Fix testBreakConnection and undo workaround

[facundominguez]

The bug:

A process PA in NA monitors a process PB in NB
NA and NB are disconnected
PA tries to send a message to another process PB1 in NB
A monitor notification about PB1 death arrives to PA
No monitor notification about PB arrives to PA.

This is observed only in tests so far (MonitorNode, MonitorLiveNode, MonitorChannel from CH). These tests break connections with testBreakConnection, which doesn't deliver EventConnectionLost. If the transport delivered EventConnectionLost, then d-p would notify the death of all processes, I hope.

Instead, d-p has a patch that workarounds the problem: haskell-distributed#246

[mboes]

These tests break connections with testBreakConnection, which doesn't deliver EventConnectionLost isn't this a bug specific to the network-transport backend being used during tests?

[facundominguez]

Yes, probably so.

[mboes]

Then move issue to e.g. n-t-tcp? Does n-t-inmemory suffer from the same problem?

[facundominguez]

testBreakConnection is not implemented by n-t-tcp, but it is rather done in d-p-tests [1].

Addressing this probably requires implementing breakConnection in n-t-tcp (now haskell-distributed/network-transport-tcp#39). n-t-inmemory already implements it and AFAICS it does deliver EventConnectionLost.

[1] https://github.com/haskell-distributed/distributed-process/blob/24cc188d83b74cd3094deaf0b94d99473c38c7b1/distributed-process-tests/tests/runTCP.hs#L25