Merge pull request #1343 from sjenning/dm-fallback

fallback to /dev/mapper device if metadata device is not set in docker info

container/docker/factory.go

@@ -22,6 +22,7 @@ import (
 	"strings"
 	"sync"
 
+	dockertypes "github.com/docker/engine-api/types"
 	"github.com/google/cadvisor/container"
 	"github.com/google/cadvisor/container/libcontainer"
 	"github.com/google/cadvisor/devicemapper"
@@ -171,6 +172,31 @@ var (
 	version_re            = regexp.MustCompile(version_regexp_string)
 )
 
+func startThinPoolWatcher(dockerInfo *dockertypes.Info) (*devicemapper.ThinPoolWatcher, error) {
+	_, err := devicemapper.ThinLsBinaryPresent()
+	if err != nil {
+		return nil, err
+	}
+
+	dockerThinPoolName, err := dockerutil.DockerThinPoolName(*dockerInfo)
+	if err != nil {
+		return nil, err
+	}
+
+	dockerMetadataDevice, err := dockerutil.DockerMetadataDevice(*dockerInfo)
+	if err != nil {
+		return nil, err
+	}
+
+	thinPoolWatcher, err := devicemapper.NewThinPoolWatcher(dockerThinPoolName, dockerMetadataDevice)
+	if err != nil {
+		return nil, err
+	}
+
+	go thinPoolWatcher.Start()
+	return thinPoolWatcher, nil
+}
+
 // Register root container before running this function!
 func Register(factory info.MachineInfoFactory, fsInfo fs.FsInfo, ignoreMetrics container.MetricSet) error {
 	client, err := Client()
@@ -191,40 +217,11 @@ func Register(factory info.MachineInfoFactory, fsInfo fs.FsInfo, ignoreMetrics c
 		return fmt.Errorf("failed to get cgroup subsystems: %v", err)
 	}
 
-	var (
+	var thinPoolWatcher *devicemapper.ThinPoolWatcher
-		dockerStorageDriver                               = storageDriver(dockerInfo.Driver)
+	if storageDriver(dockerInfo.Driver) == devicemapperStorageDriver {
-		thinPoolWatcher     *devicemapper.ThinPoolWatcher = nil
+		thinPoolWatcher, err = startThinPoolWatcher(dockerInfo)
-	)
+		if err != nil {
-
+			glog.Errorf("devicemapper filesystem stats will not be reported: %v", err)
-	if dockerStorageDriver == devicemapperStorageDriver {
-		_, err := devicemapper.ThinLsBinaryPresent()
-		if err == nil {
-			// If the storage driver is devicemapper, create and start a
-			// ThinPoolWatcher to monitor the size of container CoW layers
-			// with thin_ls.
-			dockerThinPoolName, err := dockerutil.DockerThinPoolName(*dockerInfo)
-			if err != nil {
-				return fmt.Errorf("couldn't find device mapper thin pool name: %v", err)
-			}
-
-			dockerMetadataDevice, err := dockerutil.DockerMetadataDevice(*dockerInfo)
-			if err != nil {
-				return fmt.Errorf("couldn't determine devicemapper metadata device: %v", err)
-			}
-
-			thinPoolWatcher, err = devicemapper.NewThinPoolWatcher(dockerThinPoolName, dockerMetadataDevice)
-			if err != nil {
-				return fmt.Errorf("couldn't create thin pool watcher: %v", err)
-			}
-
-			go thinPoolWatcher.Start()
-		} else {
-			msg := []string{
-				"Couldn't locate thin_ls binary; not starting thin pool watcher.",
-				"Containers backed by thin pools will not show accurate usage.",
-				"err: %v",
-			}
-			glog.Errorf(strings.Join(msg, " "), err)
 		}
 	}
 

utils/docker/docker.go

@@ -16,6 +16,7 @@ package docker
 
 import (
 	"fmt"
+	"os"
 	"strings"
 
 	dockertypes "github.com/docker/engine-api/types"
@@ -50,8 +51,19 @@ func DockerThinPoolName(info dockertypes.Info) (string, error) {
 
 func DockerMetadataDevice(info dockertypes.Info) (string, error) {
 	metadataDevice := DriverStatusValue(info.DriverStatus, DriverStatusMetadataFile)
-	if len(metadataDevice) == 0 {
+	if len(metadataDevice) != 0 {
-		return "", fmt.Errorf("Could not get the devicemapper metadata device")
+		return metadataDevice, nil
+	}
+
+	poolName, err := DockerThinPoolName(info)
+	if err != nil {
+		return "", err
+	}
+
+	metadataDevice = fmt.Sprintf("/dev/mapper/%s_tmeta", poolName)
+
+	if _, err := os.Stat(metadataDevice); err != nil {
+		return "", err
 	}
 
 	return metadataDevice, nil