syncthing/lib/scanner/walk.go

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// Copyright (C) 2014 The Syncthing Authors.
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//
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// 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/.
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package scanner
import (
"context"
"errors"
"runtime"
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"sync/atomic"
"time"
"unicode/utf8"
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"github.com/rcrowley/go-metrics"
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"github.com/syncthing/syncthing/lib/events"
"github.com/syncthing/syncthing/lib/fs"
"github.com/syncthing/syncthing/lib/ignore"
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"github.com/syncthing/syncthing/lib/osutil"
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"github.com/syncthing/syncthing/lib/protocol"
"golang.org/x/text/unicode/norm"
)
var maskModePerm fs.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 fs.FileMode
// 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 = fs.ModePerm & 0755
} else {
maskModePerm = fs.ModePerm
}
}
type Config struct {
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// Folder for which the walker has been created
Folder 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
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// If CurrentFiler is not nil, it is queried for the current file before rescanning.
CurrentFiler CurrentFiler
// The Filesystem provides an abstraction on top of the actual filesystem.
Filesystem fs.Filesystem
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// If IgnorePerms is true, changes to permission bits will not be
// detected. Scanned files will get zero permission bits and the
// NoPermissionBits flag set.
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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
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// Our vector clock id
ShortID protocol.ShortID
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// Optional progress tick interval which defines how often FolderScanProgress
// events are emitted. Negative number means disabled.
ProgressTickIntervalS int
// Whether or not we should also compute weak hashes
UseWeakHashes bool
}
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type CurrentFiler interface {
// CurrentFile returns the file as seen at last scan.
CurrentFile(name string) (protocol.FileInfo, bool)
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}
func Walk(ctx context.Context, cfg Config) (chan protocol.FileInfo, error) {
w := walker{cfg}
if w.CurrentFiler == nil {
w.CurrentFiler = noCurrentFiler{}
}
if w.Filesystem == nil {
panic("no filesystem specified")
}
return w.walk(ctx)
}
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(ctx context.Context) (chan protocol.FileInfo, error) {
l.Debugln("Walk", w.Subs, w.BlockSize, w.Matcher)
if err := w.checkDir(); err != nil {
return nil, err
}
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toHashChan := make(chan protocol.FileInfo)
finishedChan := make(chan protocol.FileInfo)
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// A routine which walks the filesystem tree, and sends files which have
// been modified to the counter routine.
go func() {
hashFiles := w.walkAndHashFiles(ctx, toHashChan, finishedChan)
if len(w.Subs) == 0 {
w.Filesystem.Walk(".", hashFiles)
} else {
for _, sub := range w.Subs {
w.Filesystem.Walk(sub, hashFiles)
}
}
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close(toHashChan)
}()
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// 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(ctx, w.Filesystem, w.BlockSize, w.Hashers, finishedChan, toHashChan, nil, nil, w.UseWeakHashes)
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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
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var total int64 = 1
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for file := range toHashChan {
filesToHash = append(filesToHash, file)
total += file.Size
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}
realToHashChan := make(chan protocol.FileInfo)
done := make(chan struct{})
progress := newByteCounter()
newParallelHasher(ctx, w.Filesystem, w.BlockSize, w.Hashers, finishedChan, realToHashChan, progress, done, w.UseWeakHashes)
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// A routine which actually emits the FolderScanProgress events
// every w.ProgressTicker ticks, until the hasher routines terminate.
go func() {
defer progress.Close()
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for {
select {
case <-done:
l.Debugln("Walk progress done", w.Folder, w.Subs, w.BlockSize, w.Matcher)
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ticker.Stop()
return
case <-ticker.C:
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current := progress.Total()
rate := progress.Rate()
l.Debugf("Walk %s %s current progress %d/%d at %.01f MiB/s (%d%%)", w.Folder, w.Subs, current, total, rate/1024/1024, current*100/total)
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events.Default.Log(events.FolderScanProgress, map[string]interface{}{
"folder": w.Folder,
"current": current,
"total": total,
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"rate": rate, // bytes per second
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})
case <-ctx.Done():
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ticker.Stop()
return
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}
}
}()
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loop:
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for _, file := range filesToHash {
Implement facility based logger, debugging via REST API This implements a new debug/trace infrastructure based on a slightly hacked up logger. Instead of the traditional "if debug { ... }" I've rewritten the logger to have no-op Debugln and Debugf, unless debugging has been enabled for a given "facility". The "facility" is just a string, typically a package name. This will be slightly slower than before; but not that much as it's mostly a function call that returns immediately. For the cases where it matters (the Debugln takes a hex.Dump() of something for example, and it's not in a very occasional "if err != nil" branch) there is an l.ShouldDebug(facility) that is fast enough to be used like the old "if debug". The point of all this is that we can now toggle debugging for the various packages on and off at runtime. There's a new method /rest/system/debug that can be POSTed a set of facilities to enable and disable debug for, or GET from to get a list of facilities with descriptions and their current debug status. Similarly a /rest/system/log?since=... can grab the latest log entries, up to 250 of them (hardcoded constant in main.go) plus the initial few. Not implemented in this commit (but planned) is a simple debug GUI available on /debug that shows the current log in an easily pasteable format and has checkboxes to enable the various debug facilities. The debug instructions to a user then becomes "visit this URL, check these boxes, reproduce your problem, copy and paste the log". The actual log viewer on the hypothetical /debug URL can poll regularly for new log entries and this bypass the 250 line limit. The existing STTRACE=foo variable is still obeyed and just sets the start state of the system.
