syncthing/lib/scanner/walk.go
2017-02-09 08:04:16 +01:00

544 lines
15 KiB
Go

// Copyright (C) 2014 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
package scanner
import (
"errors"
"os"
"path/filepath"
"runtime"
"sync/atomic"
"time"
"unicode/utf8"
"github.com/rcrowley/go-metrics"
"github.com/syncthing/syncthing/lib/events"
"github.com/syncthing/syncthing/lib/ignore"
"github.com/syncthing/syncthing/lib/osutil"
"github.com/syncthing/syncthing/lib/protocol"
"golang.org/x/text/unicode/norm"
)
var maskModePerm os.FileMode
func init() {
if runtime.GOOS == "windows" {
// There is no user/group/others in Windows' read-only
// attribute, and all "w" bits are set in os.FileInfo
// if the file is not read-only. Do not send these
// group/others-writable bits to other devices in order to
// avoid unexpected world-writable files on other platforms.
maskModePerm = os.ModePerm & 0755
} else {
maskModePerm = os.ModePerm
}
}
type Config struct {
// Folder for which the walker has been created
Folder string
// Dir is the base directory for the walk
Dir string
// Limit walking to these paths within Dir, or no limit if Sub is empty
Subs []string
// BlockSize controls the size of the block used when hashing.
BlockSize int
// If Matcher is not nil, it is used to identify files to ignore which were specified by the user.
Matcher *ignore.Matcher
// Number of hours to keep temporary files for
TempLifetime time.Duration
// If CurrentFiler is not nil, it is queried for the current file before rescanning.
CurrentFiler CurrentFiler
// The Lstater provides reliable mtimes on top of the regular filesystem.
Lstater Lstater
// If IgnorePerms is true, changes to permission bits will not be
// detected. Scanned files will get zero permission bits and the
// NoPermissionBits flag set.
IgnorePerms bool
// When AutoNormalize is set, file names that are in UTF8 but incorrect
// normalization form will be corrected.
AutoNormalize bool
// Number of routines to use for hashing
Hashers int
// Our vector clock id
ShortID protocol.ShortID
// Optional progress tick interval which defines how often FolderScanProgress
// events are emitted. Negative number means disabled.
ProgressTickIntervalS int
// Signals cancel from the outside - when closed, we should stop walking.
Cancel chan struct{}
// Wether or not we should also compute weak hashes
UseWeakHashes bool
}
type CurrentFiler interface {
// CurrentFile returns the file as seen at last scan.
CurrentFile(name string) (protocol.FileInfo, bool)
}
type Lstater interface {
Lstat(name string) (os.FileInfo, error)
}
func Walk(cfg Config) (chan protocol.FileInfo, error) {
w := walker{cfg}
if w.CurrentFiler == nil {
w.CurrentFiler = noCurrentFiler{}
}
if w.Lstater == nil {
w.Lstater = defaultLstater{}
}
return w.walk()
}
type walker struct {
Config
}
// Walk returns the list of files found in the local folder by scanning the
// file system. Files are blockwise hashed.
func (w *walker) walk() (chan protocol.FileInfo, error) {
l.Debugln("Walk", w.Dir, w.Subs, w.BlockSize, w.Matcher)
if err := w.checkDir(); err != nil {
return nil, err
}
toHashChan := make(chan protocol.FileInfo)
finishedChan := make(chan protocol.FileInfo)
// A routine which walks the filesystem tree, and sends files which have
// been modified to the counter routine.
go func() {
hashFiles := w.walkAndHashFiles(toHashChan, finishedChan)
if len(w.Subs) == 0 {
filepath.Walk(w.Dir, hashFiles)
} else {
for _, sub := range w.Subs {
filepath.Walk(filepath.Join(w.Dir, sub), hashFiles)
}
}
close(toHashChan)
}()
// We're not required to emit scan progress events, just kick off hashers,
// and feed inputs directly from the walker.
