kubelet/rkt: Add RunPod() for rkt.

pkg/kubelet/rkt/rkt.go

@@ -17,9 +17,17 @@ limitations under the License.
 package rkt
 
 import (
+	"encoding/json"
 	"fmt"
+	"hash/adler32"
+	"io"
+	"io/ioutil"
+	"os"
 	"os/exec"
+	"path"
 	"strings"
+	"syscall"
+	"time"
 
 	"github.com/GoogleCloudPlatform/kubernetes/pkg/credentialprovider"
 	"github.com/coreos/go-systemd/dbus"
@@ -138,3 +146,146 @@ func (r *Runtime) runCommand(args ...string) ([]string, error) {
 	}
 	return strings.Split(strings.TrimSpace(string(output)), "\n"), nil
 }
+
+func newUnitOption(section, name, value string) *unit.UnitOption {
+	return &unit.UnitOption{Section: section, Name: name, Value: value}
+}
+
+// TODO(yifan): Move this duplicated function to container runtime.
+// hashContainer computes the hash of one api.Container.
+func hashContainer(container *api.Container) uint64 {
+	hash := adler32.New()
+	util.DeepHashObject(hash, *container)
+	return uint64(hash.Sum32())
+}
+
+// TODO(yifan): Remove the receiver once we can solve the appName->imageID problem.
+func (r *Runtime) apiPodToRuntimePod(uuid string, pod *api.Pod) *kubecontainer.Pod {
+	p := &kubecontainer.Pod{
+		ID:        pod.UID,
+		Name:      pod.Name,
+		Namespace: pod.Namespace,
+	}
+	for i := range pod.Spec.Containers {
+		c := &pod.Spec.Containers[i]
+		imageID, err := r.getImageID(c.Image)
+		if err != nil {
+			glog.Warningf("rkt: Cannot get image id: %v", err)
+		}
+		p.Containers = append(p.Containers, &kubecontainer.Container{
+			ID:      types.UID(buildContainerID(&containerID{uuid, c.Name, imageID})),
+			Name:    c.Name,
+			Image:   c.Image,
+			Hash:    hashContainer(c),
+			Created: time.Now().Unix(),
+		})
+	}
+	return p
+}
+
+// preparePod will:
+//
+// 1. Invoke 'rkt prepare' to prepare the pod, and get the rkt pod uuid.
+// 2. Creates the unit file and save it under systemdUnitDir.
+//
+// On success, it will return a string that represents name of the unit file
+// and a boolean that indicates if the unit file needs to be reloaded (whether
+// the file is already existed).
+func (r *Runtime) preparePod(pod *api.Pod, volumeMap map[string]volume.Volume) (string, bool, error) {
+	cmds := []string{"prepare", "--quiet", "--pod-manifest"}
+
+	// Generate the pod manifest from the pod spec.
+	manifest, err := r.makePodManifest(pod, volumeMap)
+	if err != nil {
+		return "", false, err
+	}
+	manifestFile, err := ioutil.TempFile("", "manifest")
+	if err != nil {
+		return "", false, err
+	}
+	defer func() {
+		manifestFile.Close()
+		if err := os.Remove(manifestFile.Name()); err != nil {
+			glog.Warningf("rkt: Cannot remove temp manifest file %q: %v", manifestFile.Name(), err)
+		}
+	}()
+
+	data, err := json.Marshal(manifest)
+	if err != nil {
+		return "", false, err
+	}
+	// Since File.Write returns error if the written length is less than len(data),
+	// so check error is enough for us.
+	if _, err := manifestFile.Write(data); err != nil {
+		return "", false, err
+	}
+
+	cmds = append(cmds, manifestFile.Name())
+	output, err := r.runCommand(cmds...)
+	if err != nil {
+		return "", false, err
+	}
+	if len(output) != 1 {
+		return "", false, fmt.Errorf("cannot get uuid from 'rkt prepare'")
+	}
+	uuid := output[0]
+	glog.V(4).Infof("'rkt prepare' returns %q.", uuid)
+
+	p := r.apiPodToRuntimePod(uuid, pod)
+	b, err := json.Marshal(p)
+	if err != nil {
+		return "", false, err
+	}
+
+	runPrepared := fmt.Sprintf("%s run-prepared --private-net=%v %s", r.absPath, pod.Spec.HostNetwork, uuid)
+	units := []*unit.UnitOption{
+		newUnitOption(unitKubernetesSection, unitRktID, uuid),
+		newUnitOption(unitKubernetesSection, unitPodName, string(b)),
+		newUnitOption("Service", "ExecStart", runPrepared),
+	}
+
+	// Save the unit file under systemd's service directory.
+	// TODO(yifan) Garbage collect 'dead' serivce files.
+	needReload := false
+	unitName := makePodServiceFileName(pod.UID)
+	if _, err := os.Stat(path.Join(systemdServiceDir, unitName)); err == nil {
+		needReload = true
+	}
+	unitFile, err := os.Create(path.Join(systemdServiceDir, unitName))
+	if err != nil {
+		return "", false, err
+	}
+	defer unitFile.Close()
+
+	_, err = io.Copy(unitFile, unit.Serialize(units))
+	if err != nil {
+		return "", false, err
+	}
+	return unitName, needReload, nil
+}
+
+// RunPod first creates the unit file for a pod, and then calls
+// StartUnit over d-bus.
+func (r *Runtime) RunPod(pod *api.Pod, volumeMap map[string]volume.Volume) error {
+	glog.V(4).Infof("Rkt starts to run pod: name %q.", pod.Name)
+
+	name, needReload, err := r.preparePod(pod, volumeMap)
+	if err != nil {
+		return err
+	}
+	if needReload {
+		// TODO(yifan): More graceful stop. Replace with StopUnit and wait for a timeout.
+		r.systemd.KillUnit(name, int32(syscall.SIGKILL))
+		if err := r.systemd.Reload(); err != nil {
+			return err
+		}
+	}
+
+	// TODO(yifan): This is the old version of go-systemd. Should update when libcontainer updates
+	// its version of go-systemd.
+	_, err = r.systemd.StartUnit(name, "replace")
+	if err != nil {
+		return err
+	}
+	return nil
+}