Aggregate and organize streaming components
Move receive stream into streaming modules and rebrand as a "message
stream". Factor out cancellation mechanics in `.aclose()` into the
`Context` type which will soon provide the api for for cancelling portal
invocations. Comment-stage a few methods on both types in anticipation
of a new bi-directional streaming api. Add a `MsgStream` bidirectional
channel type which will be the eventual type yielded from
`Context.open_stream()`. Adjust the response/dialog types to be the set
`{'asyncfun', 'asyncgen', 'context'}`. OH, and add async func checking
in `Portal.run()` to catch and error on sync funcs early.
stream_contexts
Tyler Goodlet
parent
a5a88e2f64
commit
7f38b7225d
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@ -4,10 +4,9 @@ Portal api
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import importlib
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import inspect
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import typing
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from typing import Tuple, Any, Dict, Optional, Set, Iterator
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from typing import Tuple, Any, Dict, Optional, Set
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from functools import partial
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from dataclasses import dataclass
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from contextlib import contextmanager
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import warnings
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import trio
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@ -17,9 +16,10 @@ from ._state import current_actor
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from ._ipc import Channel
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from .log import get_logger
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from ._exceptions import unpack_error, NoResult, RemoteActorError
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from ._streaming import Context, ReceiveMsgStream
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log = get_logger('tractor')
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log = get_logger(__name__)
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@asynccontextmanager
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@ -39,113 +39,23 @@ async def maybe_open_nursery(
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yield nursery
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class ReceiveStream(trio.abc.ReceiveChannel):
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"""A wrapper around a ``trio._channel.MemoryReceiveChannel`` with
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special behaviour for signalling stream termination across an
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inter-actor ``Channel``. This is the type returned to a local task
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which invoked a remote streaming function using `Portal.run()`.
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Termination rules:
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- if the local task signals stop iteration a cancel signal is
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relayed to the remote task indicating to stop streaming
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- if the remote task signals the end of a stream, raise a
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``StopAsyncIteration`` to terminate the local ``async for``
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"""
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def __init__(
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self,
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cid: str,
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rx_chan: trio.abc.ReceiveChannel,
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portal: 'Portal',
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) -> None:
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self._cid = cid
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self._rx_chan = rx_chan
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self._portal = portal
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self._shielded = False
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# delegate directly to underlying mem channel
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def receive_nowait(self):
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return self._rx_chan.receive_nowait()
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async def receive(self):
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try:
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msg = await self._rx_chan.receive()
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return msg['yield']
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except trio.ClosedResourceError:
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# when the send is closed we assume the stream has
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# terminated and signal this local iterator to stop
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await self.aclose()
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raise StopAsyncIteration
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except trio.Cancelled:
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# relay cancels to the remote task
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await self.aclose()
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raise
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except KeyError:
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# internal error should never get here
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assert msg.get('cid'), (
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"Received internal error at portal?")
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raise unpack_error(msg, self._portal.channel)
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@contextmanager
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def shield(
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self
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) -> Iterator['ReceiveStream']: # noqa
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"""Shield this stream's underlying channel such that a local consumer task
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can be cancelled (and possibly restarted) using ``trio.Cancelled``.
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"""
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self._shielded = True
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yield self
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self._shielded = False
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async def aclose(self):
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"""Cancel associated remote actor task and local memory channel
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on close.
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"""
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if self._rx_chan._closed:
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log.warning(f"{self} is already closed")
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return
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if self._shielded:
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log.warning(f"{self} is shielded, portal channel being kept alive")
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return
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cid = self._cid
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with trio.move_on_after(0.5) as cs:
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cs.shield = True
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log.warning(
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f"Cancelling stream {cid} to "
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f"{self._portal.channel.uid}")
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# NOTE: we're telling the far end actor to cancel a task
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# corresponding to *this actor*. The far end local channel
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# instance is passed to `Actor._cancel_task()` implicitly.
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await self._portal.run_from_ns('self', '_cancel_task', cid=cid)
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if cs.cancelled_caught:
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# XXX: there's no way to know if the remote task was indeed
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# cancelled in the case where the connection is broken or
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# some other network error occurred.
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if not self._portal.channel.connected():
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log.warning(
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"May have failed to cancel remote task "
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f"{cid} for {self._portal.channel.uid}")
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with trio.CancelScope(shield=True):
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await self._rx_chan.aclose()
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def clone(self):
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return self
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class Portal:
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"""A 'portal' to a(n) (remote) ``Actor``.
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Allows for invoking remote routines and receiving results through an
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underlying ``tractor.Channel`` as though the remote (async)
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function / generator was invoked locally.
