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mirror of https://github.com/octoleo/restic.git synced 2024-06-09 12:22:34 +00:00
restic/internal/archiver/archiver.go
Michael Eischer debc4a3a99 archiver: fix race condition during worker startup
When the tomb is created with a canceled context, then the workers
started via `t.Go` exist nearly immediately. Once for the first time all
started goroutines have been stopped, it is not allowed to issue further
calls to `t.Go`. This is a problem when the started goroutines exit
immediately, as for example the first goroutine might already have
stopped before starting the second one, which is not allowed as once the
first goroutines has stopped no goroutines were running.

To fix this race condition the startup and main task of the archiver now
also run within a `t.Go` function. This also allows unifying the error
handling as it is no longer necessary to distinguish between errors
returned by the workers or the saveTree processing. The tomb now just
returns the first error encountered, which should also be the most
descriptive one.
2020-12-30 17:31:22 +01:00

844 lines
22 KiB
Go

package archiver
import (
"context"
"encoding/json"
"os"
"path"
"runtime"
"sort"
"time"
"github.com/restic/restic/internal/debug"
"github.com/restic/restic/internal/errors"
"github.com/restic/restic/internal/fs"
"github.com/restic/restic/internal/restic"
tomb "gopkg.in/tomb.v2"
)
// SelectByNameFunc returns true for all items that should be included (files and
// dirs). If false is returned, files are ignored and dirs are not even walked.
type SelectByNameFunc func(item string) bool
// SelectFunc returns true for all items that should be included (files and
// dirs). If false is returned, files are ignored and dirs are not even walked.
type SelectFunc func(item string, fi os.FileInfo) bool
// ErrorFunc is called when an error during archiving occurs. When nil is
// returned, the archiver continues, otherwise it aborts and passes the error
// up the call stack.
type ErrorFunc func(file string, fi os.FileInfo, err error) error
// ItemStats collects some statistics about a particular file or directory.
type ItemStats struct {
DataBlobs int // number of new data blobs added for this item
DataSize uint64 // sum of the sizes of all new data blobs
TreeBlobs int // number of new tree blobs added for this item
TreeSize uint64 // sum of the sizes of all new tree blobs
}
// Add adds other to the current ItemStats.
func (s *ItemStats) Add(other ItemStats) {
s.DataBlobs += other.DataBlobs
s.DataSize += other.DataSize
s.TreeBlobs += other.TreeBlobs
s.TreeSize += other.TreeSize
}
// Archiver saves a directory structure to the repo.
type Archiver struct {
Repo restic.Repository
SelectByName SelectByNameFunc
Select SelectFunc
FS fs.FS
Options Options
blobSaver *BlobSaver
fileSaver *FileSaver
treeSaver *TreeSaver
// Error is called for all errors that occur during backup.
Error ErrorFunc
// CompleteItem is called for all files and dirs once they have been
// processed successfully. The parameter item contains the path as it will
// be in the snapshot after saving. s contains some statistics about this
// particular file/dir.
//
// CompleteItem may be called asynchronously from several different
// goroutines!
CompleteItem func(item string, previous, current *restic.Node, s ItemStats, d time.Duration)
// StartFile is called when a file is being processed by a worker.
StartFile func(filename string)
// CompleteBlob is called for all saved blobs for files.
CompleteBlob func(filename string, bytes uint64)
// WithAtime configures if the access time for files and directories should
// be saved. Enabling it may result in much metadata, so it's off by
// default.
WithAtime bool
IgnoreInode bool
}
// Options is used to configure the archiver.
type Options struct {
// FileReadConcurrency sets how many files are read in concurrently. If
// it's set to zero, at most two files are read in concurrently (which
// turned out to be a good default for most situations).
FileReadConcurrency uint
// SaveBlobConcurrency sets how many blobs are hashed and saved
// concurrently. If it's set to zero, the default is the number of CPUs
// available in the system.
SaveBlobConcurrency uint
// SaveTreeConcurrency sets how many trees are marshalled and saved to the
// repo concurrently.
