import { ShortChannelId } from "@node-lightning/core" ; import { ILogger } from "@node-lightning/logger" ; import { ChannelUpdateChannelFlags } from "../flags/ChanneUpdateChannelFlags" ; import { ChannelAnnouncementMessage } from "../messages/ChannelAnnouncementMessage" ; import { ChannelUpdateMessage } from "../messages/ChannelUpdateMessage" ; import { IWireMessage } from "../messages/IWireMessage" ; import { NodeAnnouncementMessage } from "../messages/NodeAnnouncementMessage" ; import { IPeer } from "../Peer" ; /**
 * Interface for the sub-system for handling the gossip message relay,
 * also known as rumor mongering.This system is responsible for
 * periodically flushing messages to connected peers and makes a best
 * effort to not send message that have already been sent to a peer.
 *
 * The idea of rumor mongering is that a piece of information is hot. A
 * node attempts to infect connected peers with this information by
 * sending it to them. Once it has been sent, we no longer need to
 * infect them with information.
 */ export interface IGossipRelay { /**
     * The current state of gossip relay
     */ state : GossipRelayState ; /**
     * Starts gossip relay
     */ start ( ) : void ; /**
     * Stops gossip relay
     */ stop ( ) : void ; param peer addPeer ( peer ) : void ; param peer removePeer ( peer ) : void ; param msg enqueue ( msg ) : void ; } /**
 * The state of a IGossipRelay rumor mongerer
 */ export enum GossipRelayState { /**
     * Rumor mongering is not active
     */ Inactive , /**
     * Rumor mongering is active
     */ Active } /**
 * This is a basic implementation of IGossipRelay that enques all
 * messages and maintaining an index of each peer in the queue. When
 * messages are flushed, only messages that haven't been sent to a peer
 * are sent and the index position for that peer is updated. When the
 * queue of messages has reached a maximum length, older messages are
 * pruned and the index positions are updated.
 */ export class GossipRelay { private _queue : IWireMessage [ ] ; private _peers : Map < IPeer , number > ; private _timer : NodeJS . Timeout ; private _state : GossipRelayState ; constructor ( readonly logger , readonly relayPeriodMs = 60000 , readonly maxQueueLen = 10000 ) { this . _peers = new Map ( ) as Map < IPeer , number > ; this . _queue = [ ] ; this . _state = GossipRelayState . Inactive ; } /**
     * Gets the current state of gossip relay
     */ public get state ( ) : GossipRelayState { return this . _state ; } /**
     * Starts relay to peers. This enables messages to be enqueued and
     * periodically sent to the peers.
     */ public start ( ) { if ( this . _state === GossipRelayState . Active ) return ; this . logger . info ( "starting gossip relay for all peers" ) ; this . _state = GossipRelayState . Active ; this . _timer = setInterval ( this . _onTimer . bind ( this ) , this . relayPeriodMs ) ; } /**
     * Stops relay to peers.
     */ public stop ( ) { if ( this . _state === GossipRelayState . Inactive ) return ; this . logger . info ( "stopping gossip relay for all peers" ) ; clearTimeout ( this . _timer ) ; this . _state = GossipRelayState . Inactive ; } param peer public addPeer ( peer ) { this . _peers . set ( peer , this . _queue . length ) ; } param peer public removePeer ( peer ) { this . _peers . delete ( peer ) ; } param msg public enqueue ( msg ) { if ( this . state !== GossipRelayState . Active ) return ; if ( msg instanceof ChannelAnnouncementMessage ) { const existing = this . _findChanAnn ( msg . shortChannelId ) ; if ( ! existing ) { this . logger . trace ( "adding channel_announcement" , msg . shortChannelId . toString ( ) ) ; this . _queue . push ( msg ) ; return ; } } if ( msg instanceof ChannelUpdateMessage ) { const existing = this . _findChanUpd ( msg . shortChannelId , msg . channelFlags . isSet ( ChannelUpdateChannelFlags . direction ) ) ; if ( ! existing ) { this . logger . trace ( "adding channel_update" , msg . shortChannelId . toString ( ) , msg . channelFlags . isSet ( ChannelUpdateChannelFlags . direction ) ) ; this . _queue . push ( msg ) ; return ; } if ( existing && existing . timestamp < msg . timestamp ) { this . logger . trace ( "updating channel_update" , msg . shortChannelId . toString ( ) , msg . channelFlags . isSet ( ChannelUpdateChannelFlags . direction ) ) ; const idx = this . _queue . indexOf ( existing ) ; this . _queue . splice ( idx , 1 ) ; this . _queue . push ( msg ) ; return ; } } if ( msg instanceof NodeAnnouncementMessage ) { const existing = this . _findNodeAnn ( msg . nodeId ) ; if ( ! existing ) { this . logger . trace ( "adding node_announcement" , msg . nodeId . toString ( "hex" ) ) ; this . _queue . push ( msg ) ; return ; } if ( existing && existing . timestamp < msg . timestamp ) { this . logger . trace ( "updating node_announcement" , msg . nodeId . toString ( "hex" ) ) ; const idx = this . _queue . indexOf ( existing ) ; this . _queue . splice ( idx , 1 ) ; this . _queue . push ( msg ) ; return ; } } } param scid private _findChanAnn ( scid ) { return this . _queue . find ( p => p instanceof ChannelAnnouncementMessage && p . shortChannelId . toNumber ( ) === scid . toNumber ( ) ) as ChannelAnnouncementMessage ; } param scid param direction private _findChanUpd ( scid , direction ) { return this . _queue . find ( p => p instanceof ChannelUpdateMessage && p . shortChannelId . toNumber ( ) === scid . toNumber ( ) && p . channelFlags . isSet ( ChannelUpdateChannelFlags . direction ) === direction ) as ChannelUpdateMessage ; } param nodeId private _findNodeAnn ( nodeId ) { return this . _queue . find ( p => p instanceof NodeAnnouncementMessage && p . nodeId . equals ( nodeId ) ) as NodeAnnouncementMessage ; } /**
     * Fires when the timer ticks and will flush messages to peers and
     * prune the queue
     */ private _onTimer ( ) { this . logger . debug ( `periodic flush, ${ this . _peers . size } peers, ${ this . _queue . length } hot messages` ) ; for ( const peer of this . _peers . keys ( ) ) { this . _flushToPeer ( peer ) ; } this . _pruneQueue ( ) ; } param peer private _flushToPeer ( peer ) { for ( let i = this . _peers . get ( peer ) ; i < this . _queue . length ; i ++ ) { const message = this . _queue [ i ] ; peer . sendMessage ( message ) ; this . _peers . set ( peer , this . _queue . length ) ; } } /**
     * Prunes excess message
     */ private _pruneQueue ( ) { const deleteCount = Math . max ( 0 , this . _queue . length - this . maxQueueLen ) ; if ( deleteCount === 0 ) return ; this . _queue . splice ( 0 , deleteCount ) ; for ( const [ peer , index ] of this . _peers . entries ( ) ) { this . _peers . set ( peer , index - deleteCount ) ; } this . logger . debug ( `pruned ${ deleteCount } old messages` ) ; } }