Get working console websocket implementation and fix race condition

server/environment_docker.go

@@ -228,7 +228,7 @@ func (d *DockerEnvironment) FollowConsoleOutput() error {
 
 		s := bufio.NewScanner(r)
 		for s.Scan() {
-			fmt.Println(s.Text())
+			d.Server.Emit(ConsoleOutputEvent, s.Text())
 		}
 
 		if err := s.Err(); err != nil {

server/events.go

@@ -0,0 +1,46 @@
+package server
+
+type EventListeners map[string][]EventListenerFunction
+
+type EventListenerFunction *func(string)
+
+// Defines all of the possible output events for a server.
+const (
+	ConsoleOutputEvent = "console"
+)
+
+// Adds an event listener for the server instance.
+func (s *Server) AddListener(event string, f EventListenerFunction) {
+	if s.listeners == nil {
+		s.listeners = make(map[string][]EventListenerFunction)
+	}
+
+	if _, ok := s.listeners[event]; ok {
+		s.listeners[event] = append(s.listeners[event], f)
+	} else {
+		s.listeners[event] = []EventListenerFunction{f}
+	}
+}
+
+// Removes the event listener for the server instance.
+func (s *Server) RemoveListener(event string, f EventListenerFunction) {
+	if _, ok := s.listeners[event]; ok {
+		for i := range s.listeners[event] {
+			if s.listeners[event][i] == f {
+				s.listeners[event] = append(s.listeners[event][:i], s.listeners[event][i+1:]...)
+				break
+			}
+		}
+	}
+}
+
+// Emits an event to all of the active listeners for a server.
+func (s *Server) Emit(event string, data string) {
+	if _, ok := s.listeners[event]; ok {
+		for _, handler := range s.listeners[event] {
+			go func (f EventListenerFunction, d string) {
+				(*f)(d)
+			}(handler, data)
+		}
+	}
+}

server/server.go

@@ -1,7 +1,6 @@
 package server
 
 import (
-	"github.com/olebedev/emitter"
 	"github.com/patrickmn/go-cache"
 	"github.com/pkg/errors"
 	"github.com/pterodactyl/wings/config"
@@ -62,7 +61,8 @@ type Server struct {
 	// certain long operations return faster. For example, FS disk space usage.
 	Cache *cache.Cache `json:"-"`
 
-	Emitter *emitter.Emitter `json:"-"`
+	// All of the registered event listeners for this server instance.
+	listeners EventListeners
 }
 
 // The build settings for a given server that impact docker container creation and
@@ -206,7 +206,6 @@ func FromConfiguration(data []byte, cfg *config.SystemConfiguration) (*Server, e
 		return nil, err
 	}
 
-	s.Emitter = &emitter.Emitter{}
 	s.Environment = env
 	s.Cache = cache.New(time.Minute * 10, time.Minute * 15)
 	s.Filesystem = &Filesystem{

websocket.go

@@ -2,7 +2,6 @@ package main
 
 import (
 	"errors"
-	"fmt"
 	"github.com/gorilla/websocket"
 	"github.com/julienschmidt/httprouter"
 	"github.com/pterodactyl/wings/server"
@@ -10,6 +9,7 @@ import (
 	"net/http"
 	"os"
 	"strings"
+	"sync"
 )
 
 type WebsocketMessage struct {
@@ -25,11 +25,17 @@ type WebsocketMessage struct {
 	// should either omit the field or pass an empty value as it is ignored.
 	Args []string `json:"args,omitempty"`
 
-	server *server.Server
-
 	inbound bool
 }
 
+type WebsocketHandler struct {
+	Server     *server.Server
+	Mutex      sync.Mutex
+	Connection *websocket.Conn
+}
+
+// Handle a request for a specific server websocket. This will handle inbound requests as well
+// as ensure that any console output is also passed down the wire on the socket.
 func (rt *Router) routeWebsocket(w http.ResponseWriter, r *http.Request, ps httprouter.Params) {
 	c, err := rt.upgrader.Upgrade(w, r, nil)
 	if err != nil {
@@ -39,12 +45,27 @@ func (rt *Router) routeWebsocket(w http.ResponseWriter, r *http.Request, ps http
 	defer c.Close()
 
