Clean up `._transport` error-case comment

Expand and clarify the comment for the default `case _`
block in the `.send()` error matcher, noting that we
console-error and raise-thru for unexpected disconnect
conditions.

(this patch was suggested by copilot in,
 https://github.com/goodboy/tractor/pull/411)

(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code

examples/advanced_faults/ipc_failure_during_stream.py

@@ -17,6 +17,7 @@ from tractor import (
     MsgStream,
     _testing,
     trionics,
+    TransportClosed,
 )
 import trio
 import pytest
@@ -208,11 +209,15 @@ async def main(
                         # TODO: is this needed or no?
                         raise
 
-                    except trio.ClosedResourceError:
+                    except (
+                        trio.ClosedResourceError,
+                        TransportClosed,
+                    ) as _tpt_err:
                         # NOTE: don't send if we already broke the
                         # connection to avoid raising a closed-error
                         # such that we drop through to the ctl-c
                         # mashing by user.
+                        with trio.CancelScope(shield=True):
                             await trio.sleep(0.01)
 
                     # timeout: int = 1
@@ -247,6 +252,7 @@ async def main(
                     await stream.send(i)
                     pytest.fail('stream not closed?')
                 except (
+                    TransportClosed,
                     trio.ClosedResourceError,
                     trio.EndOfChannel,
                 ) as send_err:

tests/devx/conftest.py

@@ -4,6 +4,7 @@
 '''
 from __future__ import annotations
 import time
+import signal
 from typing import (
     Callable,
     TYPE_CHECKING,
@@ -69,12 +70,15 @@ def spawn(
         import os
         os.environ['PYTHON_COLORS'] = '0'
 
+    spawned: PexpectSpawner|None = None
+
     def _spawn(
         cmd: str,
         **mkcmd_kwargs,
     ) -> pty_spawn.spawn:
+        nonlocal spawned
         unset_colors()
-        return testdir.spawn(
+        spawned = testdir.spawn(
             cmd=mk_cmd(
                 cmd,
                 **mkcmd_kwargs,
@@ -84,9 +88,35 @@ def spawn(
             # ^TODO? get `pytest` core to expose underlying
             # `pexpect.spawn()` stuff?
         )
+        return spawned
 
     # such that test-dep can pass input script name.
-    return _spawn  # the `PexpectSpawner`, type alias.
+    yield _spawn  # the `PexpectSpawner`, type alias.
+
+    if (
+        spawned
+        and
+        (ptyproc := spawned.ptyproc)
+    ):
+        start: float = time.time()
+        timeout: float = 5
+        while (
+            ptyproc.isalive()
+            and
+            (
+                (_time_took := (time.time() - start))
+                 <
+                 timeout
+            )
+        ):
+            ptyproc.kill(signal.SIGINT)
+            time.sleep(0.01)
+
+        if ptyproc.isalive():
+            ptyproc.kill(signal.SIGKILL)
+
+    # TODO? ensure we've cleaned up any UDS-paths?
+    # breakpoint()
 
 
 @pytest.fixture(

tests/devx/test_debugger.py

@@ -1138,7 +1138,10 @@ def test_ctxep_pauses_n_maybe_ipc_breaks(
                 ['peer IPC channel closed abruptly?',
                  'another task closed this fd',
                  'Debug lock request was CANCELLED?',
-                 "TransportClosed: 'MsgpackUDSStream' was already closed locally ?",]
+                 "'MsgpackUDSStream' was already closed locally?",
+                 "TransportClosed: 'MsgpackUDSStream' was already closed 'by peer'?",
+                 # ?TODO^? match depending on `tpt_proto(s)`?
+                ]
 
                 # XXX races on whether these show/hit?
                  # 'Failed to REPl via `_pause()` You called `tractor.pause()` from an already cancelled scope!',

tests/test_advanced_faults.py

@@ -98,7 +98,8 @@ def test_ipc_channel_break_during_stream(
         expect_final_exc = TransportClosed
 
