constructor (client, announceUrl) {
    super(client, announceUrl)

    debug('new http tracker %s', announceUrl)

    // Determine scrape url (if http tracker supports it)
    this.scrapeUrl = null

    const match = this.announceUrl.match(HTTP_SCRAPE_SUPPORT)
    if (match) {
      const pre = this.announceUrl.slice(0, match.index)
      const post = this.announceUrl.slice(match.index + 9)
      this.scrapeUrl = `${pre}/scrape${post}`
    }

    this.cleanupFns = []
    this.maybeDestroyCleanup = null
  }
HTTP torrent tracker client (for an individual tracker)

@param {Client} client       parent bittorrent tracker client
@param {string} announceUrl  announce url of tracker
@param {Object} opts         options object