Driven by a bug found in `piker` where we'd get an inf recursion error
due to `BroadcastReceiver.receive()` being called when consumer tasks
are awoken but no value is ready to `.nowait_receive()`.
This new rework takes an approach closer to the interface and internals
of `trio.MemoryReceiveChannel` particularly in terms of,
- implementing a `BroadcastReceiver.receive_nowait()` and using it
within the async `.receive()`.
- failing over to an internal `._receive_from_underlying()` when the
`_nowait()` call raises `trio.WouldBlock`.
- adding `BroadcastState.statistics()` for debugging and testing
dropping recursion from `.receive()`.
We weren't doing this originally I *think* just because of the path
dependent nature of the way the code was developed (originally being
mega pedantic about one-way vs. bidirectional streams) but, it doesn't
seem like there's any issue just calling the stream's `.aclose()`; also
have the benefit of just being less code and logic checks B)
With the new fancy `_pytest.pathlib.import_path()` we can do real
parametrization of the example-script-module code and thus configure
whether the child, parent, or both silently break the IPC connection.
Parametrize the test for all the above mentioned cases as well as the
case where the IPC never breaks but we still simulate the user hammering
ctl-c / SIGINT to terminate the actor tree. Adjust expected errors based
on each case and heavily document each of these.
Use a task nursery in the subactor to spawn tasks which cancel the IPC
channel mid stream to simulate the most concurrent case we're likely to
see. Make `main()` accept a `debug_mode: bool` for parametrization. Fill
out detailed comments/docs on this example.
When backpressure is used and a feeder mem chan breaks during msg
delivery (usually because the IPC allocating task already terminated)
instead of raising we simply warn as we do for the non-backpressure
case.
Also, add a proper `Actor.is_arbiter` test inside `._invoke()` to avoid
doing an arbiter-registry lookup if the current actor **is** the
registrar.
The stdlib has all sorts of muckery with ignoring SIGINT in the
`Pdb._cmdloop()` but here we just override all that since we don't trust
their decisions about cancellation handling whatsoever. Adds
a `Lock.repl: MultiActorPdb` attr which is set by any task which
acquires root TTY lock indicating (via actor global state) that the
current actor is using the debugger REPL and can be expected to re-draw
the prompt on SIGINT. Further we mask out log messages from any actor
who also has the `shield_sigint_handler()` enabled to avoid logging
noise when debugging.
Tyler Goodlet
goodboy