all: Add filesystem notification support

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3986

lib/model/folder.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/syncthing/syncthing/lib/config"
+	"github.com/syncthing/syncthing/lib/watchaggregator"
 )
 
 type folder struct {
@@ -22,6 +23,9 @@ type folder struct {
 	ctx                 context.Context
 	cancel              context.CancelFunc
 	initialScanFinished chan struct{}
+	watchCancel         context.CancelFunc
+	watchChan           chan []string
+	ignoresUpdated      chan struct{} // The ignores changed, we need to restart watcher
 }
 
 func newFolder(model *Model, cfg config.FolderConfiguration) folder {
@@ -92,3 +96,35 @@ func (f *folder) scanTimerFired() {
 
 	f.scan.Reschedule()
 }
+
+func (f *folder) startWatcher() {
+	ctx, cancel := context.WithCancel(f.ctx)
+	f.model.fmut.RLock()
+	ignores := f.model.folderIgnores[f.folderID]
+	f.model.fmut.RUnlock()
+	eventChan, err := f.Filesystem().Watch(".", ignores, ctx, f.IgnorePerms)
+	if err != nil {
+		l.Warnf("Failed to start filesystem watcher for folder %s: %v", f.Description(), err)
+	} else {
+		f.watchChan = make(chan []string)
+		f.watchCancel = cancel
+		watchaggregator.Aggregate(eventChan, f.watchChan, f.FolderConfiguration, f.model.cfg, ctx)
+		l.Infoln("Started filesystem watcher for folder", f.Description())
+	}
+}
+
+func (f *folder) restartWatcher() {
+	f.watchCancel()
+	f.startWatcher()
+	f.Scan(nil)
+}
+
+func (f *folder) IgnoresUpdated() {
+	select {
+	case f.ignoresUpdated <- struct{}{}:
+	default:
+		// We might be busy doing a pull and thus not reading from this
+		// channel. The channel is 1-buffered, so one notification will be
+		// queued to ensure we recheck after the pull.
+	}
+}

lib/model/model.go

@@ -48,6 +48,7 @@ type service interface {
 	BringToFront(string)
 	DelayScan(d time.Duration)
 	IndexUpdated()              // Remote index was updated notification
+	IgnoresUpdated()            // ignore matcher was updated notification
 	Jobs() ([]string, []string) // In progress, Queued
 	Scan(subs []string) error
 	Serve()
@@ -260,6 +261,7 @@ func (m *Model) startFolderLocked(folder string) config.FolderType {
 	ffs.Hide(".stignore")
 
 	p := folderFactory(m, cfg, ver, ffs)
+
 	m.folderRunners[folder] = p
 
 	m.warnAboutOverwritingProtectedFiles(folder)
@@ -1858,7 +1860,7 @@ func (m *Model) internalScanFolderSubdirs(ctx context.Context, folder string, su
 	defer func() {
 		if ignores.Hash() != oldHash {
 			l.Debugln("Folder", folder, "ignore patterns changed; triggering puller")
-			runner.IndexUpdated()
+			runner.IgnoresUpdated()
 		}
 	}()
 

lib/model/rofolder.go

@@ -34,11 +34,20 @@ func (f *sendOnlyFolder) Serve() {
 		f.scan.timer.Stop()
 	}()
 
+	if f.FSWatcherEnabled {
+		f.startWatcher()
+	}
+
 	for {
 		select {
 		case <-f.ctx.Done():
 			return
 
+		case <-f.ignoresUpdated:
+			if f.FSWatcherEnabled {
+				f.restartWatcher()
+			}
+
 		case <-f.scan.timer.C:
 			l.Debugln(f, "Scanning subdirectories")
 			f.scanTimerFired()
@@ -48,6 +57,10 @@ func (f *sendOnlyFolder) Serve() {
 
 		case next := <-f.scan.delay:
 			f.scan.timer.Reset(next)
+
+		case fsEvents := <-f.watchChan:
+			l.Debugln(f, "filesystem notification rescan")
+			f.scanSubdirs(fsEvents)
 		}
 	}
 }

lib/model/rwfolder.go

@@ -164,6 +164,10 @@ func (f *sendReceiveFolder) Serve() {
 	var prevSec int64
 	var prevIgnoreHash string
 
+	if f.FSWatcherEnabled {
+		f.startWatcher()
+	}
+
 	for {
 		select {
 		case <-f.ctx.Done():
@@ -174,6 +178,12 @@ func (f *sendReceiveFolder) Serve() {
 			f.pullTimer.Reset(0)
 			l.Debugln(f, "remote index updated, rescheduling pull")
 
+		case <-f.ignoresUpdated:
+			if f.FSWatcherEnabled {
+				f.restartWatcher()
+			}
+			f.IndexUpdated()
+
 		case <-f.pullTimer.C:
 			select {
 			case <-f.initialScanFinished:
@@ -278,6 +288,10 @@ func (f *sendReceiveFolder) Serve() {
 
 		case next := <-f.scan.delay:
 			f.scan.timer.Reset(next)
+
+		case fsEvents := <-f.watchChan:
+			l.Debugln(f, "filesystem notification rescan")
+			f.scanSubdirs(fsEvents)
 		}
 	}
 }