bittorrent-tracker/lib/server/swarm.js

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module.exports = Swarm
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var debug = require('debug')('bittorrent-tracker:swarm')
var LRU = require('lru')
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var randomIterate = require('random-iterate')
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// Regard this as the default implementation of an interface that you
// need to support when overriding Server.createSwarm() and Server.getSwarm()
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function Swarm (infoHash, server) {
this.complete = 0
this.incomplete = 0
this.peers = new LRU({
max: server.peersCacheLength || 1000,
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maxAge: server.peersCacheTtl || 20 * 60 * 1000 // 20 minutes
})
// When a peer is evicted from the LRU cache, if it's a websocket peer,
// close the websocket.
this.peers.on('evict', function (data) {
var peer = data.value
if (peer.socket) {
try {
peer.socket.close()
peer.socket = null
} catch (err) {}
}
})
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}
Swarm.prototype.announce = function (params, cb) {
var self = this
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var id = params.type === 'ws' ? params.peer_id : params.addr
// Mark the source peer as recently used in cache
var peer = self.peers.get(id)
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if (params.event === 'started') {
self._onAnnounceStarted(params, peer, id)
} else if (params.event === 'stopped') {
self._onAnnounceStopped(params, peer, id)
} else if (params.event === 'completed') {
self._onAnnounceCompleted(params, peer, id)
} else if (params.event === 'update') {
self._onAnnounceUpdate(params, peer, id)
} else {
cb(new Error('invalid event'))
return
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}
cb(null, {
complete: self.complete,
incomplete: self.incomplete,
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peers: self._getPeers(params.numwant, params.peer_id, !!params.socket)
})
}
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Swarm.prototype.scrape = function (params, cb) {
cb(null, {
complete: this.complete,
incomplete: this.incomplete
})
}
Swarm.prototype._onAnnounceStarted = function (params, peer, id) {
if (peer) {
debug('unexpected `started` event from peer that is already in swarm')
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return this._onAnnounceUpdate(params, peer, id) // treat as an update
}
if (params.left === 0) this.complete += 1
else this.incomplete += 1
peer = this.peers.set(id, {
type: params.type,
complete: params.left === 0,
peerId: params.peer_id, // as hex
ip: params.ip,
port: params.port,
socket: params.socket // only websocket
})
}
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Swarm.prototype._onAnnounceStopped = function (params, peer, id) {
if (!peer) {
debug('unexpected `stopped` event from peer that is not in swarm')
return // do nothing
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}
if (peer.complete) this.complete -= 1
else this.incomplete -= 1
this.peers.remove(id)
}
Swarm.prototype._onAnnounceCompleted = function (params, peer, id) {
if (!peer) {
debug('unexpected `completed` event from peer that is not in swarm')
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return this._onAnnounceStarted(params, peer, id) // treat as a start
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}
if (peer.complete) {
debug('unexpected `completed` event from peer that is already completed')
return this._onAnnounceUpdate(params, peer, id) // treat as an update
}
this.complete += 1
this.incomplete -= 1
peer.complete = true
this.peers.set(id, peer)
}
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Swarm.prototype._onAnnounceUpdate = function (params, peer, id) {
if (!peer) {
debug('unexpected `update` event from peer that is not in swarm')
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return this._onAnnounceStarted(params, peer, id) // treat as a start
}
if (!peer.complete && params.left === 0) {
this.complete += 1
this.incomplete -= 1
peer.complete = true
}
this.peers.set(id, peer)
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}
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Swarm.prototype._getPeers = function (numwant, ownPeerId, isWebRTC) {
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var peers = []
var ite = randomIterate(this.peers.keys)
var peerId
while ((peerId = ite()) && peers.length < numwant) {
// Don't mark the peer as most recently used on announce
var peer = this.peers.peek(peerId)
if (!peer) continue
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if (isWebRTC && peer.peerId === ownPeerId) continue // don't send peer to itself
if ((isWebRTC && peer.type !== 'ws') || (!isWebRTC && peer.type === 'ws')) continue // send proper peer type
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peers.push(peer)
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}
return peers
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}