SaveTreeConcurrency uint
}
// ApplyDefaults returns a copy of o with the default options set for all unset
// fields.
func (o Options) ApplyDefaults() Options {
if o.FileReadConcurrency == 0 {
// two is a sweet spot for almost all situations. We've done some
// experiments documented here:
// https://github.com/borgbackup/borg/issues/3500
o.FileReadConcurrency = 2
}
if o.SaveBlobConcurrency == 0 {
o.SaveBlobConcurrency = uint(runtime.NumCPU())
}
if o.SaveTreeConcurrency == 0 {
// use a relatively high concurrency here, having multiple SaveTree
// workers is cheap
o.SaveTreeConcurrency = o.SaveBlobConcurrency * 20
}
return o
}
// New initializes a new archiver.
func New(repo restic.Repository, fs fs.FS, opts Options) *Archiver {
arch := &Archiver{
Repo: repo,
SelectByName: func(item string) bool { return true },
Select: func(item string, fi os.FileInfo) bool { return true },
FS: fs,
Options: opts.ApplyDefaults(),
CompleteItem: func(string, *restic.Node, *restic.Node, ItemStats, time.Duration) {},
StartFile: func(string) {},
CompleteBlob: func(string, uint64) {},
IgnoreInode: false,
}
return arch
}
// error calls arch.Error if it is set and the error is different from context.Canceled.
func (arch *Archiver) error(item string, fi os.FileInfo, err error) error {
if arch.Error == nil || err == nil {
return err
}
if err == context.Canceled {
return err
}
errf := arch.Error(item, fi, err)
if err != errf {
debug.Log("item %v: error was filtered by handler, before: %q, after: %v", item, err, errf)
}
return errf
}
// saveTree stores a tree in the repo. It checks the index and the known blobs
// before saving anything.
func (arch *Archiver) saveTree(ctx context.Context, t *restic.Tree) (restic.ID, ItemStats, error) {
var s ItemStats
buf, err := json.Marshal(t)
if err != nil {
return restic.ID{}, s, errors.Wrap(err, "MarshalJSON")
}
// append a newline so that the data is always consistent (json.Encoder
// adds a newline after each object)
buf = append(buf, '\n')
b := &Buffer{Data: buf}
res := arch.blobSaver.Save(ctx, restic.TreeBlob, b)
res.Wait(ctx)
if !res.Known() {
s.TreeBlobs++
s.TreeSize += uint64(len(buf))
}
// The context was canceled in the meantime, res.ID() might be invalid
if ctx.Err() != nil {
return restic.ID{}, s, ctx.Err()
}
return res.ID(), s, nil
}
// nodeFromFileInfo returns the restic node from an os.FileInfo.
func (arch *Archiver) nodeFromFileInfo(filename string, fi os.FileInfo) (*restic.Node, error) {
node, err := restic.NodeFromFileInfo(filename, fi)
if !arch.WithAtime {
node.AccessTime = node.ModTime
}
return node, errors.Wrap(err, "NodeFromFileInfo")
}
// loadSubtree tries to load the subtree referenced by node. In case of an error, nil is returned.
// If there is no node to load, then nil is returned without an error.
func (arch *Archiver) loadSubtree(ctx context.Context, node *restic.Node) (*restic.Tree, error) {
if node == nil || node.Type != "dir" || node.Subtree == nil {
return nil, nil
}
tree, err := arch.Repo.LoadTree(ctx, *node.Subtree)
if err != nil {
debug.Log("unable to load tree %v: %v", node.Subtree.Str(), err)
// a tree in the repository is not readable -> warn the user
return nil, arch.wrapLoadTreeError(*node.Subtree, err)
}
return tree, nil
}
func (arch *Archiver) wrapLoadTreeError(id restic.ID, err error) error {
if arch.Repo.Index().Has(restic.BlobHandle{ID: id, Type: restic.TreeBlob}) {
err = errors.Errorf("tree %v could not be loaded; the repository could be damaged: %v", id, err)
} else {
err = errors.Errorf("tree %v is not known; the repository could be damaged, run `rebuild-index` to try to repair it", id)
}
return err
}
// SaveDir stores a directory in the repo and returns the node. snPath is the
// path within the current snapshot.
