Add leases api

Signed-off-by: Derek McGowan <derek@mcgstyle.net>

lease.go

@@ -0,0 +1,71 @@
+package containerd
+
+import (
+	"context"
+	"time"
+
+	leasesapi "github.com/containerd/containerd/api/services/leases/v1"
+)
+
+// Lease is used to hold a reference to active resources which have not been
+// referenced by a root resource. This is useful for preventing garbage
+// collection of resources while they are actively being updated.
+type Lease struct {
+	id        string
+	createdAt time.Time
+
+	client *Client
+}
+
+// CreateLease creates a new lease
+func (c *Client) CreateLease(ctx context.Context) (Lease, error) {
+	lapi := leasesapi.NewLeasesClient(c.conn)
+	resp, err := lapi.Create(ctx, &leasesapi.CreateRequest{})
+	if err != nil {
+		return Lease{}, err
+	}
+
+	return Lease{
+		id:     resp.Lease.ID,
+		client: c,
+	}, nil
+}
+
+// ListLeases lists active leases
+func (c *Client) ListLeases(ctx context.Context) ([]Lease, error) {
+	lapi := leasesapi.NewLeasesClient(c.conn)
+	resp, err := lapi.List(ctx, &leasesapi.ListRequest{})
+	if err != nil {
+		return nil, err
+	}
+	leases := make([]Lease, len(resp.Leases))
+	for i := range resp.Leases {
+		leases[i] = Lease{
+			id:        resp.Leases[i].ID,
+			createdAt: resp.Leases[i].CreatedAt,
+			client:    c,
+		}
+	}
+
+	return leases, nil
+}
+
+// ID returns the lease ID
+func (l Lease) ID() string {
+	return l.id
+}
+
+// CreatedAt returns the time at which the lease was created
+func (l Lease) CreatedAt() time.Time {
+	return l.createdAt
+}
+
+// Delete deletes the lease, removing the reference to all resources created
+// during the lease.
+func (l Lease) Delete(ctx context.Context) error {
+	lapi := leasesapi.NewLeasesClient(l.client.conn)
+	_, err := lapi.Delete(ctx, &leasesapi.DeleteRequest{
+		ID: l.id,
+	})
+	return err
+}