I'm using libtorrent 1.2.1 and I have a torrent with several pieces set to don't download (priority 0).
The problem is that after setting the piece priority to top_download (priority 7) there is a delay of 60 seconds before the download starts.
How can I force the download to immediatly start after setting the piece priority?
to know what's going on, you need to enable logging (by setting the alert_mask). Probably both peer_log_notification and torrent_log_notification (see docs). This will post alerts about what's going on.
For example, once all your non-zero priority pieces have been downloaded, all seeds are disconnected. If you don't have any peers by the time you set piece priorities, it may take a while to reconnect new peers.
There are a fair number of configuration knobs to adjust this behaviour. It's hard to diagnose what's happening in your case specifically without more information though.
