Merge pull request #37 from tus/lockingstore

Make locking implementation flexible

cmd/tusd/main.go

@@ -44,9 +44,7 @@ func main() {
 	}
 
 	var store tusd.DataStore
-	store = filestore.FileStore{
-		Path: dir,
-	}
+	store = filestore.New(dir)
 
 	if storeSize > 0 {
 		store = limitedstore.New(storeSize, store)

concat_test.go

@@ -1,4 +1,4 @@
-package tusd
+package tusd_test
 
 import (
 	"io"
@@ -7,6 +7,8 @@ import (
 	"reflect"
 	"strings"
 	"testing"
+
+	. "github.com/tus/tusd"
 )
 
 type concatPartialStore struct {

cors_test.go

@@ -1,8 +1,10 @@
-package tusd
+package tusd_test
 
 import (
 	"net/http"
 	"testing"
+
+	. "github.com/tus/tusd"
 )
 
 func TestCORS(t *testing.T) {

datastore.go

@@ -55,3 +55,24 @@ type DataStore interface {
 	// and writing, must return os.ErrNotExist or similar.
 	Terminate(id string) error
 }
+
+// LockerDataStore is the interface required for custom lock persisting mechanisms.
+// Common ways to store this information is in memory, on disk or using an
+// external service, such as ZooKeeper.
+// When multiple processes are attempting to access an upload, whether it be
+// by reading or writing, a syncronization mechanism is required to prevent
+// data corruption, especially to ensure correct offset values and the proper
+// order of chunks inside a single upload.
+type LockerDataStore interface {
+	DataStore
+
+	// LockUpload attempts to obtain an exclusive lock for the upload specified
+	// by its id.
+	// If this operation fails because the resource is already locked, the
+	// tusd.ErrFileLocked must be returned. If no error is returned, the attempt
+	// is consider to be successful and the upload to be locked until UnlockUpload
+	// is invoked for the same upload.
+	LockUpload(id string) error
+	// UnlockUpload releases an existing lock for the given upload.
+	UnlockUpload(id string) error
+}

filestore/filestore.go

@@ -1,9 +1,18 @@
+// Package filestore provide a storage backend based on the local file system.
+//
 // FileStore is a storage backend used as a tusd.DataStore in tusd.NewHandler.
 // It stores the uploads in a directory specified in two different files: The
 // `[id].info` files are used to store the fileinfo in JSON format. The
 // `[id].bin` files contain the raw binary data uploaded.
 // No cleanup is performed so you may want to run a cronjob to ensure your disk
 // is not filled up with old and finished uploads.
+//
+// In addition, it provides an exclusive upload locking mechansim using lock files
+// which are stored on disk. Each of them stores the PID of the process which
+// aquired the lock. This allows locks to be automatically freed when a process
+// is unable to release it on its own because the process is not alive anymore.
+// For more information, consult the documentation for tusd.LockerDataStore
+// interface, which is implemented by FileStore
 package filestore
 
 import (
@@ -11,9 +20,12 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
+	"path/filepath"
 
 	"github.com/tus/tusd"
 	"github.com/tus/tusd/uid"
+
+	"github.com/nightlyone/lockfile"
 )
 
 var defaultFilePerm = os.FileMode(0775)
@@ -22,10 +34,18 @@ var defaultFilePerm = os.FileMode(0775)
 // methods.
 type FileStore struct {
 	// Relative or absolute path to store files in. FileStore does not check
-	// whether the path exists, you os.MkdirAll in this case on your own.
+	// whether the path exists, use os.MkdirAll in this case on your own.
 	Path string
 }
 
+// New creates a new file based storage backend. The directory specified will
+// be used as the only storage entry. This method does not check
+// whether the path exists, use os.MkdirAll to ensure.
+// In addition, a locking mechanism is provided.
+func New(path string) FileStore {
+	return FileStore{path}
+}
+
 func (store FileStore) NewUpload(info tusd.FileInfo) (id string, err error) {
 	id = uid.Uid()
 	info.ID = id
@@ -82,17 +102,62 @@ func (store FileStore) Terminate(id string) error {
 	return nil
 }
 
