Add Get method in dual writer (#85589)

* Add Get method in dual writer

* Update pkg/apiserver/rest/dualwriter_mode3.go

Co-authored-by: Dan Cech <dcech@grafana.com>

* Actually run the tests

* no need for t.Run()

* Update pkg/apiserver/rest/dualwriter_mode3.go

Co-authored-by: Dan Cech <dcech@grafana.com>

* Update pkg/apiserver/rest/dualwriter_mode3.go

Co-authored-by: Dan Cech <dcech@grafana.com>

* Update pkg/apiserver/rest/dualwriter_test.go

Co-authored-by: Dan Cech <dcech@grafana.com>

* Log improvements

* Fix method name

---------

Co-authored-by: Dan Cech <dcech@grafana.com>

pkg/apiserver/rest/dualwriter_mode1.go

@@ -32,3 +32,8 @@ func (d *DualWriterMode1) Create(ctx context.Context, obj runtime.Object, create
 
 	return legacy.Create(ctx, obj, createValidation, options)
 }
+
+// Get overrides the default behavior of the DualWriter and reads only to LegacyStorage.
+func (d *DualWriterMode1) Get(ctx context.Context, name string, options *metav1.GetOptions) (runtime.Object, error) {
+	return d.Legacy.Get(ctx, name, options)
+}

pkg/apiserver/rest/dualwriter_mode2.go

@@ -80,3 +80,8 @@ func enrichObject(orig, copy runtime.Object) (runtime.Object, error) {
 
 	return copy, nil
 }
+
+// Get overrides the default behavior of the Storage and retrieves an object from LegacyStorage
+func (d *DualWriterMode2) Get(ctx context.Context, name string, options *metav1.GetOptions) (runtime.Object, error) {
+	return d.Legacy.Get(ctx, name, &metav1.GetOptions{})
+}

pkg/apiserver/rest/dualwriter_mode3.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 
+	apierrors "k8s.io/apimachinery/pkg/api/errors"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apiserver/pkg/registry/rest"
@@ -38,3 +39,24 @@ func (d *DualWriterMode3) Create(ctx context.Context, obj runtime.Object, create
 	}
 	return created, nil
 }
+
+// Get overrides the default behavior of the Storage and retrieves an object from Unified Storage
+// the object is still fetched from Legacy Storage if it's not found in Unified Storage
+func (d *DualWriterMode3) Get(ctx context.Context, name string, options *metav1.GetOptions) (runtime.Object, error) {
+	legacy, ok := d.Legacy.(rest.Getter)
+	if !ok {
+		return nil, fmt.Errorf("legacy storage rest.Getter is missing")
+	}
+
+	s, err := d.Storage.Get(ctx, name, &metav1.GetOptions{})
+	if err == nil {
+		return s, err
+	}
+	if !apierrors.IsNotFound(err) {
+		return nil, err
+	}
+
+	klog.Info("object not found in unified storage. Getting it from legacy", "name", name)
+
+	return legacy.Get(ctx, name, &metav1.GetOptions{})
+}

pkg/apiserver/rest/dualwriter_mode4.go

@@ -23,3 +23,8 @@ func NewDualWriterMode4(legacy LegacyStorage, storage Storage) *DualWriterMode4
 func (d *DualWriterMode4) Create(ctx context.Context, obj runtime.Object, createValidation rest.ValidateObjectFunc, options *metav1.CreateOptions) (runtime.Object, error) {
 	return d.Storage.Create(ctx, obj, createValidation, options)
 }
+
+// Get overrides the default behavior of the Storage and retrieves an object from Unified Storage
+func (d *DualWriterMode4) Get(ctx context.Context, name string, options *metav1.GetOptions) (runtime.Object, error) {
+	return d.Storage.Get(ctx, name, &metav1.GetOptions{})
+}

pkg/apiserver/rest/dualwriter_test.go

@@ -0,0 +1,75 @@
+package rest
+
+import (
+	"context"
+	"testing"
+
+	"github.com/zeebo/assert"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+)
+
+const kind = "dummy"
+
+func Test_Mode1(t *testing.T) {
+	var ls = (LegacyStorage)(nil)
+	var s = (Storage)(nil)
+	lsSpy := NewLegacyStorageSpyClient(ls)
+	sSpy := NewStorageSpyClient(s)
+
+	dw := NewDualWriterMode1(lsSpy, sSpy)
+
+	_, err := dw.Get(context.Background(), kind, &metav1.GetOptions{})
+	assert.NoError(t, err)
+
+	// it should use the Legacy Get implementation
+	assert.Equal(t, 1, lsSpy.Counts("LegacyStorage.Get"))
+	assert.Equal(t, 0, sSpy.Counts("Storage.Get"))
+}
+
+func Test_Mode2(t *testing.T) {
+	var ls = (LegacyStorage)(nil)
+	var s = (Storage)(nil)
+	lsSpy := NewLegacyStorageSpyClient(ls)
+	sSpy := NewStorageSpyClient(s)
+
+	dw := NewDualWriterMode2(lsSpy, sSpy)
+
+	_, err := dw.Get(context.Background(), kind, &metav1.GetOptions{})
+	assert.NoError(t, err)
+
+	// it should use the Legacy Get implementation
+	assert.Equal(t, 1, lsSpy.Counts("LegacyStorage.Get"))
+	assert.Equal(t, 0, sSpy.Counts("Storage.Get"))
+}
+
+func Mode3_Test(t *testing.T) {
+	var ls = (LegacyStorage)(nil)
+	var s = (Storage)(nil)
+	lsSpy := NewLegacyStorageSpyClient(ls)
+	sSpy := NewStorageSpyClient(s)
+
+	dw := NewDualWriterMode3(lsSpy, sSpy)
+
+	_, err := dw.Get(context.Background(), kind, &metav1.GetOptions{})
+	assert.NoError(t, err)
+
+	// it should use the Unified Storage Get implementation
+	assert.Equal(t, 0, lsSpy.Counts("LegacyStorage.Get"))
+	assert.Equal(t, 1, sSpy.Counts("Storage.Get"))
+}
+
+func Test_Mode4(t *testing.T) {
+	var ls = (LegacyStorage)(nil)
+	var s = (Storage)(nil)
+	lsSpy := NewLegacyStorageSpyClient(ls)
+	sSpy := NewStorageSpyClient(s)
+
+	dw := NewDualWriterMode3(lsSpy, sSpy)
+
+	_, err := dw.Get(context.Background(), kind, &metav1.GetOptions{})
+	assert.NoError(t, err)
+
+	// it should use the Unified Storage Get implementation
+	assert.Equal(t, 0, lsSpy.Counts("LegacyStorage.Get"))
+	assert.Equal(t, 1, sSpy.Counts("Storage.Get"))
+}