func (arch *Archiver) SaveDir(ctx context.Context, snPath string, fi os.FileInfo, dir string, previous *restic.Tree, complete CompleteFunc) (d FutureTree, err error) {
debug.Log("%v %v", snPath, dir)
treeNode, err := arch.nodeFromFileInfo(dir, fi)
if err != nil {
return FutureTree{}, err
}
names, err := readdirnames(arch.FS, dir, fs.O_NOFOLLOW)
if err != nil {
return FutureTree{}, err
}
sort.Strings(names)
nodes := make([]FutureNode, 0, len(names))
for _, name := range names {
// test if context has been cancelled
if ctx.Err() != nil {
debug.Log("context has been cancelled, aborting")
return FutureTree{}, ctx.Err()
}
pathname := arch.FS.Join(dir, name)
oldNode := previous.Find(name)
snItem := join(snPath, name)
fn, excluded, err := arch.Save(ctx, snItem, pathname, oldNode)
// return error early if possible
if err != nil {
err = arch.error(pathname, fi, err)
if err == nil {
// ignore error
continue
}
return FutureTree{}, err
}
if excluded {
continue
}
nodes = append(nodes, fn)
}
ft := arch.treeSaver.Save(ctx, snPath, treeNode, nodes, complete)
return ft, nil
}
// FutureNode holds a reference to a node, FutureFile, or FutureTree.
type FutureNode struct {
snPath, target string
// kept to call the error callback function
absTarget string
fi os.FileInfo
node *restic.Node
stats ItemStats
err error
isFile bool
file FutureFile
isTree bool
tree FutureTree
}
func (fn *FutureNode) wait(ctx context.Context) {
switch {
case fn.isFile:
// wait for and collect the data for the file
fn.file.Wait(ctx)
fn.node = fn.file.Node()
fn.err = fn.file.Err()
fn.stats = fn.file.Stats()
// ensure the other stuff can be garbage-collected
fn.file = FutureFile{}
fn.isFile = false
case fn.isTree:
// wait for and collect the data for the dir
fn.tree.Wait(ctx)
fn.node = fn.tree.Node()
fn.stats = fn.tree.Stats()
// ensure the other stuff can be garbage-collected
fn.tree = FutureTree{}
fn.isTree = false
}
}
// allBlobsPresent checks if all blobs (contents) of the given node are
// present in the index.
func (arch *Archiver) allBlobsPresent(previous *restic.Node) bool {
// check if all blobs are contained in index
for _, id := range previous.Content {
if !arch.Repo.Index().Has(restic.BlobHandle{ID: id, Type: restic.DataBlob}) {
return false
}
}
return true
}
// Save saves a target (file or directory) to the repo. If the item is
// excluded, this function returns a nil node and error, with excluded set to
// true.
//
// Errors and completion needs to be handled by the caller.
//
// snPath is the path within the current snapshot.
func (arch *Archiver) Save(ctx context.Context, snPath, target string, previous *restic.Node) (fn FutureNode, excluded bool, err error) {
start := time.Now()
fn = FutureNode{
snPath: snPath,
target: target,
}
debug.Log("%v target %q, previous %v", snPath, target, previous)
abstarget, err := arch.FS.Abs(target)
if err != nil {
return FutureNode{}, false, err
}
fn.absTarget = abstarget
// exclude files by path before running Lstat to reduce number of lstat calls
if !arch.SelectByName(abstarget) {
debug.Log("%v is excluded by path", target)
return FutureNode{}, true, nil
}
// get file info and run remaining select functions that require file information
fi, err := arch.FS.Lstat(target)
if err != nil {
debug.Log("lstat() for %v returned error: %v", target, err)
err = arch.error(abstarget, fi, err)
if err != nil {
return FutureNode{}, false, errors.Wrap(err, "Lstat")
}
return FutureNode{}, true, nil
}
if !arch.Select(abstarget, fi) {
debug.Log("%v is excluded", target)
return FutureNode{}, true, nil
}
switch {
case fs.IsRegularFile(fi):
debug.Log(" %v regular file", target)
start := time.Now()
// check if the file has not changed before performing a fopen operation (more expensive, specially
// in network filesystems)
if previous != nil && !fileChanged(fi, previous, arch.IgnoreInode) {
if arch.allBlobsPresent(previous) {
debug.Log("%v hasn't changed, using old list of blobs", target)
arch.CompleteItem(snPath, previous, previous, ItemStats{}, time.Since(start))
arch.CompleteBlob(snPath, previous.Size)
fn.node, err = arch.nodeFromFileInfo(target, fi)
if err != nil {
return FutureNode{}, false, err
}
// copy list of blobs
fn.node.Content = previous.Content
return fn, false, nil
}
debug.Log("%v hasn't changed, but contents are missing!", target)
// There are contents missing - inform user!
