to_asyncio: mask error logging, not sure it adds that much

By spawning an actor task that immediately shuts down the transport
server and then sleeps, verify that attempting to connect via the
`._discovery.find_actor()` helper delivers `None` for the `Portal`
value.

Relates to #184 and #216

docs/README.rst

@@ -3,8 +3,8 @@
 |gh_actions|
 |docs|
 
-``tractor`` is a `structured concurrent`_, multi-processing_ runtime
+``tractor`` is a `structured concurrent`_, (optionally
-built on trio_.
+distributed_) multi-processing_ runtime built on trio_.
 
 Fundamentally, ``tractor`` gives you parallelism via
 ``trio``-"*actors*": independent Python processes (aka
@@ -17,11 +17,20 @@ protocol" constructed on top of multiple Pythons each running a ``trio``
 scheduled runtime - a call to ``trio.run()``.
 
 We believe the system adheres to the `3 axioms`_ of an "`actor model`_"
-but likely *does not* look like what *you* probably think an "actor
+but likely **does not** look like what **you** probably *think* an "actor
-model" looks like, and that's *intentional*.
+model" looks like, and that's **intentional**.
 
-The first step to grok ``tractor`` is to get the basics of ``trio`` down.
+
-A great place to start is the `trio docs`_ and this `blog post`_.
+Where do i start!?
+------------------
+The first step to grok ``tractor`` is to get an intermediate
+knowledge of ``trio`` and **structured concurrency** B)
+
+Some great places to start are,
+- the seminal `blog post`_
+- obviously the `trio docs`_
+- wikipedia's nascent SC_ page
+- the fancy diagrams @ libdill-docs_
 
 
 Features
@@ -593,6 +602,7 @@ matrix seems too hip, we're also mostly all in the the `trio gitter
 channel`_!
 
 .. _structured concurrent: https://trio.discourse.group/t/concise-definition-of-structured-concurrency/228
+.. _distributed: https://en.wikipedia.org/wiki/Distributed_computing
 .. _multi-processing: https://en.wikipedia.org/wiki/Multiprocessing
 .. _trio: https://github.com/python-trio/trio
 .. _nurseries: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/#nurseries-a-structured-replacement-for-go-statements
@@ -611,8 +621,9 @@ channel`_!
 .. _trio docs: https://trio.readthedocs.io/en/latest/
 .. _blog post: https://vorpus.org/blog/notes-on-structured-concurrency-or-go-statement-considered-harmful/
 .. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
+.. _SC: https://en.wikipedia.org/wiki/Structured_concurrency
+.. _libdill-docs: https://sustrik.github.io/libdill/structured-concurrency.html
 .. _structured chadcurrency: https://en.wikipedia.org/wiki/Structured_concurrency
-.. _structured concurrency: https://en.wikipedia.org/wiki/Structured_concurrency
 .. _unrequirements: https://en.wikipedia.org/wiki/Actor_model#Direct_communication_and_asynchrony
 .. _async generators: https://www.python.org/dev/peps/pep-0525/
 .. _trio-parallel: https://github.com/richardsheridan/trio-parallel

examples/debugging/asyncio_bp.py

@@ -0,0 +1,117 @@
+import asyncio
+
+import trio
+import tractor
+from tractor import to_asyncio
+
+
+async def aio_sleep_forever():
+    await asyncio.sleep(float('inf'))
+
+
+async def bp_then_error(
+    to_trio: trio.MemorySendChannel,
+    from_trio: asyncio.Queue,
+
+    raise_after_bp: bool = True,
+
+) -> None:
+
+    # sync with ``trio``-side (caller) task
+    to_trio.send_nowait('start')
+
+    # NOTE: what happens here inside the hook needs some refinement..
+    # => seems like it's still `._debug._set_trace()` but
+    #    we set `Lock.local_task_in_debug = 'sync'`, we probably want
+    #    some further, at least, meta-data about the task/actoq in debug
+    #    in terms of making it clear it's asyncio mucking about.
+    breakpoint()
+
+    # short checkpoint / delay
+    await asyncio.sleep(0.5)
+
+    if raise_after_bp:
+        raise ValueError('blah')
+
+    # TODO: test case with this so that it gets cancelled?
+    else:
+        # XXX NOTE: this is required in order to get the SIGINT-ignored
+        # hang case documented in the module script section!
+        await aio_sleep_forever()
+
+
+@tractor.context
+async def trio_ctx(
+    ctx: tractor.Context,
+    bp_before_started: bool = False,
+):
+
+    # this will block until the ``asyncio`` task sends a "first"
+    # message, see first line in above func.
+    async with (
+
+        to_asyncio.open_channel_from(
+            bp_then_error,
+            raise_after_bp=not bp_before_started,
+        ) as (first, chan),
+
+        trio.open_nursery() as n,
+    ):
+
+        assert first == 'start'
+
+        if bp_before_started:
+            await tractor.breakpoint()
+
+        await ctx.started(first)
+
+        n.start_soon(
+            to_asyncio.run_task,
+            aio_sleep_forever,
+        )
+        await trio.sleep_forever()
+
+
+async def main(
+    bps_all_over: bool = False,
+
+) -> None:
+
+    async with tractor.open_nursery() as n:
+
+        p = await n.start_actor(
+            'aio_daemon',
+            enable_modules=[__name__],
+            infect_asyncio=True,
+            debug_mode=True,
+            loglevel='cancel',
+        )
+
+        async with p.open_context(
+            trio_ctx,
+            bp_before_started=bps_all_over,
+        ) as (ctx, first):
+
+            assert first == 'start'
+
+            if bps_all_over:
+                await tractor.breakpoint()
+
+            # await trio.sleep_forever()
+            await ctx.cancel()
+            assert 0
+
+        # TODO: case where we cancel from trio-side while asyncio task
+        # has debugger lock?
+        # await p.cancel_actor()
+
+
+if __name__ == '__main__':
+
+    # works fine B)
+    trio.run(main)
+
+    # will hang and ignores SIGINT !!
+    # NOTE: you'll need to send a SIGQUIT (via ctl-\) to kill it
+    # manually..
+    # trio.run(main, True)

requirements-test.txt

@@ -6,3 +6,4 @@ mypy
 trio_typing
 pexpect
 towncrier
+numpy

setup.py

@@ -41,6 +41,9 @@ setup(
     ],
     install_requires=[
 
+        # discovery subsys
+        'bidict',
+
         # trio related
         # proper range spec:
         # https://packaging.python.org/en/latest/discussions/install-requires-vs-requirements/#id5

tests/conftest.py

@@ -219,7 +219,8 @@ def daemon(
     arb_addr: tuple[str, int],
 ):
     '''
-    Run a daemon actor as a "remote arbiter".
+    Run a daemon actor as a "remote registrar" and/or plain ol
+    separate actor (service) tree.
 
     '''
     if loglevel in ('trace', 'debug'):

tests/test_clustering.py

@@ -49,7 +49,7 @@ async def worker(
     await ctx.started()
 
     async with ctx.open_stream(
-        backpressure=True,
+        allow_overruns=True,
     ) as stream:
 
         # TODO: this with the below assert causes a hang bug?

tests/test_context_stream_semantics.py

@@ -13,7 +13,10 @@ from typing import Optional
 import pytest
 import trio
 import tractor
-from tractor._exceptions import StreamOverrun
+from tractor._exceptions import (
+    StreamOverrun,
+    ContextCancelled,
+)
 
 from conftest import tractor_test
 
@@ -91,7 +94,10 @@ async def not_started_but_stream_opened(
 
 @pytest.mark.parametrize(
     'target',
-    [too_many_starteds, not_started_but_stream_opened],
+    [
+        too_many_starteds,
+        not_started_but_stream_opened,
+    ],
     ids='misuse_type={}'.format,
 )
 def test_started_misuse(target):
@@ -228,6 +234,88 @@ def test_simple_context(
         trio.run(main)
 
 
+@pytest.mark.parametrize(
+    'callee_returns_early',
+    [True, False],
+    ids=lambda item: f'callee_returns_early={item}'
+)
+@pytest.mark.parametrize(
+    'cancel_method',
+    ['ctx', 'portal'],
+    ids=lambda item: f'cancel_method={item}'
+)
+@pytest.mark.parametrize(
+    'chk_ctx_result_before_exit',
+    [True, False],
+    ids=lambda item: f'chk_ctx_result_before_exit={item}'
+)
+def test_caller_cancels(
+    cancel_method: str,
+    chk_ctx_result_before_exit: bool,
+    callee_returns_early: bool,
+):
+    '''
+    Verify that when the opening side of a context (aka the caller)
+    cancels that context, the ctx does not raise a cancelled when
+    either calling `.result()` or on context exit.
+
+    '''
+    async def check_canceller(
+        ctx: tractor.Context,
+    ) -> None:
+        # should not raise yet return the remote
+        # context cancelled error.
+        res = await ctx.result()
+
+        if callee_returns_early:
+            assert res == 'yo'
+
+        else:
+            err = res
+            assert isinstance(err, ContextCancelled)
+            assert (
+                tuple(err.canceller)
+                ==
+                tractor.current_actor().uid
+            )
+
+    async def main():
+        async with tractor.open_nursery() as nursery:
+            portal = await nursery.start_actor(
+                'simple_context',
+                enable_modules=[__name__],
+            )
+            timeout = 0.5 if not callee_returns_early else 2
+            with trio.fail_after(timeout):
+                async with portal.open_context(
+                    simple_setup_teardown,
+                    data=10,
+                    block_forever=not callee_returns_early,
+                ) as (ctx, sent):
+
+                    if callee_returns_early:
+                        # ensure we block long enough before sending
+                        # a cancel such that the callee has already
+                        # returned it's result.
+                        await trio.sleep(0.5)
+
+                    if cancel_method == 'ctx':
+                        await ctx.cancel()
+                    else:
+                        await portal.cancel_actor()
+
+                    if chk_ctx_result_before_exit:
+                        await check_canceller(ctx)
+
+            if not chk_ctx_result_before_exit:
+                await check_canceller(ctx)
+
+            if cancel_method != 'portal':
+                await portal.cancel_actor()
+
+    trio.run(main)
+
+
 # basic stream terminations:
 # - callee context closes without using stream
 # - caller context closes without using stream
@@ -506,7 +594,6 @@ async def test_callee_cancels_before_started():
                 cancel_self,
             ) as (ctx, sent):
                 async with ctx.open_stream():
-
                     await trio.sleep_forever()
 
         # raises a special cancel signal
@@ -559,7 +646,6 @@ async def keep_sending_from_callee(
     'overrun_by',
     [
         ('caller', 1, never_open_stream),
-        ('cancel_caller_during_overrun', 1, never_open_stream),
         ('callee', 0, keep_sending_from_callee),
     ],
     ids='overrun_condition={}'.format,
@@ -589,14 +675,13 @@ def test_one_end_stream_not_opened(overrun_by):
                 if 'caller' in overrunner:
 
                     async with ctx.open_stream() as stream:
+
+                        # itersend +1 msg more then the buffer size
+                        # to cause the most basic overrun.
                         for i in range(buf_size):
                             print(f'sending {i}')
                             await stream.send(i)
 
-                        if 'cancel' in overrunner:
-                            # without this we block waiting on the child side
-                            await ctx.cancel()
-
                         else:
                             # expect overrun error to be relayed back
                             # and this sleep interrupted
@@ -610,7 +695,9 @@ def test_one_end_stream_not_opened(overrun_by):
 
     # 2 overrun cases and the no overrun case (which pushes right up to
     # the msg limit)
-    if overrunner == 'caller' or 'cance' in overrunner:
+    if (
+        overrunner == 'caller'
+    ):
         with pytest.raises(tractor.RemoteActorError) as excinfo:
             trio.run(main)
 
@@ -634,40 +721,102 @@ async def echo_back_sequence(
 
     ctx:  tractor.Context,
     seq: list[int],
-    msg_buffer_size: Optional[int] = None,
+    wait_for_cancel: bool,
+    allow_overruns_side: str,
+    be_slow: bool = False,
+    msg_buffer_size: int = 1,
 
 ) -> None:
     '''
-    Send endlessly on the calleee stream.
+    Send endlessly on the calleee stream using a small buffer size
+    setting on the contex to simulate backlogging that would normally
+    cause overruns.
 
     '''
+    # NOTE: ensure that if the caller is expecting to cancel this task
+    # that we stay echoing much longer then they are so we don't
+    # return early instead of receive the cancel msg.
+    total_batches: int = 1000 if wait_for_cancel else 6
+
     await ctx.started()
+    # await tractor.breakpoint()
     async with ctx.open_stream(
         msg_buffer_size=msg_buffer_size,
+
+        # literally the point of this test XD
+        allow_overruns=(allow_overruns_side in {'child', 'both'}),
     ) as stream:
 
-        seq = list(seq)  # bleh, `msgpack`...
+        # ensure mem chan settings are correct
-        count = 0
+        assert (
-        while count < 3:
+            ctx._send_chan._state.max_buffer_size
+            ==
+            msg_buffer_size
+        )
+
+        seq = list(seq)  # bleh, msgpack sometimes ain't decoded right
+        for _ in range(total_batches):
             batch = []
             async for msg in stream:
                 batch.append(msg)
                 if batch == seq:
                     break
 
+                if be_slow:
+                    await trio.sleep(0.05)
+
+                print('callee waiting on next')
+
             for msg in batch:
                 print(f'callee sending {msg}')
                 await stream.send(msg)
 
-            count += 1
+    print(
-
+        'EXITING CALLEEE:\n'
+        f'{ctx.cancel_called_remote}'
+    )
     return 'yo'
 
 
-def test_stream_backpressure():
+@pytest.mark.parametrize(
+    # aka the side that will / should raise
+    # and overrun under normal conditions.
+    'allow_overruns_side',
+    ['parent', 'child', 'none', 'both'],
+    ids=lambda item: f'allow_overruns_side={item}'
+)
+@pytest.mark.parametrize(
+    # aka the side that will / should raise
+    # and overrun under normal conditions.
+    'slow_side',
+    ['parent', 'child'],
+    ids=lambda item: f'slow_side={item}'
+)
+@pytest.mark.parametrize(
+    'cancel_ctx',
+    [True, False],
+    ids=lambda item: f'cancel_ctx={item}'
+)
+def test_maybe_allow_overruns_stream(
+    cancel_ctx: bool,
+    slow_side: str,
+    allow_overruns_side: str,
+    loglevel: str,
+):
     '''
     Demonstrate small overruns of each task back and forth
-    on a stream not raising any errors by default.
+    on a stream not raising any errors by default by setting
+    the ``allow_overruns=True``.
+
+    The original idea here was to show that if you set the feeder mem
+    chan to a size smaller then the # of msgs sent you could could not
+    get a `StreamOverrun` crash plus maybe get all the msgs that were
+    sent. The problem with the "real backpressure" case is that due to
+    the current arch it can result in the msg loop being blocked and thus
+    blocking cancellation - which is like super bad. So instead this test
+    had to be adjusted to more or less just "not send overrun errors" so
+    as to handle the case where the sender just moreso cares about not getting
+    errored out when it send to fast..
 
