bugfix: avoid creating dup-process of dfget server.

Signed-off-by: zhouchencheng <zhouchencheng@bilibili.com>

dfget/core/uploader/peer_server_executor.go

@@ -21,12 +21,14 @@ import (
 	"io"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"sync/atomic"
 	"time"
 
 	"github.com/dragonflyoss/Dragonfly/dfget/config"
+	"github.com/dragonflyoss/Dragonfly/pkg/fileutils"
 	"github.com/dragonflyoss/Dragonfly/version"
 
 	"github.com/sirupsen/logrus"
@@ -74,6 +76,12 @@ func (pe *peerServerExecutor) StartPeerServerProcess(cfg *config.Config) (port i
 		return port, nil
 	}
 
+	fileLock := fileutils.NewFileLock(filepath.Dir(cfg.RV.MetaPath))
+	if err = fileLock.Lock(); err != nil {
+		return 0, err
+	}
+	defer fileLock.Unlock()
+
 	cmd := exec.Command(os.Args[0], "server",
 		"--ip", cfg.RV.LocalIP,
 		"--port", strconv.Itoa(cfg.RV.PeerPort),

pkg/fileutils/filelock.go

@@ -0,0 +1,78 @@
+/*
+ * Copyright The Dragonfly Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package fileutils
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+
+	"github.com/pkg/errors"
+)
+
+// FileLock defines a file lock implemented by syscall.Flock
+type FileLock struct {
+	fileName string
+	fd       *os.File
+}
+
+// NewFileLock create a FileLock instance
+func NewFileLock(name string) *FileLock {
+	return &FileLock{
+		fileName: name,
+	}
+}
+
+// Lock locks file.
+// If the file is already locked, the calling goroutine blocks until the file is unlocked.
+// If lock has been invoked without unlock, lock again will return an error.
+func (l *FileLock) Lock() error {
+	var (
+		fd  *os.File
+		err error
+	)
+
+	if l.fd != nil {
+		return fmt.Errorf("file %s has already been locked", l.fileName)
+	}
+
+	if fd, err = os.Open(l.fileName); err != nil {
+		return err
+	}
+	l.fd = fd
+
+	if err := syscall.Flock(int(l.fd.Fd()), syscall.LOCK_EX); err != nil {
+		return errors.Wrapf(err, "file %s lock failed", l.fileName)
+	}
+	return nil
+}
+
+// Unlock unlocks file.
+// If lock has not been invoked before unlock, unlock will return an error.
+func (l *FileLock) Unlock() error {
+	if l.fd == nil {
+		return fmt.Errorf("file %s descriptor is nil", l.fileName)
+	}
+	fd := l.fd
+	l.fd = nil
+
+	defer fd.Close()
+	if err := syscall.Flock(int(fd.Fd()), syscall.LOCK_UN); err != nil {
+		return errors.Wrapf(err, "file %s unlock failed", l.fileName)
+	}
+	return nil
+}

pkg/fileutils/filelock_test.go

@@ -0,0 +1,76 @@
+/*
+ * Copyright The Dragonfly Authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package fileutils
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"time"
+
+	"github.com/go-check/check"
+)
+
+type FileLockTestSuite struct {
+	tmpDir string
+	flockA *FileLock
+	flockB *FileLock
+}
+
+func init() {
+	check.Suite(&FileLockTestSuite{})
+}
+
+func (s *FileLockTestSuite) SetUpSuite(c *check.C) {
+	tmpDir, _ := ioutil.TempDir("/tmp", "dfget-FileLockTestSuite-")
+	os.Create(tmpDir)
+	s.tmpDir = tmpDir
+	s.flockA = NewFileLock(tmpDir)
+	s.flockB = NewFileLock(tmpDir)
+}
+
+func (s *FileLockTestSuite) TearDownSuite(c *check.C) {
+	if s.tmpDir != "" {
+		if err := os.RemoveAll(s.tmpDir); err != nil {
+			fmt.Printf("remove path:%s error", s.tmpDir)
+		}
+	}
+}
+
+func (s *FileLockTestSuite) TestFileLock(c *check.C) {
+	err := s.flockA.Lock()
+	c.Assert(err, check.IsNil)
+
+	err = s.flockA.Lock()
+	c.Assert(err, check.NotNil)
+
+	err = s.flockA.Unlock()
+	c.Assert(err, check.IsNil)
+
+	err = s.flockA.Unlock()
+	c.Assert(err, check.NotNil)
+
+	s.flockA.Lock()
+	start := time.Now()
+	go func() {
+		time.Sleep(time.Second)
+		s.flockA.Unlock()
+	}()
+	s.flockB.Lock()
+	c.Assert(time.Since(start) >= time.Second, check.Equals, true)
+	s.flockB.Unlock()
+}