node/deps/npm/node_modules/request/forever.js

module.exports = ForeverAgent

var util = require('util')
  , Agent = require('http').Agent
  , net = require('net')

function ForeverAgent(options) {
  var self = this
  self.options = options || {}
  self.requests = {}
  self.sockets = {}
  self.freeSockets = {}
  self.maxSockets = self.options.maxSockets || Agent.defaultMaxSockets
  self.minSockets = self.options.minSockets || ForeverAgent.defaultMinSockets
  self.on('free', function(socket, host, port) {
    var name = host + ':' + port
    if (self.requests[name] && self.requests[name].length) {
      self.requests[name].shift().onSocket(socket)
    } else if (self.sockets[name].length < self.minSockets) {
      if (!self.freeSockets[name]) self.freeSockets[name] = []
      self.freeSockets[name].push(socket)
      
      // if an error happens while we don't use the socket anyway, meh, throw the socket away
      function onIdleError() {
        socket.destroy()
      }
      socket._onIdleError = onIdleError
      socket.on('error', onIdleError)
    } else {
      // If there are no pending requests just destroy the
      // socket and it will get removed from the pool. This
      // gets us out of timeout issues and allows us to
      // default to Connection:keep-alive.
      socket.destroy();
    }
  })
  self.createConnection = net.createConnection
}
util.inherits(ForeverAgent, Agent)

ForeverAgent.defaultMinSockets = 5

ForeverAgent.prototype.addRequestNoreuse = Agent.prototype.addRequest
ForeverAgent.prototype.addRequest = function(req, host, port) {
  var name = host + ':' + port
  if (this.freeSockets[name] && this.freeSockets[name].length > 0 && !req.useChunkedEncodingByDefault) {
    var idleSocket = this.freeSockets[name].pop()
    idleSocket.removeListener('error', idleSocket._onIdleError)
    delete idleSocket._onIdleError
    req._reusedSocket = true
    req.onSocket(idleSocket)
  } else {
    this.addRequestNoreuse(req, host, port)
  }
}

ForeverAgent.prototype.removeSocket = function(s, name, host, port) {
  if (this.sockets[name]) {
    var index = this.sockets[name].indexOf(s);
    if (index !== -1) {
      this.sockets[name].splice(index, 1);
    }
  } else if (this.sockets[name] && this.sockets[name].length === 0) {
    // don't leak
    delete this.sockets[name];
    delete this.requests[name];
  }
  
  if (this.freeSockets[name]) {
    var index = this.freeSockets[name].indexOf(s)
    if (index !== -1) {
      this.freeSockets[name].splice(index, 1)
      if (this.freeSockets[name].length === 0) {
        delete this.freeSockets[name]
      }
    }
  }

  if (this.requests[name] && this.requests[name].length) {
    // If we have pending requests and a socket gets closed a new one
    // needs to be created to take over in the pool for the one that closed.
    this.createSocket(name, host, port).emit('free');
  }
}