virtiofsd: Improve logging

[ port from runtime commit 882a82393305a4b11a77744b5fc77b98e42d15b9 ]

Send virtiofsd logs to syslog in the same way that qemu implementation
does. This requires not to wait for messages from virtiofsd stdout. This
takes the qemu implementation approach. Give the socket fd to virtiofsd.

Signed-off-by: Jose Carlos Venegas Munoz <jose.carlos.venegas.munoz@intel.com>
Signed-off-by: Peng Tao <bergwolf@hyper.sh>

src/runtime/virtcontainers/virtiofsd.go

@@ -10,8 +10,10 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"net"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"strings"
 	"syscall"
 	"time"
@@ -58,6 +60,26 @@ type virtiofsd struct {
 	wait virtiofsdWaitFunc
 }
 
+// Open socket on behalf of virtiofsd
+// return file descriptor to be used by virtiofsd.
+func (v *virtiofsd) getSocketFD() (*os.File, error) {
+	var listener *net.UnixListener
+
+	if _, err := os.Stat(filepath.Dir(v.socketPath)); err != nil {
+		return nil, errors.Errorf("Socket directory does not exist %s", filepath.Dir(v.socketPath))
+	}
+
+	listener, err := net.ListenUnix("unix", &net.UnixAddr{Name: v.socketPath, Net: "unix"})
+	if err != nil {
+		return nil, err
+	}
+	defer listener.Close()
+
+	listener.SetUnlinkOnClose(false)
+
+	return listener.File()
+}
+
 // Start the virtiofsd daemon
 func (v *virtiofsd) Start(ctx context.Context) (int, error) {
 	span, _ := v.trace("Start")
@@ -68,20 +90,28 @@ func (v *virtiofsd) Start(ctx context.Context) (int, error) {
 		return pid, err
 	}
 
-	args, err := v.args()
+	cmd := exec.Command(v.path)
+
+	socketFD, err := v.getSocketFD()
+	if err != nil {
+		return 0, err
+	}
+
+	cmd.ExtraFiles = append(cmd.ExtraFiles, socketFD)
+
+	// Extra files start from 2 (0: stdin, 1: stdout, 2: stderr)
+	// Extra FDs for virtiofsd start from 3
+	// Get the FD number for previous added socketFD
+	socketFdNumber := 2 + uint(len(cmd.ExtraFiles))
+	args, err := v.args(socketFdNumber)
 	if err != nil {
 		return pid, err
 	}
+	cmd.Args = append(cmd.Args, args...)
 
 	v.Logger().WithField("path", v.path).Info()
 	v.Logger().WithField("args", strings.Join(args, " ")).Info()
 
-	cmd := exec.Command(v.path, args...)
-	stderr, err := cmd.StderrPipe()
-	if err != nil {
-		return pid, fmt.Errorf("failed to get stderr from virtiofsd command, error: %s", err)
-	}
-
 	if err = utils.StartCmd(cmd); err != nil {
 		return pid, err
 	}
@@ -96,7 +126,7 @@ func (v *virtiofsd) Start(ctx context.Context) (int, error) {
 		v.wait = waitVirtiofsReady
 	}
 
-	return cmd.Process.Pid, v.wait(cmd, stderr, v.debug)
+	return pid, socketFD.Close()
 }
 
 func (v *virtiofsd) Stop() error {
@@ -115,7 +145,7 @@ func (v *virtiofsd) Stop() error {
 	return nil
 }
 
-func (v *virtiofsd) args() ([]string, error) {
+func (v *virtiofsd) args(FdSocketNumber uint) ([]string, error) {
 	if v.sourcePath == "" {
 		return []string{}, errors.New("vitiofsd source path is empty")
 	}
@@ -125,11 +155,23 @@ func (v *virtiofsd) args() ([]string, error) {
 	}
 
 	args := []string{
+		// Send logs to syslog
+		"--syslog",
+		// foreground operation
 		"-f",
+		// cache mode for virtiofsd
 		"-o", "cache=" + v.cache,
+		// disable posix locking in daemon: bunch of basic posix locks properties are broken
+		// apt-get update is broken if enabled
 		"-o", "no_posix_lock",
+		// shared directory tree
 		"-o", "source=" + v.sourcePath,
-		"-o", "vhost_user_socket=" + v.socketPath,
+		// fd number of vhost-user socket
+		fmt.Sprintf("--fd=%v", FdSocketNumber),
+	}
+
+	if v.debug {
+		args = append(args, "-o", "debug")
 	}
 
 	if len(v.extraArgs) != 0 {

src/runtime/virtcontainers/virtiofsd_test.go

@@ -33,11 +33,19 @@ func TestVirtiofsdStart(t *testing.T) {
 	assert.NoError(err)
 	defer os.RemoveAll(sourcePath)
 
+	socketDir, err := ioutil.TempDir("", "")
+	assert.NoError(err)
+	defer os.RemoveAll(sourcePath)
+
+	socketPath := socketDir + "socket.s"
+
 	validConfig := fields{
-		path:       "/tmp/a/path",
-		socketPath: "/tmp/a/path/to/sock.sock",
+		path:       "/usr/bin/virtiofsd-path",
+		socketPath: socketPath,
 		sourcePath: sourcePath,
 	}
+	NoDirectorySocket := validConfig
+	NoDirectorySocket.socketPath = "/tmp/path/to/virtiofsd/socket.sock"
 
 	tests := []struct {
 		name    string
@@ -45,6 +53,7 @@ func TestVirtiofsdStart(t *testing.T) {
 		wantErr bool
 	}{
 		{"empty config", fields{}, true},
+		{"Directory socket does not exist", NoDirectorySocket, true},
 		{"valid config", validConfig, false},
 	}
 	for _, tt := range tests {