if w.ProgressTickIntervalS < 0 {
newParallelHasher(w.Dir, w.BlockSize, w.Hashers, finishedChan, toHashChan, nil, nil, w.Cancel, w.UseWeakHashes)
return finishedChan, nil
}
// Defaults to every 2 seconds.
if w.ProgressTickIntervalS == 0 {
w.ProgressTickIntervalS = 2
}
ticker := time.NewTicker(time.Duration(w.ProgressTickIntervalS) * time.Second)
// We need to emit progress events, hence we create a routine which buffers
// the list of files to be hashed, counts the total number of
// bytes to hash, and once no more files need to be hashed (chan gets closed),
// start a routine which periodically emits FolderScanProgress events,
// until a stop signal is sent by the parallel hasher.
// Parallel hasher is stopped by this routine when we close the channel over
// which it receives the files we ask it to hash.
go func() {
var filesToHash []protocol.FileInfo
var total int64 = 1
for file := range toHashChan {
filesToHash = append(filesToHash, file)
total += file.Size
}
realToHashChan := make(chan protocol.FileInfo)
done := make(chan struct{})
progress := newByteCounter()
newParallelHasher(w.Dir, w.BlockSize, w.Hashers, finishedChan, realToHashChan, progress, done, w.Cancel, w.UseWeakHashes)
// A routine which actually emits the FolderScanProgress events
// every w.ProgressTicker ticks, until the hasher routines terminate.
go func() {
defer progress.Close()
for {
select {
case <-done:
l.Debugln("Walk progress done", w.Dir, w.Subs, w.BlockSize, w.Matcher)
ticker.Stop()
return
case <-ticker.C:
current := progress.Total()
rate := progress.Rate()
l.Debugf("Walk %s %s current progress %d/%d at %.01f MiB/s (%d%%)", w.Dir, w.Subs, current, total, rate/1024/1024, current*100/total)
events.Default.Log(events.FolderScanProgress, map[string]interface{}{
"folder": w.Folder,
"current": current,
"total": total,
"rate": rate, // bytes per second
})
case <-w.Cancel:
ticker.Stop()
return
}
}
}()
loop:
for _, file := range filesToHash {
l.Debugln("real to hash:", file.Name)
select {
case realToHashChan <- file:
case <-w.Cancel:
break loop
}
}
close(realToHashChan)
}()
return finishedChan, nil
}
func (w *walker) walkAndHashFiles(fchan, dchan chan protocol.FileInfo) filepath.WalkFunc {
now := time.Now()
return func(absPath string, info os.FileInfo, err error) error {
// Return value used when we are returning early and don't want to
// process the item. For directories, this means do-not-descend.
var skip error // nil
// info nil when error is not nil
if info != nil && info.IsDir() {
skip = filepath.SkipDir
}
if err != nil {
l.Debugln("error:", absPath, info, err)
return skip
}
relPath, err := filepath.Rel(w.Dir, absPath)
if err != nil {
l.Debugln("rel error:", absPath, err)
return skip
}
if relPath == "." {
return nil
}
info, err = w.Lstater.Lstat(absPath)
// An error here would be weird as we've already gotten to this point, but act on it nonetheless
if err != nil {
return skip
}
if ignore.IsTemporary(relPath) {
l.Debugln("temporary:", relPath)
if info.Mode().IsRegular() && info.ModTime().Add(w.TempLifetime).Before(now) {
os.Remove(absPath)
l.Debugln("removing temporary:", relPath, info.ModTime())
}
return nil
}
if ignore.IsInternal(relPath) {
l.Debugln("ignored (internal):", relPath)
return skip
}
if w.Matcher.Match(relPath).IsIgnored() {
l.Debugln("ignored (patterns):", relPath)
return skip
}
if !utf8.ValidString(relPath) {
l.Warnf("File name %q is not in UTF8 encoding; skipping.", relPath)
return skip
}