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A portal is "opened" (and eventually closed) by one side of an
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inter-actor communication context. The side which opens the portal
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is equivalent to a "caller" in function parlance and usually is
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either the called actor's parent (in process tree hierarchy terms)
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or a client interested in scheduling work to be done remotely in a
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far process.
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The portal api allows the "caller" actor to invoke remote routines
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and receive results through an underlying ``tractor.Channel`` as
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though the remote (async) function / generator was called locally.
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It may be thought of loosely as an RPC api where native Python
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function calling semantics are supported transparently; hence it is
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like having a "portal" between the seperate actor memory spaces.
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Think of this like a native async IPC API.
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"""
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def __init__(self, channel: Channel) -> None:
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self.channel = channel
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@ -157,7 +67,7 @@ class Portal:
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self._expect_result: Optional[
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Tuple[str, Any, str, Dict[str, Any]]
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] = None
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self._streams: Set[ReceiveStream] = set()
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self._streams: Set[ReceiveMsgStream] = set()
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self.actor = current_actor()
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async def _submit(
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@ -182,55 +92,19 @@ class Portal:
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first_msg = await recv_chan.receive()
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functype = first_msg.get('functype')
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if functype == 'asyncfunc':
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resp_type = 'return'
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elif functype == 'asyncgen':
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resp_type = 'yield'
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elif 'error' in first_msg:
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if 'error' in first_msg:
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raise unpack_error(first_msg, self.channel)
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else:
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elif functype not in ('asyncfunc', 'asyncgen', 'context'):
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raise ValueError(f"{first_msg} is an invalid response packet?")
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return cid, recv_chan, resp_type, first_msg
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return cid, recv_chan, functype, first_msg
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async def _submit_for_result(self, ns: str, func: str, **kwargs) -> None:
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assert self._expect_result is None, \
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"A pending main result has already been submitted"
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self._expect_result = await self._submit(ns, func, kwargs)
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async def run(
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self,
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func_or_ns: str,
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fn_name: Optional[str] = None,
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**kwargs
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) -> Any:
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"""Submit a remote function to be scheduled and run by actor, in
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a new task, wrap and return its (stream of) result(s).
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This is a blocking call and returns either a value from the
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remote rpc task or a local async generator instance.
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"""
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if isinstance(func_or_ns, str):
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warnings.warn(
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"`Portal.run(namespace: str, funcname: str)` is now"
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"deprecated, pass a function reference directly instead\n"
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"If you still want to run a remote function by name use"
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"`Portal.run_from_ns()`",
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DeprecationWarning,
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stacklevel=2,
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)
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fn_mod_path = func_or_ns
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assert isinstance(fn_name, str)
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else: # function reference was passed directly
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fn = func_or_ns
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fn_mod_path = fn.__module__
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fn_name = fn.__name__
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return await self._return_from_resptype(
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*(await self._submit(fn_mod_path, fn_name, kwargs))
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)
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async def run_from_ns(
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self,
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namespace_path: str,
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@ -260,15 +134,19 @@ class Portal:
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resptype: str,
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first_msg: dict
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) -> Any:
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# TODO: not this needs some serious work and thinking about how
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# to make async-generators the fundamental IPC API over channels!
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# (think `yield from`, `gen.send()`, and functional reactive stuff)
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if resptype == 'yield': # stream response
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rchan = ReceiveStream(cid, recv_chan, self)
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# receive only stream
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if resptype == 'asyncgen':
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ctx = Context(self.channel, cid, _portal=self)
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rchan = ReceiveMsgStream(ctx, recv_chan, self)
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self._streams.add(rchan)
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return rchan
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elif resptype == 'return': # single response
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elif resptype == 'context': # context manager style setup/teardown
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# TODO likely not here though
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raise NotImplementedError
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elif resptype == 'asyncfunc': # single response
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msg = await recv_chan.receive()
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try:
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return msg['return']
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@ -369,6 +247,65 @@ class Portal:
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f"{self.channel} for {self.channel.uid} was already closed?")
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return False
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async def run(
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self,
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func: str,
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fn_name: Optional[str] = None,
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**kwargs
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) -> Any:
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"""Submit a remote function to be scheduled and run by actor, in
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a new task, wrap and return its (stream of) result(s).
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This is a blocking call and returns either a value from the
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remote rpc task or a local async generator instance.
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"""
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if isinstance(func, str):
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warnings.warn(
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"`Portal.run(namespace: str, funcname: str)` is now"
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"deprecated, pass a function reference directly instead\n"
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"If you still want to run a remote function by name use"
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"`Portal.run_from_ns()`",
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DeprecationWarning,
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stacklevel=2,
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)
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fn_mod_path = func
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assert isinstance(fn_name, str)
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else: # function reference was passed directly
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# TODO: ensure async
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if not (
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inspect.isasyncgenfunction(func) or
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inspect.iscoroutinefunction(func)
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):
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raise TypeError(f'{func} must be an async function!')
