Automated cherry pick of #11613 to release-3.3

mvcc/backend/backend.go

@@ -310,21 +310,35 @@ func (b *backend) defrag() error {
 	b.batchTx.unsafeCommit(true)
 	b.batchTx.tx = nil
 
-	tmpdb, err := bolt.Open(b.db.Path()+".tmp", 0600, boltOpenOptions)
+	// Create a temporary file to ensure we start with a clean slate.
+	// Snapshotter.cleanupSnapdir cleans up any of these that are found during startup.
+	dir := filepath.Dir(b.db.Path())
+	temp, err := ioutil.TempFile(dir, "db.tmp.*")
+	if err != nil {
+		return err
+	}
+	options := *boltOpenOptions
+	options.OpenFile = func(path string, i int, mode os.FileMode) (file *os.File, err error) {
+		return temp, nil
+	}
+	tdbp := temp.Name()
+	tmpdb, err := bolt.Open(tdbp, 0600, &options)
 	if err != nil {
 		return err
 	}
 
+	// gofail: var defragBeforeCopy struct{}
 	err = defragdb(b.db, tmpdb, defragLimit)
 
 	if err != nil {
 		tmpdb.Close()
-		os.RemoveAll(tmpdb.Path())
+		if rmErr := os.RemoveAll(tmpdb.Path()); rmErr != nil {
+			plog.Fatalf("failed to remove db.tmp after defragmentation completed: %v", rmErr)
+		}
 		return err
 	}
 
 	dbp := b.db.Path()
-	tdbp := tmpdb.Path()
 
 	err = b.db.Close()
 	if err != nil {
@@ -334,6 +348,7 @@ func (b *backend) defrag() error {
 	if err != nil {
 		plog.Fatalf("cannot close database (%s)", err)
 	}
+	// gofail: var defragBeforeRename struct{}
 	err = os.Rename(tdbp, dbp)
 	if err != nil {
 		plog.Fatalf("cannot rename database (%s)", err)

snap/snapshotter.go

@@ -172,6 +172,9 @@ func (s *Snapshotter) snapNames() ([]string, error) {
 	if err != nil {
 		return nil, err
 	}
+	if err = s.cleanupSnapdir(names); err != nil {
+		return nil, err
+	}
 	snaps := checkSuffix(names)
 	if len(snaps) == 0 {
 		return nil, ErrNoSnapshot
@@ -202,3 +205,17 @@ func renameBroken(path string) {
 		plog.Warningf("cannot rename broken snapshot file %v to %v: %v", path, brokenPath, err)
 	}
 }
+
+// cleanupSnapdir removes any files that should not be in the snapshot directory:
+// - db.tmp prefixed files that can be orphaned by defragmentation
+func (s *Snapshotter) cleanupSnapdir(filenames []string) error {
+	for _, filename := range filenames {
+		if strings.HasPrefix(filename, "db.tmp") {
+			plog.Infof("found orphaned defragmentation file; deleting: %s", filename)
+			if rmErr := os.Remove(filepath.Join(s.dir, filename)); rmErr != nil && !os.IsNotExist(rmErr) {
+				return fmt.Errorf("failed to remove orphaned defragmentation file %s: %v", filename, rmErr)
+			}
+		}
+	}
+	return nil
+}