Update lockfile dependency

vendor/gopkg.in/Acconut/lockfile.v1/README.md

@@ -2,13 +2,17 @@ lockfile
 =========
 Handle locking via pid files.
 
+*Attention:* This is a fork of [Ingo Oeser's amazing work](https://github.com/nightlyone/lockfile)
+whose behavior differs a bit. While the original package allows a process to
+obtain the same lock twice, this fork forbids this behavior.
+
 [![Build Status Unix][1]][2]
 [![Build status Windows][3]][4]
 
-[1]: https://secure.travis-ci.org/nightlyone/lockfile.png
-[2]: https://travis-ci.org/nightlyone/lockfile
-[3]: https://ci.appveyor.com/api/projects/status/7mojkmauj81uvp8u/branch/master?svg=true
-[4]: https://ci.appveyor.com/project/nightlyone/lockfile/branch/master
+[1]: https://secure.travis-ci.org/Acconut/lockfile.png
+[2]: https://travis-ci.org/Acconut/lockfile
+[3]: https://ci.appveyor.com/api/projects/status/bwy487h8cgue6up5?svg=true
+[4]: https://ci.appveyor.com/project/Acconut/lockfile/branch/master
 
 
 
@@ -19,7 +23,7 @@ For Windows suport, Go 1.4 or newer is required.
 
 Then run
 
-	go get github.com/nightlyone/lockfile
+	go get gopkg.in/Acconut/lockfile.v1
 
 [5]: http://golang.org
 [6]: http://golang.org/doc/install/source
@@ -31,12 +35,7 @@ BSD
 
 documentation
 -------------
-[package documentation at godoc.org](http://godoc.org/github.com/nightlyone/lockfile)
-
-install
--------------------
-	go get github.com/nightlyone/lockfile
-
+[package documentation at godoc.org](http://godoc.org/gopkg.in/Acconut/lockfile.v1)
 
 contributing
 ============
@@ -49,4 +48,3 @@ git commit hooks
 enable commit hooks via
 
         cd .git ; rm -rf hooks; ln -s ../git-hooks hooks ; cd ..
-

vendor/gopkg.in/Acconut/lockfile.v1/appveyor.yml

@@ -1,4 +1,4 @@
-clone_folder: c:\gopath\src\github.com\nightlyone\lockfile
+clone_folder: c:\gopath\src\github.com\Acconut\lockfile
 
 environment:
   GOPATH: c:\gopath
@@ -9,4 +9,5 @@ install:
   - go get -v -t ./...
 
 build_script:
-  - go test -v ./...
+  - go test -v .
+  - go vet .

vendor/gopkg.in/Acconut/lockfile.v1/lockfile.go

@@ -1,24 +1,44 @@
-// Handle pid file based locking.
+// Package lockfile handles pid file based locking.
+// While a sync.Mutex helps against concurrency issues within a single process,
+// this package is designed to help against concurrency issues between cooperating processes
+// or serializing multiple invocations of the same process.
 package lockfile
 
 import (
 	"errors"
 	"fmt"
+	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 )
 
+// Lockfile is a pid file which can be locked
 type Lockfile string
 
+// TemporaryError is a type of error where a retry after a random amount of sleep should help to mitigate it.
+type TemporaryError string
+
+func (t TemporaryError) Error() string { return string(t) }
+
+// Temporary returns always true.
+// It exists, so you can detect it via
+//	if te, ok := err.(interface{ Temporary() bool }); ok {
+//		fmt.Println("I am a temporay error situation, so wait and retry")
+//	}
+func (t TemporaryError) Temporary() bool { return true }
+
+// Various errors returned by this package
 var (
-	ErrBusy        = errors.New("Locked by other process") // If you get this, retry after a short sleep might help
+	ErrBusy          = TemporaryError("Locked by other process")             // If you get this, retry after a short sleep might help
+	ErrNotExist      = TemporaryError("Lockfile created, but doesn't exist") // If you get this, retry after a short sleep might help
 	ErrNeedAbsPath   = errors.New("Lockfiles must be given as absolute path names")
 	ErrInvalidPid    = errors.New("Lockfile contains invalid pid for system")
 	ErrDeadOwner     = errors.New("Lockfile contains pid of process not existent on this system anymore")
+	ErrRogueDeletion = errors.New("Lockfile owned by me has been removed unexpectedly")
 )
 
-// Describe a new filename located at path. It is expected to be an absolute path
+// New describes a new filename located at the given absolute path.
 func New(path string) (Lockfile, error) {
 	if !filepath.IsAbs(path) {
 		return Lockfile(""), ErrNeedAbsPath
@@ -26,7 +46,7 @@ func New(path string) (Lockfile, error) {
 	return Lockfile(path), nil
 }
 
-// Who owns the lockfile?
+// GetOwner returns who owns the lockfile.
 func (l Lockfile) GetOwner() (*os.Process, error) {
 	name := string(l)
 
@@ -36,14 +56,11 @@ func (l Lockfile) GetOwner() (*os.Process, error) {
 		return nil, err
 	}
 
-	var pid int
-	_, err = fmt.Sscanln(string(content), &pid)
-	if err != nil {
-		return nil, ErrInvalidPid
-	}
-
 	// try hard for pids. If no pid, the lockfile is junk anyway and we delete it.
-	if pid > 0 {
+	pid, err := scanPidLine(content)
+	if err != nil {
+		return nil, err
+	}
 	running, err := isRunning(pid)
 	if err != nil {
 		return nil, err
@@ -55,39 +72,37 @@ func (l Lockfile) GetOwner() (*os.Process, error) {
 			return nil, err
 		}
 		return proc, nil
-		} else {
+	}
 	return nil, ErrDeadOwner
-		}
 
