Improve event emitter/subscription abilities

server/console.go

@@ -1,6 +1,10 @@
 package server
 
-import "io"
+import (
+	"fmt"
+	"github.com/mitchellh/colorstring"
+	"io"
+)
 
 type Console struct {
 	Server      *Server
@@ -19,3 +23,12 @@ func (c Console) Write(b []byte) (int, error) {
 
 	return len(b), nil
 }
+
+// Sends output to the server console formatted to appear correctly as being sent
+// from Wings.
+func (s *Server) PublishConsoleOutputFromDaemon(data string) {
+	s.Events().Publish(
+		ConsoleOutputEvent,
+		colorstring.Color(fmt.Sprintf("[yellow][bold][Pterodactyl Daemon]:[default] %s", data)),
+	)
+}

server/crash.go

@@ -37,7 +37,7 @@ func (s *Server) handleServerCrash() error {
 		if !s.CrashDetection.Enabled {
 			zap.S().Debugw("server triggered crash detection but handler is disabled for server process", zap.String("server", s.Uuid))
 
-			s.SendConsoleOutputFromDaemon("Server detected as crashed; crash detection is disabled for this instance.")
+			s.PublishConsoleOutputFromDaemon("Server detected as crashed; crash detection is disabled for this instance.")
 		}
 
 		return nil
@@ -56,15 +56,15 @@ func (s *Server) handleServerCrash() error {
 		return nil
 	}
 
-	s.SendConsoleOutputFromDaemon("---------- Detected server process in a crashed state! ----------")
-	s.SendConsoleOutputFromDaemon(fmt.Sprintf("Exit code: %d", exitCode))
-	s.SendConsoleOutputFromDaemon(fmt.Sprintf("Out of memory: %t", oomKilled))
+	s.PublishConsoleOutputFromDaemon("---------- Detected server process in a crashed state! ----------")
+	s.PublishConsoleOutputFromDaemon(fmt.Sprintf("Exit code: %d", exitCode))
+	s.PublishConsoleOutputFromDaemon(fmt.Sprintf("Out of memory: %t", oomKilled))
 
 	c := s.CrashDetection.lastCrash
 	// If the last crash time was within the last 60 seconds we do not want to perform
 	// an automatic reboot of the process. Return an error that can be handled.
 	if !c.IsZero() && c.Add(time.Second * 60).After(time.Now()) {
-		s.SendConsoleOutputFromDaemon("Aborting automatic reboot: last crash occurred less than 60 seconds ago.")
+		s.PublishConsoleOutputFromDaemon("Aborting automatic reboot: last crash occurred less than 60 seconds ago.")
 
 		return &crashTooFrequent{}
 	}

server/environment_docker.go

@@ -388,7 +388,7 @@ func (d *DockerEnvironment) FollowConsoleOutput() error {
 
 		s := bufio.NewScanner(r)
 		for s.Scan() {
-			d.Server.Emit(ConsoleOutputEvent, s.Text())
+			d.Server.Events().Publish(ConsoleOutputEvent, s.Text())
 		}
 
 		if err := s.Err(); err != nil {
@@ -450,7 +450,7 @@ func (d *DockerEnvironment) EnableResourcePolling() error {
 			}
 
 			b, _ := json.Marshal(s.Resources)
-			s.Emit(StatsEvent, string(b))
+			s.Events().Publish(StatsEvent, string(b))
 		}
 	}(d.Server)
 

server/events.go

@@ -1,14 +1,9 @@
 package server
 
 import (
-	"fmt"
-	"github.com/mitchellh/colorstring"
+	"sync"
 )
 
-type EventListeners map[string][]EventListenerFunction
-
-type EventListenerFunction *func(string)
-
 // Defines all of the possible output events for a server.
 // noinspection GoNameStartsWithPackageName
 const (
@@ -19,47 +14,63 @@ const (
 	StatsEvent         = "stats"
 )
 
