Add container Exec support.

Signed-off-by: Lantao Liu <lantaol@google.com>

pkg/server/container_exec.go

@@ -17,14 +17,30 @@ limitations under the License.
 package server
 
 import (
-	"errors"
+	"fmt"
 
+	"github.com/golang/glog"
 	"golang.org/x/net/context"
-
 	"k8s.io/kubernetes/pkg/kubelet/apis/cri/v1alpha1/runtime"
 )
 
 // Exec prepares a streaming endpoint to execute a command in the container, and returns the address.
-func (c *criContainerdService) Exec(ctx context.Context, r *runtime.ExecRequest) (*runtime.ExecResponse, error) {
-	return nil, errors.New("not implemented")
+func (c *criContainerdService) Exec(ctx context.Context, r *runtime.ExecRequest) (retRes *runtime.ExecResponse, retErr error) {
+	glog.V(2).Infof("Exec for %q with command %+v, tty %v and stdin %v",
+		r.GetContainerId(), r.GetCmd(), r.GetTty(), r.GetStdin())
+	defer func() {
+		if retErr == nil {
+			glog.V(2).Infof("Exec for %q returns URL %q", r.GetContainerId(), retRes.Url)
+		}
+	}()
+
+	cntr, err := c.containerStore.Get(r.GetContainerId())
+	if err != nil {
+		return nil, fmt.Errorf("failed to find container in store: %v", err)
+	}
+	state := cntr.Status.Get().State()
+	if state != runtime.ContainerState_CONTAINER_RUNNING {
+		return nil, fmt.Errorf("container is in %s state", criContainerStateToString(state))
+	}
+	return c.streamServer.GetExec(r)
 }