No metadata download

Question

I'm using libtorrent 1.0.9 and custom bindings (reproducible with python). Sometimes I can not download magnets because they're stuck without metadata (while there're >200 DHT nodes available). I'm able to reproduce the issue with this magnet:

magnet:?xt=urn:btih:565DB305A27FFB321FCC7B064AFD7BD73AEDDA2B&dn=bbb_sunflower_1080p_60fps_normal.mp4&tr=udp%3a%2f%2ftracker.openbittorrent.com%3a80%2fannounce&tr=udp%3a%2f%2ftracker.publicbt.com%3a80%2fannounce&ws=http%3a%2f%2fdistribution.bbb3d.renderfarming.net%2fvideo%2fmp4%2fbbb_sunflower_1080p_60fps_normal.mp4

Meanwhile in other torrent clients (qBittorrent, Vuze) it gets the metadata very quickly. It's reproducible with following code:

import libtorrent as lt
import time

session = lt.session()
session.listen_on(6881, 6891)
session.add_extension('ut_metadata')
session.add_extension('ut_pex')
session.add_extension('metadata_transfer')
session.add_dht_router("router.utorrent.com", 6881)
session.add_dht_router("router.bittorrent.com", 6881)
session.add_dht_router("dht.transmissionbt.com", 6881)
session.add_dht_router("dht.aelitis.com", 6881)
session.start_dht()
session.start_lsd()
session.start_upnp()
session.start_natpmp()

params = { 'save_path': '/tmp/'}
link ="magnet:?xt=urn:btih:565DB305A27FFB321FCC7B064AFD7BD73AEDDA2B&dn=bbb_sunflower_1080p_60fps_normal.mp4&tr=udp%3a%2f%2ftracker.openbittorrent.com%3a80%2fannounce&tr=udp%3a%2f%2ftracker.publicbt.com%3a80%2fannounce&ws=http%3a%2f%2fdistribution.bbb3d.renderfarming.net%2fvideo%2fmp4%2fbbb_sunflower_1080p_60fps_normal.mp4"
handle = lt.add_magnet_uri(session, link, params)

print('downloading metadata...')
while (not handle.has_metadata()):
    status=session.status()
    print('dht nodes: ', status.dht_nodes)
    time.sleep(1)
print ('got metadata, starting torrent download...')
while (handle.status().state != lt.torrent_status.seeding):
    print('%d %% done' % (handle.status().progress*100))
    time.sleep(1)

What I'm doing wrong?

Arvid Arvid · Accepted Answer · 2016-10-12T05:05:11

This is most likely caused by a problem in the 1.0.x series, where some of the first responses from the DHT will make the node change its node ID (to match its external IP address, see this post).

It does this by restarting the DHT node. Any in-flight torrent announces at that time will be lost. Waiting 15 minutes for the next announce should make the announce go through. Another option is to wait for the dht_bootstrap_alert before adding the first torrent to the session.

This issue was fixed in the 1.1.x releases.

No metadata download

1 Answers