Add initial bi-directional streaming
This mostly adds the api described in https://github.com/goodboy/tractor/issues/53#issuecomment-806258798 The first draft summary: - formalize bidir steaming using the `trio.Channel` style interface which we derive as a `MsgStream` type. - add `Portal.open_context()` which provides a `trio.Nursery.start()` remote task invocation style for setting up and tearing down tasks contexts in remote actors. - add a distinct `'started'` message to the ipc protocol to facilitate `Context.start()` with a first return value. - for our `ReceiveMsgStream` type, don't cancel the remote task in `.aclose()`; this is now done explicitly by the surrounding `Context` usage: `Context.cancel()`. - streams in either direction still use a `'yield'` message keeping the proto mostly symmetric without having to worry about which side is the caller / portal opener. - subtlety: only allow sending a `'stop'` message during a 2-way streaming context from `ReceiveStream.aclose()`, detailed comment with explanation is included. Relates to #53wip_fix_asyncio_gen_streaming
Tyler Goodlet
parent
f48548ab94
commit
15fa777ddf
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@ -14,6 +14,7 @@ from types import ModuleType
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import sys
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import os
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from contextlib import ExitStack
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import warnings
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import trio # type: ignore
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from trio_typing import TaskStatus
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@ -57,13 +58,37 @@ async def _invoke(
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treat_as_gen = False
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cs = None
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cancel_scope = trio.CancelScope()
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ctx = Context(chan, cid, cancel_scope)
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ctx = Context(chan, cid, _cancel_scope=cancel_scope)
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context = False
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if getattr(func, '_tractor_stream_function', False):
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# handle decorated ``@tractor.stream`` async functions
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sig = inspect.signature(func)
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params = sig.parameters
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# compat with old api
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kwargs['ctx'] = ctx
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if 'ctx' in params:
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warnings.warn(
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"`@tractor.stream decorated funcs should now declare "
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"a `stream` arg, `ctx` is now designated for use with "
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"@tractor.context",
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DeprecationWarning,
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stacklevel=2,
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)
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elif 'stream' in params:
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assert 'stream' in params
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kwargs['stream'] = ctx
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treat_as_gen = True
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elif getattr(func, '_tractor_context_function', False):
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# handle decorated ``@tractor.context`` async function
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kwargs['ctx'] = ctx
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context = True
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# errors raised inside this block are propgated back to caller
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try:
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if not (
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@ -101,26 +126,41 @@ async def _invoke(
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# `StopAsyncIteration` system here for returning a final
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# value if desired
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await chan.send({'stop': True, 'cid': cid})
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# one way @stream func that gets treated like an async gen
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elif treat_as_gen:
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await chan.send({'functype': 'asyncgen', 'cid': cid})
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# XXX: the async-func may spawn further tasks which push
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# back values like an async-generator would but must
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# manualy construct the response dict-packet-responses as
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# above
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with cancel_scope as cs:
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task_status.started(cs)
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await coro
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if not cs.cancelled_caught:
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# task was not cancelled so we can instruct the
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# far end async gen to tear down
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await chan.send({'stop': True, 'cid': cid})
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elif context:
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# context func with support for bi-dir streaming
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await chan.send({'functype': 'context', 'cid': cid})
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with cancel_scope as cs:
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task_status.started(cs)
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await chan.send({'return': await coro, 'cid': cid})
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# if cs.cancelled_caught:
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# # task was cancelled so relay to the cancel to caller
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# await chan.send({'return': await coro, 'cid': cid})
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else:
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if treat_as_gen:
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await chan.send({'functype': 'asyncgen', 'cid': cid})
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# XXX: the async-func may spawn further tasks which push
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# back values like an async-generator would but must
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# manualy construct the response dict-packet-responses as
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# above
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with cancel_scope as cs:
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task_status.started(cs)
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await coro
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if not cs.cancelled_caught:
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# task was not cancelled so we can instruct the
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# far end async gen to tear down
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await chan.send({'stop': True, 'cid': cid})
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else:
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# regular async function
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await chan.send({'functype': 'asyncfunc', 'cid': cid})
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with cancel_scope as cs:
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task_status.started(cs)
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await chan.send({'return': await coro, 'cid': cid})
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# regular async function
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await chan.send({'functype': 'asyncfunc', 'cid': cid})
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with cancel_scope as cs:
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task_status.started(cs)
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await chan.send({'return': await coro, 'cid': cid})
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except (Exception, trio.MultiError) as err:
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@ -404,10 +444,10 @@ class Actor:
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send_chan, recv_chan = self._cids2qs[(actorid, cid)]
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assert send_chan.cid == cid # type: ignore
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if 'stop' in msg:
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log.debug(f"{send_chan} was terminated at remote end")
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# indicate to consumer that far end has stopped
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return await send_chan.aclose()
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# if 'stop' in msg:
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# log.debug(f"{send_chan} was terminated at remote end")
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# # indicate to consumer that far end has stopped
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# return await send_chan.aclose()
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try:
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log.debug(f"Delivering {msg} from {actorid} to caller {cid}")
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@ -415,6 +455,12 @@ class Actor:
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await send_chan.send(msg)
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except trio.BrokenResourceError:
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# TODO: what is the right way to handle the case where the
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# local task has already sent a 'stop' / StopAsyncInteration
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# to the other side but and possibly has closed the local
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# feeder mem chan? Do we wait for some kind of ack or just
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# let this fail silently and bubble up (currently)?
