pkg/utils: generalize file watcher

Add the capability to watch multiple files. Move it to a separate
package in order to make it reusable.

pkg/nfd-worker/nfd-worker.go

@@ -28,7 +28,6 @@ import (
 	"strings"
 	"time"
 
-	"github.com/fsnotify/fsnotify"
 	"golang.org/x/net/context"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/credentials"
@@ -169,40 +168,6 @@ func NewNfdWorker(args *Args) (NfdWorker, error) {
 	return nfd, nil
 }
 
-func addConfigWatch(path string) (*fsnotify.Watcher, map[string]struct{}, error) {
-	paths := make(map[string]struct{})
-
-	// Create watcher
-	w, err := fsnotify.NewWatcher()
-	if err != nil {
-		return w, paths, fmt.Errorf("failed to create fsnotify watcher: %v", err)
-	}
-
-	// Add watches for all directory components so that we catch e.g. renames
-	// upper in the tree
-	added := false
-	for p := path; ; p = filepath.Dir(p) {
-
-		if err := w.Add(p); err != nil {
-			klog.V(1).Infof("failed to add fsnotify watch for %q: %v", p, err)
-		} else {
-			klog.V(1).Infof("added fsnotify watch %q", p)
-			added = true
-		}
-
-		paths[p] = struct{}{}
-		if filepath.Dir(p) == p {
-			break
-		}
-	}
-
-	if !added {
-		// Want to be sure that we watch something
-		return w, paths, fmt.Errorf("failed to add any watch")
-	}
-	return w, paths, nil
-}
-
 func newDefaultConfig() *NFDConfig {
 	return &NFDConfig{
 		Core: coreConfig{
@@ -221,7 +186,7 @@ func (w *nfdWorker) Run() error {
 	klog.Infof("NodeName: '%s'", nodeName)
 
 	// Create watcher for config file and read initial configuration
-	configWatch, paths, err := addConfigWatch(w.configFilePath)
+	configWatch, err := utils.CreateFsWatcher(time.Second, w.configFilePath)
 	if err != nil {
 		return err
 	}
@@ -237,7 +202,6 @@ func (w *nfdWorker) Run() error {
 	defer w.disconnect()
 
 	labelTrigger := time.After(0)
-	var configTrigger <-chan time.Time
 	for {
 		select {
 		case <-labelTrigger:
@@ -260,32 +224,8 @@ func (w *nfdWorker) Run() error {
 				labelTrigger = time.After(w.config.Core.SleepInterval.Duration)
 			}
 
-		case e := <-configWatch.Events:
-			name := filepath.Clean(e.Name)
-
-			// If any of our paths (directories or the file itself) change
-			if _, ok := paths[name]; ok {
-				klog.Infof("fsnotify event in %q detected, reconfiguring fsnotify and reloading configuration", name)
-
-				// Blindly remove existing watch and add a new one
-				if err := configWatch.Close(); err != nil {
-					klog.Warningf("failed to close fsnotify watcher: %v", err)
-				}
-				configWatch, paths, err = addConfigWatch(w.configFilePath)
-				if err != nil {
-					return err
-				}
-
-				// Rate limiter. In certain filesystem operations we get
-				// numerous events in quick succession and we only want one
-				// config re-load
-				configTrigger = time.After(time.Second)
-			}
-
-		case e := <-configWatch.Errors:
-			klog.Errorf("config file watcher error: %v", e)
-
-		case <-configTrigger:
+		case <-configWatch.Events:
+			klog.Infof("reloading configuration")
 			if err := w.configure(w.configFilePath, w.args.Options); err != nil {
 				return err
 			}

pkg/utils/fswatcher.go

@@ -0,0 +1,159 @@
+/*
+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 utils
+
+import (
+	"fmt"
+	"path/filepath"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+	"k8s.io/klog/v2"
+)
+
+// FsWatcher is a wrapper helper for watching files
+type FsWatcher struct {
+	*fsnotify.Watcher
+
+	Events    chan struct{}
+	ratelimit time.Duration
+	names     []string
+	paths     map[string]struct{}
+}
+
+// CreateFsWatcher creates a new FsWatcher
+func CreateFsWatcher(ratelimit time.Duration, names ...string) (*FsWatcher, error) {
+	w := &FsWatcher{
+		Events:    make(chan struct{}),
+		names:     names,
+		ratelimit: ratelimit,
+	}
+
+	if err := w.reset(names...); err != nil {
+		return nil, err
+	}
+
+	go w.watch()
+
+	return w, nil
+}
+
+// reset resets the file watches
+func (w *FsWatcher) reset(names ...string) error {
+	if err := w.initWatcher(); err != nil {
+		return err
+	}
+	if err := w.add(names...); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (w *FsWatcher) initWatcher() error {
+	if w.Watcher != nil {
+		if err := w.Watcher.Close(); err != nil {
+			return fmt.Errorf("failed to close fsnotify watcher: %v", err)
+		}
+	}
+	w.paths = make(map[string]struct{})
+
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		w.Watcher = nil
+		return fmt.Errorf("failed to create fsnotify watcher: %v", err)
+	}
+	w.Watcher = watcher
+
+	return nil
+}
+
+func (w *FsWatcher) add(names ...string) error {
+	for _, name := range names {
+		if name == "" {
+			continue
+		}
+
+		added := false
+		// Add watches for all directory components so that we catch e.g. renames
+		// upper in the tree
+		for p := name; ; p = filepath.Dir(p) {
+			if _, ok := w.paths[p]; !ok {
+				if err := w.Add(p); err != nil {
+					klog.V(1).Infof("failed to add fsnotify watch for %q: %v", p, err)
+				} else {
+					klog.V(1).Infof("added fsnotify watch %q", p)
+					added = true
+				}
+
+				w.paths[p] = struct{}{}
+			} else {
+				added = true
+			}
+			if filepath.Dir(p) == p {
+				break
+			}
+		}
+		if !added {
+			// Want to be sure that we watch something
+			return fmt.Errorf("failed to add any watch")
+		}
+	}
+
+	return nil
+}
+
+func (w *FsWatcher) watch() {
+	var ratelimiter <-chan time.Time
+	for {
+		select {
+		case e, ok := <-w.Watcher.Events:
+			// Watcher has been closed
+			if !ok {
+				klog.Infof("watcher closed")
+				return
+			}
+
+			// If any of our paths change
+			name := filepath.Clean(e.Name)
+			if _, ok := w.paths[filepath.Clean(name)]; ok {
+				klog.V(2).Infof("fsnotify %s event in %q detected", e, name)
+
+				// Rate limiter. In certain filesystem operations we get
+				// numerous events in quick succession
+				ratelimiter = time.After(w.ratelimit)
+			}
+
+		case e, ok := <-w.Watcher.Errors:
+			// Watcher has been closed
+			if !ok {
+				klog.Infof("watcher closed")
+				return
+			}
+			klog.Warningf("fswatcher error event detected: %v", e)
+
+		case <-ratelimiter:
+			// Blindly remove existing watch and add a new one
+			if err := w.reset(w.names...); err != nil {
+				klog.Errorf("%v, re-trying in 60 seconds...", err)
+				ratelimiter = time.After(60 * time.Second)
+			}
+
+			w.Events <- struct{}{}
+		}
+	}
+}