     mod: ModuleType = import_path(
-        examples_dir() / 'advanced_faults'
+        examples_dir()
+        / 'advanced_faults'
         / 'ipc_failure_during_stream.py',
         root=examples_dir(),
         consider_namespace_packages=False,
@@ -113,8 +114,9 @@ def test_ipc_channel_break_during_stream(
     if (
         # only expect EoC if trans is broken on the child side,
         ipc_break['break_child_ipc_after'] is not False
+        and
         # AND we tell the child to call `MsgStream.aclose()`.
-        and pre_aclose_msgstream
+        pre_aclose_msgstream
     ):
         # expect_final_exc = trio.EndOfChannel
         # ^XXX NOPE! XXX^ since now `.open_stream()` absorbs this
@@ -160,7 +162,8 @@ def test_ipc_channel_break_during_stream(
         ipc_break['break_child_ipc_after'] is not False
         and (
             ipc_break['break_parent_ipc_after']
-            > ipc_break['break_child_ipc_after']
+            >
+            ipc_break['break_child_ipc_after']
         )
     ):
         if pre_aclose_msgstream:
@@ -248,8 +251,15 @@ def test_ipc_channel_break_during_stream(
     # get raw instance from pytest wrapper
     value = excinfo.value
     if isinstance(value, ExceptionGroup):
-        excs = value.exceptions
+        excs: tuple[Exception] = value.exceptions
-        assert len(excs) == 1
+        assert (
+            len(excs) <= 2
+            and
+            all(
+                isinstance(exc, TransportClosed)
+                for exc in excs
+            )
+        )
         final_exc = excs[0]
         assert isinstance(final_exc, expect_final_exc)
 

tests/test_inter_peer_cancellation.py

@@ -11,12 +11,13 @@ import trio
 import tractor
 from tractor import (  # typing
     Actor,
-    current_actor,
-    open_nursery,
-    Portal,
     Context,
     ContextCancelled,
+    MsgStream,
+    Portal,
     RemoteActorError,
+    current_actor,
+    open_nursery,
 )
 from tractor._testing import (
     # tractor_test,
@@ -796,8 +797,8 @@ async def basic_echo_server(
 
 ) -> None:
     '''
-    Just the simplest `MsgStream` echo server which resays what
+    Just the simplest `MsgStream` echo server which resays what you
-    you told it but with its uid in front ;)
+    told it but with its uid in front ;)
 
     '''
     actor: Actor = tractor.current_actor()
@@ -966,9 +967,14 @@ async def tell_little_bro(
 
     caller: str = '',
     err_after: float|None = None,
-    rng_seed: int = 50,
+    rng_seed: int = 100,
+    # NOTE, ensure ^ is large enough (on fast hw anyway)
+    # to ensure the peer cancel req arrives before the
+    # echoing dialog does itself Bp
 ):
     # contact target actor, do a stream dialog.
+    lb: Portal
+    echo_ipc: MsgStream
     async with (
         tractor.wait_for_actor(
             name=actor_name
@@ -983,7 +989,6 @@ async def tell_little_bro(
                 else None
             ),
         ) as (sub_ctx, first),
-
         sub_ctx.open_stream() as echo_ipc,
     ):
         actor: Actor = current_actor()
@@ -994,6 +999,7 @@ async def tell_little_bro(
                 i,
             )
             await echo_ipc.send(msg)
+            await trio.sleep(0.001)
             resp = await echo_ipc.receive()
             print(
                 f'{caller} => {actor_name}: {msg}\n'
@@ -1006,6 +1012,9 @@ async def tell_little_bro(
             assert sub_uid != uid
             assert _i == i
 
+    # XXX, usually should never get here!
+    # await tractor.pause()
+
 
 @pytest.mark.parametrize(
     'raise_client_error',

tractor/_context.py

@@ -70,6 +70,7 @@ from ._exceptions import (
     MsgTypeError,
     RemoteActorError,
     StreamOverrun,
+    TransportClosed,
     pack_from_raise,
     unpack_error,
 )
@@ -2428,10 +2429,7 @@ async def open_context_from_portal(
             try:
                 # await pause(shield=True)
                 await ctx.cancel()
-            except (
+            except TransportClosed:
-                trio.BrokenResourceError,
-                trio.ClosedResourceError,
-            ):
                 log.warning(
                     'IPC connection for context is broken?\n'
                     f'task: {ctx.cid}\n'

tractor/_discovery.py

@@ -91,10 +91,13 @@ async def get_registry(
 
 
 @acm
-async def get_root(
+async def get_root(**kwargs) -> AsyncGenerator[Portal, None]:
-    **kwargs,
+    '''
-) -> AsyncGenerator[Portal, None]:
+    Deliver the current actor's "root process" actor (yes in actor
+    and proc tree terms) by delivering a `Portal` from the spawn-time
+    provided contact address.
 
