git ssb

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'use strict'
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var ip = require('ip')
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var onWakeup = require('on-wakeup')
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var onNetwork = require('on-change-network')
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var hasNetwork = require('../../lib/has-network-debounced')
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var pull = require('pull-stream')
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function not (fn) {
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  return function (e) { return !fn(e) }
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}
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function and () {
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  var args = [].slice.call(arguments)
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  return function (value) {
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    return args.every(function (fn) { return fn.call(null, value) })
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  }
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}
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//min delay (delay since last disconnect of most recent peer in unconnected set)
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//unconnected filter delay peer < min delay
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function delay (failures, factor, max) {
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  return Math.min(Math.pow(2, failures)*factor, max || Infinity)
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}
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function maxStateChange (M, e) {
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  return Math.max(M, e.stateChange || 0)
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}
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function peerNext(peer, opts) {
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  return (peer.stateChange|0) + delay(peer.failure|0, opts.factor, opts.max)
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}
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//detect if not connected to wifi or other network
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//(i.e. if there is only localhost)
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function isOffline (e) {
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  if(ip.isLoopback(e.host) || e.host == 'localhost') return false
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  return !hasNetwork()
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}
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var isOnline = not(isOffline)
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function isLocal (e) {
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  // don't rely on private ip address, because
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  // cjdns creates fake private ip addresses.
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  // ignore localhost addresses, because sometimes they get broadcast.
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  return !ip.isLoopback(e.host) && ip.isPrivate(e.host) && e.source === 'local'
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}
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function isSeed (e) {
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  return e.source === 'seed'
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}
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function isFriend (e) {
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  return e.source === 'friends'
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}
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function isUnattempted (e) {
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  return !e.stateChange
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}
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//select peers which have never been successfully connected to yet,
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//but have been tried.
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function isInactive (e) {
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  return e.stateChange && (!e.duration || e.duration.mean == 0)
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}
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function isLongterm (e) {
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  return e.ping && e.ping.rtt && e.ping.rtt.mean > 0
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}
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//peers which we can connect to, but are not upgraded.
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//select peers which we can connect to, but are not upgraded to LT.
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//assume any peer is legacy, until we know otherwise...
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function isLegacy (peer) {
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  return peer.duration && (peer.duration && peer.duration.mean > 0) && !exports.isLongterm(peer)
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}
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function isConnect (e) {
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  return 'connected' === e.state || 'connecting' === e.state
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}
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//sort oldest to newest then take first n
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function earliest(peers, n) {
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  return peers.sort(function (a, b) {
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    return a.stateChange - b.stateChange
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  }).slice(0, Math.max(n, 0))
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}
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function select(peers, ts, filter, opts) {
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  if(opts.disable) return []
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  //opts: { quota, groupMin, min, factor, max }
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  var type = peers.filter(filter)
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  var unconnect = type.filter(not(isConnect))
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  var count = Math.max(opts.quota - type.filter(isConnect).length, 0)
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  var min = unconnect.reduce(maxStateChange, 0) + opts.groupMin
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  if(ts < min) return []
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  return earliest(unconnect.filter(function (peer) {
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    return peerNext(peer, opts) < ts
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  }), count)
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}
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var schedule = exports = module.exports =
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function (gossip, config, server) {
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  var min = 60e3, hour = 60*60e3, closed = false
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  //trigger hard reconnect after suspend or local network changes
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  onWakeup(gossip.reconnect)
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  onNetwork(gossip.reconnect)
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  function conf(name, def) {
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    if(config.gossip == null) return def
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    var value = config.gossip[name]
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    return (value == null || value === '') ? def : value
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  }
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  function connect (peers, ts, name, filter, opts) {
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    opts.group = name
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    var connected = peers.filter(isConnect).filter(filter)
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    //disconnect if over quota
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    if(connected.length > opts.quota) {
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      return earliest(connected, connected.length - opts.quota)
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        .forEach(function (peer) {
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          gossip.disconnect(peer)
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        })
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    }
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    //will return [] if the quota is full
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    var selected = select(peers, ts, and(filter, isOnline), opts)
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    selected
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      .forEach(function (peer) {