relPath, shouldSkip := w.normalizePath(absPath, relPath)
if shouldSkip {
return skip
}
switch {
case info.Mode()&os.ModeSymlink == os.ModeSymlink:
if err := w.walkSymlink(absPath, relPath, dchan); err != nil {
return err
}
if info.IsDir() {
// under no circumstances shall we descend into a symlink
return filepath.SkipDir
}
return nil
case info.Mode().IsDir():
err = w.walkDir(relPath, info, dchan)
case info.Mode().IsRegular():
err = w.walkRegular(relPath, info, fchan)
}
return err
}
}
func (w *walker) walkRegular(relPath string, info os.FileInfo, fchan chan protocol.FileInfo) error {
curMode := uint32(info.Mode())
if runtime.GOOS == "windows" && osutil.IsWindowsExecutable(relPath) {
curMode |= 0111
}
// A file is "unchanged", if it
// - exists
// - has the same permissions as previously, unless we are ignoring permissions
// - was not marked deleted (since it apparently exists now)
// - had the same modification time as it has now
// - was not a directory previously (since it's a file now)
// - was not a symlink (since it's a file now)
// - was not invalid (since it looks valid now)
// - has the same size as previously
cf, ok := w.CurrentFiler.CurrentFile(relPath)
permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Permissions, curMode)
if ok && permUnchanged && !cf.IsDeleted() && cf.ModTime().Equal(info.ModTime()) && !cf.IsDirectory() &&
!cf.IsSymlink() && !cf.IsInvalid() && cf.Size == info.Size() {
return nil
}
l.Debugln("rescan:", cf, info.ModTime().Unix(), info.Mode()&os.ModePerm)
f := protocol.FileInfo{
Name: relPath,
Type: protocol.FileInfoTypeFile,
Version: cf.Version.Update(w.ShortID),
Permissions: curMode & uint32(maskModePerm),
NoPermissions: w.IgnorePerms,
ModifiedS: info.ModTime().Unix(),
ModifiedNs: int32(info.ModTime().Nanosecond()),
ModifiedBy: w.ShortID,
Size: info.Size(),
}
l.Debugln("to hash:", relPath, f)
select {
case fchan <- f:
case <-w.Cancel:
return errors.New("cancelled")
}
return nil
}
func (w *walker) walkDir(relPath string, info os.FileInfo, dchan chan protocol.FileInfo) error {
// A directory is "unchanged", if it
// - exists
// - has the same permissions as previously, unless we are ignoring permissions
// - was not marked deleted (since it apparently exists now)
// - was a directory previously (not a file or something else)
// - was not a symlink (since it's a directory now)
// - was not invalid (since it looks valid now)
cf, ok := w.CurrentFiler.CurrentFile(relPath)
permUnchanged := w.IgnorePerms || !cf.HasPermissionBits() || PermsEqual(cf.Permissions, uint32(info.Mode()))
if ok && permUnchanged && !cf.IsDeleted() && cf.IsDirectory() && !cf.IsSymlink() && !cf.IsInvalid() {
return nil
}
f := protocol.FileInfo{
Name: relPath,
Type: protocol.FileInfoTypeDirectory,
Version: cf.Version.Update(w.ShortID),
Permissions: uint32(info.Mode() & maskModePerm),
NoPermissions: w.IgnorePerms,
ModifiedS: info.ModTime().Unix(),
ModifiedNs: int32(info.ModTime().Nanosecond()),
ModifiedBy: w.ShortID,
}
l.Debugln("dir:", relPath, f)
select {
case dchan <- f:
case <-w.Cancel:
return errors.New("cancelled")
}
return nil
}
// walkSymlink returns nil or an error, if the error is of the nature that
// it should stop the entire walk.
func (w *walker) walkSymlink(absPath, relPath string, dchan chan protocol.FileInfo) error {
// We always rehash symlinks as they have no modtime or
// permissions. We check if they point to the old target by
// checking that their existing blocks match with the blocks in
// the index.