     '''
     async def main():
@@ -675,39 +824,105 @@ def test_stream_backpressure():
             portal = await n.start_actor(
                 'callee_sends_forever',
                 enable_modules=[__name__],
+                loglevel=loglevel,
+
+                # debug_mode=True,
             )
-            seq = list(range(3))
+            seq = list(range(10))
             async with portal.open_context(
                 echo_back_sequence,
                 seq=seq,
-                msg_buffer_size=1,
+                wait_for_cancel=cancel_ctx,
+                be_slow=(slow_side == 'child'),
+                allow_overruns_side=allow_overruns_side,
             ) as (ctx, sent):
+
                 assert sent is None
 
-                async with ctx.open_stream(msg_buffer_size=1) as stream:
+                async with ctx.open_stream(
-                    count = 0
+                    msg_buffer_size=1 if slow_side == 'parent' else None,
-                    while count < 3:
+                    allow_overruns=(allow_overruns_side in {'parent', 'both'}),
+                ) as stream:
+
+                    total_batches: int = 2
+                    for _ in range(total_batches):
                         for msg in seq:
-                            print(f'caller sending {msg}')
+                            # print(f'root tx {msg}')
                             await stream.send(msg)
-                            await trio.sleep(0.1)
+                            if slow_side == 'parent':
+                                # NOTE: we make the parent slightly
+                                # slower, when it is slow, to make sure
+                                # that in the overruns everywhere case
+                                await trio.sleep(0.16)
 
                         batch = []
                         async for msg in stream:
+                            print(f'root rx {msg}')
                             batch.append(msg)
                             if batch == seq:
                                 break
 
-                        count += 1
+                if cancel_ctx:
+                    # cancel the remote task
+                    print('sending root side cancel')
+                    await ctx.cancel()
 
-            # here the context should return
+            res = await ctx.result()
-            assert await ctx.result() == 'yo'
+
+            if cancel_ctx:
+                assert isinstance(res, ContextCancelled)
+                assert tuple(res.canceller) == tractor.current_actor().uid
+
+            else:
+                print(f'RX ROOT SIDE RESULT {res}')
+                assert res == 'yo'
 
             # cancel the daemon
             await portal.cancel_actor()
 
+    if (
+        allow_overruns_side == 'both'
+        or slow_side == allow_overruns_side
+    ):
         trio.run(main)
 
+    elif (
+        slow_side != allow_overruns_side
+    ):
+
+        with pytest.raises(tractor.RemoteActorError) as excinfo:
+            trio.run(main)
+
+        err = excinfo.value
+
+        if (
+            allow_overruns_side == 'none'
+        ):
+            # depends on timing is is racy which side will
+            # overrun first :sadkitty:
+
+            # NOTE: i tried to isolate to a deterministic case here
+            # based on timeing, but i was kinda wasted, and i don't
+            # think it's sane to catch them..
+            assert err.type in (
+                tractor.RemoteActorError,
+                StreamOverrun,
+            )
+
+        elif (
+            slow_side == 'child'
+        ):
+            assert err.type == StreamOverrun
+
+        elif slow_side == 'parent':
+            assert err.type == tractor.RemoteActorError
+            assert 'StreamOverrun' in err.msgdata['tb_str']
+
+    else:
+        # if this hits the logic blocks from above are not
+        # exhaustive..
+        pytest.fail('PARAMETRIZED CASE GEN PROBLEM YO')
+
 
 @tractor.context
 async def sleep_forever(
@@ -737,18 +952,18 @@ async def attach_to_sleep_forever():
             finally:
                 # XXX: previously this would trigger local
                 # ``ContextCancelled`` to be received and raised in the
-                # local context overriding any local error due to
+                # local context overriding any local error due to logic
-                # logic inside ``_invoke()`` which checked for
+                # inside ``_invoke()`` which checked for an error set on
-                # an error set on ``Context._error`` and raised it in
+                # ``Context._error`` and raised it in a cancellation
-                # under a cancellation scenario.
+                # scenario.
-
+                # ------
-                # The problem is you can have a remote cancellation
+                # The problem is you can have a remote cancellation that
-                # that is part of a local error and we shouldn't raise
+                # is part of a local error and we shouldn't raise
-                # ``ContextCancelled`` **iff** we weren't the side of
+                # ``ContextCancelled`` **iff** we **were not** the side
-                # the context to initiate it, i.e.
+                # of the context to initiate it, i.e.
                 # ``Context._cancel_called`` should **NOT** have been
                 # set. The special logic to handle this case is now
-                # inside ``Context._may_raise_from_remote_msg()`` XD
+                # inside ``Context._maybe_raise_from_remote_msg()`` XD
                 await peer_ctx.cancel()
 
 
@@ -769,9 +984,10 @@ async def error_before_started(
 
 def test_do_not_swallow_error_before_started_by_remote_contextcancelled():
     '''
-    Verify that an error raised in a remote context which itself opens another
+    Verify that an error raised in a remote context which itself opens
-    remote context, which it cancels, does not ovverride the original error that
+    another remote context, which it cancels, does not ovverride the
-    caused the cancellation of the secondardy context.
+    original error that caused the cancellation of the secondardy
+    context.
 
     '''
     async def main():

tests/test_discovery.py

@@ -1,6 +1,7 @@
-"""
+'''
-Actor "discovery" testing
+Discovery subsystem via a "registrar" actor scenarios.
-"""
+
+'''
 import os
 import signal
 import platform
@@ -127,7 +128,10 @@ async def unpack_reg(actor_or_portal):
     else:
         msg = await actor_or_portal.run_from_ns('self', 'get_registry')
 
-    return {tuple(key.split('.')): val for key, val in msg.items()}
+    return {
+        tuple(key.split('.')): val
+        for key, val in msg.items()
+    }
 
 
 async def spawn_and_check_registry(
@@ -283,18 +287,22 @@ async def close_chans_before_nursery(
 
                 async with tractor.open_nursery() as tn:
                     portal1 = await tn.start_actor(
-                        name='consumer1', enable_modules=[__name__])
+                        name='consumer1',
+                        enable_modules=[__name__],
+                    )
                     portal2 = await tn.start_actor(
-                        'consumer2', enable_modules=[__name__])
+                        'consumer2',
+                        enable_modules=[__name__],
+                    )
 
-                    # TODO: compact this back as was in last commit once
+                    async with (
-                    # 3.9+, see https://github.com/goodboy/tractor/issues/207
+                        portal1.open_stream_from(
-                    async with portal1.open_stream_from(
                             stream_forever
-                    ) as agen1:
+                        ) as agen1,
-                        async with portal2.open_stream_from(
+                        portal2.open_stream_from(
                             stream_forever
-                        ) as agen2:
+                        ) as agen2,
+                    ):
                         async with trio.open_nursery() as n:
                             n.start_soon(streamer, agen1)
                             n.start_soon(cancel, use_signal, .5)
@@ -331,10 +339,12 @@ def test_close_channel_explicit(
     use_signal,
     arb_addr,
 ):
-    """Verify that closing a stream explicitly and killing the actor's
+    '''
+    Verify that closing a stream explicitly and killing the actor's
     "root nursery" **before** the containing nursery tears down also
     results in subactor(s) deregistering from the arbiter.
-    """
+
+    '''
     with pytest.raises(KeyboardInterrupt):
         trio.run(
             partial(
@@ -347,16 +357,18 @@ def test_close_channel_explicit(
 
 
 @pytest.mark.parametrize('use_signal', [False, True])
-def test_close_channel_explicit_remote_arbiter(
+def test_close_channel_explicit_remote_registrar(
     daemon,
     start_method,
     use_signal,
     arb_addr,
 ):
-    """Verify that closing a stream explicitly and killing the actor's
+    '''
+    Verify that closing a stream explicitly and killing the actor's
     "root nursery" **before** the containing nursery tears down also
     results in subactor(s) deregistering from the arbiter.
-    """
+
+    '''
     with pytest.raises(KeyboardInterrupt):
         trio.run(
             partial(
@@ -366,3 +378,51 @@ def test_close_channel_explicit_remote_arbiter(
                 remote_arbiter=True,
             ),
         )
+
+
+@tractor.context
+async def kill_transport(
+    ctx: tractor.Context,
+) -> None:
+
+    await ctx.started()
+    actor: tractor.Actor = tractor.current_actor()
+    actor.cancel_server()
+    await trio.sleep_forever()
+
+
+
+# @pytest.mark.parametrize('use_signal', [False, True])
+def test_stale_entry_is_deleted(
+    daemon,
+    start_method,
+    arb_addr,
+):
+    '''
+    Ensure that when a stale entry is detected in the registrar's table
+    that the `find_actor()` API takes care of deleting the stale entry
+    and not delivering a bad portal.
+
+    '''
+    async def main():
+
+        name: str = 'transport_fails_actor'
+        regport: tractor.Portal
+        tn: tractor.ActorNursery
+        async with (
+            tractor.open_nursery() as tn,
+            tractor.get_registrar(*arb_addr) as regport,
+        ):
+            ptl: tractor.Portal = await tn.start_actor(
+                name,
+                enable_modules=[__name__],
+            )
+            async with ptl.open_context(
+                kill_transport,
+            ) as (first, ctx):
+                async with tractor.find_actor(name) as maybe_portal:
+                    assert maybe_portal is None
+
+                await ptl.cancel_actor()
+
+    trio.run(main)

tests/test_infected_asyncio.py

@@ -15,6 +15,7 @@ import tractor
 from tractor import (
     to_asyncio,
     RemoteActorError,
+    ContextCancelled,
 )
 from tractor.trionics import BroadcastReceiver
 
@@ -224,14 +225,23 @@ def test_context_spawns_aio_task_that_errors(
 
                     await trio.sleep_forever()
 
-    with pytest.raises(RemoteActorError) as excinfo:
+        return await ctx.result()
+
+    if parent_cancels:
+        # bc the parent made the cancel request,
+        # the error is not raised locally but instead
+        # the context is exited silently
+        res = trio.run(main)
+        assert isinstance(res, ContextCancelled)
+        assert 'root' in res.canceller[0]
+
+    else:
+        expect = RemoteActorError
+        with pytest.raises(expect) as excinfo:
             trio.run(main)
 
         err = excinfo.value
-    assert isinstance(err, RemoteActorError)
+        assert isinstance(err, expect)
-    if parent_cancels:
-        assert err.type == trio.Cancelled
-    else:
         assert err.type == AssertionError
 
 

tests/test_shm.py

@@ -0,0 +1,167 @@
+"""
+Shared mem primitives and APIs.
+
+"""
+import uuid
+
+# import numpy
+import pytest
+import trio
+import tractor
+from tractor._shm import (
+    open_shm_list,
+    attach_shm_list,
+)
+
+
+@tractor.context
+async def child_attach_shml_alot(
+    ctx: tractor.Context,
+    shm_key: str,
+) -> None:
+
+    await ctx.started(shm_key)
+
+    # now try to attach a boatload of times in a loop..
+    for _ in range(1000):
+        shml = attach_shm_list(
+            key=shm_key,
+            readonly=False,
+        )
+        assert shml.shm.name == shm_key
+        await trio.sleep(0.001)
+
+
+def test_child_attaches_alot():
+    async def main():
+        async with tractor.open_nursery() as an:
+
+            # allocate writeable list in parent
+            key = f'shml_{uuid.uuid4()}'
+            shml = open_shm_list(
+                key=key,
+            )
+
+            portal = await an.start_actor(
+                'shm_attacher',
+                enable_modules=[__name__],
+            )
+
+            async with (
+                portal.open_context(
+                    child_attach_shml_alot,
+                    shm_key=shml.key,
+                ) as (ctx, start_val),
+            ):
+                assert start_val == key
+                await ctx.result()
+
+            await portal.cancel_actor()
+
+    trio.run(main)
+
+
+@tractor.context
+async def child_read_shm_list(
+    ctx: tractor.Context,
+    shm_key: str,
+    use_str: bool,
+    frame_size: int,
+) -> None:
+
+    # attach in child
+    shml = attach_shm_list(
+        key=shm_key,
+        # dtype=str if use_str else float,
+    )
+    await ctx.started(shml.key)
+
+    async with ctx.open_stream() as stream:
+        async for i in stream:
+            print(f'(child): reading shm list index: {i}')
+
+            if use_str:
+                expect = str(float(i))
+            else:
+                expect = float(i)
+
+            if frame_size == 1:
+                val = shml[i]
+                assert expect == val
+                print(f'(child): reading value: {val}')
+            else:
+                frame = shml[i - frame_size:i]
+                print(f'(child): reading frame: {frame}')
+
+
+@pytest.mark.parametrize(
+    'use_str',
+    [False, True],
+    ids=lambda i: f'use_str_values={i}',
+)
+@pytest.mark.parametrize(
+    'frame_size',
+    [1, 2**6, 2**10],
+    ids=lambda i: f'frame_size={i}',
+)
+def test_parent_writer_child_reader(
+    use_str: bool,
+    frame_size: int,
+):
+
+    async def main():
+        async with tractor.open_nursery(
+            # debug_mode=True,
+        ) as an:
+
+            portal = await an.start_actor(
+                'shm_reader',
+                enable_modules=[__name__],
+                debug_mode=True,
+            )
+
+            # allocate writeable list in parent
+            key = 'shm_list'
+            seq_size = int(2 * 2 ** 10)
+            shml = open_shm_list(
+                key=key,
+                size=seq_size,
+                dtype=str if use_str else float,
+                readonly=False,
+            )
+
+            async with (
+                portal.open_context(
+                    child_read_shm_list,
+                    shm_key=key,
+                    use_str=use_str,
+                    frame_size=frame_size,
+                ) as (ctx, sent),
+
+                ctx.open_stream() as stream,
+            ):
+
+                assert sent == key
+
+                for i in range(seq_size):
+
+                    val = float(i)
+                    if use_str:
+                        val = str(val)
+
+                    # print(f'(parent): writing {val}')
+                    shml[i] = val
+
+                    # only on frame fills do we
+                    # signal to the child that a frame's
+                    # worth is ready.
+                    if (i % frame_size) == 0:
+                        print(f'(parent): signalling frame full on {val}')
+                        await stream.send(i)
+                else:
+                    print(f'(parent): signalling final frame on {val}')
+                    await stream.send(i)
+
+            await portal.cancel_actor()
+
+    trio.run(main)

tests/test_task_broadcasting.py

@@ -86,7 +86,7 @@ async def open_sequence_streamer(
         ) as (ctx, first):
 
             assert first is None
-            async with ctx.open_stream(backpressure=True) as stream:
+            async with ctx.open_stream(allow_overruns=True) as stream:
                 yield stream
 
         await portal.cancel_actor()
@@ -413,8 +413,8 @@ def test_ensure_slow_consumers_lag_out(
                     seq = brx._state.subs[brx.key]
                     assert seq == len(brx._state.queue) - 1
 
-                # all backpressured entries in the underlying
+                # all no_overruns entries in the underlying
-                # channel should have been copied into the caster
+                # channel should have been copied into the bcaster
                 # queue trailing-window
                 async for i in rx:
                     print(f'bped: {i}')

tractor/__init__.py

@@ -15,21 +15,23 @@
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 """
-tractor: structured concurrent "actors".
+tractor: structured concurrent ``trio``-"actors".
 
 """
 from exceptiongroup import BaseExceptionGroup
 
 from ._clustering import open_actor_cluster
-from ._ipc import Channel
+from ._context import (
-from ._streaming import (
     Context,
+    context,
+)
+from ._streaming import (
     MsgStream,
     stream,
-    context,
 )
 from ._discovery import (
     get_arbiter,
+    get_registrar,
     find_actor,
     wait_for_actor,
     query_actor,
@@ -46,6 +48,8 @@ from ._exceptions import (
 )
 from ._debug import (
     breakpoint,
+    pause,
+    pause_from_sync,
     post_mortem,
 )
 from . import msg
@@ -53,31 +57,36 @@ from ._root import (
     run_daemon,
     open_root_actor,
 )
+from ._ipc import Channel
 from ._portal import Portal
 from ._runtime import Actor
 
