Here is a BitTorrent tracker that logs download statistics and ensures that every torrent has at least one seed: https://github.com/astro/prittorrent It is used by the bitlove BitTorrent podcast distribution service: http://bitlove.org/

(Tim Pritlove had the idea for both, hence the names. He didn't write any of these, though.)

Does Hefur have these kind of features?

Well there is a stat page, as you can see in the link I posted to the Debian tracker and Archlinux tracker. There is no persistant stats logging (nobody needed it yet).

Ensuring that a torrent has at least one seed is not a feature of Hefur, and I don't think that it needs it.

If you are interested in bittorrent trackers then XBT Tracker[1] and Opentracker[2] are two other open source trackers out there which you can consider using.

[1] http://xbtt.sourceforge.net/tracker/

[2] http://erdgeist.org/arts/software/opentracker/

If all data is in memory, what happens when it goes down? Is persistence not part of the use-case?

The white list of torrent is on the disk: a folder of .torrent files. So when Hefur restarts it scans this folder and recreate the white list.

The peers will recontact the tracker periodically. So the restart is safe.

If you push torrents to the tracker through RPC, then you'll have to push them again on restart.

Note that Hefur has not been designed to replace existing large scale (in the number of torrents) BitTorrent trackers.

It is very useful for small setups and distributions like Archlinux and Debian: http://tracker.archlinux.org:6969/stat http://bttracker.debian.org:6969/stat