Container changes (#320)

Added container metrics

vendor/github.com/Microsoft/hcsshim/internal/uvmfolder/locate.go

@@ -0,0 +1,35 @@
+package uvmfolder
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/sirupsen/logrus"
+)
+
+// LocateUVMFolder searches a set of layer folders to determine the "uppermost"
+// layer which has a utility VM image. The order of the layers is (for historical) reasons
+// Read-only-layers followed by an optional read-write layer. The RO layers are in reverse
+// order so that the upper-most RO layer is at the start, and the base OS layer is the
+// end.
+func LocateUVMFolder(layerFolders []string) (string, error) {
+	var uvmFolder string
+	index := 0
+	for _, layerFolder := range layerFolders {
+		_, err := os.Stat(filepath.Join(layerFolder, `UtilityVM`))
+		if err == nil {
+			uvmFolder = layerFolder
+			break
+		}
+		if !os.IsNotExist(err) {
+			return "", err
+		}
+		index++
+	}
+	if uvmFolder == "" {
+		return "", fmt.Errorf("utility VM folder could not be found in layers")
+	}
+	logrus.Debugf("hcsshim::LocateUVMFolder At %d of %d: %s", index+1, len(layerFolders), uvmFolder)
+	return uvmFolder, nil
+}