 
 __all__ = [
     'Actor',
+    'BaseExceptionGroup',
     'Channel',
     'Context',
     'ContextCancelled',
     'ModuleNotExposed',
     'MsgStream',
-    'BaseExceptionGroup',
     'Portal',
     'RemoteActorError',
     'breakpoint',
     'context',
     'current_actor',
     'find_actor',
+    'query_actor',
     'get_arbiter',
+    'get_registrar',
     'is_root_process',
     'msg',
     'open_actor_cluster',
     'open_nursery',
     'open_root_actor',
+    'pause',
     'post_mortem',
+    'pause_from_sync',
     'query_actor',
     'run_daemon',
     'stream',

tractor/_context.py

@@ -0,0 +1,778 @@
+# tractor: structured concurrent "actors".
+# Copyright 2018-eternity Tyler Goodlet.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+'''
+The fundamental cross process SC abstraction: an inter-actor,
+cancel-scope linked task "context".
+
+A ``Context`` is very similar to the ``trio.Nursery.cancel_scope`` built
+into each ``trio.Nursery`` except it links the lifetimes of memory space
+disjoint, parallel executing tasks in separate actors.
+
+'''
+from __future__ import annotations
+from collections import deque
+from contextlib import asynccontextmanager as acm
+from dataclasses import (
+    dataclass,
+    field,
+)
+from functools import partial
+import inspect
+from pprint import pformat
+from typing import (
+    Any,
+    Callable,
+    AsyncGenerator,
+    TYPE_CHECKING,
+)
+import warnings
+
+import trio
+
+from ._exceptions import (
+    unpack_error,
+    pack_error,
+    ContextCancelled,
+    StreamOverrun,
+)
+from .log import get_logger
+from ._ipc import Channel
+from ._streaming import MsgStream
+from ._state import current_actor
+
+if TYPE_CHECKING:
+    from ._portal import Portal
+
+
+log = get_logger(__name__)
+
+
+@dataclass
+class Context:
+    '''
+    An inter-actor, ``trio``-task communication context.
+
+    NB: This class should never be instatiated directly, it is delivered
+    by either,
+     - runtime machinery to a remotely started task or,
+     - by entering ``Portal.open_context()``.
+
+     and is always constructed using ``mkt_context()``.
+
+    Allows maintaining task or protocol specific state between
+    2 communicating, parallel executing actor tasks. A unique context is
+    allocated on each side of any task RPC-linked msg dialog, for
+    every request to a remote actor from a portal. On the "callee"
+    side a context is always allocated inside ``._runtime._invoke()``.
+
+    A context can be cancelled and (possibly eventually restarted) from
+    either side of the underlying IPC channel, it can also open task
+    oriented message streams,  and acts more or less as an IPC aware
+    inter-actor-task ``trio.CancelScope``.
+
+    '''
+    chan: Channel
+    cid: str
+
+    # these are the "feeder" channels for delivering
+    # message values to the local task from the runtime
+    # msg processing loop.
+    _recv_chan: trio.MemoryReceiveChannel
+    _send_chan: trio.MemorySendChannel
+
+    _remote_func_type: str | None = None
+
+    # only set on the caller side
+    _portal: Portal | None = None    # type: ignore # noqa
+    _result: Any | int = None
+    _remote_error: BaseException | None = None
+
+    # cancellation state
+    _cancel_called: bool = False
+    _cancelled_remote: tuple | None = None
+    _cancel_msg: str | None = None
+    _scope: trio.CancelScope | None = None
+    _enter_debugger_on_cancel: bool = True
+
+    @property
+    def cancel_called(self) -> bool:
+        '''
+        Records whether cancellation has been requested for this context
+        by either an explicit call to  ``.cancel()`` or an implicit call
+        due to an error caught inside the ``Portal.open_context()``
+        block.
+
+        '''
+        return self._cancel_called
+
+    @property
+    def cancel_called_remote(self) -> tuple[str, str] | None:
+        '''
+        ``Actor.uid`` of the remote actor who's task was cancelled
+        causing this side of the context to also be cancelled.
+
+        '''
+        remote_uid = self._cancelled_remote
+        if remote_uid:
+            return tuple(remote_uid)
+
+    @property
+    def cancelled_caught(self) -> bool:
+        return self._scope.cancelled_caught
+
+    # init and streaming state
+    _started_called: bool = False
+    _started_received: bool = False
+    _stream_opened: bool = False
+
+    # overrun handling machinery
+    # NOTE: none of this provides "backpressure" to the remote
+    # task, only an ability to not lose messages when the local
+    # task is configured to NOT transmit ``StreamOverrun``s back
+    # to the other side.
+    _overflow_q: deque[dict] = field(
+        default_factory=partial(
+            deque,
+            maxlen=616,
+        )
+    )
+    _scope_nursery: trio.Nursery | None = None
+    _in_overrun: bool = False
+    _allow_overruns: bool = False
+
+    async def send_yield(
+        self,
+        data: Any,
+
+    ) -> None:
+
+        warnings.warn(
+            "`Context.send_yield()` is now deprecated. "
+            "Use ``MessageStream.send()``. ",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        await self.chan.send({'yield': data, 'cid': self.cid})
+
+    async def send_stop(self) -> None:
+        await self.chan.send({'stop': True, 'cid': self.cid})
+
+    async def _maybe_cancel_and_set_remote_error(
+        self,
+        error_msg: dict[str, Any],
+
+    ) -> None:
+        '''
+        (Maybe) unpack and raise a msg error into the local scope
+        nursery for this context.
+
+        Acts as a form of "relay" for a remote error raised
+        in the corresponding remote callee task.
+
+        '''
+        # If this is an error message from a context opened by
+        # ``Portal.open_context()`` we want to interrupt any ongoing
+        # (child) tasks within that context to be notified of the remote
+        # error relayed here.
+        #
+        # The reason we may want to raise the remote error immediately
+        # is that there is no guarantee the associated local task(s)
+        # will attempt to read from any locally opened stream any time
+        # soon.
+        #
+        # NOTE: this only applies when
+        # ``Portal.open_context()`` has been called since it is assumed
+        # (currently) that other portal APIs (``Portal.run()``,
+        # ``.run_in_actor()``) do their own error checking at the point
+        # of the call and result processing.
+        error = unpack_error(
+            error_msg,
+            self.chan,
+        )
+
+        # XXX: set the remote side's error so that after we cancel
+        # whatever task is the opener of this context it can raise
+        # that error as the reason.
+        self._remote_error = error
+
+        # always record the remote actor's uid since its cancellation
+        # state is directly linked to ours (the local one).
+        self._cancelled_remote = self.chan.uid
+
+        if (
+            isinstance(error, ContextCancelled)
+        ):
+            log.cancel(
+                'Remote task-context sucessfully cancelled for '
+                f'{self.chan.uid}:{self.cid}'
+            )
+
+            if self._cancel_called:
+                # from ._debug import breakpoint
+                # await breakpoint()
+
+                # this is an expected cancel request response message
+                # and we **don't need to raise it** in local cancel
+                # scope since it will potentially override a real error.
+                return
+        else:
+            log.error(
+                f'Remote context error for {self.chan.uid}:{self.cid}:\n'
+                f'{error_msg["error"]["tb_str"]}'
+            )
+        # TODO: tempted to **not** do this by-reraising in a
+        # nursery and instead cancel a surrounding scope, detect
+        # the cancellation, then lookup the error that was set?
+        # YES! this is way better and simpler!
+        if (
+            self._scope
+        ):
+            # from trio.testing import wait_all_tasks_blocked
+            # await wait_all_tasks_blocked()
+            # self._cancelled_remote = self.chan.uid
+            self._scope.cancel()
+
+            # NOTE: this usage actually works here B)
+            # from ._debug import breakpoint
+            # await breakpoint()
+
+        # XXX: this will break early callee results sending
+        # since when `.result()` is finally called, this
+        # chan will be closed..
+        # if self._recv_chan:
+        #     await self._recv_chan.aclose()
+
+    async def cancel(
+        self,
+        msg: str | None = None,
+        timeout: float = 0.616,
+        # timeout: float = 1000,
+
+    ) -> None:
+        '''
+        Cancel this inter-actor-task context.
+
+        Request that the far side cancel it's current linked context,
+        Timeout quickly in an attempt to sidestep 2-generals...
+
+        '''
+        side = 'caller' if self._portal else 'callee'
+        if msg:
+            assert side == 'callee', 'Only callee side can provide cancel msg'
+
+        log.cancel(f'Cancelling {side} side of context to {self.chan.uid}')
+
+        self._cancel_called = True
+        # await _debug.breakpoint()
+        # breakpoint()
+
+        if side == 'caller':
+            if not self._portal:
+                raise RuntimeError(
+                    "No portal found, this is likely a callee side context"
+                )
+
+            cid = self.cid
+            with trio.move_on_after(timeout) as cs:
+                cs.shield = True
+                log.cancel(
+                    f"Cancelling stream {cid} to "
+                    f"{self._portal.channel.uid}")
+
+                # NOTE: we're telling the far end actor to cancel a task
+                # corresponding to *this actor*. The far end local channel
+                # instance is passed to `Actor._cancel_task()` implicitly.
+                await self._portal.run_from_ns(
+                    'self',
+                    '_cancel_task',
+                    cid=cid,
+                )
+                # print("EXITING CANCEL CALL")
+
+            if cs.cancelled_caught:
+                # XXX: there's no way to know if the remote task was indeed
+                # cancelled in the case where the connection is broken or
+                # some other network error occurred.
+                # if not self._portal.channel.connected():
+                if not self.chan.connected():
+                    log.cancel(
+                        "May have failed to cancel remote task "
+                        f"{cid} for {self._portal.channel.uid}")
+                else:
+                    log.cancel(
+                        "Timed out on cancelling remote task "
+                        f"{cid} for {self._portal.channel.uid}")
+
+        # callee side remote task
+        else:
+            self._cancel_msg = msg
+
+            # TODO: should we have an explicit cancel message
+            # or is relaying the local `trio.Cancelled` as an
+            # {'error': trio.Cancelled, cid: "blah"} enough?
+            # This probably gets into the discussion in
+            # https://github.com/goodboy/tractor/issues/36
+            assert self._scope
+            self._scope.cancel()
+
+    @acm
+    async def open_stream(
+
+        self,
+        allow_overruns: bool | None = False,
+        msg_buffer_size: int | None = None,
+
+    ) -> AsyncGenerator[MsgStream, None]:
+        '''
+        Open a ``MsgStream``, a bi-directional stream connected to the
+        cross-actor (far end) task for this ``Context``.
+
+        This context manager must be entered on both the caller and
+        callee for the stream to logically be considered "connected".
+
+        A ``MsgStream`` is currently "one-shot" use, meaning if you
+        close it you can not "re-open" it for streaming and instead you
+        must re-establish a new surrounding ``Context`` using
+        ``Portal.open_context()``.  In the future this may change but
+        currently there seems to be no obvious reason to support
+        "re-opening":
+            - pausing a stream can be done with a message.
+            - task errors will normally require a restart of the entire
+              scope of the inter-actor task context due to the nature of
+              ``trio``'s cancellation system.
+
+        '''
+        actor = current_actor()
+
+        # here we create a mem chan that corresponds to the
+        # far end caller / callee.
+
+        # Likewise if the surrounding context has been cancelled we error here
+        # since it likely means the surrounding block was exited or
+        # killed
+
+        if self._cancel_called:
+            task = trio.lowlevel.current_task().name
+            raise ContextCancelled(
+                f'Context around {actor.uid[0]}:{task} was already cancelled!'
+            )
+
+        if not self._portal and not self._started_called:
+            raise RuntimeError(
+                'Context.started()` must be called before opening a stream'
+            )
+
+        # NOTE: in one way streaming this only happens on the
+        # caller side inside `Actor.start_remote_task()` so if you try
+        # to send a stop from the caller to the callee in the
+        # single-direction-stream case you'll get a lookup error
+        # currently.
+        ctx = actor.get_context(
+            self.chan,
+            self.cid,
+            msg_buffer_size=msg_buffer_size,
+            allow_overruns=allow_overruns,
+        )
+        ctx._allow_overruns = allow_overruns
+        assert ctx is self
+
+        # XXX: If the underlying channel feeder receive mem chan has
+        # been closed then likely client code has already exited
+        # a ``.open_stream()`` block prior or there was some other
+        # unanticipated error or cancellation from ``trio``.
+
+        if ctx._recv_chan._closed:
+            raise trio.ClosedResourceError(
+                'The underlying channel for this stream was already closed!?')
+
+        async with MsgStream(
+            ctx=self,
+            rx_chan=ctx._recv_chan,
+        ) as stream:
+
+            if self._portal:
+                self._portal._streams.add(stream)
+
+            try:
+                self._stream_opened = True
+
+                # XXX: do we need this?
+                # ensure we aren't cancelled before yielding the stream
+                # await trio.lowlevel.checkpoint()
+                yield stream
+
+                # NOTE: Make the stream "one-shot use".  On exit, signal
+                # ``trio.EndOfChannel``/``StopAsyncIteration`` to the
+                # far end.
+                await stream.aclose()
+
+            finally:
+                if self._portal:
+                    try:
+                        self._portal._streams.remove(stream)
+                    except KeyError:
+                        log.warning(
+                            f'Stream was already destroyed?\n'
+                            f'actor: {self.chan.uid}\n'
+                            f'ctx id: {self.cid}'
+                        )
+
+    def _maybe_raise_remote_err(
+        self,
+        err: Exception,
+    ) -> None:
+        # NOTE: whenever the context's "opener" side (task) **is**
+        # the side which requested the cancellation (likekly via
+        # ``Context.cancel()``), we don't want to re-raise that
+        # cancellation signal locally (would be akin to
+        # a ``trio.Nursery`` nursery raising ``trio.Cancelled``
+        # whenever  ``CancelScope.cancel()`` was called) and instead
+        # silently reap the expected cancellation "error"-msg.
+        # if 'pikerd' in err.msgdata['tb_str']:
+        #     # from . import _debug
+        #     # await _debug.breakpoint()
+        #     breakpoint()
+
+        if (
+            isinstance(err, ContextCancelled)
+            and (
+                self._cancel_called
+                or self.chan._cancel_called
+                or tuple(err.canceller) == current_actor().uid
+            )
+        ):
+            return err
+
+        raise err  # from None
+
+    async def result(self) -> Any | Exception:
+        '''
+        From some (caller) side task, wait for and return the final
+        result from the remote (callee) side's task.
+
+        This provides a mechanism for one task running in some actor to wait
+        on another task at the other side, in some other actor, to terminate.
+
+        If the remote task is still in a streaming state (it is delivering
+        values from inside a ``Context.open_stream():`` block, then those
+        msgs are drained but discarded since it is presumed this side of
+        the context has already finished with its own streaming logic.
+
+        If the remote context (or its containing actor runtime) was
+        canceled, either by a local task calling one of
+        ``Context.cancel()`` or `Portal.cancel_actor()``, we ignore the
+        received ``ContextCancelled`` exception if the context or
+        underlying IPC channel is marked as having been "cancel called".
+        This is similar behavior to using ``trio.Nursery.cancel()``
+        wherein tasks which raise ``trio.Cancel`` are silently reaped;
+        the main different in this API is in the "cancel called" case,
+        instead of just not raising, we also return the exception *as
+        the result* since client code may be interested in the details
+        of the remote cancellation.
+
+        '''
+        assert self._portal, "Context.result() can not be called from callee!"
+        assert self._recv_chan
+
+        # from . import _debug
+        # await _debug.breakpoint()
+
+        re = self._remote_error
+        if re:
+            self._maybe_raise_remote_err(re)
+            return re
+
+        if (
+            self._result == id(self)
+            and not self._remote_error
+            and not self._recv_chan._closed  # type: ignore
+        ):
+            # wait for a final context result consuming
+            # and discarding any bi dir stream msgs still
+            # in transit from the far end.
+            while True:
+                msg = await self._recv_chan.receive()
+                try:
+                    self._result = msg['return']
+
+                    # NOTE: we don't need to do this right?
+                    # XXX: only close the rx mem chan AFTER
+                    # a final result is retreived.
+                    # if self._recv_chan:
+                    #     await self._recv_chan.aclose()
+
+                    break
+                except KeyError:  # as msgerr:
+
+                    if 'yield' in msg:
+                        # far end task is still streaming to us so discard
+                        log.warning(f'Discarding stream delivered {msg}')
+                        continue
+
+                    elif 'stop' in msg:
+                        log.debug('Remote stream terminated')
+                        continue
+
+                    # internal error should never get here
+                    assert msg.get('cid'), (
+                        "Received internal error at portal?")
+
+                    err = unpack_error(
+                        msg,
+                        self._portal.channel
+                    )  # from msgerr
+
+                    err = self._maybe_raise_remote_err(err)
+                    self._remote_err = err
+
+        return self._remote_error or self._result
+
+    async def started(
+        self,
+        value: Any | None = None
+
+    ) -> None:
+        '''
+        Indicate to calling actor's task that this linked context
+        has started and send ``value`` to the other side.
+
+        On the calling side ``value`` is the second item delivered
+        in the tuple returned by ``Portal.open_context()``.
+
+        '''
+        if self._portal:
+            raise RuntimeError(
+                f"Caller side context {self} can not call started!")
+
+        elif self._started_called:
+            raise RuntimeError(
+                f"called 'started' twice on context with {self.chan.uid}")
+
+        await self.chan.send({'started': value, 'cid': self.cid})
+        self._started_called = True
+
+    # TODO: do we need a restart api?
+    # async def restart(self) -> None:
+    #     pass
+
+    async def _drain_overflows(
+        self,
+    ) -> None:
+        '''
+        Private task spawned to push newly received msgs to the local
+        task which getting overrun by the remote side.
+
+        In order to not block the rpc msg loop, but also not discard
+        msgs received in this context, we need to async push msgs in
+        a new task which only runs for as long as the local task is in
+        an overrun state.
+
+        '''
+        self._in_overrun = True
+        try:
+            while self._overflow_q:
+                # NOTE: these msgs should never be errors since we always do
+                # the check prior to checking if we're in an overrun state
+                # inside ``.deliver_msg()``.
+                msg = self._overflow_q.popleft()
+                try:
+                    await self._send_chan.send(msg)
+                except trio.BrokenResourceError:
+                    log.warning(
+                        f"{self._send_chan} consumer is already closed"
+                    )
+                    return
+                except trio.Cancelled:
+                    # we are obviously still in overrun
+                    # but the context is being closed anyway
+                    # so we just warn that there are un received
+                    # msgs still..
+                    self._overflow_q.appendleft(msg)
+                    fmt_msgs = ''
+                    for msg in self._overflow_q:
+                        fmt_msgs += f'{pformat(msg)}\n'
+
+                    log.warning(
+                        f'Context for {self.cid} is being closed while '
+                        'in an overrun state!\n'
+                        'Discarding the following msgs:\n'
+                        f'{fmt_msgs}\n'
+                    )
+                    raise
+
+        finally:
+            # task is now finished with the backlog so mark us as
+            # no longer in backlog.
+            self._in_overrun = False
+
+    async def _deliver_msg(
+        self,
+        msg: dict,
+
+        draining: bool = False,
+
+    ) -> bool:
+
+        cid = self.cid
+        chan = self.chan
+        uid = chan.uid
+        send_chan: trio.MemorySendChannel = self._send_chan
+
+        log.runtime(
+            f"Delivering {msg} from {uid} to caller {cid}"
+        )
+
+        error = msg.get('error')
+        if error:
+            await self._maybe_cancel_and_set_remote_error(msg)
+
+        if (
+            self._in_overrun
+        ):
+            self._overflow_q.append(msg)
+            return False
+
+        try:
+            send_chan.send_nowait(msg)
+            return True
+            # if an error is deteced we should always
+            # expect it to be raised by any context (stream)
+            # consumer task
+
+        except trio.BrokenResourceError:
+            # TODO: what is the right way to handle the case where the
+            # local task has already sent a 'stop' / StopAsyncInteration
+            # to the other side but and possibly has closed the local
+            # feeder mem chan? Do we wait for some kind of ack or just
+            # let this fail silently and bubble up (currently)?
+
+            # XXX: local consumer has closed their side
+            # so cancel the far end streaming task
+            log.warning(f"{send_chan} consumer is already closed")
+            return False
+
+        # NOTE XXX: by default we do **not** maintain context-stream
+        # backpressure and instead opt to relay stream overrun errors to
+        # the sender; the main motivation is that using bp can block the
+        # msg handling loop which calls into this method!
+        except trio.WouldBlock:
+            # XXX: always push an error even if the local
+            # receiver is in overrun state.
+            # await self._maybe_cancel_and_set_remote_error(msg)
+
+            local_uid = current_actor().uid
+            lines = [
+                f'OVERRUN on actor-task context {cid}@{local_uid}!\n'
+                # TODO: put remote task name here if possible?
+                f'remote sender actor: {uid}',
+                # TODO: put task func name here and maybe an arrow
+                # from sender to overrunner?
+                # f'local task {self.func_name}'
+            ]
+            if not self._stream_opened:
+                lines.insert(
+                    1,
+                    f'\n*** No stream open on `{local_uid[0]}` side! ***\n'
+                )
+
+            text = '\n'.join(lines)
+
+            # XXX: lul, this really can't be backpressure since any
+            # blocking here will block the entire msg loop rpc sched for
+            # a whole channel.. maybe we should rename it?
+            if self._allow_overruns:
+                text += f'\nStarting overflow queuing task on msg: {msg}'
+                log.warning(text)
+                if (
+                    not self._in_overrun
+                ):
+                    self._overflow_q.append(msg)
+                    n = self._scope_nursery
+                    assert not n.child_tasks
+                    try:
+                        n.start_soon(
+                            self._drain_overflows,
+                        )
+                    except RuntimeError:
+                        # if the nursery is already cancelled due to
+                        # this context exiting or in error, we ignore
+                        # the nursery error since we never expected
+                        # anything different.
+                        return False
+            else:
+                try:
+                    raise StreamOverrun(text)
+                except StreamOverrun as err:
+                    err_msg = pack_error(err)
+                    err_msg['cid'] = cid
+                    try:
+                        await chan.send(err_msg)
+                    except trio.BrokenResourceError:
+                        # XXX: local consumer has closed their side
+                        # so cancel the far end streaming task
+                        log.warning(f"{chan} is already closed")
+
+            return False
+
+
+def mk_context(
+    chan: Channel,
+    cid: str,
+    msg_buffer_size: int = 2**6,
+
+    **kwargs,
+
+) -> Context:
+    '''
+    Internal factory to create an inter-actor task ``Context``.
+
+    This is called by internals and should generally never be called
+    by user code.
+
+    '''
+    send_chan: trio.MemorySendChannel
+    recv_chan: trio.MemoryReceiveChannel
+    send_chan, recv_chan = trio.open_memory_channel(msg_buffer_size)
+
+    ctx = Context(
+        chan,
+        cid,
+        _send_chan=send_chan,
+        _recv_chan=recv_chan,
+        **kwargs,
+    )
+    ctx._result: int | Any = id(ctx)
+    return ctx
+
+
+def context(func: Callable) -> Callable:
+    '''
+    Mark an async function as a streaming routine with ``@context``.
+
+    '''
+    # TODO: apply whatever solution ``mypy`` ends up picking for this:
+    # https://github.com/python/mypy/issues/2087#issuecomment-769266912
+    func._tractor_context_function = True  # type: ignore
+
+    sig = inspect.signature(func)
+    params = sig.parameters
+    if 'ctx' not in params:
+        raise TypeError(
+            "The first argument to the context function "
+            f"{func.__name__} must be `ctx: tractor.Context`"
+        )
+    return func