err := errors.Errorf("parts of %v not found in the repository index; storing the file again", target)
arch.error(abstarget, fi, err)
}
// reopen file and do an fstat() on the open file to check it is still
// a file (and has not been exchanged for e.g. a symlink)
file, err := arch.FS.OpenFile(target, fs.O_RDONLY|fs.O_NOFOLLOW, 0)
if err != nil {
debug.Log("Openfile() for %v returned error: %v", target, err)
err = arch.error(abstarget, fi, err)
if err != nil {
return FutureNode{}, false, errors.Wrap(err, "Lstat")
}
return FutureNode{}, true, nil
}
fi, err = file.Stat()
if err != nil {
debug.Log("stat() on opened file %v returned error: %v", target, err)
_ = file.Close()
err = arch.error(abstarget, fi, err)
if err != nil {
return FutureNode{}, false, errors.Wrap(err, "Lstat")
}
return FutureNode{}, true, nil
}
// make sure it's still a file
if !fs.IsRegularFile(fi) {
err = errors.Errorf("file %v changed type, refusing to archive")
_ = file.Close()
err = arch.error(abstarget, fi, err)
if err != nil {
return FutureNode{}, false, err
}
return FutureNode{}, true, nil
}
fn.isFile = true
// Save will close the file, we don't need to do that
fn.file = arch.fileSaver.Save(ctx, snPath, file, fi, func() {
arch.StartFile(snPath)
}, func(node *restic.Node, stats ItemStats) {
arch.CompleteItem(snPath, previous, node, stats, time.Since(start))
})
case fi.IsDir():
debug.Log(" %v dir", target)
snItem := snPath + "/"
start := time.Now()
oldSubtree, err := arch.loadSubtree(ctx, previous)
if err != nil {
arch.error(abstarget, fi, err)
}
fn.isTree = true
fn.tree, err = arch.SaveDir(ctx, snPath, fi, target, oldSubtree,
func(node *restic.Node, stats ItemStats) {
arch.CompleteItem(snItem, previous, node, stats, time.Since(start))
})
if err != nil {
debug.Log("SaveDir for %v returned error: %v", snPath, err)
return FutureNode{}, false, err
}
case fi.Mode()&os.ModeSocket > 0:
debug.Log(" %v is a socket, ignoring", target)
return FutureNode{}, true, nil
default:
debug.Log(" %v other", target)
fn.node, err = arch.nodeFromFileInfo(target, fi)
if err != nil {
return FutureNode{}, false, err
}
}
debug.Log("return after %.3f", time.Since(start).Seconds())
return fn, false, nil
}
// fileChanged returns true if the file's content has changed since the node
// was created.
func fileChanged(fi os.FileInfo, node *restic.Node, ignoreInode bool) bool {
if node == nil {
return true
}
// check type change
if node.Type != "file" {
return true
}
// check modification timestamp
if !fi.ModTime().Equal(node.ModTime) {
return true
}
// check status change timestamp
extFI := fs.ExtendedStat(fi)
if !ignoreInode && !extFI.ChangeTime.Equal(node.ChangeTime) {
return true
}
// check size
if uint64(fi.Size()) != node.Size || uint64(extFI.Size) != node.Size {
return true
}
// check inode
if !ignoreInode && node.Inode != extFI.Inode {
return true
}
return false
}
// join returns all elements separated with a forward slash.
func join(elem ...string) string {
return path.Join(elem...)
