Describe potential synchronization scenarios and desired results

[virtuald]

Synchronization in NT has never been particularly clear cut, and is not documented as clearly as I would like.

I'd like us to write out the various synchronization cases to clarify what we expect the behavior of NT to be in each situation. Then, once that's correct, there should be tests for each (mostly done for pynetworktables), and this table should be added to the NT documentation somewhere. There are terms that need to be defined here:

• Connected: both sides connected and synchronized
• Disconnect: both sides retain internal state (such as a network disconnect)
• Restart: one side does not retain internal state (such as a program restart).

For the purposes of this discussion, client and server are not connected until stated.

Writes before connection

Client writes value

Action	Global NT state	Notes
client foo=1
connected	foo=1

Server writes value

Action	Global NT state	Notes
server foo=1
connected	foo=1

Both write value

Action	Global NT state	Notes
server foo=1
client foo=2
connected	foo=2	client wins

Server restart

Client wrote value locally

Action	Global NT state	Notes
client foo=1
connected	foo=1
server restart
connected	foo=1

Server wrote value

Action	Global NT state	Notes
server foo=1
connected	foo=1
server restart
connected	foo deleted	Not an intuitive result

Both write value

Action	Global NT state	Notes
connected
client foo=1	foo=1
server foo=2	foo=2
server restart
connected	foo=2

Client restart

Action	Global NT state	Notes
client foo=1
connected	foo=1
client restart
connected	foo=1

Action	Global NT state	Notes
server foo=1
connected	foo=1
client restart
connected	foo=1

Action	Global NT state	Notes
server foo=1
connected	foo=1
client restart
server foo=2
connected	foo=2

Disconnect

Server update during disconnect - server initiated value

Action	Global NT state	Notes
connected
server foo=1	foo=1
disconnect
server foo=2
connected	foo=2

Server update during disconnect - client initiated value

Action	Global NT state	Notes
connected
client foo=1	foo=1
disconnect
server foo=2
connected	foo=1	client wins

Client update during disconnect

Action	Global NT state	Notes
connected
client foo=1	foo=1
disconnect
client foo=2
connected	foo=2
client foo=3	foo=3

Both update during disconnect

Action	Global NT state	Notes
connected
client foo=1	foo=1
disconnect
client foo=2
server foo=3
connected	foo=2
client foo=4	foo=4

Client updates during disconnect (both previously written)

Action	Global NT state	Notes
connected
client foo=1	foo=1
server foo=2	foo=2
disconnect
client foo=3
connected	foo=3	issue #270?
client foo=4	foo=4

Client and server updates during disconnect (both previously written)

Action	Global NT state	Notes
connected
client foo=1	foo=1
server foo=2	foo=2
disconnect
server foo=3
client foo=4
connected	foo=4	issue #270?
client foo=5	foo=5