use the new notify library, simplify a lot

Author: clinta

glide.lock

@@ -6,3 +6,4 @@ import:
   subpackages:
   - inotify
 - package: github.com/fsnotify/fsnotify
+- package: github.com/rjeczalik/notify

glide.yaml

@@ -7,18 +7,22 @@ import (
 	"os/signal"
 	"path/filepath"
 	"regexp"
+	"sync"
 	"time"
 
 	log "github.com/Sirupsen/logrus"
 
-	"github.com/fsnotify/fsnotify"
+	"github.com/rjeczalik/notify"
 	"github.com/urfave/cli"
 )
 
 const (
-	version = "0.2"
+	version = "0.3"
 )
 
+var resolvContent []byte
+var rcl sync.RWMutex
+
 func main() {
 
 	app := cli.NewApp()
@@ -57,23 +61,25 @@ func Run(ctx *cli.Context) error {
 		log.Info("Debug logging enabled")
 	}
 
-	resolvContent, err := refreshAll([]byte{}, true)
+	err := refreshAll(true)
 	if err != nil {
 		log.WithError(err).Error("Error doing initial refresh")
 		return err
 	}
 
-	watcher, err := fsnotify.NewWatcher()
+	resolvEvents := make(chan notify.EventInfo, 8)
+	err = notify.Watch("/etc/resolv.conf", resolvEvents, notify.Write)
 	if err != nil {
-		log.WithError(err).Error("Failed to create new watcher")
+		log.WithError(err).Error("Failed to resolv.conf notifications")
+		return err
+	}
+
+	dkrResolvEvents := make(chan notify.EventInfo, 256)
+	err = notify.Watch("/var/lib/docker/containers/...", dkrResolvEvents, notify.Write)
+	if err != nil {
+		log.WithError(err).Error("Failed to container notifications")
 		return err
 	}
-	defer func() {
-		err := watcher.Close()
-		if err != nil {
-			log.WithError(err).Error("Error closing watcher")
-		}
-	}()
 
 	stop := make(chan struct{})
 	done := make(chan struct{})
@@ -91,78 +97,40 @@ func Run(ctx *cli.Context) error {
 	refresh := ctx.Int("refresh")
 	go func() {
 		dockerResolv := regexp.MustCompile("^/var/lib/docker/containers/[A-Za-z0-9]*/resolv.conf$")
-		dockerDir := regexp.MustCompile("^/var/lib/docker/containers/[A-Za-z0-9]*$")
 		t := time.NewTicker(time.Duration(max(refresh, 1)) * time.Second)
 		if refresh <= 0 {
 			t.Stop()
 		}
 		for {
 			select {
-			case ev := <-watcher.Events:
-				if ev.Name == "/etc/resolv.conf" {
-					resolvContent, err = refreshAll(resolvContent, false)
-					if err != nil {
-						log.WithError(err).Error("Error refreshing after /etc/resolv.conf changed")
-					}
-					continue
-				}
-				if dockerResolv.MatchString(ev.Name) {
-					go fixResolvConf(ev.Name, resolvContent)
-					continue
-				}
-				if dockerDir.MatchString(ev.Name) {
-					if ev.Op&fsnotify.Remove != 0 {
-						watcher.Remove(ev.Name)
-						continue
-					}
-					fi, err := os.Stat(ev.Name)
-					if err != nil && fi != nil && fi.IsDir() {
-						err := watcher.Add(ev.Name)
-						if err != nil {
-							log.WithError(err).WithField("dir", ev.Name).Error("Error adding watch")
-						}
-						go fixResolvConf(ev.Name+"/resolv.conf", resolvContent)
-					}
-					continue
-				}
-				continue
 			case <-t.C:
-				resolvContent, err = refreshAll(resolvContent, true)
+				err = refreshAll(true)
 				if err != nil {
 					log.WithError(err).Error("Error during scheduled refresh")
 				}
 				continue
+			case ev := <-dkrResolvEvents:
+				if !dockerResolv.MatchString(ev.Path()) {
+					continue
+				}
+				go fixResolvConf(ev.Path())
+			case <-resolvEvents:
+				go func() {
+					err = refreshAll(false)
+					if err != nil {
+						log.WithError(err).Error("Error refreshing after /etc/resolv.conf changed")
+					}
+				}()
 			case <-stop:
+				notify.Stop(dkrResolvEvents)
+				notify.Stop(resolvEvents)
+				rcl.Lock() // Ensure all writing is done by locking rcl
 				close(done)
 				return
 			}
 		}
 	}()
 
