cmd/restic: Add command unlock, improve error message

cmd/restic/cmd_unlock.go

@@ -0,0 +1,43 @@
+package main
+
+import "github.com/restic/restic"
+
+type CmdUnlock struct {
+	RemoveAll bool `long:"remove-all" description:"Remove all locks, even stale ones"`
+
+	global *GlobalOptions
+}
+
+func init() {
+	_, err := parser.AddCommand("unlock",
+		"remove locks",
+		"The unlock command checks for stale locks and removes them",
+		&CmdUnlock{global: &globalOpts})
+	if err != nil {
+		panic(err)
+	}
+}
+
+func (cmd CmdUnlock) Usage() string {
+	return "[unlock-options]"
+}
+
+func (cmd CmdUnlock) Execute(args []string) error {
+	repo, err := cmd.global.OpenRepository()
+	if err != nil {
+		return err
+	}
+
+	fn := restic.RemoveStaleLocks
+	if cmd.RemoveAll {
+		fn = restic.RemoveAllLocks
+	}
+
+	err = fn(repo)
+	if err != nil {
+		return err
+	}
+
+	cmd.global.Verbosef("successfully removed locks\n")
+	return nil
+}

cmd/restic/lock.go

@@ -14,19 +14,32 @@ import (
 var globalLocks []*restic.Lock
 
 func lockRepo(repo *repository.Repository) (*restic.Lock, error) {
-	lock, err := restic.NewLock(repo)
-	if err != nil {
-		return nil, err
-	}
-
-	globalLocks = append(globalLocks, lock)
-
-	return lock, err
+	return lockRepository(repo, false)
 }
 
 func lockRepoExclusive(repo *repository.Repository) (*restic.Lock, error) {
-	lock, err := restic.NewExclusiveLock(repo)
+	return lockRepository(repo, true)
+}
+
+func lockRepository(repo *repository.Repository, exclusive bool) (*restic.Lock, error) {
+	lockFn := restic.NewLock
+	if exclusive {
+		lockFn = restic.NewExclusiveLock
+	}
+
+	lock, err := lockFn(repo)
 	if err != nil {
+		if restic.IsAlreadyLocked(err) {
+			tpe := ""
+			if exclusive {
+				tpe = " exclusive"
+			}
+			fmt.Fprintf(os.Stderr, "unable to acquire%s lock for operation:\n", tpe)
+			fmt.Fprintln(os.Stderr, err)
+			fmt.Fprintf(os.Stderr, "\nthe `unlock` command can be used to remove stale locks\n")
+			os.Exit(1)
+		}
+
 		return nil, err
 	}
 

lock.go

@@ -1,7 +1,7 @@
 package restic
 
 import (
-	"errors"
+	"fmt"
 	"os"
 	"os/signal"
 	"os/user"
@@ -33,10 +33,24 @@ type Lock struct {
 	lockID backend.ID
 }
 
-var (
-	ErrAlreadyLocked  = errors.New("already locked")
-	ErrStaleLockFound = errors.New("stale lock found")
-)
+// ErrAlreadyLocked is returned when NewLock or NewExclusiveLock are unable to
+// acquire the desired lock.
+type ErrAlreadyLocked struct {
+	otherLock *Lock
+}
+
+func (e ErrAlreadyLocked) Error() string {
+	return fmt.Sprintf("repository is already locked by %v", e.otherLock)
+}
+
+// IsAlreadyLocked returns true iff err is an instance of ErrAlreadyLocked.
+func IsAlreadyLocked(err error) bool {
+	if _, ok := err.(ErrAlreadyLocked); ok {
+		return true
+	}
+
+	return false
+}
 
 // NewLock returns a new, non-exclusive lock for the repository. If an
 // exclusive lock is already held by another process, ErrAlreadyLocked is
@@ -84,7 +98,7 @@ func newLock(repo *repository.Repository, excl bool) (*Lock, error) {
 
 	if err = lock.checkForOtherLocks(); err != nil {
 		lock.Unlock()
-		return nil, ErrAlreadyLocked
+		return nil, err
 	}
 
 	return lock, nil
@@ -130,11 +144,11 @@ func (l *Lock) checkForOtherLocks() error {
 		}
 
 		if l.Exclusive {
-			return ErrAlreadyLocked
+			return ErrAlreadyLocked{otherLock: lock}
 		}
 
 		if !l.Exclusive && lock.Exclusive {
-			return ErrAlreadyLocked
+			return ErrAlreadyLocked{otherLock: lock}
 		}
 
 		return nil
@@ -206,6 +220,19 @@ func (l *Lock) Stale() bool {
 	return false
 }
 
+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,
+		l.Time.Format("2006-01-02 15:04:05"), time.Since(l.Time),
+		l.lockID.Str())
+
+	if l.Stale() {
+		text += " (stale)"
+	}
+
+	return text
+}
+
 // listen for incoming SIGHUP and ignore
 var ignoreSIGHUP sync.Once
 
@@ -247,3 +274,9 @@ func RemoveStaleLocks(repo *repository.Repository) error {
 		return nil
 	})
 }
+
+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

@@ -67,8 +67,10 @@ func TestLockOnExclusiveLockedRepo(t *testing.T) {
 	OK(t, err)
 
 	lock, err := restic.NewLock(repo)
-	Assert(t, err == restic.ErrAlreadyLocked,
+	Assert(t, err != nil,
 		"create normal lock with exclusively locked repo didn't return an error")
+	Assert(t, restic.IsAlreadyLocked(err),
+		"create normal lock with exclusively locked repo didn't return the correct error")
 
 	OK(t, lock.Unlock())
 	OK(t, elock.Unlock())
@@ -82,8 +84,10 @@ func TestExclusiveLockOnLockedRepo(t *testing.T) {
 	OK(t, err)
 
 	lock, err := restic.NewExclusiveLock(repo)
-	Assert(t, err == restic.ErrAlreadyLocked,
-		"create exclusive lock with locked repo didn't return an error")
+	Assert(t, err != nil,
+		"create normal lock with exclusively locked repo didn't return an error")
+	Assert(t, restic.IsAlreadyLocked(err),
+		"create normal lock with exclusively locked repo didn't return the correct error")
 
 	OK(t, lock.Unlock())
 	OK(t, elock.Unlock())
@@ -170,6 +174,29 @@ func TestLockWithStaleLock(t *testing.T) {
 	OK(t, removeLock(repo, id2))
 }
 
+func TestRemoveAllLocks(t *testing.T) {
+	repo := SetupRepo()
+	defer TeardownRepo(repo)
+
+	id1, err := createFakeLock(repo, time.Now().Add(-time.Hour), os.Getpid())
+	OK(t, err)
+
+	id2, err := createFakeLock(repo, time.Now().Add(-time.Minute), os.Getpid())
+	OK(t, err)
+
+	id3, err := createFakeLock(repo, time.Now().Add(-time.Minute), os.Getpid()+500)
+	OK(t, err)
+
+	OK(t, restic.RemoveAllLocks(repo))
+
+	Assert(t, lockExists(repo, t, id1) == false,
+		"lock still exists after RemoveAllLocks was called")
+	Assert(t, lockExists(repo, t, id2) == false,
+		"lock still exists after RemoveAllLocks was called")
+	Assert(t, lockExists(repo, t, id3) == false,
+		"lock still exists after RemoveAllLocks was called")
+}
+
 func TestLockConflictingExclusiveLocks(t *testing.T) {
 	repo := SetupRepo()
 	defer TeardownRepo(repo)