lib/model: Don't set ignore bit when it's already set

This adds a metric for "committed items" to the database instance that I
use in the test code, and a couple of tests that ensure that scans that
don't change anything also don't commit anything.

There was a case in the scanner where we set the invalid bit on files
that are ignored, even though they were already ignored and had the
invalid bit set. I had assumed this would result in an extra database
commit, but it was in fact filtered out by the Set... Anyway, I think we
can save some work on not pushing that change to the Set at all.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3298

lib/db/leveldb_dbinstance.go

@@ -13,6 +13,7 @@ import (
 	"path/filepath"
 	"sort"
 	"strings"
+	"sync/atomic"
 
 	"github.com/syncthing/syncthing/lib/osutil"
 	"github.com/syncthing/syncthing/lib/protocol"
@@ -31,6 +32,7 @@ type Instance struct {
 	*leveldb.DB
 	folderIdx *smallIndex
 	deviceIdx *smallIndex
+	committed int64
 }
 
 const (
@@ -91,6 +93,11 @@ func newDBInstance(db *leveldb.DB) *Instance {
 	return i
 }
 
+// Committed returns the number of items committed to the database since startup
+func (db *Instance) Committed() int64 {
+	return atomic.LoadInt64(&db.committed)
+}
+
 func (db *Instance) genericReplace(folder, device []byte, fs []protocol.FileInfo, localSize, globalSize *sizeTracker, deleteFn deletionHandler) int64 {
 	sort.Sort(fileList(fs)) // sort list on name, same as in the database
 

lib/db/leveldb_transactions.go

@@ -8,6 +8,7 @@ package db
 
 import (
 	"bytes"
+	"sync/atomic"
 
 	"github.com/syncthing/syncthing/lib/protocol"
 	"github.com/syndtr/goleveldb/leveldb"
@@ -55,19 +56,22 @@ func (db *Instance) newReadWriteTransaction() readWriteTransaction {
 }
 
 func (t readWriteTransaction) close() {
-	if err := t.db.Write(t.Batch, nil); err != nil {
-		panic(err)
-	}
+	t.flush()
 	t.readOnlyTransaction.close()
 }
 
 func (t readWriteTransaction) checkFlush() {
 	if t.Batch.Len() > batchFlushSize {
+		t.flush()
+		t.Batch.Reset()
+	}
+}
+
+func (t readWriteTransaction) flush() {
 	if err := t.db.Write(t.Batch, nil); err != nil {
 		panic(err)
 	}
-		t.Batch.Reset()
-	}
+	atomic.AddInt64(&t.db.committed, int64(t.Batch.Len()))
 }
 
 func (t readWriteTransaction) insertFile(folder, device []byte, file protocol.FileInfo) int64 {

lib/db/set_test.go

@@ -624,6 +624,39 @@ func TestLongPath(t *testing.T) {
 	}
 }
 
+func TestCommitted(t *testing.T) {
+	// Verify that the Committed counter increases when we change things and
+	// doesn't increase when we don't.
+
+	ldb := db.OpenMemory()
+
+	s := db.NewFileSet("test", ldb)
+
+	local := []protocol.FileInfo{
+		{Name: string("file"), Version: protocol.Vector{{ID: myID, Value: 1000}}},
+	}
+
+	// Adding a file should increase the counter
+
+	c0 := ldb.Committed()
+
+	s.Replace(protocol.LocalDeviceID, local)
+
+	c1 := ldb.Committed()
+	if c1 <= c0 {
+		t.Errorf("committed data didn't increase; %d <= %d", c1, c0)
+	}
+
+	// Updating with something identical should not do anything
+
+	s.Update(protocol.LocalDeviceID, local)
+
+	c2 := ldb.Committed()
+	if c2 > c1 {
+		t.Errorf("replace with same contents should do nothing but %d > %d", c2, c1)
+	}
+}
+
 func BenchmarkUpdateOneFile(b *testing.B) {
 	local0 := fileList{
 		protocol.FileInfo{Name: "a", Version: protocol.Vector{{ID: myID, Value: 1000}}, Blocks: genBlocks(1)},

lib/model/model.go

@@ -1551,7 +1551,7 @@ func (m *Model) internalScanFolderSubdirs(folder string, subs []string) error {
 					batch = batch[:0]
 				}
 
-				if ignores.Match(f.Name).IsIgnored() || symlinkInvalid(folder, f) {
+				if !f.IsInvalid() && (ignores.Match(f.Name).IsIgnored() || symlinkInvalid(folder, f)) {
 					// File has been ignored or an unsupported symlink. Set invalid bit.
 					l.Debugln("setting invalid bit on ignored", f)
 					nf := protocol.FileInfo{

lib/model/model_test.go

@@ -1455,6 +1455,58 @@ func TestIssue3164(t *testing.T) {
 	}
 }
 
+func TestScanNoDatabaseWrite(t *testing.T) {
+	// When scanning, nothing should be committed to database unless
+	// something actually changed.
+
+	db := db.OpenMemory()
+	m := NewModel(defaultConfig, protocol.LocalDeviceID, "device", "syncthing", "dev", db, nil)
+	m.AddFolder(defaultFolderConfig)
+	m.StartFolder("default")
+	m.ServeBackground()
+
+	// Start with no ignores, and restore the previous state when the test completes
+
+	curIgn, _, err := m.GetIgnores("default")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer m.SetIgnores("default", curIgn)
+	m.SetIgnores("default", nil)
+
+	// Scan the folder twice. The second scan should be a no-op database wise
+
+	m.ScanFolder("default")
+	c0 := db.Committed()
+
+	m.ScanFolder("default")
+	c1 := db.Committed()
+
+	if c1 != c0 {
+		t.Errorf("scan should not commit data when nothing changed but %d != %d", c1, c0)
+	}
+
+	// Ignore a file we know exists. It'll be updated in the database.
+
+	m.SetIgnores("default", []string{"foo"})
+
+	m.ScanFolder("default")
+	c2 := db.Committed()
+
+	if c2 <= c1 {
+		t.Errorf("scan should commit data when something got ignored but %d <= %d", c2, c1)
+	}
+
+	// Scan again. Nothing should happen.
+
+	m.ScanFolder("default")
+	c3 := db.Committed()
+
+	if c3 != c2 {
+		t.Errorf("scan should not commit data when nothing changed (with ignores) but %d != %d", c3, c2)
+	}
+}
+
 type fakeAddr struct{}
 
 func (fakeAddr) Network() string {