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Fix deadlocks in event listener system; closes pterodactyl/panel#2298

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Fixes deadlocks that occurred when events were registered while other events were being unsubscribed and data was being flooded to these listeners. A complete mess, I hate this code, it is going to break again, but jesus I'm so tired.
This commit is contained in:
Dane Everitt
2020-09-11 23:01:54 -07:00
committed by GitHub
parent 45bcb9cd68
commit b2eebcaf6d
7 changed files with 57 additions and 32 deletions
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38
events/events.go
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@@ -2,8 +2,8 @@ package events
import (
"encoding/json"
"github.com/sasha-s/go-deadlock"
"strings"
"sync"
)
type Event struct {
@@ -12,7 +12,7 @@ type Event struct {
}
type EventBus struct {
sync.RWMutex
deadlock.RWMutex
subscribers map[string]map[chan Event]struct{}
}
@@ -47,8 +47,12 @@ func (e *EventBus) Publish(topic string, data string) {
defer e.RUnlock()
if ch, ok := e.subscribers[t]; ok {
e := Event{Data: data, Topic: topic}
for channel := range ch {
channel <- Event{Data: data, Topic: topic}
go func(channel chan Event, e Event) {
channel <- e
}(channel, e)
}
}
}()
@@ -66,29 +70,33 @@ 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) {
func (e *EventBus) Subscribe(topics []string, ch chan Event) {
e.Lock()
defer e.Unlock()
if _, exists := e.subscribers[topic]; !exists {
e.subscribers[topic] = make(map[chan Event]struct{})
}
for _, topic := range topics {
if _, exists := e.subscribers[topic]; !exists {
e.subscribers[topic] = make(map[chan Event]struct{})
}
// Only set the channel if there is not currently a matching one for this topic. This
// avoids registering two identical listeners for the same topic and causing pain in
// the unsubscribe functionality as well.
if _, exists := e.subscribers[topic][ch]; !exists {
e.subscribers[topic][ch] = struct{}{}
// Only set the channel if there is not currently a matching one for this topic. This
// avoids registering two identical listeners for the same topic and causing pain in
// the unsubscribe functionality as well.
if _, exists := e.subscribers[topic][ch]; !exists {
e.subscribers[topic][ch] = struct{}{}
}
}
}
// Unsubscribe a channel from a given topic.
func (e *EventBus) Unsubscribe(topic string, ch chan Event) {
func (e *EventBus) Unsubscribe(topics []string, ch chan Event) {
e.Lock()
defer e.Unlock()
if _, exists := e.subscribers[topic][ch]; exists {
delete(e.subscribers[topic], ch)
for _, topic := range topics {
if _, exists := e.subscribers[topic][ch]; exists {
delete(e.subscribers[topic], ch)
}
}
}