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# XXX: local consumer has closed their side
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# so cancel the far end streaming task
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log.warning(f"{send_chan} consumer is already closed")
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@ -494,6 +540,7 @@ class Actor:
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if cid:
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# deliver response to local caller/waiter
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await self._push_result(chan, cid, msg)
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log.debug(
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f"Waiting on next msg for {chan} from {chan.uid}")
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continue
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@ -312,11 +312,20 @@ class Portal:
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ctx = Context(self.channel, cid, _portal=self)
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try:
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async with ReceiveMsgStream(ctx, recv_chan, self) as rchan:
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# deliver receive only stream
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async with ReceiveMsgStream(ctx, recv_chan) as rchan:
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self._streams.add(rchan)
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yield rchan
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finally:
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# cancel the far end task on consumer close
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# NOTE: this is a special case since we assume that if using
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# this ``.open_fream_from()`` api, the stream is one a one
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# time use and we couple the far end tasks's lifetime to
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# the consumer's scope; we don't ever send a `'stop'`
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# message right now since there shouldn't be a reason to
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# stop and restart the stream, right?
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try:
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await ctx.cancel()
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except trio.ClosedResourceError:
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@ -326,16 +335,55 @@ class Portal:
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self._streams.remove(rchan)
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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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# 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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@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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"""Open an inter-actor task context.
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This is a synchronous API which allows for deterministic
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setup/teardown of a remote task. The yielded ``Context`` further
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allows for opening bidirectional streams - see
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``Context.open_stream()``.
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"""
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# conduct target func method structural checks
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if not inspect.iscoroutinefunction(func) and (
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getattr(func, '_tractor_contex_function', False)
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):
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raise TypeError(
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f'{func} must be an async generator function!')
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fn_mod_path, fn_name = func_deats(func)
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cid, recv_chan, functype, first_msg = await self._submit(
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fn_mod_path, fn_name, kwargs)
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assert functype == 'context'
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msg = await recv_chan.receive()
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try:
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# the "first" value here is delivered by the callee's
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# ``Context.started()`` call.
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first = msg['started']
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except KeyError:
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assert msg.get('cid'), ("Received internal error at context?")
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if msg.get('error'):
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# raise the error message
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raise unpack_error(msg, self.channel)
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else:
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raise
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try:
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ctx = Context(self.channel, cid, _portal=self)
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yield ctx, first
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finally:
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await recv_chan.aclose()
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await ctx.cancel()
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@dataclass
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@ -1,19 +1,195 @@
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import inspect
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from contextlib import contextmanager # , asynccontextmanager
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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, Iterator, Optional
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from typing import Any, Iterator, Optional, Callable
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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 ._state import current_actor
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from .log import get_logger
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log = get_logger(__name__)
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# TODO: generic typing like trio's receive channel
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# but with msgspec messages?
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# class ReceiveChannel(AsyncResource, Generic[ReceiveType]):
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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
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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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ctx: 'Context', # typing: ignore # noqa
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rx_chan: trio.abc.ReceiveChannel,
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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._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 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
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# - 'stop'
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# - 'error'
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# possibly just handle msg['stop'] here!
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if msg.get('stop'):
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log.debug(f"{self} was stopped at remote end")
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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 trio.EndOfChannel
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# TODO: test that shows stream raising an expected error!!!
