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backup: add --dry-run/-n flag to show what would happen.
This can be used to check how large a backup is or validate exclusions. It does not actually write any data to the underlying backend. This is implemented as a simple overlay backend that accepts writes without forwarding them, passes through reads, and generally does the minimal necessary to pretend that progress is actually happening. Fixes restic#1542 Example usage: $ restic -vv --dry-run . | grep add new /changelog/unreleased/issue-1542, saved in 0.000s (350 B added) modified /cmd/restic/cmd_backup.go, saved in 0.000s (16.543 KiB added) modified /cmd/restic/global.go, saved in 0.000s (0 B added) new /internal/backend/dry/dry_backend_test.go, saved in 0.000s (3.866 KiB added) new /internal/backend/dry/dry_backend.go, saved in 0.000s (3.744 KiB added) modified /internal/backend/test/tests.go, saved in 0.000s (0 B added) modified /internal/repository/repository.go, saved in 0.000s (20.707 KiB added) modified /internal/ui/backup.go, saved in 0.000s (9.110 KiB added) modified /internal/ui/jsonstatus/status.go, saved in 0.001s (11.055 KiB added) modified /restic, saved in 0.131s (25.542 MiB added) Would add to the repo: 25.892 MiB
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,9 @@ | ||
| Enhancement: Add --dry-run/-n option to backup command. | ||
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| We added a new --dry-run/-n option to backup, which performs all the normal | ||
| steps of a backup without actually writing data. Passing -vv will log | ||
| information about files that would be added, allowing fast verification of | ||
| backup options without any unnecessary write activity. | ||
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| https://github.com/restic/restic/issues/1542 | ||
| https://github.com/restic/restic/pull/2308 |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,188 @@ | ||
| package dryrun | ||
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| import ( | ||
| "context" | ||
| "io" | ||
| "io/ioutil" | ||
| "sync" | ||
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| "github.com/restic/restic/internal/errors" | ||
| "github.com/restic/restic/internal/restic" | ||
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| "github.com/restic/restic/internal/debug" | ||
| ) | ||
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| type sizeMap map[restic.Handle]int | ||
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| var errNotFound = errors.New("not found") | ||
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| // Backend passes reads through to an underlying layer and only records | ||
| // metadata about writes. This is used for `backup --dry-run`. | ||
| // It is directly derivted from the mem backend. | ||
| type Backend struct { | ||
| be restic.Backend | ||
| data sizeMap | ||
| m sync.Mutex | ||
| } | ||
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| // New returns a new backend that saves all data in a map in memory. | ||
| func New(be restic.Backend) *Backend { | ||
| b := &Backend{ | ||
| be: be, | ||
| data: make(sizeMap), | ||
| } | ||
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| debug.Log("created new dry backend") | ||
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| return b | ||
| } | ||
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| // Test returns whether a file exists. | ||
| func (be *Backend) Test(ctx context.Context, h restic.Handle) (bool, error) { | ||
| be.m.Lock() | ||
| defer be.m.Unlock() | ||
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| debug.Log("Test %v", h) | ||
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| if _, ok := be.data[h]; ok { | ||
| return true, nil | ||
| } | ||
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| return be.be.Test(ctx, h) | ||
| } | ||
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| // IsNotExist returns true if the file does not exist. | ||
| func (be *Backend) IsNotExist(err error) bool { | ||
| return errors.Cause(err) == errNotFound || be.be.IsNotExist(err) | ||
| } | ||
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| // Save adds new Data to the backend. | ||
| func (be *Backend) Save(ctx context.Context, h restic.Handle, rd restic.RewindReader) error { | ||
| if err := h.Valid(); err != nil { | ||
| return err | ||
| } | ||
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| be.m.Lock() | ||
| defer be.m.Unlock() | ||
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| if h.Type == restic.ConfigFile { | ||
| h.Name = "" | ||
| } | ||
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| if _, ok := be.data[h]; ok { | ||
| return errors.New("file already exists") | ||
| } | ||
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| buf, err := ioutil.ReadAll(rd) | ||
| if err != nil { | ||
| return err | ||
| } | ||
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| be.data[h] = len(buf) | ||
| debug.Log("faked saving %v bytes at %v", len(buf), h) | ||
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| return nil | ||
| } | ||
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| // Load runs fn with a reader that yields the contents of the file at h at the | ||
| // given offset. | ||
| func (be *Backend) Load(ctx context.Context, h restic.Handle, length int, offset int64, fn func(rd io.Reader) error) error { | ||
| be.m.Lock() | ||
| defer be.m.Unlock() | ||
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| if _, ok := be.data[h]; ok { | ||
| return errors.New("can't read file saved on dry backend") | ||
| } | ||
| return be.be.Load(ctx, h, length, offset, fn) | ||
| } | ||
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| // Stat returns information about a file in the backend. | ||
| func (be *Backend) Stat(ctx context.Context, h restic.Handle) (restic.FileInfo, error) { | ||
| if err := h.Valid(); err != nil { | ||
| return restic.FileInfo{}, err | ||
| } | ||
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| be.m.Lock() | ||
| defer be.m.Unlock() | ||
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| if h.Type == restic.ConfigFile { | ||
| h.Name = "" | ||
| } | ||
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| debug.Log("stat %v", h) | ||
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| s, ok := be.data[h] | ||
| if !ok { | ||
| return be.be.Stat(ctx, h) | ||
| } | ||
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| return restic.FileInfo{Size: int64(s), Name: h.Name}, nil | ||
| } | ||
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| // Remove deletes a file from the backend. | ||
| func (be *Backend) Remove(ctx context.Context, h restic.Handle) error { | ||
| be.m.Lock() | ||
| defer be.m.Unlock() | ||
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| debug.Log("Remove %v", h) | ||
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| if _, ok := be.data[h]; !ok { | ||
| return errNotFound | ||
| } | ||
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| delete(be.data, h) | ||
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| return nil | ||
| } | ||
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| // List returns a channel which yields entries from the backend. | ||
| func (be *Backend) List(ctx context.Context, t restic.FileType, fn func(restic.FileInfo) error) error { | ||
| entries := []restic.FileInfo{} | ||
| be.m.Lock() | ||
| for entry, size := range be.data { | ||
| if entry.Type != t { | ||
| continue | ||
| } | ||
| entries = append(entries, restic.FileInfo{ | ||
| Name: entry.Name, | ||
| Size: int64(size), | ||
| }) | ||
| } | ||
| be.m.Unlock() | ||
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| for _, entry := range entries { | ||
| if ctx.Err() != nil { | ||
| return ctx.Err() | ||
| } | ||
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| err := fn(entry) | ||
| if err != nil { | ||
| return err | ||
| } | ||
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| if ctx.Err() != nil { | ||
| return ctx.Err() | ||
| } | ||
| } | ||
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| if ctx.Err() != nil { | ||
| return ctx.Err() | ||
| } | ||
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| return be.be.List(ctx, t, fn) | ||
| } | ||
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| // Location returns the location of the backend (RAM). | ||
| func (be *Backend) Location() string { | ||
| return "DRY:" + be.be.Location() | ||
| } | ||
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| // Delete removes all data in the backend. | ||
| func (be *Backend) Delete(ctx context.Context) error { | ||
| return errors.New("dry-run doesn't support Delete()") | ||
| } | ||
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| // Close closes the backend. | ||
| func (be *Backend) Close() error { | ||
| return be.be.Close() | ||
| } |
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