-	err = watcher.Add("/var/lib/docker/containers/")
-	if err != nil {
-		log.WithError(err).Error("Failed to add container watch")
-		return err
-	}
-	err = watcher.Add("/etc")
-	if err != nil {
-		log.WithError(err).Error("Failed to add resolv.conf watch")
-		return err
-	}
-	conts, err := filepath.Glob("/var/lib/docker/containers/*")
-	if err != nil {
-		log.WithError(err).Error("Failed to list existing containers")
-		return err
-	}
-	if conts != nil {
-		for _, c := range conts {
-			err := watcher.Add(c)
-			if err != nil {
-				log.WithError(err).WithField("container", c).Error("Error adding watch for container")
-			}
-		}
-	}
-
 	c := make(chan os.Signal, 1)
 	signal.Notify(c, os.Interrupt)
 	defer close(c)
@@ -175,30 +143,36 @@ func Run(ctx *cli.Context) error {
 	return nil
 }
 
-func refreshAll(resolvContent []byte, force bool) (newResolvContent []byte, err error) {
-	newResolvContent, err = ioutil.ReadFile("/etc/resolv.conf")
+func refreshAll(force bool) error {
+	newResolvContent, err := ioutil.ReadFile("/etc/resolv.conf")
 	if err != nil {
 		log.WithError(err).Error("Failed to read /etc/resolv.conf")
-		return
+		return err
 	}
+	rcl.RLock()
 	if bytes.Equal(newResolvContent, resolvContent) {
 		log.Debug("/etc/resolv.conf unchanged")
 		if !force {
-			return
+			rcl.RUnlock()
+			return nil
 		}
 	}
+	rcl.RUnlock()
+	rcl.Lock()
+	resolvContent = newResolvContent
 	log.WithField("content", string(resolvContent)).Debug("/etc/resov.conf content retrieved")
+	rcl.Unlock()
 	resolvs, err := filepath.Glob("/var/lib/docker/containers/*/resolv.conf")
 	if err != nil {
 		log.WithError(err).Error("Failed to list existing resolv.conf files")
-		return
+		return err
 	}
 	if resolvs != nil {
 		for _, r := range resolvs {
-			go fixResolvConf(r, newResolvContent)
+			go fixResolvConf(r)
 		}
 	}
-	return
+	return nil
 }
 
 func max(a, b int) int {
@@ -207,3 +181,30 @@ func max(a, b int) int {
 	}
 	return b
 }
+
+func fixResolvConf(path string) {
+	_, err := os.Stat(path)
+	if err != nil {
+		log.WithField("Path", path).Debug("File does not exist")
+		return
+	}
+
+	c, err := ioutil.ReadFile(path)
+	if err != nil {
+		log.WithError(err).WithField("Path", path).Error("Failed to read file")
+		return
+	}
+
+	rcl.RLock()
+	defer rcl.RUnlock()
+	if bytes.Equal(c, resolvContent) {
+		log.WithField("Path", path).Debug("File already has correct content")
+		return
+	}
+
+	err = ioutil.WriteFile(path, resolvContent, 0644)
+	if err != nil {
+		log.WithError(err).WithField("Path", path).Error("Failed to write to file")
+	}
+	log.WithField("Path", path).Debug("File content updated")
+}