使用http维持socket长连接

module.exports.httpPost = ({ options, ctx }) => {
  return new Promise((resolve, reject) => {
    if (!ctx.users[ctx.query.uid + '']) ctx.users['' + ctx.query.uid] = {}
    let agent = ctx.users['' + ctx.query.uid].agent
    if (!agent) {
      const newAgent = new http.Agent({ keepAlive: true, maxSockets: 1 })
      newAgent.uid = ctx.query.uid      // 人为给agent对象关联uid
      newAgent.createConnection({
        port: config.BC_PORT,
        host: config.BC_SERVER
      }, () => {
        if (!_.isEmpty(newAgent.sockets)) {
          _.forIn(newAgent.sockets, (item, key) => {
            if (item.length) {
              item[0].on('close', () => {
                // 清除当前用户的agent
                ctx.users['' + newAgent.uid].agent = null   // 清除当前用户的agent
                newAgent.destroy()      // 回收agent
              }).on('data', data => {
              })
            }
          })
        }
      })
      agent = newAgent
    }
    const buf = new Buffer(ctx.request.body)
    const httpOptions = {
      headers: {
        'Content-Type': 'text/xml;charset=utf-8',
        'Content-length': buf.length
      },
      host: config.BC_SERVER, port: config.BC_PORT, method: 'POST', agent: agent
    }
    _.merge(httpOptions, options)
    const req = http.request(httpOptions, res => {
      let buffers = ''
      res.on('data', data => {
        buffers += data
      })
      res.on('end', () => {
        // 更新全局用户关联的长连接代理类agent，保证用户和链接一一对应
        ctx.users['' + ctx.query.uid].agent = agent
        resolve(buffers.toString())
      })
    })
    req.write(buf)
    req.end()
    req.on('error', err => {
      reject(err)
    })
  })
}