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l.Debugln("real to hash:", file.Name)
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select {
case realToHashChan <- file:
case <-ctx.Done():
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break loop
}
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}
close(realToHashChan)
}()
return finishedChan, nil
}
func (w *walker) walkAndHashFiles(ctx context.Context, fchan, dchan chan protocol.FileInfo) fs.WalkFunc {
now := time.Now()
return func(path string, info fs.FileInfo, err error) error {
select {
case <-ctx.Done():
return ctx.Err()
default:
}
// 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 = fs.SkipDir
}
if err != nil {
l.Debugln("error:", path, info, err)
return skip
}
if path == "." {
return nil
}
info, err = w.Filesystem.Lstat(path)
// 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 fs.IsTemporary(path) {
l.Debugln("temporary:", path)
if info.IsRegular() && info.ModTime().Add(w.TempLifetime).Before(now) {
w.Filesystem.Remove(path)
l.Debugln("removing temporary:", path, info.ModTime())
}
return nil
}
if fs.IsInternal(path) {
l.Debugln("ignored (internal):", path)
return skip
}
if w.Matcher.Match(path).IsIgnored() {
l.Debugln("ignored (patterns):", path)
return skip
}
if !utf8.ValidString(path) {
l.Warnf("File name %q is not in UTF8 encoding; skipping.", path)
return skip
}
path, shouldSkip := w.normalizePath(path)
if shouldSkip {
return skip
}
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switch {
case info.IsSymlink():
if err := w.walkSymlink(ctx, path, dchan); err != nil {
return err
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}
if info.IsDir() {
// under no circumstances shall we descend into a symlink
return fs.SkipDir
}
return nil
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case info.IsDir():
err = w.walkDir(ctx, path, info, dchan)
case info.IsRegular():
err = w.walkRegular(ctx, path, info, fchan)
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}
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return err
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}
}
func (w *walker) walkRegular(ctx context.Context, relPath string, info fs.FileInfo, fchan chan protocol.FileInfo) error {
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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
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}
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if ok {
l.Debugln("rescan:", cf, info.ModTime().Unix(), info.Mode()&fs.ModePerm)
}
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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(),
}
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l.Debugln("to hash:", relPath, f)
select {
case fchan <- f:
case <-ctx.Done():
return ctx.Err()
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}
return nil
}
func (w *walker) walkDir(ctx context.Context, relPath string, info fs.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
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}
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,
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}
l.Debugln("dir:", relPath, f)
select {
case dchan <- f:
case <-ctx.Done():
return ctx.Err()
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}
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(ctx context.Context, relPath string, dchan chan protocol.FileInfo) error {
// Symlinks are not supported on Windows. We ignore instead of returning
// an error.
if runtime.GOOS == "windows" {
return nil
}
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// 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 := w.Filesystem.ReadSymlink(relPath)
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if err != nil {
l.Debugln("readlink error:", relPath, err)
return nil
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}
// 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
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}
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,
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}
l.Debugln("symlink changedb:", relPath, f)
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select {
case dchan <- f:
case <-ctx.Done():
return ctx.Err()
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}
return nil
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}
// normalizePath returns the normalized relative path (possibly after fixing
// it on disk), or skip is true.
func (w *walker) normalizePath(path string) (normPath string, skip bool) {
if runtime.GOOS == "darwin" {
// Mac OS X file names should always be NFD normalized.
normPath = norm.NFD.String(path)
} 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(path)
}
if path != 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.", path)
return "", true
}
// We will attempt to normalize it.
if _, err := w.Filesystem.Lstat(normPath); fs.IsNotExist(err) {
// Nothing exists with the normalized filename. Good.
if err = w.Filesystem.Rename(path, normPath); err != nil {
l.Infof(`Error normalizing UTF8 encoding of file "%s": %v`, path, err)
return "", true
}
l.Infof(`Normalized UTF8 encoding of file name "%s".`, path)
} else {
// There is something already in the way at the normalized
// file name.
l.Infof(`File "%s" path has UTF8 encoding conflict with another file; ignoring.`, path)
return "", true
}
}
return path, false
}
func (w *walker) checkDir() error {
info, err := w.Filesystem.Lstat(".")
if err != nil {
return err
}
if !info.IsDir() {
return errors.New(w.Filesystem.URI() + ": not a directory")
}
l.Debugln("checkDir", w.Filesystem.Type(), w.Filesystem.URI(), info)
return nil
}
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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
}
}
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// 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
}