tractor/_debug.py

@@ -30,7 +30,6 @@ from functools import (
 from contextlib import asynccontextmanager as acm
 from typing import (
     Any,
-    Optional,
     Callable,
     AsyncIterator,
     AsyncGenerator,
@@ -40,7 +39,10 @@ from types import FrameType
 import pdbp
 import tractor
 import trio
-from trio_typing import TaskStatus
+from trio_typing import (
+    TaskStatus,
+    # Task,
+)
 
 from .log import get_logger
 from ._discovery import get_root
@@ -69,10 +71,10 @@ class Lock:
     '''
     repl: MultiActorPdb | None = None
     # placeholder for function to set a ``trio.Event`` on debugger exit
-    # pdb_release_hook: Optional[Callable] = None
+    # pdb_release_hook: Callable | None = None
 
     _trio_handler: Callable[
-        [int, Optional[FrameType]], Any
+        [int, FrameType | None], Any
     ] | int | None = None
 
     # actor-wide variable pointing to current task name using debugger
@@ -83,23 +85,23 @@ class Lock:
     # and must be cancelled if this actor is cancelled via IPC
     # request-message otherwise deadlocks with the parent actor may
     # ensure
-    _debugger_request_cs: Optional[trio.CancelScope] = None
+    _debugger_request_cs: trio.CancelScope | None = None
 
     # NOTE: set only in the root actor for the **local** root spawned task
     # which has acquired the lock (i.e. this is on the callee side of
     # the `lock_tty_for_child()` context entry).
-    _root_local_task_cs_in_debug: Optional[trio.CancelScope] = None
+    _root_local_task_cs_in_debug: trio.CancelScope | None = None
 
     # actor tree-wide actor uid that supposedly has the tty lock
-    global_actor_in_debug: Optional[tuple[str, str]] = None
+    global_actor_in_debug: tuple[str, str] = None
 
-    local_pdb_complete: Optional[trio.Event] = None
+    local_pdb_complete: trio.Event | None = None
-    no_remote_has_tty: Optional[trio.Event] = None
+    no_remote_has_tty: trio.Event | None = None
 
     # lock in root actor preventing multi-access to local tty
     _debug_lock: trio.StrictFIFOLock = trio.StrictFIFOLock()
 
-    _orig_sigint_handler: Optional[Callable] = None
+    _orig_sigint_handler: Callable | None = None
     _blocked: set[tuple[str, str]] = set()
 
     @classmethod
@@ -110,6 +112,7 @@ class Lock:
         )
 
     @classmethod
+    @pdbp.hideframe  # XXX NOTE XXX see below in `.pause_from_sync()`
     def unshield_sigint(cls):
         # always restore ``trio``'s sigint handler. see notes below in
         # the pdb factory about the nightmare that is that code swapping
@@ -129,10 +132,6 @@ class Lock:
             if owner:
                 raise
 
-        # actor-local state, irrelevant for non-root.
-        cls.global_actor_in_debug = None
-        cls.local_task_in_debug = None
-
         try:
             # sometimes the ``trio`` might already be terminated in
             # which case this call will raise.
@@ -143,6 +142,11 @@ class Lock:
             cls.unshield_sigint()
             cls.repl = None
 
+            # actor-local state, irrelevant for non-root.
+            cls.global_actor_in_debug = None
+            cls.local_task_in_debug = None
+
+
 
 class TractorConfig(pdbp.DefaultConfig):
     '''
@@ -151,7 +155,7 @@ class TractorConfig(pdbp.DefaultConfig):
     '''
     use_pygments: bool = True
     sticky_by_default: bool = False
-    enable_hidden_frames: bool = False
+    enable_hidden_frames: bool = True
 
     # much thanks @mdmintz for the hot tip!
     # fixes line spacing issue when resizing terminal B)
@@ -228,26 +232,23 @@ async def _acquire_debug_lock_from_root_task(
     to the ``pdb`` repl.
 
     '''
-    task_name = trio.lowlevel.current_task().name
+    task_name: str = trio.lowlevel.current_task().name
+    we_acquired: bool = False
 
     log.runtime(
         f"Attempting to acquire TTY lock, remote task: {task_name}:{uid}"
     )
-
-    we_acquired = False
-
     try:
         log.runtime(
             f"entering lock checkpoint, remote task: {task_name}:{uid}"
         )
-        we_acquired = True
-
         # NOTE: if the surrounding cancel scope from the
         # `lock_tty_for_child()` caller is cancelled, this line should
         # unblock and NOT leave us in some kind of
         # a "child-locked-TTY-but-child-is-uncontactable-over-IPC"
         # condition.
         await Lock._debug_lock.acquire()
+        we_acquired = True
 
         if Lock.no_remote_has_tty is None:
             # mark the tty lock as being in use so that the runtime
@@ -374,7 +375,7 @@ async def wait_for_parent_stdin_hijack(
 
     This function is used by any sub-actor to acquire mutex access to
     the ``pdb`` REPL and thus the root's TTY for interactive debugging
-    (see below inside ``_breakpoint()``). It can be used to ensure that
+    (see below inside ``_pause()``). It can be used to ensure that
     an intermediate nursery-owning actor does not clobber its children
     if they are in debug (see below inside
     ``maybe_wait_for_debugger()``).
@@ -440,17 +441,29 @@ def mk_mpdb() -> tuple[MultiActorPdb, Callable]:
     return pdb, Lock.unshield_sigint
 
 
-async def _breakpoint(
+async def _pause(
 
-    debug_func,
+    debug_func: Callable | None = None,
+    release_lock_signal: trio.Event | None = None,
 
     # TODO:
     # shield: bool = False
+    task_status: TaskStatus[trio.Event] = trio.TASK_STATUS_IGNORED
 
 ) -> None:
     '''
-    Breakpoint entry for engaging debugger instance sync-interaction,
+    A pause point (more commonly known as a "breakpoint") interrupt
-    from async code, executing in actor runtime (task).
+    instruction for engaging a blocking debugger instance to
+    conduct manual console-based-REPL-interaction from within
+    `tractor`'s async runtime, normally from some single-threaded
+    and currently executing actor-hosted-`trio`-task in some
+    (remote) process.
+
+    NOTE: we use the semantics "pause" since it better encompasses
+    the entirety of the necessary global-runtime-state-mutation any
+    actor-task must access and lock in order to get full isolated
+    control over the process tree's root TTY:
+    https://en.wikipedia.org/wiki/Breakpoint
 
     '''
     __tracebackhide__ = True
@@ -559,6 +572,19 @@ async def _breakpoint(
         Lock.repl = pdb
 
     try:
+        # breakpoint()
+        if debug_func is None:
+            # assert release_lock_signal, (
+            #     'Must pass `release_lock_signal: trio.Event` if no '
+            #     'trace func provided!'
+            # )
+            print(f"{actor.uid} ENTERING WAIT")
+            task_status.started()
+
+            # with trio.CancelScope(shield=True):
+            #     await release_lock_signal.wait()
+
+        else:
             # block here one (at the appropriate frame *up*) where
             # ``breakpoint()`` was awaited and begin handling stdio.
             log.debug("Entering the synchronous world of pdb")
@@ -583,7 +609,7 @@ async def _breakpoint(
 def shield_sigint_handler(
     signum: int,
     frame: 'frame',  # type: ignore # noqa
-    # pdb_obj: Optional[MultiActorPdb] = None,
+    # pdb_obj: MultiActorPdb | None = None,
     *args,
 
 ) -> None:
@@ -597,7 +623,7 @@ def shield_sigint_handler(
     '''
     __tracebackhide__ = True
 
-    uid_in_debug = Lock.global_actor_in_debug
+    uid_in_debug: tuple[str, str] | None = Lock.global_actor_in_debug
 
     actor = tractor.current_actor()
     # print(f'{actor.uid} in HANDLER with ')
@@ -615,14 +641,14 @@ def shield_sigint_handler(
         else:
             raise KeyboardInterrupt
 
-    any_connected = False
+    any_connected: bool = False
 
     if uid_in_debug is not None:
         # try to see if the supposed (sub)actor in debug still
         # has an active connection to *this* actor, and if not
         # it's likely they aren't using the TTY lock / debugger
         # and we should propagate SIGINT normally.
-        chans = actor._peers.get(tuple(uid_in_debug))
+        chans: list[tractor.Channel] = actor._peers.get(tuple(uid_in_debug))
         if chans:
             any_connected = any(chan.connected() for chan in chans)
             if not any_connected:
@@ -635,7 +661,7 @@ def shield_sigint_handler(
                 return do_cancel()
 
     # only set in the actor actually running the REPL
-    pdb_obj = Lock.repl
+    pdb_obj: MultiActorPdb | None = Lock.repl
 
     # root actor branch that reports whether or not a child
     # has locked debugger.
@@ -693,7 +719,7 @@ def shield_sigint_handler(
             )
             return do_cancel()
 
-        task = Lock.local_task_in_debug
+        task: str | None = Lock.local_task_in_debug
         if (
             task
             and pdb_obj
@@ -708,8 +734,8 @@ def shield_sigint_handler(
         # elif debug_mode():
 
     else:  # XXX: shouldn't ever get here?
-        print("WTFWTFWTF")
+        raise RuntimeError("WTFWTFWTF")
-        raise KeyboardInterrupt
+        # raise KeyboardInterrupt("WTFWTFWTF")
 
     # NOTE: currently (at least on ``fancycompleter`` 0.9.2)
     # it looks to be that the last command that was run (eg. ll)
@@ -737,21 +763,18 @@ def shield_sigint_handler(
         # https://github.com/goodboy/tractor/issues/130#issuecomment-663752040
         # https://github.com/prompt-toolkit/python-prompt-toolkit/blob/c2c6af8a0308f9e5d7c0e28cb8a02963fe0ce07a/prompt_toolkit/patch_stdout.py
 
-        # XXX LEGACY: lol, see ``pdbpp`` issue:
-        # https://github.com/pdbpp/pdbpp/issues/496
-
 
 def _set_trace(
     actor: tractor.Actor | None = None,
     pdb: MultiActorPdb | None = None,
 ):
     __tracebackhide__ = True
-    actor = actor or tractor.current_actor()
+    actor: tractor.Actor = actor or tractor.current_actor()
 
