, error) {
 	return d.Storage.ConvertToTable(ctx, object, tableOptions)
 }
+
+func (d *DualWriterMode4) Compare(storageObj, legacyObj runtime.Object) bool {
+	return d.Storage.Compare(storageObj, legacyObj)
+}