}
// statDir returns the file info for the directory. Symbolic links are
// resolved. If the target directory is not a directory, an error is returned.
func (arch *Archiver) statDir(dir string) (os.FileInfo, error) {
fi, err := arch.FS.Stat(dir)
if err != nil {
return nil, errors.Wrap(err, "Lstat")
}
tpe := fi.Mode() & (os.ModeType | os.ModeCharDevice)
if tpe != os.ModeDir {
return fi, errors.Errorf("path is not a directory: %v", dir)
}
return fi, nil
}
// SaveTree stores a Tree in the repo, returned is the tree. snPath is the path
// within the current snapshot.
func (arch *Archiver) SaveTree(ctx context.Context, snPath string, atree *Tree, previous *restic.Tree) (*restic.Tree, error) {
debug.Log("%v (%v nodes), parent %v", snPath, len(atree.Nodes), previous)
tree := restic.NewTree()
futureNodes := make(map[string]FutureNode)
// iterate over the nodes of atree in lexicographic (=deterministic) order
names := make([]string, 0, len(atree.Nodes))
for name := range atree.Nodes {
names = append(names, name)
}
sort.Strings(names)
for _, name := range names {
subatree := atree.Nodes[name]
// test if context has been cancelled
if ctx.Err() != nil {
return nil, ctx.Err()
}
// this is a leaf node
if subatree.Path != "" {
fn, excluded, err := arch.Save(ctx, join(snPath, name), subatree.Path, previous.Find(name))
if err != nil {
err = arch.error(subatree.Path, fn.fi, err)
if err == nil {
// ignore error
continue
}
return nil, err
}
if err != nil {
return nil, err
}
if !excluded {
futureNodes[name] = fn
}
continue
}
snItem := join(snPath, name) + "/"
start := time.Now()
oldNode := previous.Find(name)
oldSubtree, err := arch.loadSubtree(ctx, oldNode)
if err != nil {
arch.error(join(snPath, name), nil, err)
}
// not a leaf node, archive subtree
subtree, err := arch.SaveTree(ctx, join(snPath, name), &subatree, oldSubtree)
if err != nil {
return nil, err
}
id, nodeStats, err := arch.saveTree(ctx, subtree)
if err != nil {
return nil, err
}
if subatree.FileInfoPath == "" {
return nil, errors.Errorf("FileInfoPath for %v/%v is empty", snPath, name)
}
debug.Log("%v, saved subtree %v as %v", snPath, subtree, id.Str())
fi, err := arch.statDir(subatree.FileInfoPath)
if err != nil {
return nil, err
}
debug.Log("%v, dir node data loaded from %v", snPath, subatree.FileInfoPath)
node, err := arch.nodeFromFileInfo(subatree.FileInfoPath, fi)
if err != nil {
return nil, err
}
node.Name = name
node.Subtree = &id
err = tree.Insert(node)
if err != nil {
return nil, err
}
arch.CompleteItem(snItem, oldNode, node, nodeStats, time.Since(start))
}
debug.Log("waiting on %d nodes", len(futureNodes))
// process all futures
for name, fn := range futureNodes {
fn.wait(ctx)
// return the error, or ignore it
if fn.err != nil {
fn.err = arch.error(fn.target, fn.fi, fn.err)
if fn.err == nil {
// ignore error
continue
}
return nil, fn.err
}
// when the error is ignored, the node could not be saved, so ignore it
if fn.node == nil {
debug.Log("%v excluded: %v", fn.snPath, fn.target)
continue
}
fn.node.Name = name
err := tree.Insert(fn.node)
if err != nil {
return nil, err
}
}
return tree, nil
}
// flags are passed to fs.OpenFile. O_RDONLY is implied.
func readdirnames(filesystem fs.FS, dir string, flags int) ([]string, error) {
f, err := filesystem.OpenFile(dir, fs.O_RDONLY|flags, 0)
if err != nil {
return nil, errors.Wrap(err, "Open")
}
entries, err := f.Readdirnames(-1)
if err != nil {
_ = f.Close()
return nil, errors.Wrapf(err, "Readdirnames %v failed", dir)
}
err = f.Close()
if err != nil {
return nil, err
}
return entries, nil
}
// resolveRelativeTargets replaces targets that only contain relative
// directories ("." or "../../") with the contents of the directory. Each
// element of target is processed with fs.Clean().
func resolveRelativeTargets(filesys fs.FS, targets []string) ([]string, error) {
debug.Log("targets before resolving: %v", targets)
result := make([]string, 0, len(targets))
for _, target := range targets {
target = filesys.Clean(target)
pc, _ := pathComponents(filesys, target, false)
if len(pc) > 0 {
result = append(result, target)
continue
}
debug.Log("replacing %q with readdir(%q)", target, target)
entries, err := readdirnames(filesys, target, fs.O_NOFOLLOW)
if err != nil {
return nil, err
}
sort.Strings(entries)
for _, name := range entries {
result = append(result, filesys.Join(target, name))
}
}
debug.Log("targets after resolving: %v", result)
return result, nil
}
// SnapshotOptions collect attributes for a new snapshot.