     # start 2 levels up in user code
-    frame: Optional[FrameType] = sys._getframe()
+    frame: FrameType | None = sys._getframe()
     if frame:
-        frame = frame.f_back  # type: ignore
+        frame: FrameType = frame.f_back  # type: ignore
 
     if (
         frame
@@ -771,12 +794,76 @@ def _set_trace(
         Lock.local_task_in_debug = 'sync'
 
     pdb.set_trace(frame=frame)
+    # undo_
 
 
-breakpoint = partial(
+# TODO: allow pausing from sync code, normally by remapping
-    _breakpoint,
+# python's builtin breakpoint() hook to this runtime aware version.
+def pause_from_sync() -> None:
+    print("ENTER SYNC PAUSE")
+    import greenback
+    __tracebackhide__ = True
+
+    actor: tractor.Actor = tractor.current_actor()
+    # task_can_release_tty_lock = trio.Event()
+
+    # spawn bg task which will lock out the TTY, we poll
+    # just below until the release event is reporting that task as
+    # waiting.. not the most ideal but works for now ;)
+    greenback.await_(
+        actor._service_n.start(partial(
+            _pause,
+            debug_func=None,
+            # release_lock_signal=task_can_release_tty_lock,
+        ))
+    )
+
+    db, undo_sigint = mk_mpdb()
+    Lock.local_task_in_debug = 'sync'
+    # db.config.enable_hidden_frames = True
+
+    # we entered the global ``breakpoint()`` built-in from sync
+    # code?
+    frame: FrameType | None = sys._getframe()
+    # print(f'FRAME: {str(frame)}')
+    # assert not db._is_hidden(frame)
+
+    frame: FrameType = frame.f_back  # type: ignore
+    # print(f'FRAME: {str(frame)}')
+    # if not db._is_hidden(frame):
+    #     pdbp.set_trace()
+    # db._hidden_frames.append(
+    #     (frame, frame.f_lineno)
+    # )
+    db.set_trace(frame=frame)
+    # NOTE XXX: see the `@pdbp.hideframe` decoration
+    # on `Lock.unshield_sigint()`.. I have NO CLUE why
+    # the next instruction's def frame is being shown
+    # in the tb but it seems to be something wonky with
+    # the way `pdb` core works?
+    # undo_sigint()
+
+    # Lock.global_actor_in_debug = actor.uid
+    # Lock.release()
+    # task_can_release_tty_lock.set()
+
+
+# using the "pause" semantics instead since
+# that better covers actually somewhat "pausing the runtime"
+# for this particular paralell task to do debugging B)
+pause = partial(
+    _pause,
     _set_trace,
 )
+pp = pause  # short-hand for "pause point"
+
+
+async def breakpoint(**kwargs):
+    log.warning(
+        '`tractor.breakpoint()` is deprecated!\n'
+        'Please use `tractor.pause()` instead!\n'
+    )
+    await pause(**kwargs)
 
 
 def _post_mortem(
@@ -801,7 +888,7 @@ def _post_mortem(
 
 
 post_mortem = partial(
-    _breakpoint,
+    _pause,
     _post_mortem,
 )
 
@@ -883,8 +970,7 @@ async def maybe_wait_for_debugger(
         # will make the pdb repl unusable.
         # Instead try to wait for pdb to be released before
         # tearing down.
-
+        sub_in_debug: tuple[str, str] | None = None
-        sub_in_debug = None
 
         for _ in range(poll_steps):
 
@@ -904,13 +990,15 @@ async def maybe_wait_for_debugger(
 
                 debug_complete = Lock.no_remote_has_tty
                 if (
-                    (debug_complete and
+                    debug_complete
-                     not debug_complete.is_set())
+                    and sub_in_debug is not None
+                    and not debug_complete.is_set()
                 ):
-                    log.debug(
+                    log.pdb(
                         'Root has errored but pdb is in use by '
                         f'child {sub_in_debug}\n'
-                        'Waiting on tty lock to release..')
+                        'Waiting on tty lock to release..'
+                    )
 
                     await debug_complete.wait()
 

tractor/_discovery.py

@@ -35,14 +35,16 @@ from ._state import current_actor, _runtime_vars
 
 
 @acm
-async def get_arbiter(
+async def get_registrar(
 
     host: str,
     port: int,
 
 ) -> AsyncGenerator[Union[Portal, LocalPortal], None]:
-    '''Return a portal instance connected to a local or remote
+    '''
+    Return a portal instance connected to a local or remote
     arbiter.
+
     '''
     actor = current_actor()
 
@@ -54,13 +56,16 @@ async def get_arbiter(
         # (likely a re-entrant call from the arbiter actor)
         yield LocalPortal(actor, Channel((host, port)))
     else:
-        async with _connect_chan(host, port) as chan:
+        async with (
-
+            _connect_chan(host, port) as chan,
-            async with open_portal(chan) as arb_portal:
+            open_portal(chan) as arb_portal,
-
+        ):
             yield arb_portal
 
 
+get_arbiter = get_registrar
+
+
 @acm
 async def get_root(
     **kwargs,
@@ -99,7 +104,10 @@ async def query_actor(
 
         # TODO: return portals to all available actors - for now just
         # the last one that registered
-        if name == 'arbiter' and actor.is_arbiter:
+        if (
+            name == 'arbiter'
+            and actor.is_arbiter
+        ):
             raise RuntimeError("The current actor is the arbiter")
 
         yield sockaddr if sockaddr else None
@@ -110,7 +118,7 @@ async def find_actor(
     name: str,
     arbiter_sockaddr: tuple[str, int] | None = None
 
-) -> AsyncGenerator[Optional[Portal], None]:
+) -> AsyncGenerator[Portal | None, None]:
     '''
     Ask the arbiter to find actor(s) by name.
 
@@ -118,28 +126,64 @@ async def find_actor(
     known to the arbiter.
 
     '''
-    async with query_actor(
+    actor = current_actor()
+    async with get_arbiter(
+        *arbiter_sockaddr or actor._arb_addr
+    ) as arb_portal:
+
+        sockaddr = await arb_portal.run_from_ns(
+            'self',
+            'find_actor',
             name=name,
-        arbiter_sockaddr=arbiter_sockaddr,
+        )
-    ) as sockaddr:
+
+        # TODO: return portals to all available actors - for now just
+        # the last one that registered
+        if (
+            name == 'arbiter'
+            and actor.is_arbiter
+        ):
+            raise RuntimeError("The current actor is the arbiter")
 
         if sockaddr:
+            try:
                 async with _connect_chan(*sockaddr) as chan:
                     async with open_portal(chan) as portal:
                         yield portal
-        else:
+                        return
+
+            # most likely we were unable to connect the
+            # transport and there is likely a stale entry in
+            # the registry actor's table, thus we need to
+            # instruct it to clear that stale entry and then
+            # more silently (pretend there was no reason but
+            # to) indicate that the target actor can't be
+            # contacted at that addr.
+            except OSError:
+                # NOTE: ensure we delete the stale entry from the
+                # registar actor.
+                uid: tuple[str, str] = await arb_portal.run_from_ns(
+                    'self',
+                    'delete_sockaddr',
+                    sockaddr=sockaddr,
+                )
+
         yield None
 
 
 @acm
 async def wait_for_actor(
     name: str,
-    arbiter_sockaddr: tuple[str, int] | None = None
+    arbiter_sockaddr: tuple[str, int] | None = None,
+    # registry_addr: tuple[str, int] | None = None,
+
 ) -> AsyncGenerator[Portal, None]:
-    """Wait on an actor to register with the arbiter.
+    '''
+    Wait on an actor to register with the arbiter.
 
     A portal to the first registered actor is returned.
-    """
+
+    '''
     actor = current_actor()
 
     async with get_arbiter(

tractor/_entry.py

@@ -132,7 +132,7 @@ def _trio_main(
         else:
             trio.run(trio_main)
     except KeyboardInterrupt:
-        log.warning(f"Actor {actor.uid} received KBI")
+        log.cancel(f"Actor {actor.uid} received KBI")
 
     finally:
         log.info(f"Actor {actor.uid} terminated")

tractor/_exceptions.py

@@ -18,18 +18,18 @@
 Our classy exception set.
 
 """
+import builtins
+import importlib
 from typing import (
     Any,
-    Optional,
     Type,
 )
-import importlib
-import builtins
 import traceback
 
 import exceptiongroup as eg
 import trio
 
+from ._state import current_actor
 
 _this_mod = importlib.import_module(__name__)
 
@@ -44,7 +44,7 @@ class RemoteActorError(Exception):
     def __init__(
         self,
         message: str,
-        suberror_type: Optional[Type[BaseException]] = None,
+        suberror_type: Type[BaseException] | None = None,
         **msgdata
 
     ) -> None:
@@ -53,21 +53,36 @@ class RemoteActorError(Exception):
         self.type = suberror_type
         self.msgdata = msgdata
 
+    @property
+    def src_actor_uid(self) -> tuple[str, str] | None:
+        return self.msgdata.get('src_actor_uid')
+
 
 class InternalActorError(RemoteActorError):
-    """Remote internal ``tractor`` error indicating
+    '''
+    Remote internal ``tractor`` error indicating
     failure of some primitive or machinery.
-    """
+
+    '''
+
+
+class ContextCancelled(RemoteActorError):
+    '''
+    Inter-actor task context was cancelled by either a call to
+    ``Portal.cancel_actor()`` or ``Context.cancel()``.
+
+    '''
+    @property
+    def canceller(self) -> tuple[str, str] | None:
+        value = self.msgdata.get('canceller')
+        if value:
+            return tuple(value)
 
 
 class TransportClosed(trio.ClosedResourceError):
     "Underlying channel transport was closed prior to use"
 
 
-class ContextCancelled(RemoteActorError):
-    "Inter-actor task context cancelled itself on the callee side."
-
-
 class NoResult(RuntimeError):
     "No final result is expected for this actor"
 
@@ -106,12 +121,16 @@ def pack_error(
     else:
         tb_str = traceback.format_exc()
 
-    return {
+    error_msg = {
-        'error': {
         'tb_str': tb_str,
         'type_str': type(exc).__name__,
+        'src_actor_uid': current_actor().uid,
     }
-    }
+
+    if isinstance(exc, ContextCancelled):
+        error_msg.update(exc.msgdata)
+
+    return {'error': error_msg}
 
 
 def unpack_error(
@@ -136,7 +155,7 @@ def unpack_error(
 
     if type_name == 'ContextCancelled':
         err_type = ContextCancelled
-        suberror_type = trio.Cancelled
+        suberror_type = RemoteActorError
 
     else:  # try to lookup a suitable local error type
         for ns in [

tractor/_portal.py

@@ -45,10 +45,8 @@ from ._exceptions import (
     NoResult,
     ContextCancelled,
 )
-from ._streaming import (
+from ._context import Context
-    Context,
+from ._streaming import MsgStream
-    MsgStream,
-)
 
 
 log = get_logger(__name__)
@@ -103,7 +101,7 @@ class Portal:
         # When set to a ``Context`` (when _submit_for_result is called)
         # it is expected that ``result()`` will be awaited at some
         # point.
-        self._expect_result: Optional[Context] = None
+        self._expect_result: Context | None = None
         self._streams: set[MsgStream] = set()
         self.actor = current_actor()
 
@@ -209,7 +207,10 @@ class Portal:
         try:
             # send cancel cmd - might not get response
             # XXX: sure would be nice to make this work with a proper shield
-            with trio.move_on_after(timeout or self.cancel_timeout) as cs:
+            with trio.move_on_after(
+                timeout
+                or self.cancel_timeout
+            ) as cs:
                 cs.shield = True
 
                 await self.run_from_ns('self', 'cancel')
@@ -330,7 +331,9 @@ class Portal:
                     f'{async_gen_func} must be an async generator function!')
 
         fn_mod_path, fn_name = NamespacePath.from_ref(
-            async_gen_func).to_tuple()
+            async_gen_func
+        ).to_tuple()
+
         ctx = await self.actor.start_remote_task(
             self.channel,
             fn_mod_path,
@@ -377,6 +380,7 @@ class Portal:
 
         self,
         func: Callable,
+        allow_overruns: bool = False,
         **kwargs,
 
     ) -> AsyncGenerator[tuple[Context, Any], None]:
@@ -396,13 +400,26 @@ class Portal:
             raise TypeError(
                 f'{func} must be an async generator function!')
 
+        # TODO: i think from here onward should probably
+        # just be factored into an `@acm` inside a new
+        # a new `_context.py` mod.
         fn_mod_path, fn_name = NamespacePath.from_ref(func).to_tuple()
 
         ctx = await self.actor.start_remote_task(
             self.channel,
             fn_mod_path,
             fn_name,
-            kwargs
+            kwargs,
+
+            # NOTE: it's imporant to expose this since you might
+            # get the case where the parent who opened the context does
+            # not open a stream until after some slow startup/init
+            # period, in which case when the first msg is read from
+            # the feeder mem chan, say when first calling
+            # `Context.open_stream(allow_overruns=True)`, the overrun condition will be
+            # raised before any ignoring of overflow msgs can take
+            # place..
+            allow_overruns=allow_overruns,
         )
 
         assert ctx._remote_func_type == 'context'
@@ -426,29 +443,47 @@ class Portal:
                     f' but received a non-error msg:\n{pformat(msg)}'
                 )
 
-        _err: Optional[BaseException] = None
+        _err: BaseException | None = None
-        ctx._portal = self
+        ctx._portal: Portal = self
 
-        uid = self.channel.uid
+        uid: tuple = self.channel.uid
-        cid = ctx.cid
+        cid: str = ctx.cid
-        etype: Optional[Type[BaseException]] = None
+        etype: Type[BaseException] | None = None
 
-        # deliver context instance and .started() msg value in open tuple.
+        # deliver context instance and .started() msg value in enter
+        # tuple.
         try:
-            async with trio.open_nursery() as scope_nursery:
+            async with trio.open_nursery() as nurse:
-                ctx._scope_nursery = scope_nursery
+                ctx._scope_nursery = nurse
-
+                ctx._scope = nurse.cancel_scope
-                # do we need this?
-                # await trio.lowlevel.checkpoint()
 
                 yield ctx, first
 
+                # when in allow_ovveruns mode there may be lingering
+                # overflow sender tasks remaining?
+                if nurse.child_tasks:
+                    # ensure we are in overrun state with
+                    # ``._allow_overruns=True`` bc otherwise
+                    # there should be no tasks in this nursery!
+                    if (
+                        not ctx._allow_overruns
+                        or len(nurse.child_tasks) > 1
+                    ):
+                        raise RuntimeError(
+                            'Context has sub-tasks but is '
+                            'not in `allow_overruns=True` Mode!?'
+                        )
+                    ctx._scope.cancel()
+
         except ContextCancelled as err:
             _err = err
+
+            # swallow and mask cross-actor task context cancels that
+            # were initiated by *this* side's task.
             if not ctx._cancel_called:
-                # context was cancelled at the far end but was
+                # XXX: this should NEVER happen!
-                # not part of this end requesting that cancel
+                # from ._debug import breakpoint
-                # so raise for the local task to respond and handle.
+                # await breakpoint()
                 raise
 
             # if the context was cancelled by client code
@@ -468,17 +503,17 @@ class Portal:
 
         ) as err:
             etype = type(err)
-            # the context cancels itself on any cancel
-            # causing error.
 
