2023 Jan 16

• Interesting, to get a Channel from ChannelManager (with some htlc: ClaimableHTLC), you have to do something like this:

  let short_channel_id = htlc.prev_hop.short_channel_id;
  let (counterparty_node_id, chan_id) = self.short_to_chan_info.read().unwrap().get(&short_channel_id).cloned().unwrap();
  let per_peer_state = self.per_peer_state.read().unwrap();
  let peer_state = per_peer_state.get(counterparty_node_id).unwrap().lock().unwrap();
  let chan = peer_state.channel_by_id.get(chan_id).unwrap();
  

  • There might be a better way I just don’t know, but that’s how it seems to be done. I would’ve thought there might just be some hashmap of channel ids to channels as a field of ChannelManager, but it’s interesting it’s kept in peer_state.

• Getting a lot better at Helix. Some nifty shortcuts: ]g to go to next change, space f for file picker, m i <char> to do vim’s v i <char> i.e. matching inside, space k to pull up documentation on a variable/type/etc., g d to go to definition, g r to go to references. Still having trouble navigating the jumplist, and going back to previous places/managing different places at one time.

• Learned about the ChannelManager lock order. I ran into some trouble where I was violating the lock order, and my solution was to just clone short_to_chan_info to release the lock so I could then grab the lock for per_peer_state. It seemed there was no other way to find a channel from a short channel id, but it felt like cheating, although I saw it done somewhere else. I’ll hopefully come to understand more about why the lock order is the way it is as I work with the code base more.

• Also noticing there are several different structs and enums defined relating to failure codes/messages that could maybe be standardized in the future.

• Did a lot today. Finally feeling a little more familiar with at least the area of the repo I’ve been working with.