API for regular pings

[TheBlueMatt]

In general, lightning nodes should constantly be pinging their peers to ensure connectivity and ensure that we have a peer marked disconnected before we get a payment to route through them that gets stuck. This will require:

• Some general API in peer_handler that indicates a timer tick (doesn't have to be that often, just enough to quantize pings and make sure we get pongs back by the next tick).
• A regular ping generation,
• Disconnecting a peer if no pong is heard by the next timer tick.

[ariard]

@rrybarczyk, this one should be a good first issue if you're looking for something to hack on :)

[Aleru]

I would like to implement this and I think there are at least two ways the timer tick portion could be written.

One way is to use the tokio or timer crate, while I know we want to avoid using new dependencies, other files in the library already depend on these.

The other way would involve using a function pointer in place of the timer tick functionality, so the user of the library would be responsible for supplying that.

I am wondering if one of these would be preferable, or if there is a better way I am not seeing.

[TheBlueMatt]

Cool! Might also want to coordinate with @rrybarczyk who was thinking of working on this, I think. As for your question, I don't think you need anything as crazy as a function pointer, just literally a function in the PeerHandler called timer_tick_occurred which the client calls every N seconds (should define N, I assume something like 15-30). The client can schedule it in any way they want.

[Aleru]

Sounds good @TheBlueMatt

As a general rule any advice/revisions from anyone here are graciously accepted :) I am new to open source/software development so this is quite a learning experience and any advice is good advice!
@rrybarczyk If your down it would be awesome to work on this w/ you, I am a little bit unsure of the best way to go about coordinating our efforts, but I did create a fork (https://github.com/Aleru/rust-lightning) with an effort at a rough outline of the utilities I think we would need to implement. Feel free to reach out if interested!

[ariard]

You may be interested by https://bitcointechtalk.com/contributing-to-bitcoin-core-a-personal-account-35f3a594340b, specially having a skim on Pro Git.
If you don't hear feedback from @rrybarczyk, don't be worry to go forward. And if you any questions you can ask on #rust-bitcoin :)

[rrybarczyk]

Hey @Aleru, apologies for the delay.

Have you made in progress on this PR? Would definitely like to provided any assistance if needed.

[Aleru]

No worries :)
I have a fork that has the functionality and two test functions in it https://github.com/Aleru/rust-lightning. your assistance would be very much welcome and i have a comment section with a list of issues/TODO's in the fork (pretty much all of the stuff is currently near the bottom of peer_handler.rs).

Even if the code compiles and tests pass I cant be sure of the correctness of the added code and how some of the stuff i am doing would effect other parts of the program so at the very least more eye-balls are probably needed before anything would get merged.

you may want to take a look at the fork and of course feel free to reach out.

[TheBlueMatt]

Fixed by #437.