Add no_shim config for not running with a shim

This reuses the exiting shim code and services to let containerd run as
the reaper for all container processes without the use of a shim.

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

linux/shim/client.go

@@ -0,0 +1,105 @@
+package shim
+
+import (
+	"path/filepath"
+	"syscall"
+
+	shimapi "github.com/docker/containerd/api/services/shim"
+	"github.com/docker/containerd/api/types/container"
+	google_protobuf "github.com/golang/protobuf/ptypes/empty"
+	"golang.org/x/net/context"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
+)
+
+func Client(path string) shimapi.ShimClient {
+	return &client{
+		s: New(path),
+	}
+}
+
+type client struct {
+	s *Service
+}
+
+func (c *client) Create(ctx context.Context, in *shimapi.CreateRequest, opts ...grpc.CallOption) (*shimapi.CreateResponse, error) {
+	return c.s.Create(ctx, in)
+}
+
+func (c *client) Start(ctx context.Context, in *shimapi.StartRequest, opts ...grpc.CallOption) (*google_protobuf.Empty, error) {
+	return c.s.Start(ctx, in)
+}
+
+func (c *client) Delete(ctx context.Context, in *shimapi.DeleteRequest, opts ...grpc.CallOption) (*shimapi.DeleteResponse, error) {
+	return c.s.Delete(ctx, in)
+}
+
+func (c *client) Exec(ctx context.Context, in *shimapi.ExecRequest, opts ...grpc.CallOption) (*shimapi.ExecResponse, error) {
+	return c.s.Exec(ctx, in)
+}
+
+func (c *client) Pty(ctx context.Context, in *shimapi.PtyRequest, opts ...grpc.CallOption) (*google_protobuf.Empty, error) {
+	return c.s.Pty(ctx, in)
+}
+
+func (c *client) Events(ctx context.Context, in *shimapi.EventsRequest, opts ...grpc.CallOption) (shimapi.Shim_EventsClient, error) {
+	return &events{
+		c:   c.s.events,
+		ctx: ctx,
+	}, nil
+}
+
+func (c *client) State(ctx context.Context, in *shimapi.StateRequest, opts ...grpc.CallOption) (*shimapi.StateResponse, error) {
+	return c.s.State(ctx, in)
+}
+
+func (c *client) Pause(ctx context.Context, in *shimapi.PauseRequest, opts ...grpc.CallOption) (*google_protobuf.Empty, error) {
+	return c.s.Pause(ctx, in)
+}
+
+func (c *client) Resume(ctx context.Context, in *shimapi.ResumeRequest, opts ...grpc.CallOption) (*google_protobuf.Empty, error) {
+	return c.s.Resume(ctx, in)
+}
+
+func (c *client) Exit(ctx context.Context, in *shimapi.ExitRequest, opts ...grpc.CallOption) (*google_protobuf.Empty, error) {
+	// don't exit the calling process for the client
+	// but make sure we unmount the containers rootfs for this client
+	if err := syscall.Unmount(filepath.Join(c.s.path, "rootfs"), 0); err != nil {
+		return nil, err
+	}
+	return empty, nil
+}
+
+type events struct {
+	c   chan *container.Event
+	ctx context.Context
+}
+
+func (e *events) Recv() (*container.Event, error) {
+	ev := <-e.c
+	return ev, nil
+}
+
+func (e *events) Header() (metadata.MD, error) {
+	return nil, nil
+}
+
+func (e *events) Trailer() metadata.MD {
+	return nil
+}
+
+func (e *events) CloseSend() error {
+	return nil
+}
+
+func (e *events) Context() context.Context {
+	return e.ctx
+}
+
+func (e *events) SendMsg(m interface{}) error {
+	return nil
+}
+
+func (e *events) RecvMsg(m interface{}) error {
+	return nil
+}