fix hot reloading of configuration on macOS and with text editors that deletes and recreates the configuration file

internal/confwatcher/confwatcher.go

@@ -2,11 +2,17 @@ package confwatcher
 
 import (
 	"os"
+	"path/filepath"
 	"time"
 
 	"github.com/fsnotify/fsnotify"
 )
 
+const (
+	minInterval    = 1 * time.Second
+	additionalWait = 10 * time.Millisecond
+)
+
 // ConfWatcher is a configuration file watcher.
 type ConfWatcher struct {
 	inner *fsnotify.Watcher
@@ -24,7 +30,10 @@ func New(confPath string) (*ConfWatcher, error) {
 	}
 
 	if _, err := os.Stat(confPath); err == nil {
-		err := inner.Add(confPath)
+		// use absolute path to support Darwin
+		absolutePath, _ := filepath.Abs(confPath)
+
+		err := inner.Add(absolutePath)
 		if err != nil {
 			inner.Close()
 			return nil, err
@@ -54,13 +63,22 @@ func (w *ConfWatcher) Close() {
 func (w *ConfWatcher) run() {
 	defer close(w.done)
 
+	var lastCalled time.Time
+
 outer:
 	for {
 		select {
 		case event := <-w.inner.Events:
-			if (event.Op & fsnotify.Write) == fsnotify.Write {
-				// wait some additional time to avoid EOF
-				time.Sleep(10 * time.Millisecond)
+			if time.Since(lastCalled) < minInterval {
+				continue
+			}
+
+			if (event.Op&fsnotify.Write) == fsnotify.Write ||
+				(event.Op&fsnotify.Create) == fsnotify.Create {
+				// wait some additional time to allow the writer to complete its job
+				time.Sleep(additionalWait)
+
+				lastCalled = time.Now()
 				w.signal <- struct{}{}
 			}
 
@@ -72,7 +90,7 @@ outer:
 	close(w.signal)
 }
 
-// Watch returns when the configuration file has changed.
+// Watch returns a channel that is called when the configuration file has changed.
 func (w *ConfWatcher) Watch() chan struct{} {
 	return w.signal
 }

main.go

@@ -68,13 +68,20 @@ func newProgram(args []string) (*program, error) {
 		return nil, err
 	}
 
-	err = p.createResources(true)
+	err = p.createDynamicResources(true)
 	if err != nil {
-		p.closeResources()
+		p.closeAllResources()
+		return nil, err
+	}
+
+	p.confWatcher, err = confwatcher.New(p.confPath)
+	if err != nil {
+		p.closeAllResources()
 		return nil, err
 	}
 
 	go p.run()
+
 	return p, nil
 }
 
@@ -110,10 +117,10 @@ outer:
 		}
 	}
 
-	p.closeResources()
+	p.closeAllResources()
 }
 
-func (p *program) createResources(initial bool) error {
+func (p *program) createDynamicResources(initial bool) error {
 	var err error
 
 	if p.stats == nil {
@@ -187,17 +194,10 @@ func (p *program) createResources(initial bool) error {
 			p.pathMan, p.serverTcp, p)
 	}
 
-	if p.confWatcher == nil {
-		p.confWatcher, err = confwatcher.New(p.confPath)
-		if err != nil {
-			return err
-		}
-	}
-
 	return nil
 }
 
-func (p *program) closeResources() {
+func (p *program) closeAllResources() {
 	if p.confWatcher != nil {
 		p.confWatcher.Close()
 	}
@@ -243,10 +243,6 @@ func (p *program) reloadConf() error {
 		return err
 	}
 
-	// always recreate confWatcher to avoid reloading twice
-	p.confWatcher.Close()
-	p.confWatcher = nil
-
 	closeLogHandler := false
 	if !reflect.DeepEqual(conf.LogDestinationsParsed, p.conf.LogDestinationsParsed) ||
 		conf.LogFile != p.conf.LogFile {
@@ -345,7 +341,7 @@ func (p *program) reloadConf() error {
 	}
 
 	p.conf = conf
-	return p.createResources(false)
+	return p.createDynamicResources(false)
 }
 
 func main() {