Start work on execution server implementation

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

services/execution/service.go

@@ -0,0 +1,67 @@
+package execution
+
+import (
+	"context"
+
+	"github.com/docker/containerd"
+	api "github.com/docker/containerd/api/execution"
+	"github.com/docker/containerd/executors"
+)
+
+type Opts struct {
+	Root    string
+	Runtime string
+}
+
+func New(o Opts) (*Service, error) {
+	executor, err := executors.Get(o.Runtime)(o.Root)
+	if err != nil {
+		return nil, err
+	}
+	return &Service{
+		o:        o,
+		executor: executor,
+	}, nil
+}
+
+type Service struct {
+	o        Opts
+	executor containerd.Executor
+}
+
+func (s *Service) Create(ctx context.Context, r *api.CreateContainerRequest) (*api.CreateContainerResponse, error) {
+	// TODO: write io and bundle path to dir
+	container, err := s.executor.Create(r.ID, r.BundlePath, &IO{})
+	if err != nil {
+		return nil, err
+	}
+
+	s.supervisor.Add(container.Process())
+
+	return &api.CreateContainerResponse{
+		Container: toGRPCContainer(container),
+	}, nil
+}
+
+func (s *Service) Delete(ctx context.Context, r *api.DeleteContainerRequest) (*api.Empty, error) {
+	if err := s.executor.Delete(r.ID); err != nil {
+		return nil, err
+	}
+	return nil, nil
+}
+
+func (s *Service) List(ctx context.Context, r *api.ListContainerRequest) (*api.ListContainerResponse, error) {
+	containers, err := s.executor.List()
+	if err != nil {
+		return nil, err
+	}
+	for _, c := range containers {
+		r.Containers = append(r.Containers, toGRPCContainer(c))
+	}
+	return r, nil
+}
+
+var (
+	_ = (api.ExecutionServiceServer)(&Service{})
+	_ = (api.ContainerServiceServer)(&Service{})
+)