148 lines
3.6 KiB
Go
148 lines
3.6 KiB
Go
package server
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import (
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"encoding/json"
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"strings"
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"sync"
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)
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// Defines all of the possible output events for a server.
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// noinspection GoNameStartsWithPackageName
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const (
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DaemonMessageEvent = "daemon message"
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InstallOutputEvent = "install output"
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InstallStartedEvent = "install started"
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InstallCompletedEvent = "install completed"
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ConsoleOutputEvent = "console output"
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StatusEvent = "status"
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StatsEvent = "stats"
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BackupCompletedEvent = "backup completed"
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)
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type Event struct {
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Data string
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Topic string
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}
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type EventBus struct {
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sync.RWMutex
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subscribers map[string][]chan Event
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}
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// Returns the server's emitter instance.
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func (s *Server) Events() *EventBus {
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s.emitterLock.Lock()
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defer s.emitterLock.Unlock()
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if s.emitter == nil {
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s.emitter = &EventBus{
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subscribers: map[string][]chan Event{},
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}
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}
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return s.emitter
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}
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// Publish data to a given topic.
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func (e *EventBus) Publish(topic string, data string) {
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go func() {
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e.RLock()
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defer e.RUnlock()
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t := topic
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// Some of our topics for the socket support passing a more specific namespace,
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// such as "backup completed:1234" to indicate which specific backup was completed.
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//
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// In these cases, we still need to the send the event using the standard listener
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// name of "backup completed".
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if strings.Contains(topic, ":") {
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parts := strings.SplitN(topic, ":", 2)
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if len(parts) == 2 {
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t = parts[0]
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}
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}
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if ch, ok := e.subscribers[t]; ok {
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data := Event{Data: data, Topic: topic}
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for _, channel := range ch {
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channel <- data
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}
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}
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}()
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}
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func (e *EventBus) PublishJson(topic string, data interface{}) error {
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b, err := json.Marshal(data)
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if err != nil {
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return err
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}
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e.Publish(topic, string(b))
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return nil
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}
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// Subscribe to an emitter topic using a channel.
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func (e *EventBus) Subscribe(topic string, ch chan Event) {
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e.Lock()
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defer e.Unlock()
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p, ok := e.subscribers[topic]
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// If there is nothing currently subscribed to this topic just go ahead and create
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// the item and then return.
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if !ok {
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e.subscribers[topic] = append([]chan Event{}, ch)
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return
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}
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// If this topic is already setup, first iterate over the event channels currently in there
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// and confirm there is not a match. If there _is_ a match do nothing since that means this
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// channel is already being tracked. This avoids registering two identical handlers for the
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// same topic, and means the Unsubscribe function can safely assume there will only be a
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// single match for an event.
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for i := range e.subscribers[topic] {
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if ch == e.subscribers[topic][i] {
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return
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}
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}
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e.subscribers[topic] = append(p, ch)
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}
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// Unsubscribe a channel from a topic.
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func (e *EventBus) Unsubscribe(topic string, ch chan Event) {
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e.Lock()
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defer e.Unlock()
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if _, ok := e.subscribers[topic]; ok {
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for i := range e.subscribers[topic] {
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if ch == e.subscribers[topic][i] {
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e.subscribers[topic] = append(e.subscribers[topic][:i], e.subscribers[topic][i+1:]...)
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// Subscribe enforces a unique event channel for the topic, so we can safely exit
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// this loop once matched since there should not be any additional matches after
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// this point.
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break
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}
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}
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}
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}
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// Removes all of the event listeners for the server. This is used when a server
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// is being deleted to avoid a bunch of de-reference errors cropping up. Obviously
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// should also check elsewhere and handle a server reference going nil, but this
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// won't hurt.
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func (e *EventBus) UnsubscribeAll() {
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e.Lock()
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defer e.Unlock()
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// Loop over all of the subscribers and just remove all of the events
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// for them.
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for t := range e.subscribers {
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e.subscribers[t] = make([]chan Event, 0)
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}
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}
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