Add checkpoint and restore to client package

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

container_linux.go

@@ -0,0 +1,127 @@
+package containerd
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+
+	"github.com/containerd/containerd/api/services/containers"
+	"github.com/containerd/containerd/api/services/execution"
+	"github.com/containerd/containerd/api/types/descriptor"
+	"github.com/containerd/containerd/content"
+	"github.com/containerd/containerd/images"
+	"github.com/containerd/containerd/snapshot"
+	protobuf "github.com/gogo/protobuf/types"
+	digest "github.com/opencontainers/go-digest"
+	"github.com/opencontainers/image-spec/identity"
+	"github.com/opencontainers/image-spec/specs-go/v1"
+	specs "github.com/opencontainers/runtime-spec/specs-go"
+)
+
+func WithSpec(spec *specs.Spec) NewContainerOpts {
+	return func(ctx context.Context, client *Client, c *containers.Container) error {
+		data, err := json.Marshal(spec)
+		if err != nil {
+			return err
+		}
+		c.Spec = &protobuf.Any{
+			TypeUrl: spec.Version,
+			Value:   data,
+		}
+		return nil
+	}
+}
+
+func WithCheckpoint(desc v1.Descriptor, rootfsID string) NewContainerOpts {
+	// set image and rw, and spec
+	return func(ctx context.Context, client *Client, c *containers.Container) error {
+		id := desc.Digest
+		store := client.ContentStore()
+		index, err := decodeIndex(ctx, store, id)
+		if err != nil {
+			return err
+		}
+		var rw *v1.Descriptor
+		for _, m := range index.Manifests {
+			switch m.MediaType {
+			case v1.MediaTypeImageLayer:
+				fk := m
+				rw = &fk
+			case images.MediaTypeDockerSchema2Manifest:
+				config, err := images.Config(ctx, store, m)
+				if err != nil {
+					return err
+				}
+				diffIDs, err := images.RootFS(ctx, store, config)
+				if err != nil {
+					return err
+				}
+				if _, err := client.SnapshotService().Prepare(ctx, rootfsID, identity.ChainID(diffIDs).String()); err != nil {
+					if !snapshot.IsExist(err) {
+						return err
+					}
+				}
+				c.Image = index.Annotations["image.name"]
+			case images.MediaTypeContainerd1CheckpointConfig:
+				r, err := store.Reader(ctx, m.Digest)
+				if err != nil {
+					return err
+				}
+				data, err := ioutil.ReadAll(r)
+				r.Close()
+				if err != nil {
+					return err
+				}
+				c.Spec = &protobuf.Any{
+					TypeUrl: specs.Version,
+					Value:   data,
+				}
+			}
+		}
+		if rw != nil {
+			// apply the rw snapshot to the new rw layer
+			mounts, err := client.SnapshotService().Mounts(ctx, rootfsID)
+			if err != nil {
+				return err
+			}
+			if _, err := client.DiffService().Apply(ctx, *rw, mounts); err != nil {
+				return err
+			}
+		}
+		c.RootFS = rootfsID
+		return nil
+	}
+}
+
+func WithTaskCheckpoint(desc v1.Descriptor) NewTaskOpts {
+	return func(ctx context.Context, c *Client, r *execution.CreateRequest) error {
+		id := desc.Digest
+		index, err := decodeIndex(ctx, c.ContentStore(), id)
+		if err != nil {
+			return err
+		}
+		for _, m := range index.Manifests {
+			if m.MediaType == images.MediaTypeContainerd1Checkpoint {
+				r.Checkpoint = &descriptor.Descriptor{
+					MediaType: m.MediaType,
+					Size_:     m.Size,
+					Digest:    m.Digest,
+				}
+				return nil
+			}
+		}
+		return fmt.Errorf("checkpoint not found in index %s", id)
+	}
+}
+
+func decodeIndex(ctx context.Context, store content.Store, id digest.Digest) (*v1.Index, error) {
+	var index v1.Index
+	r, err := store.Reader(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	err = json.NewDecoder(r).Decode(&index)
+	r.Close()
+	return &index, err
+}