As much as is possible given we currently do some graceful
cancellation join-waiting on any connected sub-actors whenever an active
`local_nursery: AcrtorNursery` in the post-rpc teardown sequence of
`handle_stream_from_peer()` is detected. In such cases we try to allow
the higher level inter-actor (task) context(s) to fully cancelled-ack
before conducting IPC machinery shutdown.
The main immediate motivation for all this is to support unit testing
the `.ipc._server` APIs but in the future may be useful for anyone
wanting to use our modular IPC transport layer sin-"actors".
Impl deats,
- drop passing an `actor: Actor` ref from as many routines in
`.ipc._server` as possible instead opting to use
`._state.current_actor()` where abs needed; thus the fns dropping an
`actor` input param are:
- `open_ipc_server()`
- `IPCServer.listen_on()`
- `._serve_ipc_eps()`
- `.handle_stream_from_peer()`
- factor the above mentioned graceful remote-cancel-ack waiting into
a new `maybe_wait_on_canced_subs()` which is called from
`handle_stream_from_peer()` and delivers a
maybe-`local_nursery: ActorNursery` for downstream logic; it's this
new fn which primarily still needs to call `current_actor()`.
- in `handle_stream_from_peer()` also use `current_actor()` to check if
a handshake is needed (or if it was called as part of some
actor-runtime-less operation like our unit test suite!).
- also don't pass an `actor` to `._rpc.process_messages()` see how-n-why
below..
Surrounding ipc-server client/caller adjustments,
- `._rpc.process_messages()` no longer takes an `actor` input and
now calls `current_actor()` instead.
- `._portal.open_portal()` is adjusted to ^.
- `._runtime.async_main()` is adjusted to the `.ipc._server`'s removal
of `actor` ref passing.
Also,
- drop some server `log.info()`s to `.runtime()`
082d373947