Code cleanup for event listening and publishing

Co-Authored-By: Jakob <schrej@users.noreply.github.com>
This commit is contained in:
Dane Everitt 2020-07-31 21:02:25 -07:00
parent da26b4c5c7
commit cf33a2464a
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@ -27,7 +27,7 @@ type Event struct {
type EventBus struct {
sync.RWMutex
subscribers map[string][]chan Event
subscribers map[string]map[chan Event]struct{}
}
// Returns the server's emitter instance.
@ -37,7 +37,7 @@ func (s *Server) Events() *EventBus {
if s.emitter == nil {
s.emitter = &EventBus{
subscribers: map[string][]chan Event{},
subscribers: make(map[string]map[chan Event]struct{}),
}
}
@ -46,29 +46,30 @@ func (s *Server) Events() *EventBus {
// Publish data to a given topic.
func (e *EventBus) Publish(topic string, data string) {
t := topic
// Some of our topics for the socket support passing a more specific namespace,
// such as "backup completed:1234" to indicate which specific backup was completed.
//
// In these cases, we still need to the send the event using the standard listener
// name of "backup completed".
if strings.Contains(topic, ":") {
parts := strings.SplitN(topic, ":", 2)
if len(parts) == 2 {
t = parts[0]
}
}
// Acquire a read lock and loop over all of the channels registered for the topic. This
// avoids a panic crash if the process tries to unregister the channel while this routine
// is running.
go func() {
e.RLock()
defer e.RUnlock()
t := topic
// Some of our topics for the socket support passing a more specific namespace,
// such as "backup completed:1234" to indicate which specific backup was completed.
//
// In these cases, we still need to the send the event using the standard listener
// name of "backup completed".
if strings.Contains(topic, ":") {
parts := strings.SplitN(topic, ":", 2)
if len(parts) == 2 {
t = parts[0]
}
}
if ch, ok := e.subscribers[t]; ok {
data := Event{Data: data, Topic: topic}
for _, channel := range ch {
channel <- data
for channel := range ch {
channel <- Event{Data: data, Topic: topic}
}
}
}()
@ -90,44 +91,25 @@ func (e *EventBus) Subscribe(topic string, ch chan Event) {
e.Lock()
defer e.Unlock()
p, ok := e.subscribers[topic]
// If there is nothing currently subscribed to this topic just go ahead and create
// the item and then return.
if !ok {
e.subscribers[topic] = append([]chan Event{}, ch)
return
if _, exists := e.subscribers[topic]; !exists {
e.subscribers[topic] = make(map[chan Event]struct{})
}
// If this topic is already setup, first iterate over the event channels currently in there
// and confirm there is not a match. If there _is_ a match do nothing since that means this
// channel is already being tracked. This avoids registering two identical handlers for the
// same topic, and means the Unsubscribe function can safely assume there will only be a
// single match for an event.
for i := range e.subscribers[topic] {
if ch == e.subscribers[topic][i] {
return
}
// 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{}{}
}
e.subscribers[topic] = append(p, ch)
}
// Unsubscribe a channel from a topic.
// Unsubscribe a channel from a given topic.
func (e *EventBus) Unsubscribe(topic string, ch chan Event) {
e.Lock()
defer e.Unlock()
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:]...)
// Subscribe enforces a unique event channel for the topic, so we can safely exit
// this loop once matched since there should not be any additional matches after
// this point.
break
}
}
if _, exists := e.subscribers[topic][ch]; exists {
delete(e.subscribers[topic], ch)
}
}
@ -139,9 +121,6 @@ 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)
}
// Reset the entire struct into an empty map.
e.subscribers = make(map[string]map[chan Event]struct{})
}