From 2e055cf6301e983c23cd1565ef34b7097da222f5 Mon Sep 17 00:00:00 2001
From: Dane Everitt <dane@daneeveritt.com>
Date: Sun, 3 May 2020 21:30:16 -0700
Subject: [PATCH] Unsubscribe any open event listeners when deleting a server

---
 router/router_server.go |  3 +++
 server/events.go        | 30 +++++++++++++++++++++++-------
 2 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/router/router_server.go b/router/router_server.go
index c93c8e7..0412d7d 100644
--- a/router/router_server.go
+++ b/router/router_server.go
@@ -178,6 +178,9 @@ func deleteServer(c *gin.Context) {
 		zap.S().Warnw("failed to delete server archive during deletion process", zap.String("server", s.Uuid), zap.Error(err))
 	}
 
+	// Unsubscribe all of the event listeners.
+	s.Events().UnsubscribeAll()
+
 	// Destroy the environment; in Docker this will handle a running container and
 	// forcibly terminate it before removing the container, so we do not need to handle
 	// that here.
diff --git a/server/events.go b/server/events.go
index c22ebb1..5ea6ceb 100644
--- a/server/events.go
+++ b/server/events.go
@@ -23,8 +23,9 @@ type Event struct {
 }
 
 type EventBus struct {
+	sync.RWMutex
+
 	subscribers map[string][]chan Event
-	mu          sync.Mutex
 }
 
 // Returns the server's emitter instance.
@@ -40,8 +41,8 @@ func (s *Server) Events() *EventBus {
 
 // Publish data to a given topic.
 func (e *EventBus) Publish(topic string, data string) {
-	e.mu.Lock()
-	defer e.mu.Unlock()
+	e.RLock()
+	defer e.RUnlock()
 
 	t := topic
 	// Some of our topics for the socket support passing a more specific namespace,
@@ -79,8 +80,8 @@ func (e *EventBus) PublishJson(topic string, data interface{}) error {
 
 // Subscribe to an emitter topic using a channel.
 func (e *EventBus) Subscribe(topic string, ch chan Event) {
-	e.mu.Lock()
-	defer e.mu.Unlock()
+	e.Lock()
+	defer e.Unlock()
 
 	if p, ok := e.subscribers[topic]; ok {
 		e.subscribers[topic] = append(p, ch)
@@ -91,8 +92,8 @@ func (e *EventBus) Subscribe(topic string, ch chan Event) {
 
 // Unsubscribe a channel from a topic.
 func (e *EventBus) Unsubscribe(topic string, ch chan Event) {
-	e.mu.Lock()
-	defer e.mu.Unlock()
+	e.Lock()
+	defer e.Unlock()
 
 	if _, ok := e.subscribers[topic]; ok {
 		for i := range e.subscribers[topic] {
@@ -102,3 +103,18 @@ func (e *EventBus) Unsubscribe(topic string, ch chan Event) {
 		}
 	}
 }
+
+// Removes all of the event listeners for the server. This is used when a server
+// is being deleted to avoid a bunch of de-reference errors cropping up. Obviously
+// should also check elsewhere and handle a server reference going nil, but this
+// won't hurt.
+func (e *EventBus) UnsubscribeAll() {
+	e.Lock()
+	defer e.Unlock()
+
+	// Loop over all of the subscribers and just remove all of the events
+	// for them.
+	for t := range e.subscribers {
+		e.subscribers[t] = make([]chan Event, 0)
+	}
+}