Add containers streaming API

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

services/containers/local.go

@@ -18,6 +18,7 @@ package containers
 
 import (
 	"context"
+	"io"
 
 	"github.com/boltdb/bolt"
 	eventstypes "github.com/containerd/containerd/api/events"
@@ -31,6 +32,7 @@ import (
 	ptypes "github.com/gogo/protobuf/types"
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
+	grpcm "google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/status"
 )
 
@@ -78,18 +80,30 @@ func (l *local) Get(ctx context.Context, req *api.GetContainerRequest, _ ...grpc
 
 func (l *local) List(ctx context.Context, req *api.ListContainersRequest, _ ...grpc.CallOption) (*api.ListContainersResponse, error) {
 	var resp api.ListContainersResponse
-
 	return &resp, errdefs.ToGRPC(l.withStoreView(ctx, func(ctx context.Context, store containers.Store) error {
 		containers, err := store.List(ctx, req.Filters...)
 		if err != nil {
 			return err
 		}
-
 		resp.Containers = containersToProto(containers)
 		return nil
 	}))
 }
 
+func (l *local) ListStream(ctx context.Context, req *api.ListContainersRequest, _ ...grpc.CallOption) (api.Containers_ListStreamClient, error) {
+	stream := &localStream{
+		ctx: ctx,
+	}
+	return stream, errdefs.ToGRPC(l.withStoreView(ctx, func(ctx context.Context, store containers.Store) error {
+		containers, err := store.List(ctx, req.Filters...)
+		if err != nil {
+			return err
+		}
+		stream.containers = containersToProto(containers)
+		return nil
+	}))
+}
+
 func (l *local) Create(ctx context.Context, req *api.CreateContainerRequest, _ ...grpc.CallOption) (*api.CreateContainerResponse, error) {
 	var resp api.CreateContainerResponse
 
@@ -188,3 +202,44 @@ func (l *local) withStoreView(ctx context.Context, fn func(ctx context.Context,
 func (l *local) withStoreUpdate(ctx context.Context, fn func(ctx context.Context, store containers.Store) error) error {
 	return l.db.Update(l.withStore(ctx, fn))
 }
+
+type localStream struct {
+	ctx        context.Context
+	containers []api.Container
+	i          int
+}
+
+func (s *localStream) Recv() (*api.ListContainerMessage, error) {
+	if s.i >= len(s.containers) {
+		return nil, io.EOF
+	}
+	c := s.containers[s.i]
+	s.i++
+	return &api.ListContainerMessage{
+		Container: &c,
+	}, nil
+}
+
+func (s *localStream) Context() context.Context {
+	return s.ctx
+}
+
+func (s *localStream) CloseSend() error {
+	return nil
+}
+
+func (s *localStream) Header() (grpcm.MD, error) {
+	return nil, nil
+}
+
+func (s *localStream) Trailer() grpcm.MD {
+	return nil
+}
+
+func (s *localStream) SendMsg(m interface{}) error {
+	return nil
+}
+
+func (s *localStream) RecvMsg(m interface{}) error {
+	return nil
+}