Add our own "transport closed" signal

This change some super old (and bad) code from the project's very early
days. For some redic reason i must have thought masking `trio`'s
internal stream / transport errors and a TCP EOF as `StopAsyncIteration`
somehow a good idea. The reality is you probably
want to know the difference between an unexpected transport error
and a simple EOF lol. This begins to resolve that by adding our own
special `TransportClosed` error to signal the "graceful" termination of
a channel's underlying transport. Oh, and this builds on the `msgspec`
integration which helped shed light on the core issues here B)

tractor/_exceptions.py

@@ -41,6 +41,10 @@ class ContextCancelled(RemoteActorError):
     "Inter-actor task context cancelled itself on the callee side."
 
 
+class TransportClosed(trio.ClosedResourceError):
+    "Underlying channel transport was closed prior to use"
+
+
 class NoResult(RuntimeError):
     "No final result is expected for this actor"
 
@@ -66,12 +70,15 @@ def pack_error(exc: BaseException) -> Dict[str, Any]:
 
 
 def unpack_error(
+
     msg: Dict[str, Any],
     chan=None,
     err_type=RemoteActorError
+
 ) -> Exception:
     """Unpack an 'error' message from the wire
     into a local ``RemoteActorError``.
+
     """
     error = msg['error']
 

tractor/_ipc.py

@@ -2,6 +2,7 @@
 Inter-process comms abstractions
 """
 from functools import partial
+import math
 import struct
 import typing
 from typing import Any, Tuple, Optional
@@ -13,6 +14,7 @@ import trio
 from async_generator import asynccontextmanager
 
 from .log import get_logger
+from ._exceptions import TransportClosed
 log = get_logger(__name__)
 
 # :eyeroll:
@@ -24,7 +26,7 @@ except ImportError:
     Unpacker = partial(msgpack.Unpacker, strict_map_key=False)
 
 
-class MsgpackStream:
+class MsgpackTCPStream:
     '''A ``trio.SocketStream`` delivering ``msgpack`` formatted data
     using ``msgpack-python``.
 
@@ -47,7 +49,10 @@ class MsgpackStream:
         assert isinstance(rsockname, tuple)
         self._raddr = rsockname[:2]
 
+        # start and seed first entry to read loop
         self._agen = self._iter_packets()
+        # self._agen.asend(None) is None
+
         self._send_lock = trio.StrictFIFOLock()
 
     async def _iter_packets(self) -> typing.AsyncGenerator[dict, None]:
@@ -58,16 +63,13 @@ class MsgpackStream:
             use_list=False,
         )
         while True:
-            try:
             data = await self.stream.receive_some(2**10)
             log.trace(f"received {data}")  # type: ignore
-            except trio.BrokenResourceError:
-                log.warning(f"Stream connection {self.raddr} broke")
-                return
 
             if data == b'':
-                log.debug(f"Stream connection {self.raddr} was closed")
-                return
+                raise TransportClosed(
+                    f'transport {self} was already closed prior ro read'
+                )
 
             unpacker.feed(data)
             for packet in unpacker:
@@ -98,7 +100,7 @@ class MsgpackStream:
         return self.stream.socket.fileno() != -1
 
 
-class MsgspecStream(MsgpackStream):
+class MsgspecTCPStream(MsgpackTCPStream):
     '''A ``trio.SocketStream`` delivering ``msgpack`` formatted data
     using ``msgspec``.
 
@@ -123,12 +125,16 @@ class MsgspecStream(MsgpackStream):
         while True:
             try:
                 header = await self.recv_stream.receive_exactly(4)
-                if header is None:
-                    continue
+
+            except (ValueError):
+                raise TransportClosed(
+                    f'transport {self} was already closed prior ro read'
+                )
 
             if header == b'':
-                    log.debug(f"Stream connection {self.raddr} was closed")
-                    return
+                raise TransportClosed(
+                    f'transport {self} was already closed prior ro read'
+                )
 
             size, = struct.unpack("<I", header)
 
@@ -136,12 +142,6 @@ class MsgspecStream(MsgpackStream):
 
             msg_bytes = await self.recv_stream.receive_exactly(size)
 
-            # the value error here is to catch a connect with immediate
-            # disconnect that will cause an EOF error inside `tricycle`.
-            except (ValueError, trio.BrokenResourceError):
-                log.warning(f"Stream connection {self.raddr} broke")
-                return
-
             log.trace(f"received {msg_bytes}")  # type: ignore
             yield decoder.decode(msg_bytes)
 
@@ -169,8 +169,9 @@ class Channel:
         on_reconnect: typing.Callable[..., typing.Awaitable] = None,
         auto_reconnect: bool = False,
         stream: trio.SocketStream = None,  # expected to be active
-        # stream_serializer: type = MsgpackStream,
-        stream_serializer_type: type = MsgspecStream,
+
+        # stream_serializer_type: type = MsgspecTCPStream,
+        stream_serializer_type: type = MsgpackTCPStream,
 
     ) -> None:
 
@@ -192,6 +193,8 @@ class Channel:
         self._exc: Optional[Exception] = None
         self._agen = self._aiter_recv()
 
+        self._closed: bool = False
+
     def __repr__(self) -> str:
         if self.msgstream:
             return repr(
@@ -208,35 +211,52 @@ class Channel:
         return self.msgstream.raddr if self.msgstream else None
 
     async def connect(
-        self, destaddr: Tuple[Any, ...] = None,
+        self,
+        destaddr: Tuple[Any, ...] = None,
         **kwargs
+
     ) -> trio.SocketStream:
+
         if self.connected():
             raise RuntimeError("channel is already connected?")
+
         destaddr = destaddr or self._destaddr
         assert isinstance(destaddr, tuple)
-        stream = await trio.open_tcp_stream(*destaddr, **kwargs)
+
+        stream = await trio.open_tcp_stream(
+            *destaddr,
+            happy_eyeballs_delay=math.inf,
+            **kwargs
+        )
         self.msgstream = self.stream_serializer_type(stream)
         return stream
 
     async def send(self, item: Any) -> None:
+
         log.trace(f"send `{item}`")  # type: ignore
         assert self.msgstream
+
         await self.msgstream.send(item)
 
     async def recv(self) -> Any:
         assert self.msgstream
+
         try:
             return await self.msgstream.recv()
+
         except trio.BrokenResourceError:
             if self._autorecon:
                 await self._reconnect()
                 return await self.recv()
 
+            raise
+
     async def aclose(self) -> None:
         log.debug(f"Closing {self}")
         assert self.msgstream
         await self.msgstream.stream.aclose()
+        self._closed = True
+        log.error(f'CLOSING CHAN {self}')
 
     async def __aenter__(self):
         await self.connect()