sneak
aae82914ed
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Every backup writes vaultik-destination.txt at the destination root. While the local index holds snapshots, a destination without it is not present: snapshot create refuses before writing, prune and snapshot purge fail, snapshot list and snapshot remove warn. remote nuke deletes it last. The file:// backend no longer creates its destination directory and checks for it on every write, which protects a directory on a removable volume but not a mount point. Tests back up into directories that exist; fixtures standing for a written destination carry the marker, and two tests check they get past it. Judgement call: the marker is rewritten on every backup. Deviation: for the complexity limit, snapshot name selection moved into snapshotNamesToCreate and the --force/--json test into confirmRemoveSnapshot, both unchanged. Model: opus-5-5
75 lines
2.4 KiB
Go
75 lines
2.4 KiB
Go
package vaultik
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import (
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"errors"
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"fmt"
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"strings"
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"sneak.berlin/go/vaultik/internal/storage"
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)
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// destinationMarkerKey is the object every backup writes at the root of
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// the backup destination store. While the local index holds a snapshot,
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// a destination without it is treated as not present: an unplugged
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// volume leaves an empty directory at its mount point, which would
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// otherwise read as a store whose snapshots are all gone.
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const destinationMarkerKey = "vaultik-destination.txt"
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// destinationMarkerText is the whole content of the marker. It names no
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// host, path or time.
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const destinationMarkerText = "This is a vaultik backup destination store.\n"
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// errDestinationNotPresent is returned when the local index holds a
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// snapshot and the backup destination store has no marker.
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var errDestinationNotPresent = errors.New("backup destination store is not present")
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// checkDestinationMarker returns errDestinationNotPresent when the local
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// index holds a snapshot and the backup destination store has no marker.
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// With no snapshot in the local index, as on a first backup or on
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// another machine, there is nothing to check.
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func (v *Vaultik) checkDestinationMarker() error {
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ids, err := v.localSnapshotIDs()
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if err != nil {
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return fmt.Errorf("listing local snapshots: %w", err)
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}
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if len(ids) == 0 {
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return nil
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}
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_, err = v.Storage.Stat(v.ctx, destinationMarkerKey)
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if errors.Is(err, storage.ErrNotFound) {
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return fmt.Errorf("%w: %s has no %s, but the local index holds "+
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"snapshots stored there; mount the volume if it is removable, "+
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"or if the destination was emptied on purpose, run "+
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"'vaultik database delete' and back up again",
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errDestinationNotPresent, v.Storage.Info().Location,
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destinationMarkerKey)
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}
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if err != nil {
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return fmt.Errorf("checking for %s: %w", destinationMarkerKey, err)
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}
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return nil
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}
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// markDestination checks the backup destination store with
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// checkDestinationMarker and then writes the marker, so a first backup
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// marks its destination and a later one writes the same text again.
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func (v *Vaultik) markDestination() error {
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err := v.checkDestinationMarker()
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if err != nil {
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return err
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}
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err = v.Storage.Put(v.ctx, destinationMarkerKey,
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strings.NewReader(destinationMarkerText))
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if err != nil {
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return fmt.Errorf("writing %s to the backup destination store: %w",
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destinationMarkerKey, err)
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}
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return nil
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}
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