rpc rewrite: control RPCs using gRPC + separate RPC for data transfer

transport/ssh: update go-netssh to new version
    => supports CloseWrite and Deadlines
    => build: require Go 1.11 (netssh requires it)

rpc/dataconn/dataconn_server.go

@@ -0,0 +1,178 @@
+package dataconn
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+
+	"github.com/golang/protobuf/proto"
+	"github.com/zrepl/zrepl/logger"
+	"github.com/zrepl/zrepl/replication/pdu"
+	"github.com/zrepl/zrepl/rpc/dataconn/stream"
+	"github.com/zrepl/zrepl/transport"
+	"github.com/zrepl/zrepl/zfs"
+)
+
+// WireInterceptor has a chance to exchange the context and connection on each client connection.
+type WireInterceptor func(ctx context.Context, rawConn *transport.AuthConn) (context.Context, *transport.AuthConn)
+
+// Handler implements the functionality that is exposed by Server to the Client.
+type Handler interface {
+	// Send handles a SendRequest.
+	// The returned io.ReadCloser is allowed to be nil, for example if the requested Send is a dry-run.
+	Send(ctx context.Context, r *pdu.SendReq) (*pdu.SendRes, zfs.StreamCopier, error)
+	// Receive handles a ReceiveRequest.
+	// It is guaranteed that Server calls Receive with a stream that holds the IdleConnTimeout
+	// configured in ServerConfig.Shared.IdleConnTimeout.
+	Receive(ctx context.Context, r *pdu.ReceiveReq, receive zfs.StreamCopier) (*pdu.ReceiveRes, error)
+}
+
+type Logger = logger.Logger
+
+type Server struct {
+	h   Handler
+	wi  WireInterceptor
+	log Logger
+}
+
+func NewServer(wi WireInterceptor, logger Logger, handler Handler) *Server {
+	return &Server{
+		h:   handler,
+		wi:  wi,
+		log: logger,
+	}
+}
+
+// Serve consumes the listener, closes it as soon as ctx is closed.
+// No accept errors are returned: they are logged to the Logger passed
+// to the constructor.
+func (s *Server) Serve(ctx context.Context, l transport.AuthenticatedListener) {
+
+	go func() {
+		<-ctx.Done()
+		s.log.Debug("context done")
+		if err := l.Close(); err != nil {
+			s.log.WithError(err).Error("cannot close listener")
+		}
+	}()
+	conns := make(chan *transport.AuthConn)
+	go func() {
+		for {
+			conn, err := l.Accept(ctx)
+			if err != nil {
+				if ctx.Done() != nil {
+					s.log.Debug("stop accepting after context is done")
+					return
+				}
+				s.log.WithError(err).Error("accept error")
+				continue
+			}
+			conns <- conn
+		}
+	}()
+	for conn := range conns {
+		go s.serveConn(conn)
+	}
+}
+
+func (s *Server) serveConn(nc *transport.AuthConn) {
+	s.log.Debug("serveConn begin")
+	defer s.log.Debug("serveConn done")
+
+	ctx := context.Background()
+	if s.wi != nil {
+		ctx, nc = s.wi(ctx, nc)
+	}
+
+	c := stream.Wrap(nc, HeartbeatInterval, HeartbeatPeerTimeout)
+	defer func() {
+		s.log.Debug("close client connection")
+		if err := c.Close(); err != nil {
+			s.log.WithError(err).Error("cannot close client connection")
+		}
+	}()
+
+	header, err := c.ReadStreamedMessage(ctx, RequestHeaderMaxSize, ReqHeader)
+	if err != nil {
+		s.log.WithError(err).Error("error reading structured part")
+		return
+	}
+	endpoint := string(header)
+
+	reqStructured, err := c.ReadStreamedMessage(ctx, RequestStructuredMaxSize, ReqStructured)
+	if err != nil {
+		s.log.WithError(err).Error("error reading structured part")
+		return
+	}
+
+	s.log.WithField("endpoint", endpoint).Debug("calling handler")
+
+	var res proto.Message
+	var sendStream zfs.StreamCopier
+	var handlerErr error
+	switch endpoint {
+	case EndpointSend:
+		var req pdu.SendReq
+		if err := proto.Unmarshal(reqStructured, &req); err != nil {
+			s.log.WithError(err).Error("cannot unmarshal send request")
+			return
+		}
+		res, sendStream, handlerErr = s.h.Send(ctx, &req) // SHADOWING
+	case EndpointRecv:
+		var req pdu.ReceiveReq
+		if err := proto.Unmarshal(reqStructured, &req); err != nil {
+			s.log.WithError(err).Error("cannot unmarshal receive request")
+			return
+		}
+		res, handlerErr = s.h.Receive(ctx, &req, &streamCopier{streamConn: c, closeStreamOnClose: false}) // SHADOWING
+	default:
+		s.log.WithField("endpoint", endpoint).Error("unknown endpoint")
+		handlerErr = fmt.Errorf("requested endpoint does not exist")
+		return
+	}
+
+	s.log.WithField("endpoint", endpoint).WithField("errType", fmt.Sprintf("%T", handlerErr)).Debug("handler returned")
+
+	// prepare protobuf now to return the protobuf error in the header
+	// if marshaling fails. We consider failed marshaling a handler error
+	var protobuf *bytes.Buffer
+	if handlerErr == nil {
+		protobufBytes, err := proto.Marshal(res)
+		if err != nil {
+			s.log.WithError(err).Error("cannot marshal handler protobuf")
+			handlerErr = err
+		}
+		protobuf = bytes.NewBuffer(protobufBytes) // SHADOWING
+	}
+
+	var resHeaderBuf bytes.Buffer
+	if handlerErr == nil {
+		resHeaderBuf.WriteString(responseHeaderHandlerOk)
+	} else {
+		resHeaderBuf.WriteString(responseHeaderHandlerErrorPrefix)
+		resHeaderBuf.WriteString(handlerErr.Error())
+	}
+	if err := c.WriteStreamedMessage(ctx, &resHeaderBuf, ResHeader); err != nil {
+		s.log.WithError(err).Error("cannot write response header")
+		return
+	}
+
+	if handlerErr != nil {
+		s.log.Debug("early exit after handler error")
+		return
+	}
+
+	if err := c.WriteStreamedMessage(ctx, protobuf, ResStructured); err != nil {
+		s.log.WithError(err).Error("cannot write structured part of response")
+		return
+	}
+
+	if sendStream != nil {
+		err := c.SendStream(ctx, sendStream, ZFSStream)
+		if err != nil {
+			s.log.WithError(err).Error("cannot write send stream")
+		}
+	}
+
+	return
+}