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        gossip.connect(peer)
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      })
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  }
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  var lastMessageAt
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  server.post(function (data) {
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    if(data.value.author != server.id) lastMessageAt = Date.now()
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  })
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  function isCurrentlyDownloading () {
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    // don't schedule gossip if currently downloading messages
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    if (lastMessageAt && lastMessageAt > Date.now() - 500) {
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      return true
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    }
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  }
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  var connecting = false
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  function connections () {
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    if(connecting || closed) return
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    connecting = true
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    var timer = setTimeout(function () {
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      connecting = false
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      // don't attempt to connect while migration is running
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      if (!server.ready() || isCurrentlyDownloading()) return
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      var ts = Date.now()
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      var peers = gossip.peers()
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      var connected = peers.filter(and(isConnect, not(isLocal), not(isFriend))).length
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      var connectedFriends = peers.filter(and(isConnect, isFriend)).length
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      if(conf('friends', true))
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        connect(peers, ts, 'friends', isFriend, {
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          quota: 3, factor: 2e3, max: 10*min, groupMin: 1e3,
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        })
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      if(conf('seed', true))
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        connect(peers, ts, 'seeds', isSeed, {
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          quota: 3, factor: 2e3, max: 10*min, groupMin: 1e3,
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        })
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      if(conf('local', true))
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        connect(peers, ts, 'local', isLocal, {
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          quota: 3, factor: 2e3, max: 10*min, groupMin: 1e3,
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        })
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      if(conf('global', true)) {
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        // prioritize friends
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        connect(peers, ts, 'friends', and(exports.isFriend, exports.isLongterm), {
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          quota: 2, factor: 10e3, max: 10*min, groupMin: 5e3,
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        })
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        if (connectedFriends < 2)
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          connect(peers, ts, 'attemptFriend', and(exports.isFriend, exports.isUnattempted), {
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            min: 0, quota: 1, factor: 0, max: 0, groupMin: 0,
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          })
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        connect(peers, ts, 'retryFriends', and(exports.isFriend, exports.isInactive), {
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          min: 0,
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          quota: 3, factor: 60e3, max: 3*60*60e3, groupMin: 5*60e3,
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        })
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        // standard longterm peers
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        connect(peers, ts, 'longterm', and(
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          exports.isLongterm,
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          not(exports.isFriend),
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          not(exports.isLocal)
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        ), {
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          quota: 2, factor: 10e3, max: 10*min, groupMin: 5e3,
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        })
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        if(!connected)
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          connect(peers, ts, 'attempt', exports.isUnattempted, {
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            min: 0, quota: 1, factor: 0, max: 0, groupMin: 0,
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          })
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        //quota, groupMin, min, factor, max
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        connect(peers, ts, 'retry', exports.isInactive, {
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          min: 0,
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          quota: 3, factor: 5*60e3, max: 3*60*60e3, groupMin: 5*50e3,
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        })
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        var longterm = peers.filter(isConnect).filter(isLongterm).length
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        connect(peers, ts, 'legacy', exports.isLegacy, {
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          quota: 3 - longterm,
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          factor: 5*min, max: 3*hour, groupMin: 5*min,
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        })
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      }
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      peers.filter(isConnect).forEach(function (e) {
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        var permanent = exports.isLongterm(e) || exports.isLocal(e)
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        if((!permanent || e.state === 'connecting') && e.stateChange + 10e3 < ts) {
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          gossip.disconnect(e)
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        }
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      })
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    }, 100*Math.random())
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    if(timer.unref) timer.unref()
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  }
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  pull(
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    gossip.changes(),
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    pull.drain(function (ev) {
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      if(ev.type == 'disconnect')
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        connections()
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    }, function () {
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      console.warn('[gossip/dc] warning: this can happen if the database closes', arguments)
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    })
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  )
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  var int = setInterval(connections, 2e3)
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  if(int.unref) int.unref()
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  connections()
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  return function onClose () {
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    closed = true
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  }
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}
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exports.isUnattempted = isUnattempted
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exports.isInactive = isInactive
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exports.isLongterm = isLongterm
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exports.isLegacy = isLegacy
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exports.isLocal = isLocal
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exports.isFriend = isFriend
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exports.isConnectedOrConnecting = isConnect
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exports.select = select
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