Add streaming service

Adds a service capable of streaming Any objects bi-directionally.
This can be used by services to send data, received data, or to
initiate requests from server to client.

Signed-off-by: Derek McGowan <derek@mcg.dev>

services/services.go

@@ -37,4 +37,6 @@ const (
 	SandboxStoreService = "sandbox-store-service"
 	// SandboxControllerService is the id of Sandbox's controller service
 	SandboxControllerService = "sandbox-controller-service"
+	// Streaming service is the id of the streaming service
+	StreamingService = "streaming-service"
 )

services/streaming/service.go

@@ -0,0 +1,123 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package streaming
+
+import (
+	"io"
+
+	api "github.com/containerd/containerd/api/services/streaming/v1"
+	"github.com/containerd/containerd/errdefs"
+	"github.com/containerd/containerd/log"
+	"github.com/containerd/containerd/pkg/streaming"
+	"github.com/containerd/containerd/plugin"
+	"github.com/containerd/containerd/protobuf"
+	ptypes "github.com/containerd/containerd/protobuf/types"
+	"github.com/containerd/typeurl"
+	"google.golang.org/grpc"
+)
+
+func init() {
+	plugin.Register(&plugin.Registration{
+		Type: plugin.GRPCPlugin,
+		ID:   "streaming",
+		Requires: []plugin.Type{
+			plugin.StreamingPlugin,
+		},
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
+			i, err := ic.GetByID(plugin.StreamingPlugin, "manager")
+			if err != nil {
+				return nil, err
+			}
+			return &service{manager: i.(streaming.StreamManager)}, nil
+		},
+	})
+}
+
+type service struct {
+	manager streaming.StreamManager
+	api.UnimplementedStreamingServer
+}
+
+func (s *service) Register(server *grpc.Server) error {
+	api.RegisterStreamingServer(server, s)
+	return nil
+}
+
+func (s *service) Stream(srv api.Streaming_StreamServer) error {
+	// TODO: Timeout waiting
+	a, err := srv.Recv()
+	if err != nil {
+		return err
+	}
+	var i api.StreamInit
+	if err := typeurl.UnmarshalTo(a, &i); err != nil {
+		return err
+	}
+
+	// TODO: Save this response to avoid marshaling everytime
+	response, err := typeurl.MarshalAny(&ptypes.Empty{})
+	if err != nil {
+		return err
+	}
+	if err := srv.Send(protobuf.FromAny(response)); err != nil {
+		return err
+	}
+
+	cc := make(chan struct{})
+	ss := &serviceStream{
+		s:  srv,
+		cc: cc,
+	}
+	log.G(srv.Context()).WithField("stream", i.ID).Debug("registering stream")
+	if err := s.manager.Register(srv.Context(), i.ID, ss); err != nil {
+		return err
+	}
+
+	select {
+	case <-srv.Context().Done():
+		// TODO: Should return error if not cancelled?
+	case <-cc:
+	}
+
+	return nil
+}
+
+type serviceStream struct {
+	s  api.Streaming_StreamServer
+	cc chan struct{}
+}
+
+func (ss *serviceStream) Send(a typeurl.Any) error {
+	return errdefs.FromGRPC(ss.s.Send(protobuf.FromAny(a)))
+}
+
+func (ss *serviceStream) Recv() (a typeurl.Any, err error) {
+	a, err = ss.s.Recv()
+	if err != io.EOF {
+		err = errdefs.FromGRPC(err)
+	}
+	return
+}
+
+func (ss *serviceStream) Close() error {
+	select {
+	case <-ss.cc:
+	default:
+		close(ss.cc)
+	}
+	return nil
+}