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fn = func
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fn_mod_path = fn.__module__
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fn_name = fn.__name__
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return await self._return_from_resptype(
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*(await self._submit(fn_mod_path, fn_name, kwargs))
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)
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# @asynccontextmanager
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# async def open_stream_from(
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# self,
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# async_gen: 'AsyncGeneratorFunction',
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# **kwargs,
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# ) -> ReceiveMsgStream:
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# # TODO
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# pass
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# @asynccontextmanager
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# async def open_context(
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# self,
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# func: Callable,
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# **kwargs,
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# ) -> Context:
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# # TODO
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# pass
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@dataclass
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class LocalPortal:
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@ -1,14 +1,17 @@
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import inspect
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from contextvars import ContextVar
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from contextlib import contextmanager # , asynccontextmanager
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from dataclasses import dataclass
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from typing import Any
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from typing import Any, Iterator, Optional
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import warnings
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import trio
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from ._ipc import Channel
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from ._exceptions import unpack_error
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from .log import get_logger
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_context: ContextVar['Context'] = ContextVar('context')
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log = get_logger(__name__)
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@dataclass(frozen=True)
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@ -18,22 +21,73 @@ class Context:
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Allows maintaining task or protocol specific state between communicating
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actors. A unique context is created on the receiving end for every request
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to a remote actor.
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A context can be cancelled and (eventually) restarted from
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either side of the underlying IPC channel.
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A context can be used to open task oriented message streams.
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"""
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chan: Channel
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cid: str
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cancel_scope: trio.CancelScope
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# only set on the caller side
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_portal: Optional['Portal'] = None # type: ignore # noqa
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# only set on the callee side
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_cancel_scope: Optional[trio.CancelScope] = None
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async def send_yield(self, data: Any) -> None:
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warnings.warn(
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"`Context.send_yield()` is now deprecated. "
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"Use ``MessageStream.send()``. ",
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DeprecationWarning,
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stacklevel=2,
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)
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await self.chan.send({'yield': data, 'cid': self.cid})
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async def send_stop(self) -> None:
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await self.chan.send({'stop': True, 'cid': self.cid})
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async def cancel(self) -> None:
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"""Cancel this inter-actor-task context.
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Request that the far side cancel it's current linked context,
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timeout quickly to sidestep 2-generals...
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def current_context():
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"""Get the current task's context instance.
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"""
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return _context.get()
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cid = self.cid
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with trio.move_on_after(0.5) as cs:
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cs.shield = True
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log.warning(
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f"Cancelling stream {cid} to "
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f"{self._portal.channel.uid}")
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|
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# NOTE: we're telling the far end actor to cancel a task
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# corresponding to *this actor*. The far end local channel
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# instance is passed to `Actor._cancel_task()` implicitly.
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await self._portal.run_from_ns('self', '_cancel_task', cid=cid)
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|
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if cs.cancelled_caught:
|
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# XXX: there's no way to know if the remote task was indeed
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# cancelled in the case where the connection is broken or
|
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# some other network error occurred.
|
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if not self._portal.channel.connected():
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log.warning(
|
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"May have failed to cancel remote task "
|
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f"{cid} for {self._portal.channel.uid}")
|
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# async def restart(self) -> None:
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# # TODO
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# pass
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|
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# @asynccontextmanager
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# async def open_stream(
|
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# self,
|
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# ) -> AsyncContextManager:
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# # TODO
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# pass
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|
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|
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def stream(func):
|
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|
|
@ -47,3 +101,146 @@ def stream(func):
|
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f"{func.__name__} must be `ctx: tractor.Context`"
|
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)
|
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return func
|
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|
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|
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class ReceiveMsgStream(trio.abc.ReceiveChannel):
|
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"""A wrapper around a ``trio._channel.MemoryReceiveChannel`` with
|
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special behaviour for signalling stream termination across an
|
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inter-actor ``Channel``. This is the type returned to a local task
|
||||
which invoked a remote streaming function using `Portal.run()`.