-// Return the path to the .bin storing the binary data
+func (store FileStore) LockUpload(id string) error {
+	lock, err := store.newLock(id)
+	if err != nil {
+		return err
+	}
+
+	err = lock.TryLock()
+	if err == lockfile.ErrBusy {
+		return tusd.ErrFileLocked
+	}
+
+	return err
+}
+
+func (store FileStore) UnlockUpload(id string) error {
+	lock, err := store.newLock(id)
+	if err != nil {
+		return err
+	}
+
+	err = lock.Unlock()
+
+	// A "no such file or directory" will be returned if no lockfile was found.
+	// Since this means that the file has never been locked, we drop the error
+	// and continue as if nothing happend.
+	if os.IsNotExist(err) {
+		err = nil
+	}
+
+	return nil
+}
+
+// newLock contructs a new Lockfile instance.
+func (store FileStore) newLock(id string) (lockfile.Lockfile, error) {
+	path, err := filepath.Abs(store.Path + "/" + id + ".lock")
+	if err != nil {
+		return lockfile.Lockfile(""), err
+	}
+
+	// We use Lockfile directly instead of lockfile.New to bypass the unnecessary
+	// check whether the provided path is absolute since we just resolved it
+	// on our own.
+	return lockfile.Lockfile(path), nil
+}
+
+// binPath returns the path to the .bin storing the binary data.
 func (store FileStore) binPath(id string) string {
 	return store.Path + "/" + id + ".bin"
 }
 
-// Return the path to the .info file storing the file's info
+// infoPath returns the path to the .info file storing the file's info.
 func (store FileStore) infoPath(id string) string {
 	return store.Path + "/" + id + ".info"
 }
 
-// Update the entire information. Everything will be overwritten.
+// writeInfo updates the entire information. Everything will be overwritten.
 func (store FileStore) writeInfo(id string, info tusd.FileInfo) error {
 	data, err := json.Marshal(info)
 	if err != nil {
@@ -101,7 +166,7 @@ func (store FileStore) writeInfo(id string, info tusd.FileInfo) error {
 	return ioutil.WriteFile(store.infoPath(id), data, defaultFilePerm)
 }
 
-// Update the .info file using the new upload.
+// setOffset updates the .info file to match the new offset.
 func (store FileStore) setOffset(id string, offset int64) error {
 	info, err := store.GetInfo(id)
 	if err != nil {

filestore/filestore_test.go

@@ -95,3 +95,29 @@ func TestFilestore(t *testing.T) {
 		t.Fatal("expected os.ErrIsNotExist")
 	}
 }
+
+func TestFileLocker(t *testing.T) {
+	dir, err := ioutil.TempDir("", "tusd-file-locker")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var locker tusd.LockerDataStore
+	locker = FileStore{dir}
+
+	if err := locker.LockUpload("one"); err != nil {
+		t.Errorf("unexpected error when locking file: %s", err)
+	}
+
+	if err := locker.LockUpload("one"); err != tusd.ErrFileLocked {
+		t.Errorf("expected error when locking locked file: %s", err)
+	}
+
+	if err := locker.UnlockUpload("one"); err != nil {
+		t.Errorf("unexpected error when unlocking file: %s", err)
+	}
+
+	if err := locker.UnlockUpload("one"); err != nil {
+		t.Errorf("unexpected error when unlocking file again: %s", err)
+	}
+}

get_test.go

@@ -1,4 +1,4 @@
-package tusd
+package tusd_test
 
 import (
 	"io"
@@ -6,6 +6,8 @@ import (
 	"os"
 	"strings"
 	"testing"
+
+	. "github.com/tus/tusd"
 )
 
 type getStore struct {

handler.go

@@ -1,3 +1,4 @@
+// Package tusd provides ways to accept tusd calls using HTTP.
 package tusd
 
 import (

handler_test.go

@@ -1,4 +1,4 @@
-package tusd
+package tusd_test
 
 import (
 	"io"
@@ -7,6 +7,8 @@ import (
 	"os"
 	"strings"
 	"testing"
+
+	. "github.com/tus/tusd"
 )
 
