lock: add Refresh method

lock.go

@@ -20,6 +20,9 @@ import (
 // There are two types of locks: exclusive and non-exclusive. There may be many
 // different non-exclusive locks, but at most one exclusive lock, which can
 // only be acquired while no non-exclusive lock is held.
+//
+// A lock must be refreshed regularly to not be considered stale, this must be
+// triggered by regularly calling Refresh.
 type Lock struct {
 	Time      time.Time `json:"time"`
 	Exclusive bool      `json:"exclusive"`
@@ -89,7 +92,7 @@ func newLock(repo *repository.Repository, excl bool) (*Lock, error) {
 		return nil, err
 	}
 
-	err = lock.createLock()
+	lock.lockID, err = lock.createLock()
 	if err != nil {
 		return nil, err
 	}
@@ -171,14 +174,13 @@ func eachLock(repo *repository.Repository, f func(backend.ID, *Lock, error) erro
 }
 
 // createLock acquires the lock by creating a file in the repository.
-func (l *Lock) createLock() error {
+func (l *Lock) createLock() (backend.ID, error) {
 	id, err := l.repo.SaveJSONUnpacked(backend.Lock, l)
 	if err != nil {
-		return err
+		return nil, err
 	}
 
-	l.lockID = id
-	return nil
+	return id, nil
 }
 
 // Unlock removes the lock from the repository.
@@ -220,6 +222,24 @@ func (l *Lock) Stale() bool {
 	return false
 }
 
+// Refresh refreshes the lock by creating a new file in the backend with a new
+// timestamp. Afterwards the old lock is removed.
+func (l *Lock) Refresh() error {
+	id, err := l.createLock()
+	if err != nil {
+		return err
+	}
+
+	err = l.repo.Backend().Remove(backend.Lock, l.lockID.String())
+	if err != nil {
+		return err
+	}
+
+	l.lockID = id
+
+	return nil
+}
+
 func (l Lock) String() string {
 	text := fmt.Sprintf("PID %d on %s by %s (UID %d, GID %d)\nlock was created at %s (%s ago)\nstorage ID %v",
 		l.PID, l.Hostname, l.Username, l.UID, l.GID,
@@ -275,6 +295,7 @@ func RemoveStaleLocks(repo *repository.Repository) error {
 	})
 }
 
+// RemoveAllLocks removes all locks forcefully.
 func RemoveAllLocks(repo *repository.Repository) error {
 	return eachLock(repo, func(id backend.ID, lock *Lock, err error) error {
 		return repo.Backend().Remove(backend.Lock, id.String())

lock_test.go

@@ -195,3 +195,33 @@ func TestRemoveAllLocks(t *testing.T) {
 	Assert(t, lockExists(repo, t, id3) == false,
 		"lock still exists after RemoveAllLocks was called")
 }
+
+func TestLockRefresh(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	lock, err := restic.NewLock(repo)
+	OK(t, err)
+
+	var lockID backend.ID
+	for id := range repo.List(backend.Lock, nil) {
+		if lockID != nil {
+			t.Error("more than one lock found")
+		}
+		lockID = id
+	}
+
+	OK(t, lock.Refresh())
+
+	var lockID2 backend.ID
+	for id := range repo.List(backend.Lock, nil) {
+		if lockID2 != nil {
+			t.Error("more than one lock found")
+		}
+		lockID2 = id
+	}
+
+	Assert(t, !lockID.Equal(lockID2),
+		"expected a new ID after lock refresh, got the same")
+	OK(t, lock.Unlock())
+}