-	} else {
-		return nil, ErrInvalidPid
-	}
-	panic("Not reached")
 }
 
-// Try to get Lockfile lock. Returns nil, if successful and and error describing the reason, it didn't work out.
-// Please note, that existing lockfiles containing pids of dead processes and lockfiles containing no pid at all
-// are deleted.
+// TryLock tries to own the lock.
+// It Returns nil, if successful and and error describing the reason, it didn't work out.
+// Please note, that existing lockfiles containing pids of dead processes
+// and lockfiles containing no pid at all are simply deleted.
 func (l Lockfile) TryLock() error {
 	name := string(l)
 
 	// This has been checked by New already. If we trigger here,
 	// the caller didn't use New and re-implemented it's functionality badly.
 	// So panic, that he might find this easily during testing.
-	if !filepath.IsAbs(string(name)) {
+	if !filepath.IsAbs(name) {
 		panic(ErrNeedAbsPath)
 	}
 
 	tmplock, err := ioutil.TempFile(filepath.Dir(name), "")
 	if err != nil {
 		return err
-	} else {
-		defer tmplock.Close()
-		defer os.Remove(tmplock.Name())
 	}
 
-	_, err = tmplock.WriteString(fmt.Sprintf("%d\n", os.Getpid()))
-	if err != nil {
+	cleanup := func() {
+		_ = tmplock.Close()
+		_ = os.Remove(tmplock.Name())
+	}
+	defer cleanup()
+
+	if err := writePidLine(tmplock, os.Getpid()); err != nil {
 		return err
 	}
 
@@ -100,6 +115,10 @@ func (l Lockfile) TryLock() error {
 	}
 	fiLock, err := os.Lstat(name)
 	if err != nil {
+		// tell user that a retry would be a good idea
+		if os.IsNotExist(err) {
+			return ErrNotExist
+		}
 		return err
 	}
 
@@ -114,6 +133,10 @@ func (l Lockfile) TryLock() error {
 		// Other errors -> defensively fail and let caller handle this
 		return err
 	case nil:
+		// This fork differs from the upstream repository in this line. We do
+		// not want a process to obtain a lock if this lock is already help by
+		// the same process. Therefore, we always return ErrBusy if the lockfile
+		// contains a non-dead PID.
 		return ErrBusy
 	case ErrDeadOwner, ErrInvalidPid:
 		// cases we can fix below
@@ -122,14 +145,57 @@ func (l Lockfile) TryLock() error {
 	// clean stale/invalid lockfile
 	err = os.Remove(name)
 	if err != nil {
+		// If it doesn't exist, then it doesn't matter who removed it.
+		if !os.IsNotExist(err) {
 			return err
 		}
+	}
 
-	// now that we cleaned up the stale lockfile, let's recurse
+	// now that the stale lockfile is gone, let's recurse
 	return l.TryLock()
 }
 
-// Release a lock again. Returns any error that happend during release of lock.
+// Unlock a lock again, if we owned it. Returns any error that happend during release of lock.
 func (l Lockfile) Unlock() error {
+	proc, err := l.GetOwner()
+	switch err {
+	case ErrInvalidPid, ErrDeadOwner:
+		return ErrRogueDeletion
+	case nil:
+		if proc.Pid == os.Getpid() {
+			// we really own it, so let's remove it.
 			return os.Remove(string(l))
+		}
+		// Not owned by me, so don't delete it.
+		return ErrRogueDeletion
+	default:
+		// This is an application error or system error.
+		// So give a better error for logging here.
+		if os.IsNotExist(err) {
+			return ErrRogueDeletion
+		}
+		// Other errors -> defensively fail and let caller handle this
+		return err
+	}
+}
+
+func writePidLine(w io.Writer, pid int) error {
+	_, err := io.WriteString(w, fmt.Sprintf("%d\n", pid))
+	return err
+}
+
+func scanPidLine(content []byte) (int, error) {
+	if len(content) == 0 {
+		return 0, ErrInvalidPid
+	}
+
+	var pid int
+	if _, err := fmt.Sscanln(string(content), &pid); err != nil {
+		return 0, ErrInvalidPid
+	}
+
+	if pid <= 0 {
+		return 0, ErrInvalidPid
+	}
+	return pid, nil
 }

vendor/gopkg.in/Acconut/lockfile.v1/lockfile_unix.go

@@ -11,12 +11,10 @@ func isRunning(pid int) (bool, error) {
 	proc, err := os.FindProcess(pid)
 	if err != nil {
 		return false, err
-	} else {
-		err := proc.Signal(syscall.Signal(0))
-		if err == nil {
-			return true, nil
-		} else {
+	}
+
+	if err := proc.Signal(syscall.Signal(0)); err != nil {
 		return false, nil
 	}
-	}
+	return true, nil
 }

vendor/vendor.json

@@ -33,10 +33,10 @@
 			"revisionTime": "2016-06-15T09:26:46Z"
 		},
 		{
-			"checksumSHA1": "0zBf3a7Gzqypt1sWefwx4NkOEIc=",
+			"checksumSHA1": "BpFC/4q4mc/SfCvsXGzCF8s9fSE=",
 			"path": "gopkg.in/Acconut/lockfile.v1",
-			"revision": "941fc61ce4d67dd432b94ed0bd445ad5fb9391a9",
-			"revisionTime": "2016-05-20T15:30:20Z"
+			"revision": "ea910fd69bd541bb592c5729c94f595c696413ab",
+			"revisionTime": "2017-03-03T10:08:22Z"
 		}
 	],
 	"rootPath": "github.com/tus/tusd"