 type zeroStore struct{}

head_test.go

@@ -1,9 +1,11 @@
-package tusd
+package tusd_test
 
 import (
 	"net/http"
 	"os"
 	"testing"
+
+	. "github.com/tus/tusd"
 )
 
 type headStore struct {

limitedstore/limitedstore.go

@@ -1,4 +1,6 @@
-// Package limitedstore implements a simple wrapper around existing
+// Package limitedstore provides a storage with a limited space.
+//
+// This goal is achieved by using a simple wrapper around existing
 // datastores (tusd.DataStore) while limiting the used storage size.
 // It will start terminating existing uploads if not enough space is left in
 // order to create a new upload.

memorylocker/memorylocker.go

@@ -0,0 +1,53 @@
+// Package memorylocker provides an in-memory locking mechanism
+//
+// When multiple processes are attempting to access an upload, whether it be
+// by reading or writing, a syncronization mechanism is required to prevent
+// data corruption, especially to ensure correct offset values and the proper
+// order of chunks inside a single upload.
+//
+// MemoryLocker persists locks using memory and therefore allowing a simple and
+// cheap mechansim. Locks will only exist as long as this object is kept in
+// reference and will be erased if the program exits.
+package memorylocker
+
+import (
+	"github.com/tus/tusd"
+)
+
+// MemoryLocker persists locks using memory and therefore allowing a simple and
+// cheap mechansim. Locks will only exist as long as this object is kept in
+// reference and will be erased if the program exits.
+type MemoryLocker struct {
+	tusd.DataStore
+	locks map[string]bool
+}
+
+// New creates a new lock memory wrapper around the provided storage.
+func NewMemoryLocker(store tusd.DataStore) *MemoryLocker {
+	return &MemoryLocker{
+		DataStore: store,
+		locks:     make(map[string]bool),
+	}
+}
+
+// LockUpload tries to obtain the exclusive lock.
+func (locker *MemoryLocker) LockUpload(id string) error {
+
+	// Ensure file is not locked
+	if _, ok := locker.locks[id]; ok {
+		return tusd.ErrFileLocked
+	}
+
+	locker.locks[id] = true
+
+	return nil
+}
+
+// UnlockUpload releases a lock. If no such lock exists, no error will be returned.
+func (locker *MemoryLocker) UnlockUpload(id string) error {
+	// Deleting a non-existing key does not end in unexpected errors or panic
+	// since this operation results in a no-op
+	delete(locker.locks, id)
+
+	return nil
+}

memorylocker/memorylocker_test.go

@@ -0,0 +1,50 @@
+package memorylocker
+
+import (
+	"io"
+	"testing"
+
+	"github.com/tus/tusd"
+)
+
+type zeroStore struct{}
+
+func (store zeroStore) NewUpload(info tusd.FileInfo) (string, error) {
+	return "", nil
+}
+func (store zeroStore) WriteChunk(id string, offset int64, src io.Reader) (int64, error) {
+	return 0, nil
+}
+
+func (store zeroStore) GetInfo(id string) (tusd.FileInfo, error) {
+	return tusd.FileInfo{}, nil
+}
+
+func (store zeroStore) GetReader(id string) (io.Reader, error) {
+	return nil, tusd.ErrNotImplemented
+}
+
+func (store zeroStore) Terminate(id string) error {
+	return tusd.ErrNotImplemented
+}
+
+func TestMemoryLocker(t *testing.T) {
+	var locker tusd.LockerDataStore
+	locker = NewMemoryLocker(&zeroStore{})
+
+	if err := locker.LockUpload("one"); err != nil {
+		t.Errorf("unexpected error when locking file: %s", err)
+	}
+
+	if err := locker.LockUpload("one"); err != tusd.ErrFileLocked {
+		t.Errorf("expected error when locking locked file: %s", err)
+	}
+
+	if err := locker.UnlockUpload("one"); err != nil {
+		t.Errorf("unexpected error when unlocking file: %s", err)
+	}
+
+	if err := locker.UnlockUpload("one"); err != nil {
+		t.Errorf("unexpected error when unlocking file again: %s", err)
+	}
+}