+    '''
     # TODO: rename mailbox to `_root_maddr` when we finally
     # add and impl libp2p multi-addrs?
     addr = _runtime_vars['_root_mailbox']
@@ -193,6 +196,11 @@ async def maybe_open_portal(
     addr: UnwrappedAddress,
     name: str,
 ):
+    '''
+    Open a `Portal` to the actor serving @ `addr` or `None` if no
+    peer can be contacted or found.
+
+    '''
     async with query_actor(
         name=name,
         regaddr=addr,

tractor/_portal.py

@@ -329,18 +329,7 @@ class Portal:
             # if we get here some weird cancellation case happened
             return False
 
-        except (
+        except TransportClosed as tpt_err:
-            # XXX, should never really get raised unless we aren't
-            # wrapping them in the below type by mistake?
-            #
-            # Leaving the catch here for now until we're very sure
-            # all the cases (for various tpt protos) have indeed been
-            # re-wrapped ;p
-            trio.ClosedResourceError,
-            trio.BrokenResourceError,
-
-            TransportClosed,
-        ) as tpt_err:
             ipc_borked_report: str = (
                 f'IPC for actor already closed/broken?\n\n'
                 f'\n'

tractor/_rpc.py

@@ -284,9 +284,14 @@ async def _errors_relayed_via_ipc(
     try:
         yield  # run RPC invoke body
 
-    except TransportClosed:
+    # NOTE, never REPL any pseudo-expected tpt-disconnect.
-        log.exception('Tpt disconnect during remote-exc relay?')
+    except TransportClosed as err:
-        raise
+        rpc_err = err
+        log.warning(
+            f'Tpt disconnect during remote-exc relay due to,\n'
+            f'{err!r}\n'
+        )
+        raise err
 
     # box and ship RPC errors for wire-transit via
     # the task's requesting parent IPC-channel.
@@ -323,9 +328,6 @@ async def _errors_relayed_via_ipc(
                         and debug_kbis
                     )
                 )
-                # TODO? better then `debug_filter` below?
-                and
-                not isinstance(err, TransportClosed)
             ):
                 # XXX QUESTION XXX: is there any case where we'll
                 # want to debug IPC disconnects as a default?
@@ -346,13 +348,6 @@ async def _errors_relayed_via_ipc(
                 entered_debug = await debug._maybe_enter_pm(
                     err,
                     api_frame=inspect.currentframe(),
-
-                    # don't REPL any psuedo-expected tpt-disconnect
-                    # debug_filter=lambda exc: (
-                    #     type (exc) not in {
-                    #         TransportClosed,
-                    #     }
-                    # ),
                 )
                 if not entered_debug:
                     # if we prolly should have entered the REPL but
@@ -438,7 +433,7 @@ async def _errors_relayed_via_ipc(
             # cancel scope will not have been inserted yet
             if is_rpc:
                 log.warning(
-                    'RPC task likely errored or cancelled before start?\n'
+                    'RPC task likely crashed or cancelled before start?\n'
                     f'|_{ctx._task}\n'
                     f'  >> {ctx.repr_rpc}\n'
                 )
@@ -694,22 +689,6 @@ async def _invoke(
                     f'{pretty_struct.pformat(return_msg)}\n'
                 )
                 await chan.send(return_msg)
-                # ?TODO, remove the below since .send() already
-                # doesn't raise on tpt-closed?
-                # try:
-                #     await chan.send(return_msg)
-                # except TransportClosed:
-                #     log.exception(
-                #         f"Failed send final result to 'parent'-side of IPC-ctx!\n"
-                #         f'\n'
-                #         f'{chan}\n'
-                #         f'Channel already disconnected ??\n'
-                #         f'\n'
-                #         f'{pretty_struct.pformat(return_msg)}'
-                #     )
-                #     # ?TODO? will this ever be true though?
-                #     if chan.connected():
-                #         raise
 
             # NOTE: this happens IFF `ctx._scope.cancel()` is
             # called by any of,
@@ -935,6 +914,11 @@ async def try_ship_error_to_remote(
 