-// 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)
+type Event struct {
+	Data  string
+	Topic string
+}
+
+type EventBus struct {
+	subscribers map[string][]chan Event
+	mu          sync.Mutex
+}
+
+// Returns the server's emitter instance.
+func (s *Server) Events() *EventBus {
+	if s.emitter == nil {
+		s.emitter = &EventBus{
+			subscribers: map[string][]chan Event{},
+		}
 	}
 
-	if _, ok := s.listeners[event]; ok {
-		s.listeners[event] = append(s.listeners[event], f)
+	return s.emitter
+}
+
+// Publish data to a given topic.
+func (e *EventBus) Publish(topic string, data string) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	if ch, ok := e.subscribers[topic]; ok {
+		go func(data Event, cs []chan Event) {
+			for _, channel := range cs {
+				channel <- data
+			}
+		}(Event{Data: data, Topic: topic}, ch)
+	}
+}
+
+// Subscribe to an emitter topic using a channel.
+func (e *EventBus) Subscribe(topic string, ch chan Event) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+
+	if p, ok := e.subscribers[topic]; ok {
+		e.subscribers[topic] = append(p, ch)
 	} else {
-		s.listeners[event] = []EventListenerFunction{f}
+		e.subscribers[topic] = append([]chan Event{}, ch)
 	}
 }
 
-// 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
-			}
-		}
-	}
-}
+// Unsubscribe a channel from a topic.
+func (e *EventBus) Unsubscribe(topic string, ch chan Event) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
 
-// 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)
+	if _, ok := e.subscribers[topic]; ok {
+		for i := range e.subscribers[topic] {
+			if ch == e.subscribers[topic][i] {
+				e.subscribers[topic] = append(e.subscribers[topic][:i], e.subscribers[topic][i+1:]...)
+			}
 		}
 	}
 }
-
-// Sends output to the server console formatted to appear correctly as being sent
-// from Wings.
-func (s *Server) SendConsoleOutputFromDaemon(data string) {
-	s.Emit(
-		ConsoleOutputEvent,
-		colorstring.Color(fmt.Sprintf("[yellow][bold][Pterodactyl Daemon]:[default] %s", data)),
-	)
-}

server/install.go

@@ -268,7 +268,7 @@ func (ip *InstallationProcess) Execute(installPath string) (string, error) {
 	}
 
 	go func(id string) {
-		ip.Server.Emit(DaemonMessageEvent, "Starting installation process, this could take a few minutes...")
+		ip.Server.Events().Publish(DaemonMessageEvent, "Starting installation process, this could take a few minutes...")
 		if err := ip.StreamOutput(id); err != nil {
 			zap.S().Errorw(
 				"error handling streaming output for server install process",
@@ -276,7 +276,7 @@ func (ip *InstallationProcess) Execute(installPath string) (string, error) {
 				zap.Error(err),
 			)
 		}
-		ip.Server.Emit(DaemonMessageEvent, "Installation process completed.")
+		ip.Server.Events().Publish(DaemonMessageEvent, "Installation process completed.")
 	}(r.ID)
 
 	sChann, eChann := ip.client.ContainerWait(ctx, r.ID, container.WaitConditionNotRunning)
@@ -309,7 +309,7 @@ func (ip *InstallationProcess) StreamOutput(id string) error {
 
 	s := bufio.NewScanner(reader)
 	for s.Scan() {
-		ip.Server.Emit(InstallOutputEvent, s.Text())
+		ip.Server.Events().Publish(InstallOutputEvent, s.Text())
 	}
 
 	if err := s.Err(); err != nil {

server/listeners.go

@@ -6,19 +6,24 @@ import (
 	"strings"
 )
 
-
 // Adds all of the internal event listeners we want to use for a server.
 func (s *Server) AddEventListeners() {
-	s.AddListener(ConsoleOutputEvent, s.onConsoleOutput())
-}
+	consoleChannel := make(chan Event)
+	s.Events().Subscribe(ConsoleOutputEvent, consoleChannel)
 
-var onConsoleOutputListener func(string)
+	go func() {
+		for {
+			select {
+			case data := <-consoleChannel:
+				s.onConsoleOutput(data.Data)
+			}
+		}
+	}()
+}
 