options_test.go

@@ -1,8 +1,10 @@
-package tusd
+package tusd_test
 
 import (
 	"net/http"
 	"testing"
+
+	. "github.com/tus/tusd"
 )
 
 func TestOptions(t *testing.T) {

patch_test.go

@@ -1,4 +1,4 @@
-package tusd
+package tusd_test
 
 import (
 	"io"
@@ -7,6 +7,8 @@ import (
 	"os"
 	"strings"
 	"testing"
+
+	. "github.com/tus/tusd"
 )
 
 type patchStore struct {
@@ -204,3 +206,87 @@ func TestPatchOverflow(t *testing.T) {
 		Code:    http.StatusNoContent,
 	}).Run(handler, t)
 }
+
+const (
+	LOCK = iota
+	INFO
+	WRITE
+	UNLOCK
+	END
+)
+
+type lockingPatchStore struct {
+	zeroStore
+	callOrder chan int
+}
+
+func (s lockingPatchStore) GetInfo(id string) (FileInfo, error) {
+	s.callOrder <- INFO
+
+	return FileInfo{
+		Offset: 0,
+		Size:   20,
+	}, nil
+}
+
+func (s lockingPatchStore) WriteChunk(id string, offset int64, src io.Reader) (int64, error) {
+	s.callOrder <- WRITE
+
+	return 5, nil
+}
+
+func (s lockingPatchStore) LockUpload(id string) error {
+	s.callOrder <- LOCK
+	return nil
+}
+
+func (s lockingPatchStore) UnlockUpload(id string) error {
+	s.callOrder <- UNLOCK
+	return nil
+}
+
+func TestLockingPatch(t *testing.T) {
+	callOrder := make(chan int, 10)
+
+	handler, _ := NewHandler(Config{
+		DataStore: lockingPatchStore{
+			callOrder: callOrder,
+		},
+	})
+
+	(&httpTest{
+		Name:   "Uploading to locking store",
+		Method: "PATCH",
+		URL:    "yes",
+		ReqHeader: map[string]string{
+			"Tus-Resumable": "1.0.0",
+			"Content-Type":  "application/offset+octet-stream",
+			"Upload-Offset": "0",
+		},
+		ReqBody: strings.NewReader("hello"),
+		Code:    http.StatusNoContent,
+	}).Run(handler, t)
+
+	callOrder <- END
+	close(callOrder)
+
+	if <-callOrder != LOCK {
+		t.Error("expected call to LockUpload")
+	}
+
+	if <-callOrder != INFO {
+		t.Error("expected call to GetInfo")
+	}
+
+	if <-callOrder != WRITE {
+		t.Error("expected call to WriteChunk")
+	}
+
+	if <-callOrder != UNLOCK {
+		t.Error("expected call to UnlockUpload")
+	}
+
+	if <-callOrder != END {
+		t.Error("expected no more calls to happen")
+	}
+}

post_test.go

@@ -1,8 +1,10 @@
-package tusd
+package tusd_test
 
 import (
 	"net/http"
 	"testing"
+
+	. "github.com/tus/tusd"
 )
 
 type postStore struct {

terminate_test.go

@@ -1,8 +1,10 @@
-package tusd
+package tusd_test
 
 import (
 	"net/http"
 	"testing"
+
+	. "github.com/tus/tusd"
 )
 
 type terminateStore struct {

unrouted_handler.go

@@ -75,7 +75,6 @@ type UnroutedHandler struct {
 	dataStore     DataStore
 	isBasePathAbs bool
 	basePath      string
-	locks         map[string]bool
 	logger        *log.Logger
 
