cmd/dlv: add flag to make headless server accept multiple clients

cmd/dlv/main.go

@@ -32,6 +32,8 @@ var (
 	Log bool
 	// Headless is whether to run without terminal.
 	Headless bool
+	// Allows multiple clients to connect to the same server
+	AcceptMulti bool
 	// Addr is the debugging server listen address.
 	Addr string
 	// InitFile is the path to initialization file.
@@ -74,6 +76,7 @@ func init() {
 	rootCommand.PersistentFlags().StringVarP(&Addr, "listen", "l", "localhost:0", "Debugging server listen address.")
 	rootCommand.PersistentFlags().BoolVarP(&Log, "log", "", false, "Enable debugging server logging.")
 	rootCommand.PersistentFlags().BoolVarP(&Headless, "headless", "", false, "Run debug server only, in headless mode.")
+	rootCommand.PersistentFlags().BoolVarP(&AcceptMulti, "accept-multiclient", "", false, "Allows a headless server to accept multiple client connection. Note that the server API is not reentrant and clients will have to coordinate")
 	rootCommand.PersistentFlags().StringVar(&InitFile, "init", "", "Init file, executed by the terminal client.")
 	rootCommand.PersistentFlags().StringVar(&BuildFlags, "build-flags", buildFlagsDefault, "Build flags, to be passed to the compiler.")
 
@@ -351,6 +354,7 @@ func execute(attachPid int, processArgs []string, conf *config.Config) int {
 		Listener:    listener,
 		ProcessArgs: processArgs,
 		AttachPid:   attachPid,
+		AcceptMulti: AcceptMulti,
 	}, Log)
 	if err := server.Run(); err != nil {
 		fmt.Fprintln(os.Stderr, err)

service/config.go

@@ -16,4 +16,7 @@ type Config struct {
 	// AttachPid is the PID of an existing process to which the debugger should
 	// attach.
 	AttachPid int
+	// AcceptMulti configures the server to accept multiple connection
+	// Note that the server API is not reentrant and clients will have to coordinate
+	AcceptMulti bool
 }

service/rpc/server.go

@@ -23,6 +23,8 @@ type RPCServer struct {
 	config *service.Config
 	// listener is used to serve HTTP.
 	listener net.Listener
+	// stopChan is used to stop the listener goroutine
+	stopChan chan struct{}
 	// debugger is a debugger service.
 	debugger *debugger.Debugger
 }
@@ -38,13 +40,22 @@ func NewServer(config *service.Config, logEnabled bool) *ServerImpl {
 		&RPCServer{
 			config:   config,
 			listener: config.Listener,
+			stopChan: make(chan struct{}),
 		},
 	}
 }
 
 // Stop detaches from the debugger and waits for it to stop.
 func (s *ServerImpl) Stop(kill bool) error {
-	return s.s.debugger.Detach(kill)
+	if s.s.config.AcceptMulti {
+		close(s.s.stopChan)
+		s.s.listener.Close()
+	}
+	err := s.s.debugger.Detach(kill)
+	if err != nil {
+		return err
+	}
+	return nil
 }
 
 // Run starts a debugger and exposes it with an HTTP server. The debugger
@@ -60,16 +71,27 @@ func (s *ServerImpl) Run() error {
 		return err
 	}
 
+	rpcs := grpc.NewServer()
+	rpcs.Register(s.s)
+
 	go func() {
-		c, err := s.s.listener.Accept()
-		if err != nil {
-			panic(err)
-		}
 		defer s.s.listener.Close()
-
-		rpcs := grpc.NewServer()
-		rpcs.Register(s.s)
-		rpcs.ServeCodec(jsonrpc.NewServerCodec(c))
+		for {
+			c, err := s.s.listener.Accept()
+			if err != nil {
+				select {
+				case <-s.s.stopChan:
+					// We were supposed to exit, do nothing and return
+					return
+				default:
+					panic(err)
+				}
+			}
+			go rpcs.ServeCodec(jsonrpc.NewServerCodec(c))
+			if !s.s.config.AcceptMulti {
+				break
+			}
+		}
 	}()
 	return nil
 }