type SnapshotOptions struct {
Tags restic.TagList
Hostname string
Excludes []string
Time time.Time
ParentSnapshot restic.ID
}
// loadParentTree loads a tree referenced by snapshot id. If id is null, nil is returned.
func (arch *Archiver) loadParentTree(ctx context.Context, snapshotID restic.ID) *restic.Tree {
if snapshotID.IsNull() {
return nil
}
debug.Log("load parent snapshot %v", snapshotID)
sn, err := restic.LoadSnapshot(ctx, arch.Repo, snapshotID)
if err != nil {
debug.Log("unable to load snapshot %v: %v", snapshotID, err)
return nil
}
if sn.Tree == nil {
debug.Log("snapshot %v has empty tree %v", snapshotID)
return nil
}
debug.Log("load parent tree %v", *sn.Tree)
tree, err := arch.Repo.LoadTree(ctx, *sn.Tree)
if err != nil {
debug.Log("unable to load tree %v: %v", *sn.Tree, err)
arch.error("/", nil, arch.wrapLoadTreeError(*sn.Tree, err))
return nil
}
return tree
}
// runWorkers starts the worker pools, which are stopped when the context is cancelled.
func (arch *Archiver) runWorkers(ctx context.Context, t *tomb.Tomb) {
arch.blobSaver = NewBlobSaver(ctx, t, arch.Repo, arch.Options.SaveBlobConcurrency)
arch.fileSaver = NewFileSaver(ctx, t,
arch.blobSaver.Save,
arch.Repo.Config().ChunkerPolynomial,
arch.Options.FileReadConcurrency, arch.Options.SaveBlobConcurrency)
arch.fileSaver.CompleteBlob = arch.CompleteBlob
arch.fileSaver.NodeFromFileInfo = arch.nodeFromFileInfo
arch.treeSaver = NewTreeSaver(ctx, t, arch.Options.SaveTreeConcurrency, arch.saveTree, arch.Error)
}
// Snapshot saves several targets and returns a snapshot.
func (arch *Archiver) Snapshot(ctx context.Context, targets []string, opts SnapshotOptions) (*restic.Snapshot, restic.ID, error) {
cleanTargets, err := resolveRelativeTargets(arch.FS, targets)
if err != nil {
return nil, restic.ID{}, err
}
atree, err := NewTree(arch.FS, cleanTargets)
if err != nil {
return nil, restic.ID{}, err
}
var t tomb.Tomb
wctx := t.Context(ctx)
start := time.Now()
var rootTreeID restic.ID
var stats ItemStats
t.Go(func() error {
arch.runWorkers(wctx, &t)
debug.Log("starting snapshot")
tree, err := arch.SaveTree(wctx, "/", atree, arch.loadParentTree(wctx, opts.ParentSnapshot))
if err != nil {
return err
}
if len(tree.Nodes) == 0 {
return errors.New("snapshot is empty")
}
rootTreeID, stats, err = arch.saveTree(wctx, tree)
// trigger shutdown but don't set an error
t.Kill(nil)
return err
})
err = t.Wait()
debug.Log("err is %v", err)
if err != nil {
debug.Log("error while saving tree: %v", err)
return nil, restic.ID{}, err
}
arch.CompleteItem("/", nil, nil, stats, time.Since(start))
err = arch.Repo.Flush(ctx)
if err != nil {
return nil, restic.ID{}, err
}
sn, err := restic.NewSnapshot(targets, opts.Tags, opts.Hostname, opts.Time)
if err != nil {
return nil, restic.ID{}, err
}
sn.Excludes = opts.Excludes
if !opts.ParentSnapshot.IsNull() {
id := opts.ParentSnapshot
sn.Parent = &id
}
sn.Tree = &rootTreeID
id, err := arch.Repo.SaveJSONUnpacked(ctx, restic.SnapshotFile, sn)
if err != nil {
return nil, restic.ID{}, err
}
return sn, id, nil
}