 // Custom listener for console output events that will check if the given line
 // of output matches one that should mark the server as started or not.
-func (s *Server) onConsoleOutput() *func(string) {
-	if onConsoleOutputListener == nil {
-		onConsoleOutputListener = func (data string) {
+func (s *Server) onConsoleOutput(data string) {
 	// If the specific line of output is one that would mark the server as started,
 	// set the server to that state. Only do this if the server is not currently stopped
 	// or stopping.
@@ -38,8 +43,4 @@ func (s *Server) onConsoleOutput() *func(string) {
 			s.SetState(ProcessStoppingState)
 		}
 	}
-		}
-	}
-
-	return &onConsoleOutputListener
 }

server/server.go

@@ -64,8 +64,8 @@ type Server struct {
 	// certain long operations return faster. For example, FS disk space usage.
 	Cache *cache.Cache `json:"-" yaml:"-"`
 
-	// All of the registered event listeners for this server instance.
-	listeners EventListeners
+	// Events emitted by the server instance.
+	emitter *EventBus
 
 	// Defines the process configuration for the server instance. This is dynamically
 	// fetched from the Pterodactyl Server instance each time the server process is
@@ -199,7 +199,6 @@ func LoadDirectory(dir string, cfg *config.SystemConfiguration) error {
 
 // Initializes the default required internal struct components for a Server.
 func (s *Server) Init() {
-	s.listeners = make(map[string][]EventListenerFunction)
 	s.mutex = &sync.Mutex{}
 }
 
@@ -357,7 +356,7 @@ func (s *Server) SetState(state string) error {
 	zap.S().Debugw("saw server status change event", zap.String("server", s.Uuid), zap.String("status", s.State))
 
 	// Emit the event to any listeners that are currently registered.
-	s.Emit(StatusEvent, s.State)
+	s.Events().Publish(StatusEvent, s.State)
 
 	// If server was in an online state, and is now in an offline state we should handle
 	// that as a crash event. In that scenario, check the last crash time, and the crash

websocket.go

@@ -164,7 +164,6 @@ func (rt *Router) routeWebsocket(w http.ResponseWriter, r *http.Request, ps http
 		JWT:        nil,
 	}
 
-	// Register all of the event handlers.
 	events := []string{
 		server.StatsEvent,
 		server.StatusEvent,
@@ -173,24 +172,29 @@ func (rt *Router) routeWebsocket(w http.ResponseWriter, r *http.Request, ps http
 		server.DaemonMessageEvent,
 	}
 
-	var eventFuncs = make(map[string]*func(string))
+	eventChannel := make(chan server.Event)
 	for _, event := range events {
-		var e = event
-		var fn = func(data string) {
+		s.Events().Subscribe(event, eventChannel)
+	}
+
+	defer func() {
+		for _, event := range events {
+			s.Events().Unsubscribe(event, eventChannel)
+		}
+
+		close(eventChannel)
+	}()
+
+	// Listen for different events emitted by the server and respond to them appropriately.
+	go func() {
+		for {
+			select {
+			case d := <-eventChannel:
 				handler.SendJson(&WebsocketMessage{
-				Event: e,
-				Args:  []string{data},
+					Event: d.Topic,
+					Args:  []string{d.Data},
 				})
 			}
-
-		eventFuncs[event] = &fn
-		s.AddListener(event, &fn)
-	}
-
-	// When done with the socket, remove all of the event handlers we had registered.
-	defer func() {
-		for event, action := range eventFuncs {
-			s.RemoveListener(event, action)
 		}
 	}()
 
@@ -354,7 +358,7 @@ func (wsh *WebsocketHandler) HandleInbound(m WebsocketMessage) error {
 
 			// On every authentication event, send the current server status back
 			// to the client. :)
-			wsh.Server.Emit(server.StatusEvent, wsh.Server.State)
+			wsh.Server.Events().Publish(server.StatusEvent, wsh.Server.State)
 
 			wsh.unsafeSendJson(WebsocketMessage{
 				Event: AuthenticationSuccessEvent,