         # XXX NOTE XXX in SC terms this is one of the worst things
         # that can happen and provides for a 2-general's dilemma..
+        #
+        # FURHTER, we should never really have to handle these
+        # lowlevel excs from `trio` since the `Channel.send()` layers
+        # downward should be mostly wrapping such cases in a
+        # tpt-closed; the `.critical()` usage is warranted.
         except (
             trio.ClosedResourceError,
             trio.BrokenResourceError,

tractor/_runtime.py

@@ -183,6 +183,14 @@ class Actor:
     def is_registrar(self) -> bool:
         return self.is_arbiter
 
+    @property
+    def is_root(self) -> bool:
+        '''
+        This actor is the parent most in the tree?
+
+        '''
+        return _state.is_root_process()
+
     msg_buffer_size: int = 2**6
 
     # nursery placeholders filled in by `async_main()`,

tractor/_streaming.py

@@ -38,6 +38,7 @@ import trio
 from ._exceptions import (
     ContextCancelled,
     RemoteActorError,
+    TransportClosed,
 )
 from .log import get_logger
 from .trionics import (
@@ -409,10 +410,8 @@ class MsgStream(trio.abc.Channel):
             # it).
             with trio.CancelScope(shield=True):
                 await self._ctx.send_stop()
-
         except (
-            trio.BrokenResourceError,
+            TransportClosed,
-            trio.ClosedResourceError
         ) as re:
             # the underlying channel may already have been pulled
             # in which case our stop message is meaningless since
@@ -593,9 +592,8 @@ class MsgStream(trio.abc.Channel):
                 ),
             )
         except (
-            trio.ClosedResourceError,
-            trio.BrokenResourceError,
             BrokenPipeError,
+            TransportClosed,
         ) as _trans_err:
             trans_err = _trans_err
             if (

tractor/devx/debug/_trace.py

@@ -1257,3 +1257,26 @@ async def breakpoint(
         api_frame=inspect.currentframe(),
         **kwargs,
     )
+
+
+async def maybe_pause_bp():
+    '''
+    Internal (ONLY for now) `breakpoint()`-er fn which only tries to
+    use the multi-actor `.pause()` API when the current actor is the
+    root.
+
+    ?! BUT WHY !?
+       -------
+
+    This is useful when debugging cases where the tpt layer breaks
+    (or is intentionally broken, say during resiliency testing) in
+    the case where a child can no longer contact the root process to
+    acquire the process-tree-singleton TTY lock.
+
+    '''
+    import tractor
+    actor = tractor.current_actor()
+    if actor.aid.name == 'root':
+        await tractor.pause(shield=True)
+    else:
+        tractor.devx.mk_pdb().set_trace()

tractor/ipc/_chan.py

@@ -307,7 +307,12 @@ class Channel:
 
     ) -> None:
         '''
-        Send a coded msg-blob over the transport.
+        Send a coded msg-blob over the underlying IPC transport.
+
+        This fn raises `TransportClosed` on comms failures and is
+        normally handled by higher level runtime machinery for the
+        expected-graceful cases, normally ephemercal
+        (re/dis)connects.
 
         '''
         __tracebackhide__: bool = hide_tb
@@ -334,9 +339,10 @@ class Channel:
                     except KeyError:
                         raise err
                 case TransportClosed():
+                    src_exc_str: str = err.repr_src_exc()
                     log.transport(
-                        f'Transport stream closed due to\n'
+                        f'Transport stream closed due to,\n'
-                        f'{err.repr_src_exc()}\n'
+                        f'{src_exc_str}'
                     )
 
                 case _:
@@ -345,6 +351,11 @@ class Channel:
             raise
 
     async def recv(self) -> Any:
+        '''
+        Receive the latest (queued) msg-blob from the underlying IPC
+        transport.
+
+        '''
         assert self._transport
         return await self._transport.recv()
 
@@ -418,16 +429,18 @@ class Channel:
         self
     ) -> AsyncGenerator[Any, None]:
         '''
-        Yield `MsgType` IPC msgs decoded and deliverd from
+        Yield `MsgType` IPC msgs decoded and deliverd from an
-        an underlying `MsgTransport` protocol.
+        underlying `MsgTransport` protocol.
 
-        This is a streaming routine alo implemented as an async-gen
+        This is a streaming routine alo implemented as an
-        func (same a `MsgTransport._iter_pkts()`) gets allocated by
+        async-generator func (same a `MsgTransport._iter_pkts()`)
-        a `.__call__()` inside `.__init__()` where it is assigned to
+        gets allocated by a `.__call__()` inside `.__init__()` where
-        the `._aiter_msgs` attr.
+        it is assigned to the `._aiter_msgs` attr.
 
