Serialize scans and pulls (fixes #1391)

internal/model/rwfolder.go

@@ -32,7 +32,7 @@ import (
 const (
 	pauseIntv     = 60 * time.Second
 	nextPullIntv  = 10 * time.Second
-	shortPullIntv = 5 * time.Second
+	shortPullIntv = time.Second
 )
 
 // A pullBlockState is passed to the puller routine for each block that needs
@@ -90,6 +90,7 @@ type rwFolder struct {
 	scanTimer   *time.Timer
 	pullTimer   *time.Timer
 	delayScan   chan time.Duration
+	scanNow     chan rescanRequest
 	remoteIndex chan struct{} // An index update was received, we should re-evaluate needs
 }
 
@@ -118,6 +119,7 @@ func newRWFolder(m *Model, shortID uint64, cfg config.FolderConfiguration) *rwFo
 		pullTimer:   time.NewTimer(shortPullIntv),
 		scanTimer:   time.NewTimer(time.Millisecond), // The first scan should be done immediately.
 		delayScan:   make(chan time.Duration),
+		scanNow:     make(chan rescanRequest),
 		remoteIndex: make(chan struct{}, 1), // This needs to be 1-buffered so that we queue a notification if we're busy doing a pull when it comes.
 	}
 }
@@ -278,7 +280,7 @@ func (p *rwFolder) Serve() {
 				l.Debugln(p, "rescan")
 			}
 
-			if err := p.model.ScanFolder(p.folder); err != nil {
+			if err := p.model.internalScanFolderSubs(p.folder, nil); err != nil {
 				// Potentially sets the error twice, once in the scanner just
 				// by doing a check, and once here, if the error returned is
 				// the same one as returned by CheckFolderHealth, though
@@ -296,6 +298,29 @@ func (p *rwFolder) Serve() {
 				initialScanCompleted = true
 			}
 
+		case req := <-p.scanNow:
+			if err := p.model.CheckFolderHealth(p.folder); err != nil {
+				l.Infoln("Skipping folder", p.folder, "scan due to folder error:", err)
+				req.err <- err
+				continue
+			}
+
+			if debug {
+				l.Debugln(p, "forced rescan")
+			}
+
+			if err := p.model.internalScanFolderSubs(p.folder, req.subs); err != nil {
+				// Potentially sets the error twice, once in the scanner just
+				// by doing a check, and once here, if the error returned is
+				// the same one as returned by CheckFolderHealth, though
+				// duplicate set is handled by setError.
+				p.setError(err)
+				req.err <- err
+				continue
+			}
+
+			req.err <- nil
+
 		case next := <-p.delayScan:
 			p.scanTimer.Reset(next)
 		}
@@ -317,6 +342,15 @@ func (p *rwFolder) IndexUpdated() {
 	}
 }
 
+func (p *rwFolder) Scan(subs []string) error {
+	req := rescanRequest{
+		subs: subs,
+		err:  make(chan error),
+	}
+	p.scanNow <- req
+	return <-req.err
+}
+
 func (p *rwFolder) String() string {
 	return fmt.Sprintf("rwFolder/%s@%p", p.folder, p)
 }