Announce request should support event `completed` and `stopped`

[charleshuang3]

torrent/tracker_scraper.go

Lines 231 to 236 in fae873d

	e := tracker.Started
	for {
	ar := me.announce(ctx, e)
	// after first announce, get back to regular "none"
	e = tracker.None

Currently, we only support started and none. Without event, private tracker may have trouble to record stats.

How to impl

• stopped: we should call trackerScraper.announceStopped when client.dropTorrent - torrent.close. Another case is grateful stop.
• completed: I don't have a good idea in anacrolix/torrent maybe expose func announceCompleted in torrent. and let client make the call. For example https://github.com/GopeedLab/gopeed/blob/3262e5a11b04cb7e84c9af7dac9175eeb8505bdb/internal/protocol/bt/fetcher.go#L216

@anacrolix wdyt? I can work on impl, if you want.

[anacrolix]

Thanks. I thought I had those events, I'll check and let you know.

[charleshuang3]

@anacrolix any finding?

[anacrolix]

You are correct. I think you could call AnnounceStopped here:

torrent/torrent.go

Line 2878 in 67fe9f4

t.dataDownloadDisallowed.Set()

, and/or on similar events that indicate the client doesn't intend to download anymore. It does look like announceStopped is called if a torrent is closed though. Have you seen that not occur or did you determine it statically.

For completed, it should be enough to call it here:

torrent/torrent.go

Line 3053 in 67fe9f4

// TODO: Announce complete to trackers?

.

[charleshuang3]

I was wrong. stopped is called in drop()

torrent/t.go

Lines 102 to 107 in 67fe9f4

	func (t *Torrent) Drop() {
	var wg sync.WaitGroup
	defer wg.Wait()
	t.cl.lock()
	defer t.cl.unlock()
	err := t.cl.dropTorrent(t, &wg)

torrent/client.go

Lines 1545 to 1549 in 1e3f1bf

	func (cl *Client) dropTorrent(t *Torrent, wg *sync.WaitGroup) (err error) {
	t.eachShortInfohash(func(short [20]byte) {
	delete(cl.torrentsByShortHash, short)
	})
	err = t.close(wg)

torrent/torrent.go

Lines 1028 to 1029 in 67fe9f4

	func (t *Torrent) close(wg *sync.WaitGroup) (err error) {
	if !t.closed.Set() {

then func (me *trackerScraper) Run() got the close signal

torrent/tracker_scraper.go

Line 271 in 67fe9f4

case <-me.t.closed.Done():

call defer close()

torrent/tracker_scraper.go

Lines 218 to 219 in 67fe9f4

	func (me *trackerScraper) Run() {
	defer me.announceStopped()

[anacrolix]

I don't have time to do this atm. But it is on the radar.