lnrpc: Add subscribe peer events rpc

[carlaKC]

This PR adds a subscribe peer events rpc stream, following on from #3354. The motivation for adding this stream would be to provide information for people who want to write their own autopilot logic external to LND.

Pull Request Checklist

• All changes are Go version 1.12 compliant
• Code is commented, has been formatted with go fmt and lines are wrapped at 80
• Running make check, go vet andmake lint ok
• All commits are logically structured, build properly and pass tests

[halseth]

Code LGTM! Question more becomes whether this RPC is useful to expose

[wpaulino]

LGTM. As far as the RPC, are there any plans to extend it with other notification types that could make it more useful to expose?

[carlaKC]

Code LGTM! Question more becomes whether this RPC is useful to expose

I think that it's useful in the context of people building their own channel closing logic? If we're going to expose the final channel insights metrics (rather than time series), be it an all time value of with start/end params, I think that it makes sense to expose the individual elements over RPC so that people can easily build from scratch if they want to.

[carlaKC]

LGTM. As far as the RPC, are there any plans to extend it with other notification types that could make it more useful to expose?

None at present, but I can look into it if online/offline aren't enough to justify adding a new endpoint?

[halseth]

Also useful for wallets that want to show the number of connected peers without having to poll listpeers I think :)

[carlaKC]

This one has been sitting around for a while now. Should I rebase for merge or close because we don't want to add this rpc endpoint?

[halseth]

I think it is still useful, but we can let it sit around a bit longer until someone has a specific use case for it in mind.

[carlaKC]

Ok cool 😀 didn’t want to leave it hanging around without following up.

[fusion44]

I have a usecase :)

In my Wallet, I display a list of currently connected peers. Wherever possible, I use subscriptions to make the app feel more responsive and dynamic. Subscribing to this means I don't have to implement pull to refresh and save some bytes of data transfered.

https://github.com/fusion44/sendmany/blob/master/docs/screenshots/screenshot_3.png

[carlaKC]

I have a usecase :)

Awesome!

Rebased on master just in case we want to merge this :D

[halseth]

Needs another rebase! 😅

[carlaKC]

rerebased 😂 going to add it to the 0.9 milestone so it gets some attention