         '''
-        assert self._transport
+        if not self._transport:
+            raise RuntimeError('No IPC transport initialized!?')
+
         while True:
             try:
                 async for msg in self._transport:
@@ -462,7 +475,15 @@ class Channel:
             #     continue
 
     def connected(self) -> bool:
-        return self._transport.connected() if self._transport else False
+        '''
+        Predicate whether underlying IPC tpt is connected.
+
+        '''
+        return (
+            self._transport.connected()
+            if self._transport
+            else False
+        )
 
     async def _do_handshake(
         self,
@@ -493,8 +514,11 @@ async def _connect_chan(
     addr: UnwrappedAddress
 ) -> typing.AsyncGenerator[Channel, None]:
     '''
-    Create and connect a channel with disconnect on context manager
+    Create and connect a `Channel` to the provided `addr`, disconnect
-    teardown.
+    it on cm exit.
+
+    NOTE, this is a lowlevel, normally internal-only iface. You
+    should likely use `.open_portal()` instead.
 
     '''
     chan = await Channel.from_addr(addr)

tractor/ipc/_transport.py

@@ -154,7 +154,6 @@ class MsgTransport(Protocol):
     #     ...
 
 
-
 class MsgpackTransport(MsgTransport):
 
     # TODO: better naming for this?
@@ -278,14 +277,18 @@ class MsgpackTransport(MsgTransport):
             except trio.ClosedResourceError as cre:
                 closure_err = cre
 
+                # await tractor.devx._trace.maybe_pause_bp()
+
                 raise TransportClosed(
                     message=(
-                        f'{tpt_name} was already closed locally ?\n'
+                        f'{tpt_name} was already closed locally?'
                     ),
                     src_exc=closure_err,
                     loglevel='error',
                     raise_on_report=(
-                        'another task closed this fd' in closure_err.args
+                        'another task closed this fd'
+                        in
+                        closure_err.args
                     ),
                 ) from closure_err
 
@@ -435,6 +438,11 @@ class MsgpackTransport(MsgTransport):
                 trans_err = _re
                 tpt_name: str = f'{type(self).__name__!r}'
 
+                trans_err_msg: str = trans_err.args[0]
+                by_whom: str = {
+                    'another task closed this fd': 'locally',
+                    'this socket was already closed': 'by peer',
+                }.get(trans_err_msg)
                 match trans_err:
 
                     # XXX, specifc to UDS transport and its,
@@ -446,13 +454,13 @@ class MsgpackTransport(MsgTransport):
                     case trio.BrokenResourceError() if (
                         '[Errno 32] Broken pipe'
                         in
-                        trans_err.args[0]
+                        trans_err_msg
                     ):
                         tpt_closed = TransportClosed.from_src_exc(
                             message=(
                                 f'{tpt_name} already closed by peer\n'
                             ),
-                            body=f'{self}\n',
+                            body=f'{self}',
                             src_exc=trans_err,
                             raise_on_report=True,
                             loglevel='transport',
@@ -462,24 +470,26 @@ class MsgpackTransport(MsgTransport):
                     # ??TODO??, what case in piker does this and HOW
                     # CAN WE RE-PRODUCE IT?!?!?
                     case trio.ClosedResourceError() if (
-                        'this socket was already closed'
+                        by_whom
-                        in
-                        trans_err.args[0]
                     ):
                         tpt_closed = TransportClosed.from_src_exc(
                             message=(
-                                f'{tpt_name} already closed by peer\n'
+                                f'{tpt_name} was already closed {by_whom!r}?\n'
                             ),
-                            body=f'{self}\n',
+                            body=f'{self}',
                             src_exc=trans_err,
                             raise_on_report=True,
                             loglevel='transport',
                         )
+
+                        # await tractor.devx._trace.maybe_pause_bp()
                         raise tpt_closed from trans_err
 
-                    # unless the disconnect condition falls under "a
+                    # XXX, unless the disconnect condition falls
-                    # normal operation breakage" we usualy console warn
+                    # under "a normal/expected operating breakage"
-                    # about it.
+                    # (per the `trans_err_msg` guards in the cases
+                    # above) we usualy console-error about it and
+                    # raise-thru. about it.
                     case _:
                         log.exception(
                             f'{tpt_name} layer failed pre-send ??\n'