torrents get lost

[Xuefer]

steps to reproduce:

1. make sure there're more than 128 torrents added, in any state
2. use ltconfig plugin to set alert_queue_size to 100 (or load preset: minimal memory usage, which use 100 for alert_queue_size)
3. restart deluge

only about 126~130 torrents get loaded. restart deluge again you'll see size of torrents.state get slim down to a few kbytes from mbytes "Finished loading 427 torrents in 0:00:06.760026" is not appearing in the log. unless the count is slim down

alert_queue_size = 100 is not required for this to happen

Reason: loading existing torrents, rely on alert_queue as callback Suggestion: need a reliable callback mechanic other than alert_queue which is limited by size.

[Cas]

Yes Deluge has a queue size default of 10000 since the queue is critical to functionality so not unexpected that a very low value would cause issues

Alerts is the main mechanism for libtorrent to report errors and events.

Deluge requires the queue for events but there are potential improvements to alert handling.