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elif msg.get('error'):
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# raise the error message
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raise unpack_error(msg, self._ctx.chan)
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else:
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raise
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except (trio.ClosedResourceError, StopAsyncIteration):
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# XXX: this indicates that a `stop` message was
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# sent by the far side of the underlying channel.
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# Currently this is triggered by calling ``.aclose()`` on
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# the send side of the channel inside
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# ``Actor._push_result()``, but maybe it should be put here?
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# to avoid exposing the internal mem chan closing mechanism?
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# in theory we could instead do some flushing of the channel
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# if needed to ensure all consumers are complete before
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# triggering closure too early?
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# Locally, we want to close this stream gracefully, by
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# terminating any local consumers tasks deterministically.
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# We **don't** want to be closing this send channel and not
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# relaying a final value to remaining consumers who may not
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# have been scheduled to receive it yet?
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# lots of testing to do here
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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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# await self._ctx.send_stop()
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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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@contextmanager
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def shield(
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self
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) -> Iterator['ReceiveMsgStream']: # 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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# TODO: proper adherance to trio's `.aclose()` semantics:
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# https://trio.readthedocs.io/en/stable/reference-io.html#trio.abc.AsyncResource.aclose
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rx_chan = self._rx_chan
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if rx_chan._closed:
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log.warning(f"{self} is already closed")
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return
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# TODO: broadcasting to multiple consumers
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# stats = rx_chan.statistics()
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# if stats.open_receive_channels > 1:
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# # if we've been cloned don't kill the stream
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# log.debug(
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# "there are still consumers running keeping stream alive")
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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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# NOTE: this is super subtle IPC messaging stuff:
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# Relay stop iteration to far end **iff** we're
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# in bidirectional mode. If we're only streaming
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# *from* one side then that side **won't** have an
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# entry in `Actor._cids2qs` (maybe it should though?).
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# So any `yield` or `stop` msgs sent from the caller side
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# will cause key errors on the callee side since there is
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# no entry for a local feeder mem chan since the callee task
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# isn't expecting messages to be sent by the caller.
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# Thus, we must check that this context DOES NOT
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# have a portal reference to ensure this is indeed the callee
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# side and can relay a 'stop'. In the bidirectional case,
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# `Context.open_stream()` will create the `Actor._cids2qs`
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# entry from a call to `Actor.get_memchans()`.
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if not self._ctx._portal:
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# only for 2 way streams can we can send
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# stop from the caller side
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await self._ctx.send_stop()
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# close the local mem chan
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rx_chan.close()
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# TODO: but make it broadcasting to consumers
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# def clone(self):
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# """Clone this receive channel allowing for multi-task
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# consumption from the same channel.
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# """
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# return ReceiveStream(
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# self._cid,
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# self._rx_chan.clone(),
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# self._portal,
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# )
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class MsgStream(ReceiveMsgStream, trio.abc.Channel):
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"""
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Bidirectional message stream for use within an inter-actor actor
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``Context```.
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"""
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async def send(
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self,
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data: Any
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) -> None:
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await self._ctx.chan.send({'yield': data, 'cid': self._ctx.cid})
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@dataclass(frozen=True)
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class Context:
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"""An IAC (inter-actor communication) context.
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@ -31,6 +207,10 @@ class Context:
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chan: Channel
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cid: str
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# TODO: should we have seperate types for caller vs. callee
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# side contexts? The caller always opens a portal whereas the callee
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# is always responding back through a context-stream
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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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@ -57,46 +237,97 @@ class Context:
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timeout quickly to sidestep 2-generals...
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"""
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assert self._portal, (
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"No portal found, this is likely a callee side context")
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if self._portal: # caller side:
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if not self._portal:
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raise RuntimeError(
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"No portal found, this is likely a callee side context"
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)
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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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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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"May have failed to cancel remote task "
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f"{cid} for {self._portal.channel.uid}")
|
||||
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.warning(
|
||||
"May have failed to cancel remote task "
|
||||
f"{cid} for {self._portal.channel.uid}")
|
||||
else:
|
||||
# ensure callee side
|
||||
assert self._cancel_scope
|
||||
# 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
|
||||
self._cancel_scope.cancel()