|
||||
|
||||
Termination rules:
|
||||
- if the local task signals stop iteration a cancel signal is
|
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relayed to the remote task indicating to stop streaming
|
||||
- if the remote task signals the end of a stream, raise a
|
||||
``StopAsyncIteration`` to terminate the local ``async for``
|
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|
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"""
|
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def __init__(
|
||||
self,
|
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ctx: Context,
|
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rx_chan: trio.abc.ReceiveChannel,
|
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portal: 'Portal', # noqa
|
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) -> None:
|
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self._ctx = ctx
|
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self._rx_chan = rx_chan
|
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self._portal = portal
|
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# self._chan = portal.channel
|
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self._shielded = False
|
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|
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# delegate directly to underlying mem channel
|
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def receive_nowait(self):
|
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return self._rx_chan.receive_nowait()
|
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|
||||
async def receive(self):
|
||||
try:
|
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msg = await self._rx_chan.receive()
|
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return msg['yield']
|
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# return msg['yield']
|
||||
|
||||
except KeyError:
|
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# internal error should never get here
|
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assert msg.get('cid'), ("Received internal error at portal?")
|
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|
||||
# TODO: handle 2 cases with 3.10 match syntax
|
||||
# - 'stop'
|
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# - 'error'
|
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# possibly just handle msg['stop'] here!
|
||||
|
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# TODO: test that shows stream raising an expected error!!!
|
||||
if msg.get('error'):
|
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# raise the error message
|
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raise unpack_error(msg, self._portal.channel)
|
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|
||||
except trio.ClosedResourceError:
|
||||
# XXX: this indicates that a `stop` message was
|
||||
# sent by the far side of the underlying channel.
|
||||
# Currently this is triggered by calling ``.aclose()`` on
|
||||
# the send side of the channel inside
|
||||
# ``Actor._push_result()``, but maybe it should be put here?
|
||||
# to avoid exposing the internal mem chan closing mechanism?
|
||||
# in theory we could instead do some flushing of the channel
|
||||
# if needed to ensure all consumers are complete before
|
||||
# triggering closure too early?
|
||||
|
||||
# Locally, we want to close this stream gracefully, by
|
||||
# terminating any local consumers tasks deterministically.
|
||||
# We **don't** want to be closing this send channel and not
|
||||
# relaying a final value to remaining consumers who may not
|
||||
# have been scheduled to receive it yet?
|
||||
|
||||
# lots of testing to do here
|
||||
|
||||
# when the send is closed we assume the stream has
|
||||
# terminated and signal this local iterator to stop
|
||||
await self.aclose()
|
||||
raise StopAsyncIteration
|
||||
|
||||
except trio.Cancelled:
|
||||
# relay cancels to the remote task
|
||||
await self.aclose()
|
||||
raise
|
||||
|
||||
@contextmanager
|
||||
def shield(
|
||||
self
|
||||
) -> Iterator['ReceiveStream']: # noqa
|
||||
"""Shield this stream's underlying channel such that a local consumer task
|
||||
can be cancelled (and possibly restarted) using ``trio.Cancelled``.
|
||||
|
||||
"""
|
||||
self._shielded = True
|
||||
yield self
|
||||
self._shielded = False
|
||||
|
||||
async def aclose(self):
|
||||
"""Cancel associated remote actor task and local memory channel
|
||||
on close.
|
||||
"""
|
||||
rx_chan = self._rx_chan
|
||||
|
||||
if rx_chan._closed:
|
||||
log.warning(f"{self} is already closed")
|
||||
return
|
||||
|
||||
# stats = rx_chan.statistics()
|
||||
# if stats.open_receive_channels > 1:
|
||||
# # if we've been cloned don't kill the stream
|
||||
# log.debug(
|
||||
# "there are still consumers running keeping stream alive")
|
||||
# return
|
||||
|
||||
if self._shielded:
|
||||
log.warning(f"{self} is shielded, portal channel being kept alive")
|
||||
return
|
||||
|
||||
# close the local mem chan
|
||||
rx_chan.close()
|
||||
|
||||
# cancel surrounding IPC context
|
||||
await self._ctx.cancel()
|
||||
|
||||
# TODO: but make it broadcasting to consumers
|
||||
# def clone(self):
|
||||
# """Clone this receive channel allowing for multi-task
|
||||
# consumption from the same channel.
|
||||
|
||||
# """
|
||||
# return ReceiveStream(
|
||||
# self._cid,
|
||||
# self._rx_chan.clone(),
|
||||
# self._portal,
|
||||
# )
|
||||
|
||||
|
||||
class MsgStream(ReceiveMsgStream, trio.abc.Channel):
|
||||
"""
|
||||
Bidirectional message stream for use within an inter-actor actor
|
||||
``Context```.
|
||||
|
||||
"""
|
||||
async def send(
|
||||
self,
|
||||
data: Any
|
||||
) -> None:
|
||||
await self._chan.send({'yield': data, 'cid': self._cid})
|
||||
|
|
|
|||
Loading…
Reference in New Issue