Split implementations from generic code

core/pkg/watch/file_watcher.go

@@ -0,0 +1,75 @@
+/*
+Copyright 2016 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 watch
+
+import (
+	"log"
+	"path"
+
+	"gopkg.in/fsnotify.v1"
+)
+
+// FileWatcher defines a watch over a file
+type FileWatcher struct {
+	file    string
+	watcher *fsnotify.Watcher
+	// onEvent callback to be invoked after the file being watched changes
+	onEvent func()
+}
+
+// NewFileWatcher creates a new FileWatcher
+func NewFileWatcher(file string, onEvent func()) (FileWatcher, error) {
+	fw := FileWatcher{
+		file:    file,
+		onEvent: onEvent,
+	}
+	err := fw.watch()
+	return fw, err
+}
+
+// Close ends the watch
+func (f FileWatcher) Close() error {
+	return f.watcher.Close()
+}
+
+// watch creates a fsnotify watcher for a file and create of write events
+func (f *FileWatcher) watch() error {
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		return err
+	}
+	f.watcher = watcher
+
+	dir, file := path.Split(f.file)
+	go func(file string) {
+		for {
+			select {
+			case event := <-watcher.Events:
+				if event.Op&fsnotify.Write == fsnotify.Write ||
+					event.Op&fsnotify.Create == fsnotify.Create &&
+						event.Name == file {
+					f.onEvent()
+				}
+			case err := <-watcher.Errors:
+				if err != nil {
+					log.Printf("error watching file: %v\n", err)
+				}
+			}
+		}
+	}(file)
+	return watcher.Add(dir)
+}

core/pkg/watch/file_watcher_test.go

@@ -0,0 +1,45 @@
+/*
+Copyright 2015 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 watch
+
+import (
+	"io/ioutil"
+	"testing"
+)
+
+func TestFileWatcher(t *testing.T) {
+	file, err := ioutil.TempFile("", "fw")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	defer file.Close()
+	count := 0
+	fw, err := NewFileWatcher(file.Name(), func() {
+		count++
+		if count != 1 {
+			t.Fatalf("expected 1 but returned %v", count)
+		}
+	})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	defer fw.Close()
+	if count != 0 {
+		t.Fatalf("expected 0 but returned %v", count)
+	}
+	ioutil.WriteFile(file.Name(), []byte{}, 0644)
+}