target, err := os.Readlink(absPath)
if err != nil {
l.Debugln("readlink error:", absPath, err)
return nil
}
// A symlink is "unchanged", if
// - it exists
// - it wasn't deleted (because it isn't now)
// - it was a symlink
// - it wasn't invalid
// - the symlink type (file/dir) was the same
// - the target was the same
cf, ok := w.CurrentFiler.CurrentFile(relPath)
if ok && !cf.IsDeleted() && cf.IsSymlink() && !cf.IsInvalid() && cf.SymlinkTarget == target {
return nil
}
f := protocol.FileInfo{
Name: relPath,
Type: protocol.FileInfoTypeSymlink,
Version: cf.Version.Update(w.ShortID),
NoPermissions: true, // Symlinks don't have permissions of their own
SymlinkTarget: target,
}
l.Debugln("symlink changedb:", absPath, f)
select {
case dchan <- f:
case <-w.Cancel:
return errors.New("cancelled")
}
return nil
}
// normalizePath returns the normalized relative path (possibly after fixing
// it on disk), or skip is true.
func (w *walker) normalizePath(absPath, relPath string) (normPath string, skip bool) {
if runtime.GOOS == "darwin" {
// Mac OS X file names should always be NFD normalized.
normPath = norm.NFD.String(relPath)
} else {
// Every other OS in the known universe uses NFC or just plain
// doesn't bother to define an encoding. In our case *we* do care,
// so we enforce NFC regardless.
normPath = norm.NFC.String(relPath)
}
if relPath != normPath {
// The file name was not normalized.
if !w.AutoNormalize {
// We're not authorized to do anything about it, so complain and skip.
l.Warnf("File name %q is not in the correct UTF8 normalization form; skipping.", relPath)
return "", true
}
// We will attempt to normalize it.
normalizedPath := filepath.Join(w.Dir, normPath)
if _, err := w.Lstater.Lstat(normalizedPath); os.IsNotExist(err) {
// Nothing exists with the normalized filename. Good.
if err = os.Rename(absPath, normalizedPath); err != nil {
l.Infof(`Error normalizing UTF8 encoding of file "%s": %v`, relPath, err)
return "", true
}
l.Infof(`Normalized UTF8 encoding of file name "%s".`, relPath)
} else {
// There is something already in the way at the normalized
// file name.
l.Infof(`File "%s" has UTF8 encoding conflict with another file; ignoring.`, relPath)
return "", true
}
}
return normPath, false
}
func (w *walker) checkDir() error {
if info, err := w.Lstater.Lstat(w.Dir); err != nil {
return err
} else if !info.IsDir() {
return errors.New(w.Dir + ": not a directory")
} else {
l.Debugln("checkDir", w.Dir, info)
}
return nil
}
func PermsEqual(a, b uint32) bool {
switch runtime.GOOS {
case "windows":
// There is only writeable and read only, represented for user, group
// and other equally. We only compare against user.
return a&0600 == b&0600
default:
// All bits count
return a&0777 == b&0777
}
}
// A byteCounter gets bytes added to it via Update() and then provides the
// Total() and one minute moving average Rate() in bytes per second.
type byteCounter struct {
total int64
metrics.EWMA
stop chan struct{}
}
func newByteCounter() *byteCounter {
c := &byteCounter{
EWMA: metrics.NewEWMA1(), // a one minute exponentially weighted moving average
stop: make(chan struct{}),
}
go c.ticker()
return c
}
func (c *byteCounter) ticker() {
// The metrics.EWMA expects clock ticks every five seconds in order to
// decay the average properly.
t := time.NewTicker(5 * time.Second)
for {
select {
case <-t.C:
c.Tick()
case <-c.stop:
t.Stop()
return
}
}
}
func (c *byteCounter) Update(bytes int64) {
atomic.AddInt64(&c.total, bytes)
c.EWMA.Update(bytes)
}
func (c *byteCounter) Total() int64 {
return atomic.LoadInt64(&c.total)
}
func (c *byteCounter) Close() {
close(c.stop)
}
// A no-op CurrentFiler
type noCurrentFiler struct{}
func (noCurrentFiler) CurrentFile(name string) (protocol.FileInfo, bool) {
return protocol.FileInfo{}, false
}
// A no-op Lstater
type defaultLstater struct{}
func (defaultLstater) Lstat(name string) (os.FileInfo, error) {
return osutil.Lstat(name)
}