Add event handlers + prometheus to the cli

[russelltg]

No description provided.

[codecov]

Codecov Report

Merging #54 (d282d53) into master (12cc266) will increase coverage by 2.15%.
The diff coverage is 82.30%.

@@            Coverage Diff             @@
##           master      #54      +/-   ##
==========================================
+ Coverage   78.01%   80.17%   +2.15%     
==========================================
  Files          36       37       +1     
  Lines        3279     2925     -354     
==========================================
- Hits         2558     2345     -213     
+ Misses        721      580     -141     

Impacted Files	Coverage Δ
srt-protocol/src/protocol/receiver/buffer.rs	68.29% <35.48%> (-2.87%)	⬇️
srt-tokio/src/tokio/socket.rs	78.81% <93.10%> (-1.62%)	⬇️
srt-protocol/src/protocol/sender/buffers.rs	86.36% <94.11%> (+1.36%)	⬆️
srt-protocol/src/event.rs	100.00% <100.00%> (ø)
srt-protocol/src/protocol/mod.rs	88.37% <100.00%> (+0.42%)	⬆️
srt-protocol/src/protocol/receiver/mod.rs	83.76% <100.00%> (-3.63%)	⬇️
...protocol/src/protocol/sender/congestion_control.rs	92.15% <100.00%> (ø)
srt-protocol/src/protocol/sender/mod.rs	85.47% <100.00%> (-3.75%)	⬇️
srt-tokio/src/builder.rs	95.34% <100.00%> (+3.34%)	⬆️
srt-protocol/src/packet.rs	73.33% <0.00%> (-10.00%)	⬇️
... and 28 more

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[robertream]

This is way out of date, plus I'd like to discuss taking an approach for metrics that is closer to what both of the prominent QUIC rust libraries do for metrics: metrics scraping via a bare stats struct. We should least do this with the API for the tokio library. We could end up with an event driven interface for protocol, DuplexConnection in particular, but I'd like to work from the outside in, and creep up on an event driven approach via refactoring. I'd like to bubble events up to the tokio API (e.g. connection errors, key rotations, etc.) but this is a secondary concern, a nice to have. I'd like to just get a few basic metrics implemented first. Just a simple packet tx/rx count would be fine, to start with.

[russelltg]

Yeah, this branch is definitely too stable to be useful, and I think that sounds great--stats is definitely a huge missing feature right now.