Refactor NetworkTables implementation to be more efficent and easier to understand about robotpy-wpilib

[PeterJohnson]

I actually don't think it's that inefficient.. we're writing single bytes but it is buffered by socket.makefile(). I can do some network captures to confirm.

[virtuald]

Maybe.

Another problem that I think I just noticed (I could be wrong) is that you're writing to the network from the robot thread, so the robot will block on network delays. The C++ library had this problem too.

[virtuald]

Actually, there might be a thread in there somewhere.

[PeterJohnson]

It's in a separate thread (WriteManager). I agree the code is very convoluted (the original is a prime example of violating you-aint-gonna-need-it). I've simplified it somewhat from the Java version, but it is still hard to trace how things like updates actually happen.

[virtuald]

Yeah, it is somewhat simpler, but it's still very confusing.

At some point, I'd like to refactor it so it's easier to follow, because there's way too much indirection happening everywhere. I'll change the title of this bug for that.

First though, probably makes sense to get the tests working to validate that the implementation is working, before refactoring.

[PeterJohnson]

I've already started to do some "easy" refactors (merging classes that are only used in one place and the like). Agreed tests are needed, but right now it's almost too convoluted to test efficiently.

[PeterJohnson]

I've also confirmed (with wireshark) we are NOT sending 1-byte payload packets - it's properly buffering and flushing.

[virtuald]

Ok, cool.

[virtuald]

Also, Patrick from WPI had started on a reimplementation of NetworkTables in C++. It could be useful to look at: https://bitbucket.org/byteit101/nwtpp/src

[virtuald]

A good simplification would be to change some (or all) of the listeners to accept callables, instead of requiring overriding a class. Definitely more pythonic.

[PeterJohnson]

We should move this ticket (or rather, close this one and create a new one) to the pynetworktables repo.

[virtuald]

robotpy/pynetworktables#7