-            if ctx.chan.connected():
+            # cancel ourselves on any error.
             log.cancel(
                 'Context cancelled for task, sending cancel request..\n'
                 f'task:{cid}\n'
                 f'actor:{uid}'
             )
+            try:
+
                 await ctx.cancel()
-            else:
+            except trio.BrokenResourceError:
                 log.warning(
                     'IPC connection for context is broken?\n'
                     f'task:{cid}\n'
@@ -487,12 +522,7 @@ class Portal:
 
             raise
 
-        finally:
+        else:
-            # in the case where a runtime nursery (due to internal bug)
-            # or a remote actor transmits an error we want to be
-            # sure we get the error the underlying feeder mem chan.
-            # if it's not raised here it *should* be raised from the
-            # msg loop nursery right?
             if ctx.chan.connected():
                 log.info(
                     'Waiting on final context-task result for\n'
@@ -505,6 +535,7 @@ class Portal:
                     f'value from callee `{result}`'
                 )
 
+        finally:
             # though it should be impossible for any tasks
             # operating *in* this scope to have survived
             # we tear down the runtime feeder chan last

tractor/_root.py

@@ -89,7 +89,7 @@ async def open_root_actor(
     # https://github.com/python-trio/trio/issues/1155#issuecomment-742964018
     builtin_bp_handler = sys.breakpointhook
     orig_bp_path: str | None = os.environ.get('PYTHONBREAKPOINT', None)
-    os.environ['PYTHONBREAKPOINT'] = 'tractor._debug._set_trace'
+    os.environ['PYTHONBREAKPOINT'] = 'tractor._debug.pause_from_sync'
 
     # attempt to retreive ``trio``'s sigint handler and stash it
     # on our debugger lock state.
@@ -235,9 +235,10 @@ async def open_root_actor(
                 BaseExceptionGroup,
             ) as err:
 
-                entered = await _debug._maybe_enter_pm(err)
+                if (
-
+                    not (await _debug._maybe_enter_pm(err))
-                if not entered and not is_multi_cancelled(err):
+                    and not is_multi_cancelled(err)
+                ):
                     logger.exception("Root actor crashed:")
 
                 # always re-raise
@@ -254,7 +255,9 @@ async def open_root_actor(
                 #         tempn.start_soon(an.exited.wait)
 
                 logger.cancel("Shutting down root actor")
-                await actor.cancel()
+                await actor.cancel(
+                    requesting_uid=actor.uid,
+                )
     finally:
         _state._current_actor = None
 

tractor/_shm.py

@@ -0,0 +1,833 @@
+# tractor: structured concurrent "actors".
+# Copyright 2018-eternity Tyler Goodlet.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+"""
+SC friendly shared memory management geared at real-time
+processing.
+
+Support for ``numpy`` compatible array-buffers is provided but is
+considered optional within the context of this runtime-library.
+
+"""
+from __future__ import annotations
+from sys import byteorder
+import time
+from typing import Optional
+from multiprocessing import shared_memory as shm
+from multiprocessing.shared_memory import (
+    SharedMemory,
+    ShareableList,
+)
+
+from msgspec import Struct
+import tractor
+
+from .log import get_logger
+
+
+_USE_POSIX = getattr(shm, '_USE_POSIX', False)
+if _USE_POSIX:
+    from _posixshmem import shm_unlink
+
+
+try:
+    import numpy as np
+    from numpy.lib import recfunctions as rfn
+    import nptyping
+except ImportError:
+    pass
+
+
+log = get_logger(__name__)
+
+
+def disable_mantracker():
+    '''
+    Disable all ``multiprocessing``` "resource tracking" machinery since
+    it's an absolute multi-threaded mess of non-SC madness.
+
+    '''
+    from multiprocessing import resource_tracker as mantracker
+
+    # Tell the "resource tracker" thing to fuck off.
+    class ManTracker(mantracker.ResourceTracker):
+        def register(self, name, rtype):
+            pass
+
+        def unregister(self, name, rtype):
+            pass
+
+        def ensure_running(self):
+            pass
+
+    # "know your land and know your prey"
+    # https://www.dailymotion.com/video/x6ozzco
+    mantracker._resource_tracker = ManTracker()
+    mantracker.register = mantracker._resource_tracker.register
+    mantracker.ensure_running = mantracker._resource_tracker.ensure_running
+    mantracker.unregister = mantracker._resource_tracker.unregister
+    mantracker.getfd = mantracker._resource_tracker.getfd
+
+
+disable_mantracker()
+
+
+class SharedInt:
+    '''
+    Wrapper around a single entry shared memory array which
+    holds an ``int`` value used as an index counter.
+
+    '''
+    def __init__(
+        self,
+        shm: SharedMemory,
+    ) -> None:
+        self._shm = shm
+
+    @property
+    def value(self) -> int:
+        return int.from_bytes(self._shm.buf, byteorder)
+
+    @value.setter
+    def value(self, value) -> None:
+        self._shm.buf[:] = value.to_bytes(self._shm.size, byteorder)
+
+    def destroy(self) -> None:
+        if _USE_POSIX:
+            # We manually unlink to bypass all the "resource tracker"
+            # nonsense meant for non-SC systems.
+            name = self._shm.name
+            try:
+                shm_unlink(name)
+            except FileNotFoundError:
+                # might be a teardown race here?
+                log.warning(f'Shm for {name} already unlinked?')
+
+
+class NDToken(Struct, frozen=True):
+    '''
+    Internal represenation of a shared memory ``numpy`` array "token"
+    which can be used to key and load a system (OS) wide shm entry
+    and correctly read the array by type signature.
+
+    This type is msg safe.
+
+    '''
+    shm_name: str  # this servers as a "key" value
+    shm_first_index_name: str
+    shm_last_index_name: str
+    dtype_descr: tuple
+    size: int  # in struct-array index / row terms
+
+    # TODO: use nptyping here on dtypes
+    @property
+    def dtype(self) -> list[tuple[str, str, tuple[int, ...]]]:
+        return np.dtype(
+            list(
+                map(tuple, self.dtype_descr)
+            )
+        ).descr
+
+    def as_msg(self):
+        return self.to_dict()
+
+    @classmethod
+    def from_msg(cls, msg: dict) -> NDToken:
+        if isinstance(msg, NDToken):
+            return msg
+
+        # TODO: native struct decoding
+        # return _token_dec.decode(msg)
+
+        msg['dtype_descr'] = tuple(map(tuple, msg['dtype_descr']))
+        return NDToken(**msg)
+
+
+# _token_dec = msgspec.msgpack.Decoder(NDToken)
+
+# TODO: this api?
+# _known_tokens = tractor.ActorVar('_shm_tokens', {})
+# _known_tokens = tractor.ContextStack('_known_tokens', )
+# _known_tokens = trio.RunVar('shms', {})
+
+# TODO: this should maybe be provided via
+# a `.trionics.maybe_open_context()` wrapper factory?
+# process-local store of keys to tokens
+_known_tokens: dict[str, NDToken] = {}
+
+
+def get_shm_token(key: str) -> NDToken | None:
+    '''
+    Convenience func to check if a token
+    for the provided key is known by this process.
+
+    Returns either the ``numpy`` token or a string for a shared list.
+
+    '''
+    return _known_tokens.get(key)
+
+
+def _make_token(
+    key: str,
+    size: int,
+    dtype: np.dtype,
+
+) -> NDToken:
+    '''
+    Create a serializable token that can be used
+    to access a shared array.
+
+    '''
+    return NDToken(
+        shm_name=key,
+        shm_first_index_name=key + "_first",
+        shm_last_index_name=key + "_last",
+        dtype_descr=tuple(np.dtype(dtype).descr),
+        size=size,
+    )
+
+
+class ShmArray:
+    '''
+    A shared memory ``numpy.ndarray`` API.
+
+    An underlying shared memory buffer is allocated based on
+    a user specified ``numpy.ndarray``. This fixed size array
+    can be read and written to by pushing data both onto the "front"
+    or "back" of a set index range. The indexes for the "first" and
+    "last" index are themselves stored in shared memory (accessed via
+    ``SharedInt`` interfaces) values such that multiple processes can
+    interact with the same array using a synchronized-index.
+
+    '''
+    def __init__(
+        self,
+        shmarr: np.ndarray,
+        first: SharedInt,
+        last: SharedInt,
+        shm: SharedMemory,
+        # readonly: bool = True,
+    ) -> None:
+        self._array = shmarr
+
+        # indexes for first and last indices corresponding
+        # to fille data
+        self._first = first
+        self._last = last
+
+        self._len = len(shmarr)
+        self._shm = shm
+        self._post_init: bool = False
+
+        # pushing data does not write the index (aka primary key)
+        self._write_fields: list[str] | None = None
+        dtype = shmarr.dtype
+        if dtype.fields:
+            self._write_fields = list(shmarr.dtype.fields.keys())[1:]
+
+    # TODO: ringbuf api?
+
+    @property
+    def _token(self) -> NDToken:
+        return NDToken(
+            shm_name=self._shm.name,
+            shm_first_index_name=self._first._shm.name,
+            shm_last_index_name=self._last._shm.name,
+            dtype_descr=tuple(self._array.dtype.descr),
+            size=self._len,
+        )
+
+    @property
+    def token(self) -> dict:
+        """Shared memory token that can be serialized and used by
+        another process to attach to this array.
+        """
+        return self._token.as_msg()
+
+    @property
+    def index(self) -> int:
+        return self._last.value % self._len
+
+    @property
+    def array(self) -> np.ndarray:
+        '''
+        Return an up-to-date ``np.ndarray`` view of the
+        so-far-written data to the underlying shm buffer.
+
+        '''
+        a = self._array[self._first.value:self._last.value]
+
+        # first, last = self._first.value, self._last.value
+        # a = self._array[first:last]
+
+        # TODO: eventually comment this once we've not seen it in the
+        # wild in a long time..
+        # XXX: race where first/last indexes cause a reader
+        # to load an empty array..
+        if len(a) == 0 and self._post_init:
+            raise RuntimeError('Empty array race condition hit!?')
+            # breakpoint()
+
+        return a
+
+    def ustruct(
+        self,
+        fields: Optional[list[str]] = None,
+
+        # type that all field values will be cast to
+        # in the returned view.
+        common_dtype: np.dtype = float,
+
+    ) -> np.ndarray:
+
+        array = self._array
+
+        if fields:
+            selection = array[fields]
+            # fcount = len(fields)
+        else:
+            selection = array
+            # fcount = len(array.dtype.fields)
+
+        # XXX: manual ``.view()`` attempt that also doesn't work.
+        # uview = selection.view(
+        #     dtype='<f16',
+        # ).reshape(-1, 4, order='A')
+
+        # assert len(selection) == len(uview)
+
+        u = rfn.structured_to_unstructured(
+            selection,
+            # dtype=float,
+            copy=True,
+        )
+
+        # unstruct = np.ndarray(u.shape, dtype=a.dtype, buffer=shm.buf)
+        # array[:] = a[:]
+        return u
+        # return ShmArray(
+        #     shmarr=u,
+        #     first=self._first,
+        #     last=self._last,
+        #     shm=self._shm
+        # )
+
+    def last(
+        self,
+        length: int = 1,
+
+    ) -> np.ndarray:
+        '''
+        Return the last ``length``'s worth of ("row") entries from the
+        array.
+
+        '''
+        return self.array[-length:]
+
+    def push(
+        self,
+        data: np.ndarray,
+
+        field_map: Optional[dict[str, str]] = None,
+        prepend: bool = False,
+        update_first: bool = True,
+        start: int | None = None,
+
+    ) -> int:
+        '''
+        Ring buffer like "push" to append data
+        into the buffer and return updated "last" index.
+
+        NB: no actual ring logic yet to give a "loop around" on overflow
+        condition, lel.
+
+        '''
+        length = len(data)
+
+        if prepend:
+            index = (start or self._first.value) - length
+
+            if index < 0:
+                raise ValueError(
+                    f'Array size of {self._len} was overrun during prepend.\n'
+                    f'You have passed {abs(index)} too many datums.'
+                )
+
+        else:
+            index = start if start is not None else self._last.value
+
+        end = index + length
+
+        if field_map:
+            src_names, dst_names = zip(*field_map.items())
+        else:
+            dst_names = src_names = self._write_fields
+
+        try:
+            self._array[
+                list(dst_names)
+            ][index:end] = data[list(src_names)][:]
+
+            # NOTE: there was a race here between updating
+            # the first and last indices and when the next reader
+            # tries to access ``.array`` (which due to the index
+            # overlap will be empty). Pretty sure we've fixed it now
+            # but leaving this here as a reminder.
+            if (
+                prepend
+                and update_first
+                and length
+            ):
+                assert index < self._first.value
+
+            if (
+                index < self._first.value
+                and update_first
+            ):
+                assert prepend, 'prepend=True not passed but index decreased?'
+                self._first.value = index
+
+            elif not prepend:
+                self._last.value = end
+
+            self._post_init = True
+            return end
+
+        except ValueError as err:
+            if field_map:
+                raise
+
+            # should raise if diff detected
+            self.diff_err_fields(data)
+            raise err
+
+    def diff_err_fields(
+        self,
+        data: np.ndarray,
+    ) -> None:
+        # reraise with any field discrepancy
+        our_fields, their_fields = (
+            set(self._array.dtype.fields),
+            set(data.dtype.fields),
+        )
+
+        only_in_ours = our_fields - their_fields
+        only_in_theirs = their_fields - our_fields
+
+        if only_in_ours:
+            raise TypeError(
+                f"Input array is missing field(s): {only_in_ours}"
+            )
+        elif only_in_theirs:
+            raise TypeError(
+                f"Input array has unknown field(s): {only_in_theirs}"
+            )
+
+    # TODO: support "silent" prepends that don't update ._first.value?
+    def prepend(
+        self,
+        data: np.ndarray,
+    ) -> int:
+        end = self.push(data, prepend=True)
+        assert end
+
+    def close(self) -> None:
+        self._first._shm.close()
+        self._last._shm.close()
+        self._shm.close()
+
+    def destroy(self) -> None:
+        if _USE_POSIX:
+            # We manually unlink to bypass all the "resource tracker"
+            # nonsense meant for non-SC systems.
+            shm_unlink(self._shm.name)
+
+        self._first.destroy()
+        self._last.destroy()
+
+    def flush(self) -> None:
+        # TODO: flush to storage backend like markestore?
+        ...
+
+
+def open_shm_ndarray(
+    size: int,
+    key: str | None = None,
+    dtype: np.dtype | None = None,
+    append_start_index: int | None = None,
+    readonly: bool = False,
+
+) -> ShmArray:
+    '''
+    Open a memory shared ``numpy`` using the standard library.
+
+    This call unlinks (aka permanently destroys) the buffer on teardown
+    and thus should be used from the parent-most accessor (process).
+
+    '''
+    # create new shared mem segment for which we
+    # have write permission
+    a = np.zeros(size, dtype=dtype)
+    a['index'] = np.arange(len(a))
+
+    shm = SharedMemory(
+        name=key,
+        create=True,
+        size=a.nbytes
+    )
+    array = np.ndarray(
+        a.shape,
+        dtype=a.dtype,
+        buffer=shm.buf
+    )
+    array[:] = a[:]
+    array.setflags(write=int(not readonly))
+
+    token = _make_token(
+        key=key,
+        size=size,
+        dtype=dtype,
+    )
+
+    # create single entry arrays for storing an first and last indices
+    first = SharedInt(
+        shm=SharedMemory(
+            name=token.shm_first_index_name,
+            create=True,
+            size=4,  # std int
+        )
+    )
+
+    last = SharedInt(
+        shm=SharedMemory(
+            name=token.shm_last_index_name,
+            create=True,
+            size=4,  # std int
+        )
+    )
+
+    # Start the "real-time" append-updated (or "pushed-to") section
+    # after some start index: ``append_start_index``. This allows appending
+    # from a start point in the array which isn't the 0 index and looks
+    # something like,
+    # -------------------------
+    # |              |        i
+    # _________________________
+    # <-------------> <------->
+    #  history         real-time
+    #
+    # Once fully "prepended", the history section will leave the
+    # ``ShmArray._start.value: int = 0`` and the yet-to-be written
+    # real-time section will start at ``ShmArray.index: int``.
+
+    # this sets the index to nearly 2/3rds into the the length of
+    # the buffer leaving at least a "days worth of second samples"
+    # for the real-time section.
+    if append_start_index is None:
+        append_start_index = round(size * 0.616)
+
+    last.value = first.value = append_start_index
+
+    shmarr = ShmArray(
+        array,
+        first,
+        last,
+        shm,
+    )
+
+    assert shmarr._token == token
+    _known_tokens[key] = shmarr.token
+
+    # "unlink" created shm on process teardown by
+    # pushing teardown calls onto actor context stack
+    stack = tractor.current_actor().lifetime_stack
+    stack.callback(shmarr.close)
+    stack.callback(shmarr.destroy)
+
+    return shmarr
+
+
+def attach_shm_ndarray(
+    token: tuple[str, str, tuple[str, str]],
+    readonly: bool = True,
+
+) -> ShmArray:
+    '''
+    Attach to an existing shared memory array previously
+    created by another process using ``open_shared_array``.
+
+    No new shared mem is allocated but wrapper types for read/write
+    access are constructed.
+
+    '''
+    token = NDToken.from_msg(token)
+    key = token.shm_name
+
+    if key in _known_tokens:
+        assert NDToken.from_msg(_known_tokens[key]) == token, "WTF"
+
+    # XXX: ugh, looks like due to the ``shm_open()`` C api we can't
+    # actually place files in a subdir, see discussion here:
+    # https://stackoverflow.com/a/11103289
+
+    # attach to array buffer and view as per dtype
+    _err: Optional[Exception] = None
+    for _ in range(3):
+        try:
+            shm = SharedMemory(
+                name=key,
+                create=False,
+            )
+            break
+        except OSError as oserr:
+            _err = oserr
+            time.sleep(0.1)
+    else:
+        if _err:
+            raise _err
+
+    shmarr = np.ndarray(
+        (token.size,),
+        dtype=token.dtype,
+        buffer=shm.buf
+    )
+    shmarr.setflags(write=int(not readonly))
+
+    first = SharedInt(
+        shm=SharedMemory(
+            name=token.shm_first_index_name,
+            create=False,
+            size=4,  # std int
+        ),
+    )
+    last = SharedInt(
+        shm=SharedMemory(
+            name=token.shm_last_index_name,
+            create=False,
+            size=4,  # std int
+        ),
+    )
+
+    # make sure we can read
+    first.value
+
+    sha = ShmArray(
+        shmarr,
+        first,
+        last,
+        shm,
+    )
+    # read test
+    sha.array
+
+    # Stash key -> token knowledge for future queries
+    # via `maybe_opepn_shm_array()` but only after we know
+    # we can attach.
+    if key not in _known_tokens:
+        _known_tokens[key] = token
+
+    # "close" attached shm on actor teardown
+    tractor.current_actor().lifetime_stack.callback(sha.close)
+
+    return sha
+
+
+def maybe_open_shm_ndarray(
+    key: str,  # unique identifier for segment
+    size: int,
+    dtype: np.dtype | None = None,
+    append_start_index: int = 0,
+    readonly: bool = True,
+
+) -> tuple[ShmArray, bool]:
+    '''
+    Attempt to attach to a shared memory block using a "key" lookup
+    to registered blocks in the users overall "system" registry
+    (presumes you don't have the block's explicit token).
+
+    This function is meant to solve the problem of discovering whether
+    a shared array token has been allocated or discovered by the actor
+    running in **this** process. Systems where multiple actors may seek
+    to access a common block can use this function to attempt to acquire
+    a token as discovered by the actors who have previously stored
+    a "key" -> ``NDToken`` map in an actor local (aka python global)
+    variable.
+
+    If you know the explicit ``NDToken`` for your memory segment instead
+    use ``attach_shm_array``.
+
+    '''
+    try:
+        # see if we already know this key
+        token = _known_tokens[key]
+        return (
+            attach_shm_ndarray(
+                token=token,
+                readonly=readonly,
+            ),
+            False,  # not newly opened
+        )
+    except KeyError:
+        log.warning(f"Could not find {key} in shms cache")
+        if dtype:
+            token = _make_token(
+                key,
+                size=size,
+                dtype=dtype,
+            )
+        else:
+
+            try:
+                return (
+                    attach_shm_ndarray(
+                        token=token,
+                        readonly=readonly,
+                    ),
+                    False,
+                )
+            except FileNotFoundError:
+                log.warning(f"Could not attach to shm with token {token}")
+
+        # This actor does not know about memory
+        # associated with the provided "key".
+        # Attempt to open a block and expect
+        # to fail if a block has been allocated
+        # on the OS by someone else.
+        return (
+            open_shm_ndarray(
+                key=key,
+                size=size,
+                dtype=dtype,
+                append_start_index=append_start_index,
+                readonly=readonly,
+            ),
+            True,
+        )
+
+
+class ShmList(ShareableList):
+    '''
+    Carbon copy of ``.shared_memory.ShareableList`` with a few
+    enhancements:
+
+    - readonly mode via instance var flag  `._readonly: bool`
+    - ``.__getitem__()`` accepts ``slice`` inputs
+    - exposes the underlying buffer "name" as a ``.key: str``
+
+    '''
+    def __init__(
+        self,
+        sequence: list | None = None,
+        *,
+        name: str | None = None,
+        readonly: bool = True
+
+    ) -> None:
+        self._readonly = readonly
+        self._key = name
+        return super().__init__(
+            sequence=sequence,
+            name=name,
+        )
+
+    @property
+    def key(self) -> str:
+        return self._key
+
+    @property
+    def readonly(self) -> bool:
+        return self._readonly
+
+    def __setitem__(
+        self,
+        position,
+        value,
+
+    ) -> None:
+
+        # mimick ``numpy`` error
+        if self._readonly:
+            raise ValueError('assignment destination is read-only')
+
+        return super().__setitem__(position, value)
+
+    def __getitem__(
+        self,
+        indexish,
+    ) -> list:
+
+        # NOTE: this is a non-writeable view (copy?) of the buffer
+        # in a new list instance.
+        if isinstance(indexish, slice):
+            return list(self)[indexish]
+
+        return super().__getitem__(indexish)
+
+    # TODO: should we offer a `.array` and `.push()` equivalent
+    # to the `ShmArray`?
+    # currently we have the following limitations:
+    # - can't write slices of input using traditional slice-assign
+    #   syntax due to the ``ShareableList.__setitem__()`` implementation.
+    # - ``list(shmlist)`` returns a non-mutable copy instead of
+    #   a writeable view which would be handier numpy-style ops.
+
+
+def open_shm_list(
+    key: str,
+    sequence: list | None = None,
+    size: int = int(2 ** 10),
+    dtype: float | int | bool | str | bytes | None = float,
+    readonly: bool = True,
+
+) -> ShmList:
+
+    if sequence is None:
+        default = {
+            float: 0.,
+            int: 0,
+            bool: True,
+            str: 'doggy',
+            None: None,
+        }[dtype]
+        sequence = [default] * size
+
+    shml = ShmList(
+        sequence=sequence,
+        name=key,
+        readonly=readonly,
+    )
+
+    # "close" attached shm on actor teardown
+    try:
+        actor = tractor.current_actor()
+        actor.lifetime_stack.callback(shml.shm.close)
+        actor.lifetime_stack.callback(shml.shm.unlink)
+    except RuntimeError:
+        log.warning('tractor runtime not active, skipping teardown steps')
+
+    return shml
+
+
+def attach_shm_list(
+    key: str,
+    readonly: bool = False,
+
+) -> ShmList:
+
+    return ShmList(
+        name=key,
+        readonly=readonly,
+    )

