package cache import ( "fmt" "io/ioutil" "os" "path/filepath" "regexp" "strconv" "time" "github.com/pkg/errors" "github.com/restic/restic/internal/debug" "github.com/restic/restic/internal/fs" "github.com/restic/restic/internal/restic" ) // Cache manages a local cache. type Cache struct { path string Base string Created bool PerformReadahead func(restic.Handle) bool } const dirMode = 0700 const fileMode = 0644 func readVersion(dir string) (v uint, err error) { buf, err := ioutil.ReadFile(filepath.Join(dir, "version")) if errors.Is(err, os.ErrNotExist) { return 0, nil } if err != nil { return 0, errors.Wrap(err, "readVersion") } ver, err := strconv.ParseUint(string(buf), 10, 32) if err != nil { return 0, errors.Wrap(err, "readVersion") } return uint(ver), nil } const cacheVersion = 1 var cacheLayoutPaths = map[restic.FileType]string{ restic.PackFile: "data", restic.SnapshotFile: "snapshots", restic.IndexFile: "index", } const cachedirTagSignature = "Signature: 8a477f597d28d172789f06886806bc55\n" func writeCachedirTag(dir string) error { if err := fs.MkdirAll(dir, dirMode); err != nil { return errors.WithStack(err) } tagfile := filepath.Join(dir, "CACHEDIR.TAG") _, err := fs.Lstat(tagfile) if err != nil && !errors.Is(err, os.ErrNotExist) { return errors.WithStack(err) } f, err := fs.OpenFile(tagfile, os.O_CREATE|os.O_EXCL|os.O_WRONLY, fileMode) if err != nil { if errors.Is(err, os.ErrExist) { return nil } return errors.WithStack(err) } debug.Log("Create CACHEDIR.TAG at %v", dir) if _, err := f.Write([]byte(cachedirTagSignature)); err != nil { _ = f.Close() return errors.WithStack(err) } return errors.WithStack(f.Close()) } // New returns a new cache for the repo ID at basedir. If basedir is the empty // string, the default cache location (according to the XDG standard) is used. // // For partial files, the complete file is loaded and stored in the cache when // performReadahead returns true. func New(id string, basedir string) (c *Cache, err error) { if basedir == "" { basedir, err = DefaultDir() if err != nil { return nil, err } } err = fs.MkdirAll(basedir, 0700) if err != nil { return nil, errors.WithStack(err) } // create base dir and tag it as a cache directory if err = writeCachedirTag(basedir); err != nil { return nil, err } cachedir := filepath.Join(basedir, id) debug.Log("using cache dir %v", cachedir) v, err := readVersion(cachedir) if err != nil { return nil, err } if v > cacheVersion { return nil, errors.New("cache version is newer") } // create the repo cache dir if it does not exist yet var created bool _, err = fs.Lstat(cachedir) if errors.Is(err, os.ErrNotExist) { err = fs.MkdirAll(cachedir, dirMode) if err != nil { return nil, errors.WithStack(err) } created = true } // update the timestamp so that we can detect old cache dirs err = updateTimestamp(cachedir) if err != nil { return nil, err } if v < cacheVersion { err = ioutil.WriteFile(filepath.Join(cachedir, "version"), []byte(fmt.Sprintf("%d", cacheVersion)), fileMode) if err != nil { return nil, errors.WithStack(err) } } for _, p := range cacheLayoutPaths { if err = fs.MkdirAll(filepath.Join(cachedir, p), dirMode); err != nil { return nil, errors.WithStack(err) } } c = &Cache{ path: cachedir, Base: basedir, Created: created, PerformReadahead: func(restic.Handle) bool { // do not perform readahead by default return false }, } return c, nil } // updateTimestamp sets the modification timestamp (mtime and atime) for the // directory d to the current time. func updateTimestamp(d string) error { t := time.Now() return fs.Chtimes(d, t, t) } // MaxCacheAge is the default age (30 days) after which cache directories are considered old. const MaxCacheAge = 30 * 24 * time.Hour func validCacheDirName(s string) bool { r := regexp.MustCompile(`^[a-fA-F0-9]{64}$`) return r.MatchString(s) } // listCacheDirs returns the list of cache directories. func listCacheDirs(basedir string) ([]os.FileInfo, error) { f, err := fs.Open(basedir) if err != nil { if errors.Is(err, os.ErrNotExist) { err = nil } return nil, err } entries, err := f.Readdir(-1) if err != nil { return nil, err } err = f.Close() if err != nil { return nil, err } result := make([]os.FileInfo, 0, len(entries)) for _, entry := range entries { if !entry.IsDir() { continue } if !validCacheDirName(entry.Name()) { continue } result = append(result, entry) } return result, nil } // All returns a list of cache directories. func All(basedir string) (dirs []os.FileInfo, err error) { return listCacheDirs(basedir) } // OlderThan returns the list of cache directories older than max. func OlderThan(basedir string, max time.Duration) ([]os.FileInfo, error) { entries, err := listCacheDirs(basedir) if err != nil { return nil, err } var oldCacheDirs []os.FileInfo for _, fi := range entries { if !IsOld(fi.ModTime(), max) { continue } oldCacheDirs = append(oldCacheDirs, fi) } debug.Log("%d old cache dirs found", len(oldCacheDirs)) return oldCacheDirs, nil } // Old returns a list of cache directories with a modification time of more // than 30 days ago. func Old(basedir string) ([]os.FileInfo, error) { return OlderThan(basedir, MaxCacheAge) } // IsOld returns true if the timestamp is considered old. func IsOld(t time.Time, maxAge time.Duration) bool { oldest := time.Now().Add(-maxAge) return t.Before(oldest) } // Wrap returns a backend with a cache. func (c *Cache) Wrap(be restic.Backend) restic.Backend { return newBackend(be, c) } // BaseDir returns the base directory. func (c *Cache) BaseDir() string { return c.Base }