source/local: implement FeatureSource

Separate feature discovery (i.e. running hooks and reading feature
files) and creation of feature labels in the local source.

Also, add minimalist unit test.

source/local/local.go

@@ -27,23 +27,30 @@ import (
 
 	"k8s.io/klog/v2"
 
+	"sigs.k8s.io/node-feature-discovery/pkg/api/feature"
+	"sigs.k8s.io/node-feature-discovery/pkg/utils"
 	"sigs.k8s.io/node-feature-discovery/source"
 )
 
 const Name = "local"
 
+const LabelFeature = "label"
+
 // Config
 var (
 	featureFilesDir = "/etc/kubernetes/node-feature-discovery/features.d/"
 	hookDir         = "/etc/kubernetes/node-feature-discovery/source.d/"
 )
 
-// localSource implements the LabelSource interface.
-type localSource struct{}
+// localSource implements the FeatureSource and LabelSource interfaces.
+type localSource struct {
+	features *feature.DomainFeatures
+}
 
 // Singleton source instance
 var (
 	src localSource
+	_   source.FeatureSource = &src
 	_   source.LabelSource   = &src
 )
 
@@ -55,6 +62,19 @@ func (s *localSource) Priority() int { return 20 }
 
 // GetLabels method of the LabelSource interface
 func (s *localSource) GetLabels() (source.FeatureLabels, error) {
+	labels := make(source.FeatureLabels)
+	features := s.GetFeatures()
+
+	for k, v := range features.Values[LabelFeature].Elements {
+		labels[k] = v
+	}
+	return labels, nil
+}
+
+// Discover method of the FeatureSource interface
+func (s *localSource) Discover() error {
+	s.features = feature.NewDomainFeatures()
+
 	featuresFromHooks, err := getFeaturesFromHooks()
 	if err != nil {
 		klog.Error(err)
@@ -68,17 +88,28 @@ func (s *localSource) GetLabels() (source.FeatureLabels, error) {
 	// Merge features from hooks and files
 	for k, v := range featuresFromHooks {
 		if old, ok := featuresFromFiles[k]; ok {
-			klog.Warningf("overriding label '%s': value changed from '%s' to '%s'",
+			klog.Warningf("overriding '%s': value changed from '%s' to '%s'",
 				k, old, v)
 		}
 		featuresFromFiles[k] = v
 	}
+	s.features.Values[LabelFeature] = feature.NewValueFeatures(featuresFromFiles)
 
-	return featuresFromFiles, nil
+	utils.KlogDump(3, "discovered local features:", "  ", s.features)
+
+	return nil
 }
 
-func parseFeatures(lines [][]byte, prefix string) source.FeatureLabels {
-	features := source.FeatureLabels{}
+// GetFeatures method of the FeatureSource Interface
+func (s *localSource) GetFeatures() *feature.DomainFeatures {
+	if s.features == nil {
+		s.features = feature.NewDomainFeatures()
+	}
+	return s.features
+}
+
+func parseFeatures(lines [][]byte, prefix string) map[string]string {
+	features := make(map[string]string)
 
 	for _, line := range lines {
 		if len(line) > 0 {
@@ -109,8 +140,8 @@ func parseFeatures(lines [][]byte, prefix string) source.FeatureLabels {
 }
 
 // Run all hooks and get features
-func getFeaturesFromHooks() (source.FeatureLabels, error) {
-	features := source.FeatureLabels{}
+func getFeaturesFromHooks() (map[string]string, error) {
+	features := make(map[string]string)
 
 	files, err := ioutil.ReadDir(hookDir)
 	if err != nil {
@@ -184,8 +215,8 @@ func runHook(file string) ([][]byte, error) {
 }
 
 // Read all files to get features
-func getFeaturesFromFiles() (source.FeatureLabels, error) {
-	features := source.FeatureLabels{}
+func getFeaturesFromFiles() (map[string]string, error) {
+	features := make(map[string]string)
 
 	files, err := ioutil.ReadDir(featureFilesDir)
 	if err != nil {

source/local/local_test.go

@@ -0,0 +1,36 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package local
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"sigs.k8s.io/node-feature-discovery/pkg/api/feature"
+)
+
+func TestLocalSource(t *testing.T) {
+	assert.Equal(t, src.Name(), Name)
+
+	// Check that GetLabels works with empty features
+	src.features = feature.NewDomainFeatures()
+	l, err := src.GetLabels()
+
+	assert.Nil(t, err, err)
+	assert.Empty(t, l)
+
+}