tractor/_spawn.py

@@ -19,6 +19,7 @@ Machinery for actor process spawning using multiple backends.
 
 """
 from __future__ import annotations
+import multiprocessing as mp
 import sys
 import platform
 from typing import (
@@ -53,7 +54,6 @@ from ._exceptions import ActorFailure
 
 if TYPE_CHECKING:
     from ._supervise import ActorNursery
-    import multiprocessing as mp
     ProcessType = TypeVar('ProcessType', mp.Process, trio.Process)
 
 log = get_logger('tractor')
@@ -70,7 +70,6 @@ _spawn_method: SpawnMethodKey = 'trio'
 
 if platform.system() == 'Windows':
 
-    import multiprocessing as mp
     _ctx = mp.get_context("spawn")
 
     async def proc_waiter(proc: mp.Process) -> None:
@@ -457,7 +456,7 @@ async def trio_proc(
 
             # cancel result waiter that may have been spawned in
             # tandem if not done already
-            log.warning(
+            log.cancel(
                 "Cancelling existing result waiter task for "
                 f"{subactor.uid}")
             nursery.cancel_scope.cancel()

tractor/_state.py

@@ -23,11 +23,6 @@ from typing import (
     Any,
 )
 
-import trio
-
-from ._exceptions import NoRuntime
-
-
 _current_actor: Optional['Actor'] = None  # type: ignore # noqa
 _runtime_vars: dict[str, Any] = {
     '_debug_mode': False,
@@ -37,8 +32,11 @@ _runtime_vars: dict[str, Any] = {
 
 
 def current_actor(err_on_no_runtime: bool = True) -> 'Actor':  # type: ignore # noqa
-    """Get the process-local actor instance.
+    '''
-    """
+    Get the process-local actor instance.
+
+    '''
+    from ._exceptions import NoRuntime
     if _current_actor is None and err_on_no_runtime:
         raise NoRuntime("No local actor has been initialized yet")
 
@@ -46,16 +44,20 @@ def current_actor(err_on_no_runtime: bool = True) -> 'Actor':  # type: ignore #
 
 
 def is_main_process() -> bool:
-    """Bool determining if this actor is running in the top-most process.
+    '''
-    """
+    Bool determining if this actor is running in the top-most process.
+
+    '''
     import multiprocessing as mp
     return mp.current_process().name == 'MainProcess'
 
 
 def debug_mode() -> bool:
-    """Bool determining if "debug mode" is on which enables
+    '''
+    Bool determining if "debug mode" is on which enables
     remote subactor pdb entry on crashes.
-    """
+
+    '''
     return bool(_runtime_vars['_debug_mode'])
 
 

tractor/_streaming.py

@@ -14,31 +14,36 @@
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-"""
+'''
 Message stream types and APIs.
 
-"""
+The machinery and types behind ``Context.open_stream()``
+
+'''
 from __future__ import annotations
 import inspect
-from contextlib import asynccontextmanager
+from contextlib import asynccontextmanager as acm
-from dataclasses import dataclass
 from typing import (
     Any,
-    Optional,
     Callable,
-    AsyncGenerator,
+    AsyncIterator,
-    AsyncIterator
+    TYPE_CHECKING,
 )
-
 import warnings
 
 import trio
 
-from ._ipc import Channel
+from ._exceptions import (
-from ._exceptions import unpack_error, ContextCancelled
+    unpack_error,
-from ._state import current_actor
+)
 from .log import get_logger
-from .trionics import broadcast_receiver, BroadcastReceiver
+from .trionics import (
+    broadcast_receiver,
+    BroadcastReceiver,
+)
+
+if TYPE_CHECKING:
+    from ._context import Context
 
 
 log = get_logger(__name__)
@@ -70,9 +75,9 @@ class MsgStream(trio.abc.Channel):
     '''
     def __init__(
         self,
-        ctx: 'Context',  # typing: ignore # noqa
+        ctx: Context,  # typing: ignore # noqa
         rx_chan: trio.MemoryReceiveChannel,
-        _broadcaster: Optional[BroadcastReceiver] = None,
+        _broadcaster: BroadcastReceiver | None = None,
 
     ) -> None:
         self._ctx = ctx
@@ -275,7 +280,7 @@ class MsgStream(trio.abc.Channel):
         # still need to consume msgs that are "in transit" from the far
         # end (eg. for ``Context.result()``).
 
-    @asynccontextmanager
+    @acm
     async def subscribe(
         self,
 
@@ -335,8 +340,8 @@ class MsgStream(trio.abc.Channel):
         Send a message over this stream to the far end.
 
         '''
-        if self._ctx._error:
+        if self._ctx._remote_error:
-            raise self._ctx._error  # from None
+            raise self._ctx._remote_error  # from None
 
         if self._closed:
             raise trio.ClosedResourceError('This stream was already closed')
@@ -344,371 +349,11 @@ class MsgStream(trio.abc.Channel):
         await self._ctx.chan.send({'yield': data, 'cid': self._ctx.cid})
 
 
-@dataclass
-class Context:
-    '''
-    An inter-actor, ``trio`` task communication context.
-
-    NB: This class should never be instatiated directly, it is delivered
-    by either runtime machinery to a remotely started task or by entering
-    ``Portal.open_context()``.
-
-    Allows maintaining task or protocol specific state between
-    2 communicating actor tasks. A unique context is created on the
-    callee side/end for every request to a remote actor from a portal.
-
-    A context can be cancelled and (possibly eventually restarted) from
-    either side of the underlying IPC channel, open task oriented
-    message streams and acts as an IPC aware inter-actor-task cancel
-    scope.
-
-    '''
-    chan: Channel
-    cid: str
-
-    # these are the "feeder" channels for delivering
-    # message values to the local task from the runtime
-    # msg processing loop.
-    _recv_chan: trio.MemoryReceiveChannel
-    _send_chan: trio.MemorySendChannel
-
-    _remote_func_type: Optional[str] = None
-
-    # only set on the caller side
-    _portal: Optional['Portal'] = None    # type: ignore # noqa
-    _result: Optional[Any] = False
-    _error: Optional[BaseException] = None
-
-    # status flags
-    _cancel_called: bool = False
-    _cancel_msg: Optional[str] = None
-    _enter_debugger_on_cancel: bool = True
-    _started_called: bool = False
-    _started_received: bool = False
-    _stream_opened: bool = False
-
-    # only set on the callee side
-    _scope_nursery: Optional[trio.Nursery] = None
-
-    _backpressure: bool = False
-
-    async def send_yield(self, data: Any) -> None:
-
-        warnings.warn(
-            "`Context.send_yield()` is now deprecated. "
-            "Use ``MessageStream.send()``. ",
-            DeprecationWarning,
-            stacklevel=2,
-        )
-        await self.chan.send({'yield': data, 'cid': self.cid})
-
-    async def send_stop(self) -> None:
-        await self.chan.send({'stop': True, 'cid': self.cid})
-
-    async def _maybe_raise_from_remote_msg(
-        self,
-        msg: dict[str, Any],
-
-    ) -> None:
-        '''
-        (Maybe) unpack and raise a msg error into the local scope
-        nursery for this context.
-
-        Acts as a form of "relay" for a remote error raised
-        in the corresponding remote callee task.
-
-        '''
-        error = msg.get('error')
-        if error:
-            # If this is an error message from a context opened by
-            # ``Portal.open_context()`` we want to interrupt any ongoing
-            # (child) tasks within that context to be notified of the remote
-            # error relayed here.
-            #
-            # The reason we may want to raise the remote error immediately
-            # is that there is no guarantee the associated local task(s)
-            # will attempt to read from any locally opened stream any time
-            # soon.
-            #
-            # NOTE: this only applies when
-            # ``Portal.open_context()`` has been called since it is assumed
-            # (currently) that other portal APIs (``Portal.run()``,
-            # ``.run_in_actor()``) do their own error checking at the point
-            # of the call and result processing.
-            log.error(
-                f'Remote context error for {self.chan.uid}:{self.cid}:\n'
-                f'{msg["error"]["tb_str"]}'
-            )
-            error = unpack_error(msg, self.chan)
-            if (
-                isinstance(error, ContextCancelled) and
-                self._cancel_called
-            ):
-                # this is an expected cancel request response message
-                # and we don't need to raise it in scope since it will
-                # potentially override a real error
-                return
-
-            self._error = error
-
-            # TODO: tempted to **not** do this by-reraising in a
-            # nursery and instead cancel a surrounding scope, detect
-            # the cancellation, then lookup the error that was set?
-            if self._scope_nursery:
-
-                async def raiser():
-                    raise self._error from None
-
-                # from trio.testing import wait_all_tasks_blocked
-                # await wait_all_tasks_blocked()
-                if not self._scope_nursery._closed:  # type: ignore
-                    self._scope_nursery.start_soon(raiser)
-
-    async def cancel(
-        self,
-        msg: Optional[str] = None,
-
-    ) -> None:
-        '''
-        Cancel this inter-actor-task context.
-
-        Request that the far side cancel it's current linked context,
-        Timeout quickly in an attempt to sidestep 2-generals...
-
-        '''
-        side = 'caller' if self._portal else 'callee'
-        if msg:
-            assert side == 'callee', 'Only callee side can provide cancel msg'
-
-        log.cancel(f'Cancelling {side} side of context to {self.chan.uid}')
-
-        self._cancel_called = True
-
-        if side == 'caller':
-            if not self._portal:
-                raise RuntimeError(
-                    "No portal found, this is likely a callee side context"
-                )
-
-            cid = self.cid
-            with trio.move_on_after(0.5) as cs:
-                cs.shield = True
-                log.cancel(
-                    f"Cancelling stream {cid} to "
-                    f"{self._portal.channel.uid}")
-
-                # NOTE: we're telling the far end actor to cancel a task
-                # corresponding to *this actor*. The far end local channel
-                # instance is passed to `Actor._cancel_task()` implicitly.
-                await self._portal.run_from_ns('self', '_cancel_task', cid=cid)
-
-            if cs.cancelled_caught:
-                # XXX: there's no way to know if the remote task was indeed
-                # cancelled in the case where the connection is broken or
-                # some other network error occurred.
-                # if not self._portal.channel.connected():
-                if not self.chan.connected():
-                    log.cancel(
-                        "May have failed to cancel remote task "
-                        f"{cid} for {self._portal.channel.uid}")
-                else:
-                    log.cancel(
-                        "Timed out on cancelling remote task "
-                        f"{cid} for {self._portal.channel.uid}")
-
-        # callee side remote task
-        else:
-            self._cancel_msg = msg
-
-            # TODO: should we have an explicit cancel message
-            # or is relaying the local `trio.Cancelled` as an
-            # {'error': trio.Cancelled, cid: "blah"} enough?
-            # This probably gets into the discussion in
-            # https://github.com/goodboy/tractor/issues/36
-            assert self._scope_nursery
-            self._scope_nursery.cancel_scope.cancel()
-
-        if self._recv_chan:
-            await self._recv_chan.aclose()
-
-    @asynccontextmanager
-    async def open_stream(
-
-        self,
-        backpressure: Optional[bool] = True,
-        msg_buffer_size: Optional[int] = None,
-
-    ) -> AsyncGenerator[MsgStream, None]:
-        '''
-        Open a ``MsgStream``, a bi-directional stream connected to the
-        cross-actor (far end) task for this ``Context``.
-
-        This context manager must be entered on both the caller and
-        callee for the stream to logically be considered "connected".
-
-        A ``MsgStream`` is currently "one-shot" use, meaning if you
-        close it you can not "re-open" it for streaming and instead you
-        must re-establish a new surrounding ``Context`` using
-        ``Portal.open_context()``.  In the future this may change but
-        currently there seems to be no obvious reason to support
-        "re-opening":
-            - pausing a stream can be done with a message.
-            - task errors will normally require a restart of the entire
-              scope of the inter-actor task context due to the nature of
-              ``trio``'s cancellation system.
-
-        '''
-        actor = current_actor()
-
-        # here we create a mem chan that corresponds to the
-        # far end caller / callee.
-
-        # Likewise if the surrounding context has been cancelled we error here
-        # since it likely means the surrounding block was exited or
-        # killed
-
-        if self._cancel_called:
-            task = trio.lowlevel.current_task().name
-            raise ContextCancelled(
-                f'Context around {actor.uid[0]}:{task} was already cancelled!'
-            )
-
-        if not self._portal and not self._started_called:
-            raise RuntimeError(
-                'Context.started()` must be called before opening a stream'
-            )
-
-        # NOTE: in one way streaming this only happens on the
-        # caller side inside `Actor.start_remote_task()` so if you try
-        # to send a stop from the caller to the callee in the
-        # single-direction-stream case you'll get a lookup error
-        # currently.
-        ctx = actor.get_context(
-            self.chan,
-            self.cid,
-            msg_buffer_size=msg_buffer_size,
-        )
-        ctx._backpressure = backpressure
-        assert ctx is self
-
-        # XXX: If the underlying channel feeder receive mem chan has
-        # been closed then likely client code has already exited
-        # a ``.open_stream()`` block prior or there was some other
-        # unanticipated error or cancellation from ``trio``.
-
-        if ctx._recv_chan._closed:
-            raise trio.ClosedResourceError(
-                'The underlying channel for this stream was already closed!?')
-
-        async with MsgStream(
-            ctx=self,
-            rx_chan=ctx._recv_chan,
-        ) as stream:
-
-            if self._portal:
-                self._portal._streams.add(stream)
-
-            try:
-                self._stream_opened = True
-
-                # XXX: do we need this?
-                # ensure we aren't cancelled before yielding the stream
-                # await trio.lowlevel.checkpoint()
-                yield stream
-
-                # NOTE: Make the stream "one-shot use".  On exit, signal
-                # ``trio.EndOfChannel``/``StopAsyncIteration`` to the
-                # far end.
-                await stream.aclose()
-
-            finally:
-                if self._portal:
-                    try:
-                        self._portal._streams.remove(stream)
-                    except KeyError:
-                        log.warning(
-                            f'Stream was already destroyed?\n'
-                            f'actor: {self.chan.uid}\n'
-                            f'ctx id: {self.cid}'
-                        )
-
-    async def result(self) -> Any:
-        '''
-        From a caller side, wait for and return the final result from
-        the callee side task.
-
-        '''
-        assert self._portal, "Context.result() can not be called from callee!"
-        assert self._recv_chan
-
-        if self._result is False:
-
-            if not self._recv_chan._closed:  # type: ignore
-
-                # wait for a final context result consuming
-                # and discarding any bi dir stream msgs still
-                # in transit from the far end.
-                while True:
-
-                    msg = await self._recv_chan.receive()
-                    try:
-                        self._result = msg['return']
-                        break
-                    except KeyError as msgerr:
-
-                        if 'yield' in msg:
-                            # far end task is still streaming to us so discard
-                            log.warning(f'Discarding stream delivered {msg}')
-                            continue
-
-                        elif 'stop' in msg:
-                            log.debug('Remote stream terminated')
-                            continue
-
-                        # internal error should never get here
-                        assert msg.get('cid'), (
-                            "Received internal error at portal?")
-
-                        raise unpack_error(
-                            msg, self._portal.channel
-                        ) from msgerr
-
-        return self._result
-
-    async def started(
-        self,
-        value: Optional[Any] = None
-
-    ) -> None:
-        '''
-        Indicate to calling actor's task that this linked context
-        has started and send ``value`` to the other side.
-
-        On the calling side ``value`` is the second item delivered
-        in the tuple returned by ``Portal.open_context()``.
-
-        '''
-        if self._portal:
-            raise RuntimeError(
-                f"Caller side context {self} can not call started!")
-
-        elif self._started_called:
-            raise RuntimeError(
-                f"called 'started' twice on context with {self.chan.uid}")
-
-        await self.chan.send({'started': value, 'cid': self.cid})
-        self._started_called = True
-
-    # TODO: do we need a restart api?
-    # async def restart(self) -> None:
-    #     pass
-
-
 def stream(func: Callable) -> Callable:
-    """Mark an async function as a streaming routine with ``@stream``.
+    '''
+    Mark an async function as a streaming routine with ``@stream``.
 
