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A simple event queue

🧱 Design simple en Go

🎛️ Structure Event

type EventType string

const (
	EventStart   EventType = "start"
	EventStop    EventType = "stop"
	EventReboot  EventType = "reboot"
	EventAttach  EventType = "attach-disk"
	EventDetach  EventType = "detach-disk"
)

type VMEvent struct {
	Type   EventType
	VMID   string
	Params map[string]string // optionnel selon le type
}

---

📬 EventQueue (thread-safe FIFO + notify)

type EventQueue struct {
	queue  []VMEvent
	lock   sync.Mutex
	signal chan struct{}
}

func NewEventQueue() *EventQueue {
	return &EventQueue{
		queue:  make([]VMEvent, 0),
		signal: make(chan struct{}, 1),
	}
}

func (eq *EventQueue) Push(ev VMEvent) {
	eq.lock.Lock()
	defer eq.lock.Unlock()
	eq.queue = append(eq.queue, ev)

	select {
	case eq.signal <- struct{}{}:
	default:
		// si déjà notify, pas besoin de spammer
	}
}

func (eq *EventQueue) Pop() (VMEvent, bool) {
	eq.lock.Lock()
	defer eq.lock.Unlock()

	if len(eq.queue) == 0 {
		return VMEvent{}, false
	}

	ev := eq.queue[0]
	eq.queue = eq.queue[1:]
	return ev, true
}

---

🔁 Boucle d'exécution FIFO

func StartEventLoop(eq *EventQueue, manager *Manager) {
	go func() {
		for {
			<-eq.signal // bloquant jusqu'à ce qu’un event arrive

			for {
				ev, ok := eq.Pop()
				if !ok {
					break
				}

				log.Printf("⏳ Processing event %s for VM %s", ev.Type, ev.VMID)

				switch ev.Type {
				case EventStart:
					manager.StartVMByID(ev.VMID)
				case EventStop:
					manager.StopVMByID(ev.VMID)
				case EventAttach:
					manager.AttachDisk(ev.VMID, ev.Params["path"])
				case EventDetach:
					manager.DetachDisk(ev.VMID, ev.Params["path"])
				default:
					log.Printf("⚠️ Unknown event type: %s", ev.Type)
				}
			}
		}
	}()
}

---

🌐 Exposition via HTTP (exemple minimal)

func handleStartVM(w http.ResponseWriter, r *http.Request, eq *EventQueue) {
	vmID := r.URL.Query().Get("id")
	if vmID == "" {
		http.Error(w, "missing id", 400)
		return
	}
	eq.Push(VMEvent{Type: EventStart, VMID: vmID})
	fmt.Fprintf(w, "Start request enqueued")
}

---

🔔 Résumé de la comm' inter-composants

[API HTTP]   --(Push VMEvent)-->   [EventQueue] --(notify chan)--> [EventLoop]
                                                       |
                                       [Pop / Switch exec based on event type]