|
||||
|
||||
# TODO: do we need a restart api?
|
||||
# async def restart(self) -> None:
|
||||
# # TODO
|
||||
# pass
|
||||
|
||||
# @asynccontextmanager
|
||||
# async def open_stream(
|
||||
# self,
|
||||
# ) -> AsyncContextManager:
|
||||
# # TODO
|
||||
# pass
|
||||
@asynccontextmanager
|
||||
async def open_stream(
|
||||
self,
|
||||
) -> MsgStream:
|
||||
# TODO
|
||||
|
||||
actor = current_actor()
|
||||
|
||||
# here we create a mem chan that corresponds to the
|
||||
# far end caller / callee.
|
||||
|
||||
# NOTE: in one way streaming this only happens on the
|
||||
# caller side inside `Actor.send_cmd()` 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.
|
||||
_, recv_chan = actor.get_memchans(
|
||||
self.chan.uid,
|
||||
self.cid
|
||||
)
|
||||
|
||||
async with MsgStream(ctx=self, rx_chan=recv_chan) as rchan:
|
||||
|
||||
if self._portal:
|
||||
self._portal._streams.add(rchan)
|
||||
|
||||
try:
|
||||
yield rchan
|
||||
|
||||
finally:
|
||||
await self.send_stop()
|
||||
if self._portal:
|
||||
self._portal._streams.add(rchan)
|
||||
|
||||
async def started(self, value: Any) -> None:
|
||||
|
||||
if self._portal:
|
||||
raise RuntimeError(
|
||||
f"Caller side context {self} can not call started!")
|
||||
|
||||
await self.chan.send({'started': value, 'cid': self.cid})
|
||||
|
||||
|
||||
def stream(func):
|
||||
def stream(func: Callable) -> Callable:
|
||||
"""Mark an async function as a streaming routine with ``@stream``.
|
||||
|
||||
"""
|
||||
# annotate
|
||||
func._tractor_stream_function = True
|
||||
|
||||
sig = inspect.signature(func)
|
||||
params = sig.parameters
|
||||
if 'stream' not in params and 'ctx' in params:
|
||||
|
|
@ -114,147 +345,24 @@ def stream(func):
|
|||
):
|
||||
raise TypeError(
|
||||
"The first argument to the stream function "
|
||||
f"{func.__name__} must be `ctx: tractor.Context`"
|
||||
f"{func.__name__} must be `ctx: tractor.Context` "
|
||||
"(Or ``to_trio`` if using ``asyncio`` in guest mode)."
|
||||
)
|
||||
return func
|
||||
|
||||
|
||||
class ReceiveMsgStream(trio.abc.ReceiveChannel):
|
||||
"""A wrapper around a ``trio._channel.MemoryReceiveChannel`` with
|
||||
special behaviour for signalling stream termination across an
|
||||
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
|
||||
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``
|
||||
def context(func: Callable) -> Callable:
|
||||
"""Mark an async function as a streaming routine with ``@context``.
|
||||
|
||||
"""
|
||||
def __init__(
|
||||
self,
|
||||
ctx: Context,
|
||||
rx_chan: trio.abc.ReceiveChannel,
|
||||
portal: 'Portal', # type: ignore # noqa
|
||||
) -> None:
|
||||
self._ctx = ctx
|
||||
self._rx_chan = rx_chan
|
||||
self._portal = portal
|
||||
self._shielded = False
|
||||
# annotate
|
||||
func._tractor_context_function = True
|
||||
|
||||
# delegate directly to underlying mem channel
|
||||
def receive_nowait(self):
|
||||
return self._rx_chan.receive_nowait()
|
||||
|
||||
async def receive(self):
|
||||
try:
|
||||
msg = await self._rx_chan.receive()
|
||||
return msg['yield']
|
||||
|
||||
except KeyError:
|
||||
# internal error should never get here
|
||||
assert msg.get('cid'), ("Received internal error at portal?")
|
||||
|
||||
# TODO: handle 2 cases with 3.10 match syntax
|
||||
# - 'stop'
|
||||
# - 'error'
|
||||
# possibly just handle msg['stop'] here!
|
||||
|
||||
# TODO: test that shows stream raising an expected error!!!
|
||||
if msg.get('error'):
|
||||
# raise the error message
|
||||
raise unpack_error(msg, self._portal.channel)
|
||||
|
||||
except (trio.ClosedResourceError, StopAsyncIteration):
|
||||
# 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['ReceiveMsgStream']: # 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._ctx.chan.send({'yield': data, 'cid': self._ctx.cid})
|
||||
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
|
||||
|
|
|
|||
Loading…
Reference in New Issue