package peernotifier import ( "sync" "github.com/lightningnetwork/lnd/subscribe" ) // PeerNotifier is a subsystem which observes peer offline and online events. // It takes subscriptions for its events, and whenever it observes a new event // it notifies its subscribers over the proper channel. type PeerNotifier struct { started sync.Once stopped sync.Once ntfnServer *subscribe.Server } // PeerOnlineEvent represents a new event where a peer comes online. type PeerOnlineEvent struct { // PubKey is the peer's compressed public key. PubKey [33]byte } // PeerOfflineEvent represents a new event where a peer goes offline. type PeerOfflineEvent struct { // PubKey is the peer's compressed public key. PubKey [33]byte } // New creates a new peer notifier which notifies clients of peer online // and offline events. func New() *PeerNotifier { return &PeerNotifier{ ntfnServer: subscribe.NewServer(), } } // Start starts the PeerNotifier's subscription server. func (p *PeerNotifier) Start() error { var err error p.started.Do(func() { log.Info("PeerNotifier starting") err = p.ntfnServer.Start() }) return err } // Stop signals the notifier for a graceful shutdown. func (p *PeerNotifier) Stop() { p.stopped.Do(func() { log.Info("Stopping PeerNotifier") p.ntfnServer.Stop() }) } // SubscribePeerEvents returns a subscribe.Client that will receive updates // any time the Server is informed of a peer event. func (p *PeerNotifier) SubscribePeerEvents() (*subscribe.Client, error) { return p.ntfnServer.Subscribe() } // NotifyPeerOnline sends a peer online event to all clients subscribed to the // peer notifier. func (p *PeerNotifier) NotifyPeerOnline(pubKey [33]byte) { event := PeerOnlineEvent{PubKey: pubKey} log.Debugf("PeerNotifier notifying peer: %x online", pubKey) if err := p.ntfnServer.SendUpdate(event); err != nil { log.Warnf("Unable to send peer online update: %v", err) } } // NotifyPeerOffline sends a peer offline event to all the clients subscribed // to the peer notifier. func (p *PeerNotifier) NotifyPeerOffline(pubKey [33]byte) { event := PeerOfflineEvent{PubKey: pubKey} log.Debugf("PeerNotifier notifying peer: %x offline", pubKey) if err := p.ntfnServer.SendUpdate(event); err != nil { log.Warnf("Unable to send peer offline update: %v", err) } }