Ipc failure while streaming

examples/advanced_faults/ipc_failure_during_stream.py

@@ -0,0 +1,151 @@
+'''
+Complex edge case where during real-time streaming the IPC tranport
+channels are wiped out (purposely in this example though it could have
+been an outage) and we want to ensure that despite being in debug mode
+(or not) the user can sent SIGINT once they notice the hang and the
+actor tree will eventually be cancelled without leaving any zombies.
+
+'''
+import trio
+from tractor import (
+    open_nursery,
+    context,
+    Context,
+    MsgStream,
+)
+
+
+async def break_channel_silently_then_error(
+    stream: MsgStream,
+):
+    async for msg in stream:
+        await stream.send(msg)
+
+        # XXX: close the channel right after an error is raised
+        # purposely breaking the IPC transport to make sure the parent
+        # doesn't get stuck in debug or hang on the connection join.
+        # this more or less simulates an infinite msg-receive hang on
+        # the other end.
+        await stream._ctx.chan.send(None)
+        assert 0
+
+
+async def close_stream_and_error(
+    stream: MsgStream,
+):
+    async for msg in stream:
+        await stream.send(msg)
+
+        # wipe out channel right before raising
+        await stream._ctx.chan.send(None)
+        await stream.aclose()
+        assert 0
+
+
+@context
+async def recv_and_spawn_net_killers(
+
+    ctx: Context,
+    break_ipc_after: bool | int = False,
+
+) -> None:
+    '''
+    Receive stream msgs and spawn some IPC killers mid-stream.
+
+    '''
+    await ctx.started()
+    async with (
+        ctx.open_stream() as stream,
+        trio.open_nursery() as n,
+    ):
+        async for i in stream:
+            print(f'child echoing {i}')
+            await stream.send(i)
+            if (
+                break_ipc_after
+                and i > break_ipc_after
+            ):
+                '#################################\n'
+                'Simulating child-side IPC BREAK!\n'
+                '#################################'
+                n.start_soon(break_channel_silently_then_error, stream)
+                n.start_soon(close_stream_and_error, stream)
+
+
+async def main(
+    debug_mode: bool = False,
+    start_method: str = 'trio',
+
+    # by default we break the parent IPC first (if configured to break
+    # at all), but this can be changed so the child does first (even if
+    # both are set to break).
+    break_parent_ipc_after: int | bool = False,
+    break_child_ipc_after: int | bool = False,
+
+) -> None:
+
+    async with (
+        open_nursery(
+            start_method=start_method,
+
+            # NOTE: even debugger is used we shouldn't get
+            # a hang since it never engages due to broken IPC
+            debug_mode=debug_mode,
+            loglevel='warning',
+
+        ) as an,
+    ):
+        portal = await an.start_actor(
+            'chitty_hijo',
+            enable_modules=[__name__],
+        )
+
+        async with portal.open_context(
+            recv_and_spawn_net_killers,
+            break_ipc_after=break_child_ipc_after,
+
+        ) as (ctx, sent):
+            async with ctx.open_stream() as stream:
+                for i in range(1000):
+
+                    if (
+                        break_parent_ipc_after
+                        and i > break_parent_ipc_after
+                    ):
+                        print(
+                            '#################################\n'
+                            'Simulating parent-side IPC BREAK!\n'
+                            '#################################'
+                        )
+                        await stream._ctx.chan.send(None)
+
+                    # it actually breaks right here in the
+                    # mp_spawn/forkserver backends and thus the zombie
+                    # reaper never even kicks in?
+                    print(f'parent sending {i}')
+                    await stream.send(i)
+
+                    with trio.move_on_after(2) as cs:
+
+                        # NOTE: in the parent side IPC failure case this
+                        # will raise an ``EndOfChannel`` after the child
+                        # is killed and sends a stop msg back to it's
+                        # caller/this-parent.
+                        rx = await stream.receive()
+
+                        print(f"I'm a happy user and echoed to me is {rx}")
+
+                    if cs.cancelled_caught:
+                        # pretend to be a user seeing no streaming action
+                        # thinking it's a hang, and then hitting ctl-c..
+                        print("YOO i'm a user anddd thingz hangin..")
+
+                print(
+                    "YOO i'm mad send side dun but thingz hangin..\n"
+                    'MASHING CTlR-C Ctl-c..'
+                )
+                raise KeyboardInterrupt
+
+
+if __name__ == '__main__':
+    trio.run(main)

nooz/346.bugfix.rst

@@ -0,0 +1,15 @@
+Fixes to ensure IPC (channel) breakage doesn't result in hung actor
+trees; the zombie reaping and general supervision machinery will always
+clean up and terminate.
+
+This includes not only the (mostly minor) fixes to solve these cases but
+also a new extensive test suite in `test_advanced_faults.py` with an
+accompanying highly configurable example module-script in
+`examples/advanced_faults/ipc_failure_during_stream.py`. Tests ensure we
+never get hang or zombies despite operating in debug mode and attempt to
+simulate all possible IPC transport failure cases for a local-host actor
+tree.
+
+Further we simplify `Context.open_stream.__aexit__()` to just call
+`MsgStream.aclose()` directly more or less avoiding a pure duplicate
+code path.

tests/conftest.py

@@ -7,6 +7,7 @@
 import random
 import signal
 import platform
+import pathlib
 import time
 import inspect
 from functools import partial, wraps
@@ -113,14 +114,21 @@ async def _main():
 )
 
 
-def repodir():
-    """Return the abspath to the repo directory.
-    """
-    dirname = os.path.dirname
-    dirpath = os.path.abspath(
-        dirname(dirname(os.path.realpath(__file__)))
-        )
-    return dirpath
+def repodir() -> pathlib.Path:
+    '''
+    Return the abspath to the repo directory.
+
+    '''
+    # 2 parents up to step up through tests/<repo_dir>
+    return pathlib.Path(__file__).parent.parent.absolute()
+
+
+def examples_dir() -> pathlib.Path:
+    '''
+    Return the abspath to the examples directory as `pathlib.Path`.
+
+    '''
+    return repodir() / 'examples'
 
 
 def pytest_addoption(parser):
@@ -151,7 +159,7 @@ def loglevel(request):
 
 
 @pytest.fixture(scope='session')
-def spawn_backend(request):
+def spawn_backend(request) -> str:
     return request.config.option.spawn_backend