-    """
+    '''
-    # annotate
     # TODO: apply whatever solution ``mypy`` ends up picking for this:
     # https://github.com/python/mypy/issues/2087#issuecomment-769266912
     func._tractor_stream_function = True  # type: ignore
@@ -734,22 +379,3 @@ def stream(func: Callable) -> Callable:
             "(Or ``to_trio`` if using ``asyncio`` in guest mode)."
         )
     return func
-
-
-def context(func: Callable) -> Callable:
-    """Mark an async function as a streaming routine with ``@context``.
-
-    """
-    # annotate
-    # TODO: apply whatever solution ``mypy`` ends up picking for this:
-    # https://github.com/python/mypy/issues/2087#issuecomment-769266912
-    func._tractor_context_function = True  # type: ignore
-
-    sig = inspect.signature(func)
-    params = sig.parameters
-    if 'ctx' not in params:
-        raise TypeError(
-            "The first argument to the context function "
-            f"{func.__name__} must be `ctx: tractor.Context`"
-        )
-    return func

tractor/experimental/_pubsub.py

@@ -37,7 +37,7 @@ import trio
 import wrapt
 
 from ..log import get_logger
-from .._streaming import Context
+from .._context import Context
 
 
 __all__ = ['pub']
@@ -148,7 +148,8 @@ def pub(
     *,
     tasks: set[str] = set(),
 ):
-    """Publisher async generator decorator.
+    '''
+    Publisher async generator decorator.
 
     A publisher can be called multiple times from different actors but
     will only spawn a finite set of internal tasks to stream values to
@@ -227,7 +228,8 @@ def pub(
     running in a single actor to stream data to an arbitrary number of
     subscribers. If you are ok to have a new task running for every call
     to ``pub_service()`` then probably don't need this.
-    """
+
+    '''
     global _pubtask2lock
 
     # handle the decorator not called with () case

tractor/log.py

@@ -82,6 +82,10 @@ class StackLevelAdapter(logging.LoggerAdapter):
         msg: str,
 
     ) -> None:
+        '''
+        IPC level msg-ing.
+
+        '''
         return self.log(5, msg)
 
     def runtime(
@@ -94,12 +98,20 @@ class StackLevelAdapter(logging.LoggerAdapter):
         self,
         msg: str,
     ) -> None:
+        '''
+        Cancellation logging, mostly for runtime reporting.
+
+        '''
         return self.log(16, msg)
 
     def pdb(
         self,
         msg: str,
     ) -> None:
+        '''
+        Debugger logging.
+
+        '''
         return self.log(500, msg)
 
     def log(self, level, msg, *args, **kwargs):
@@ -181,15 +193,39 @@ def get_logger(
     '''
     log = rlog = logging.getLogger(_root_name)
 
-    if name and name != _proj_name:
+    if (
+        name
+        and name != _proj_name
+    ):
 
-        # handling for modules that use ``get_logger(__name__)`` to
+        # NOTE: for handling for modules that use ``get_logger(__name__)``
-        # avoid duplicate project-package token in msg output
+        # we make the following stylistic choice:
-        rname, _, tail = name.partition('.')
+        # - always avoid duplicate project-package token
-        if rname == _root_name:
+        #   in msg output: i.e. tractor.tractor _ipc.py in header
-            name = tail
+        #   looks ridiculous XD
+        # - never show the leaf module name in the {name} part
+        #   since in python the {filename} is always this same
+        #   module-file.
+
+        sub_name: None | str = None
+        rname, _, sub_name = name.partition('.')
+        pkgpath, _, modfilename = sub_name.rpartition('.')
+
+        # NOTE: for tractor itself never include the last level
+        # module key in the name such that something like: eg.
+        # 'tractor.trionics._broadcast` only includes the first
+        # 2 tokens in the (coloured) name part.
+        if rname == 'tractor':
+            sub_name = pkgpath
+
+        if _root_name in sub_name:
+            duplicate, _, sub_name = sub_name.partition('.')
+
+        if not sub_name:
+            log = rlog
+        else:
+            log = rlog.getChild(sub_name)
 
-        log = rlog.getChild(name)
         log.level = rlog.level
 
     # add our actor-task aware adapter which will dynamically look up
@@ -242,3 +278,7 @@ def get_console_log(
 
 def get_loglevel() -> str:
     return _default_loglevel
+
+
+# global module logger for tractor itself
+log = get_logger('tractor')

tractor/msg.py

@@ -43,38 +43,62 @@ Built-in messaging patterns, types, APIs and helpers.
 # - https://github.com/msgpack/msgpack-python#packingunpacking-of-custom-data-type
 
 from __future__ import annotations
+from inspect import isfunction
 from pkgutil import resolve_name
 
 
 class NamespacePath(str):
     '''
-    A serializeable description of a (function) Python object location
+    A serializeable description of a (function) Python object
-    described by the target's module path and namespace key meant as
+    location described by the target's module path and namespace
-    a message-native "packet" to allows actors to point-and-load objects
+    key meant as a message-native "packet" to allows actors to
-    by absolute reference.
+    point-and-load objects by an absolute ``str`` (and thus
+    serializable) reference.
 
     '''
-    _ref: object = None
+    _ref: object | type | None = None
 
-    def load_ref(self) -> object:
+    def load_ref(self) -> object | type:
         if self._ref is None:
             self._ref = resolve_name(self)
         return self._ref
 
-    def to_tuple(
+    @staticmethod
-        self,
+    def _mk_fqnp(ref: type | object) -> tuple[str, str]:
+        '''
+        Generate a minial ``str`` pair which describes a python
+        object's namespace path and object/type name.
 
-    ) -> tuple[str, str]:
+        In more precise terms something like:
-        ref = self.load_ref()
+          - 'py.namespace.path:object_name',
-        return ref.__module__, getattr(ref, '__name__', '')
+          - eg.'tractor.msg:NamespacePath' will be the ``str`` form
+            of THIS type XD
+
+        '''
+        if (
+            isinstance(ref, object)
+            and not isfunction(ref)
+        ):
+            name: str = type(ref).__name__
+        else:
+            name: str = getattr(ref, '__name__')
+
+        # fully qualified namespace path, tuple.
+        fqnp: tuple[str, str] = (
+            ref.__module__,
+            name,
+        )
+        return fqnp
 
     @classmethod
     def from_ref(
         cls,
-        ref,
+        ref: type | object,
 
     ) -> NamespacePath:
-        return cls(':'.join(
+
-            (ref.__module__,
+        fqnp: tuple[str, str] = cls._mk_fqnp(ref)
-             getattr(ref, '__name__', ''))
+        return cls(':'.join(fqnp))
-        ))
+
+    def to_tuple(self) -> tuple[str, str]:
+        return self._mk_fqnp(self.load_ref())

tractor/to_asyncio.py

@@ -28,7 +28,6 @@ from typing import (
     Callable,
     AsyncIterator,
     Awaitable,
-    Optional,
 )
 
 import trio
@@ -65,9 +64,9 @@ class LinkedTaskChannel(trio.abc.Channel):
     _trio_exited: bool = False
 
     # set after ``asyncio.create_task()``
-    _aio_task: Optional[asyncio.Task] = None
+    _aio_task: asyncio.Task | None = None
-    _aio_err: Optional[BaseException] = None
+    _aio_err: BaseException | None = None
-    _broadcaster: Optional[BroadcastReceiver] = None
+    _broadcaster: BroadcastReceiver | None = None
 
     async def aclose(self) -> None:
         await self._from_aio.aclose()
@@ -188,7 +187,7 @@ def _run_asyncio_task(
 
     cancel_scope = trio.CancelScope()
     aio_task_complete = trio.Event()
-    aio_err: Optional[BaseException] = None
+    aio_err: BaseException | None = None
 
     chan = LinkedTaskChannel(
         aio_q,  # asyncio.Queue
@@ -217,7 +216,7 @@ def _run_asyncio_task(
         try:
             result = await coro
         except BaseException as aio_err:
-            log.exception('asyncio task errored')
+            # log.exception('asyncio task errored:')
             chan._aio_err = aio_err
             raise
 
@@ -263,7 +262,7 @@ def _run_asyncio_task(
         '''
         nonlocal chan
         aio_err = chan._aio_err
-        task_err: Optional[BaseException] = None
+        task_err: BaseException | None = None
 
         # only to avoid ``asyncio`` complaining about uncaptured
         # task exceptions
@@ -301,7 +300,7 @@ def _run_asyncio_task(
             elif task_err is None:
                 assert aio_err
                 aio_err.with_traceback(aio_err.__traceback__)
-                log.error('infected task errorred')
+                # log.error('infected task errorred')
 
             # XXX: alway cancel the scope on error
             # in case the trio task is blocking
@@ -329,11 +328,11 @@ async def translate_aio_errors(
     '''
     trio_task = trio.lowlevel.current_task()
 
-    aio_err: Optional[BaseException] = None
+    aio_err: BaseException | None = None
 
     # TODO: make thisi a channel method?
     def maybe_raise_aio_err(
-        err: Optional[Exception] = None
+        err: Exception | None = None
     ) -> None:
         aio_err = chan._aio_err
         if (
@@ -357,7 +356,7 @@ async def translate_aio_errors(
         # relay cancel through to called ``asyncio`` task
         assert chan._aio_task
         chan._aio_task.cancel(
-            msg=f'the `trio` caller task was cancelled: {trio_task.name}'
+            msg=f'`trio`-side caller task cancelled: {trio_task.name}'
         )
         raise
 
@@ -367,7 +366,7 @@ async def translate_aio_errors(
         trio.ClosedResourceError,
         # trio.BrokenResourceError,
     ):
-        aio_err = chan._aio_err
+        aio_err: BaseException = chan._aio_err
         if (
             task.cancelled() and
             type(aio_err) is CancelledError

tractor/trionics/_broadcast.py

@@ -25,8 +25,16 @@ from collections import deque
 from contextlib import asynccontextmanager
 from functools import partial
 from operator import ne
-from typing import Optional, Callable, Awaitable, Any, AsyncIterator, Protocol
+from typing import (
-from typing import Generic, TypeVar
+    Optional,
+    Callable,
+    Awaitable,
+    Any,
+    AsyncIterator,
+    Protocol,
+    Generic,
+    TypeVar,
+)
 
 import trio
 from trio._core._run import Task

tractor/trionics/_mngrs.py

@@ -237,7 +237,7 @@ async def maybe_open_context(
         yielded = _Cache.values[ctx_key]
 
     except KeyError:
-        log.info(f'Allocating new {acm_func} for {ctx_key}')
+        log.debug(f'Allocating new {acm_func} for {ctx_key}')
         mngr = acm_func(**kwargs)
         resources = _Cache.resources
         assert not resources.get(ctx_key), f'Resource exists? {ctx_key}'
@@ -265,7 +265,7 @@ async def maybe_open_context(
         if yielded is not None:
             # if no more consumers, teardown the client
             if _Cache.users <= 0:
-                log.info(f'De-allocating resource for {ctx_key}')
+                log.debug(f'De-allocating resource for {ctx_key}')
 
                 # XXX: if we're cancelled we the entry may have never
                 # been entered since the nursery task was killed.