 	s := rt.Servers.Get(ps.ByName("server"))
+	handler := WebsocketHandler{
+		Server: s,
+		Mutex:  sync.Mutex{},
+		Connection: c,
+	}
+
+	handleOutput := func(data string) {
+		handler.SendJson(&WebsocketMessage{
+			Event: "console output",
+			Args:  []string{data},
+		})
+	}
+
+	s.AddListener(server.ConsoleOutputEvent, &handleOutput)
+	defer s.RemoveListener(server.ConsoleOutputEvent, &handleOutput)
 
 	for {
-		j := WebsocketMessage{server: s, inbound: true}
+		j := WebsocketMessage{inbound: true}
 
 		if _, _, err := c.ReadMessage(); err != nil {
-			if !websocket.IsCloseError(err, websocket.CloseNormalClosure, websocket.CloseGoingAway, websocket.CloseServiceRestart) {
+			if !websocket.IsCloseError(err, websocket.CloseNormalClosure, websocket.CloseGoingAway, websocket.CloseNoStatusReceived, websocket.CloseServiceRestart) {
 				zap.S().Errorw("error handling websocket message", zap.Error(err))
 			}
 			break
@@ -57,34 +78,42 @@ func (rt *Router) routeWebsocket(w http.ResponseWriter, r *http.Request, ps http
 			continue
 		}
 
-		fmt.Printf("%s received: %s = %s\n", s.Uuid, j.Event, strings.Join(j.Args, " "))
-		if err := j.HandleInbound(c); err != nil {
+		if err := handler.HandleInbound(j); err != nil {
 			zap.S().Warnw("error handling inbound websocket request", zap.Error(err))
 			break
 		}
 	}
-
-	zap.S().Debugw("disconnected from instance", zap.String("ip", c.RemoteAddr().String()))
 }
 
-func (wsm *WebsocketMessage) HandleInbound(c *websocket.Conn) error {
-	if !wsm.inbound {
+// Perform a blocking send operation on the websocket since we want to avoid any
+// concurrent writes to the connection, which would cause a runtime panic and cause
+// the program to crash out.
+func (wsh *WebsocketHandler) SendJson(v interface{}) error {
+	wsh.Mutex.Lock()
+	defer wsh.Mutex.Unlock()
+
+	return wsh.Connection.WriteJSON(v)
+}
+
+// Handle the inbound socket request and route it to the proper server action.
+func (wsh *WebsocketHandler) HandleInbound(m WebsocketMessage) error {
+	if !m.inbound {
 		return errors.New("cannot handle websocket message, not an inbound connection")
 	}
 
-	switch wsm.Event {
+	switch m.Event {
 	case "set state":
 		{
 			var err error
-			switch strings.Join(wsm.Args, "") {
+			switch strings.Join(m.Args, "") {
 			case "start":
-				err = wsm.server.Environment.Start()
+				err = wsh.Server.Environment.Start()
 				break
 			case "stop":
-				err = wsm.server.Environment.Stop()
+				err = wsh.Server.Environment.Stop()
 				break
 			case "restart":
-				err = wsm.server.Environment.Terminate(os.Kill)
+				err = wsh.Server.Environment.Terminate(os.Kill)
 				break
 			}
 
@@ -94,13 +123,13 @@ func (wsm *WebsocketMessage) HandleInbound(c *websocket.Conn) error {
 		}
 	case "send logs":
 		{
-			logs, err := wsm.server.Environment.Readlog(1024 * 5)
+			logs, err := wsh.Server.Environment.Readlog(1024 * 5)
 			if err != nil {
 				return err
 			}
 
 			for _, line := range logs {
-				c.WriteJSON(&WebsocketMessage{
+				wsh.SendJson(&WebsocketMessage{
 					Event: "console output",
 					Args:  []string{line},
 				})
@@ -110,7 +139,7 @@ func (wsm *WebsocketMessage) HandleInbound(c *websocket.Conn) error {
 		}
 	case "send command":
 		{
-			return wsm.server.Environment.SendCommand(strings.Join(wsm.Args, ""))
+			return wsh.Server.Environment.SendCommand(strings.Join(m.Args, ""))
 		}
 	}