 	// For each finished upload the corresponding info object will be sent using
@@ -114,7 +113,6 @@ func NewUnroutedHandler(config Config) (*UnroutedHandler, error) {
 		dataStore:       config.DataStore,
 		basePath:        base,
 		isBasePathAbs:   uri.IsAbs(),
-		locks:           make(map[string]bool),
 		CompleteUploads: make(chan FileInfo),
 		logger:          logger,
 	}
@@ -259,6 +257,16 @@ func (handler *UnroutedHandler) HeadFile(w http.ResponseWriter, r *http.Request)
 		handler.sendError(w, r, err)
 		return
 	}
+
+	if locker, ok := handler.dataStore.(LockerDataStore); ok {
+		if err := locker.LockUpload(id); err != nil {
+			handler.sendError(w, r, err)
+			return
+		}
+
+		defer locker.UnlockUpload(id)
+	}
+
 	info, err := handler.dataStore.GetInfo(id)
 	if err != nil {
 		handler.sendError(w, r, err)
@@ -288,17 +296,16 @@ func (handler *UnroutedHandler) HeadFile(w http.ResponseWriter, r *http.Request)
 	w.WriteHeader(http.StatusNoContent)
 }
 
-// PatchFile adds a chunk to an upload. Only allowed if the upload is not
-// locked and enough space is left.
+// PatchFile adds a chunk to an upload. Only allowed enough space is left.
 func (handler *UnroutedHandler) PatchFile(w http.ResponseWriter, r *http.Request) {
 
-	//Check for presence of application/offset+octet-stream
+	// Check for presence of application/offset+octet-stream
 	if r.Header.Get("Content-Type") != "application/offset+octet-stream" {
 		handler.sendError(w, r, ErrInvalidContentType)
 		return
 	}
 
-	//Check for presence of a valid Upload-Offset Header
+	// Check for presence of a valid Upload-Offset Header
 	offset, err := strconv.ParseInt(r.Header.Get("Upload-Offset"), 10, 64)
 	if err != nil || offset < 0 {
 		handler.sendError(w, r, ErrInvalidOffset)
@@ -311,20 +318,15 @@ func (handler *UnroutedHandler) PatchFile(w http.ResponseWriter, r *http.Request
 		return
 	}
 
-	// Ensure file is not locked
-	if _, ok := handler.locks[id]; ok {
-		handler.sendError(w, r, ErrFileLocked)
-		return
+	if locker, ok := handler.dataStore.(LockerDataStore); ok {
+		if err := locker.LockUpload(id); err != nil {
+			handler.sendError(w, r, err)
+			return
+		}
+
+		defer locker.UnlockUpload(id)
 	}
 
-	// Lock file for further writes (heads are allowed)
-	handler.locks[id] = true
-
-	// File will be unlocked regardless of an error or success
-	defer func() {
-		delete(handler.locks, id)
-	}()
-
 	info, err := handler.dataStore.GetInfo(id)
 	if err != nil {
 		handler.sendError(w, r, err)
@@ -387,20 +389,15 @@ func (handler *UnroutedHandler) GetFile(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	// Ensure file is not locked
-	if _, ok := handler.locks[id]; ok {
-		handler.sendError(w, r, ErrFileLocked)
-		return
+	if locker, ok := handler.dataStore.(LockerDataStore); ok {
+		if err := locker.LockUpload(id); err != nil {
+			handler.sendError(w, r, err)
+			return
+		}
+
+		defer locker.UnlockUpload(id)
 	}
 
-	// Lock file for further writes (heads are allowed)
-	handler.locks[id] = true
-
-	// File will be unlocked regardless of an error or success
-	defer func() {
-		delete(handler.locks, id)
-	}()
-
 	info, err := handler.dataStore.GetInfo(id)
 	if err != nil {
 		handler.sendError(w, r, err)
@@ -438,20 +435,15 @@ func (handler *UnroutedHandler) DelFile(w http.ResponseWriter, r *http.Request)
 		return
 	}
 
-	// Ensure file is not locked
-	if _, ok := handler.locks[id]; ok {
-		handler.sendError(w, r, ErrFileLocked)
-		return
+	if locker, ok := handler.dataStore.(LockerDataStore); ok {
+		if err := locker.LockUpload(id); err != nil {
+			handler.sendError(w, r, err)
+			return
+		}
+
+		defer locker.UnlockUpload(id)
 	}
 
-	// Lock file for further writes (heads are allowed)
-	handler.locks[id] = true
-
-	// File will be unlocked regardless of an error or success
-	defer func() {
-		delete(handler.locks, id)
-	}()
-
 	err = handler.dataStore.Terminate(id)
 	if err != nil {
 		handler.sendError(w, r, err)