Stat cache bucket changes (#2138)

* adds get folder implementation for fast stat cache

* adds unit test for fast stat cache get folder implementation

internal/storage/caching/fast_stat_bucket.go

@@ -115,6 +115,14 @@ func (b *fastStatBucket) lookUp(name string) (hit bool, m *gcs.MinObject) {
 	return
 }
 
+func (b *fastStatBucket) lookUpFolder(name string) (bool, *gcs.Folder) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	hit, f := b.cache.LookUpFolder(name, b.clock.Now())
+	return hit, f
+}
+
 ////////////////////////////////////////////////////////////////////////
 // Bucket interface
 ////////////////////////////////////////////////////////////////////////
@@ -298,17 +306,23 @@ func (b *fastStatBucket) StatObjectFromGcs(ctx context.Context,
 
 func (b *fastStatBucket) GetFolder(
 	ctx context.Context,
-	prefix string) (folder *gcs.Folder, err error) {
-	// Fetch the listing.
-	folder, err = b.wrapped.GetFolder(ctx, prefix)
-	if err != nil {
-		return
-	}
+	prefix string) (*gcs.Folder, error) {
 
-	// TODO: add folder metadata in stat cache
-	// b.insertFolder(folder)
+	if hit, entry := b.lookUpFolder(prefix); hit {
+		// Negative entries result in NotFoundError.
+		if entry == nil {
+			err := &gcs.NotFoundError{
+				Err: fmt.Errorf("negative cache entry for folder %v", prefix),
+			}
 
-	return
+			return nil, err
+		}
+
+		return entry, nil
+	}
+
+	// Fetch the Folder
+	return b.wrapped.GetFolder(ctx, prefix)
 }
 
 func (b *fastStatBucket) RenameFolder(ctx context.Context, folderName string, destinationFolderId string) (o *control.RenameFolderOperation, err error) {

internal/storage/caching/fast_stat_bucket_test.go

@@ -725,3 +725,46 @@ func (t *DeleteObjectTest) WrappedSucceeds() {
 	err = t.deleteObject(name)
 	AssertEq(nil, err)
 }
+
+func (t *StatObjectTest) TestShouldReturnFromCacheWhenEntryIsPresent() {
+	const name = "some-name"
+	folder := &gcs.Folder{
+		Name: name,
+	}
+	ExpectCall(t.cache, "LookUpFolder")(name, Any()).
+		WillOnce(Return(true, folder))
+
+	result, err := t.bucket.GetFolder(context.TODO(), name)
+
+	AssertEq(nil, err)
+	ExpectThat(result, Pointee(DeepEquals(*folder)))
+}
+
+func (t *StatObjectTest) TestShouldReturnNotFoundErrorWhenNilEntryIsReturned() {
+	const name = "some-name"
+
+	ExpectCall(t.cache, "LookUpFolder")(name, Any()).
+		WillOnce(Return(true, nil))
+
+	result, err := t.bucket.GetFolder(context.TODO(), name)
+
+	ExpectThat(err, HasSameTypeAs(&gcs.NotFoundError{}))
+	AssertEq(nil, result)
+}
+
+func (t *StatObjectTest) TestShouldCallGetFolderWhenEntryIsNotPresent() {
+	const name = "some-name"
+	folder := &gcs.Folder{
+		Name: name,
+	}
+
+	ExpectCall(t.cache, "LookUpFolder")(name, Any()).
+		WillOnce(Return(false, nil))
+	ExpectCall(t.wrapped, "GetFolder")(Any(), name).
+		WillOnce(Return(folder, nil))
+
+	result, err := t.bucket.GetFolder(context.TODO(), name)
+
+	AssertEq(nil, err)
+	ExpectThat(result, Pointee(DeepEquals(*folder)))
+}

internal/storage/mock_bucket.go

@@ -359,7 +359,7 @@ func (m *mockBucket) GetFolder(
 		"GetFolder",
 		file,
 		line,
-		[]interface{}{})
+		[]interface{}{ctx, prefix})
 
 	if len(retVals) != 2 {
 		panic(fmt.Sprintf("mockBucket.GetFolder: invalid return values: %v", retVals))