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Use `tractor.Context` throughout the runtime core 

Instead of tracking feeder mem chans per RPC dialog, store `Context`
instances which (now) hold refs to the underlying RPC-task feeder chans
and track them inside a `Actor._contexts` map. This begins a transition
to making the "context" idea the primitive abstraction for representing
messaging dialogs between tasks in different memory domains (i.e.
usually separate processes).

A slew of changes made this possible:
- change `Actor.get_memchans()` -> `.get_context()`.
- Add new `Context._send_chan` and `._recv_chan` vars.
- implicitly create a new context on every `Actor.send_cmd()` call.
- use the context created by `.send_cmd()` in `Portal.open_context()`
  instead of manually creating one.
- call `Actor.get_context()` inside tasks run from `._invoke()`
  such that feeder chans are implicitly created for callee tasks
  thus fixing the bug #265.

NB: We might change some of the internal semantics to do with *when* the
feeder chans are actually created to denote whether or not a far end
task is actually *read to receive* messages. For example, in the cases
where it **never** will be ready to receive messages (one-way streaming,
a context that never opens a stream, etc.) we will likely want some kind
of error or at least warning to the caller that messages can't be sent
(yet).
stricter_context_starting
Tyler Goodlet 2021-12-03 14:27:04 -05:00
parent 3f6099f161
commit c5c3f7e789
3 changed files with 99 additions and 75 deletions
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90
tractor/_actor.py
View File

@ -50,6 +50,7 @@ async def _invoke(
chan: Channel,
func: typing.Callable,
kwargs: dict[str, Any],
is_rpc: bool = True,
task_status: TaskStatus[
Union[trio.CancelScope, BaseException]
@ -68,9 +69,10 @@ async def _invoke(
tb = None
cancel_scope = trio.CancelScope()
# activated cancel scope ref
cs: Optional[trio.CancelScope] = None
ctx = Context(chan, cid)
ctx = actor.get_context(chan, cid)
context: bool = False
if getattr(func, '_tractor_stream_function', False):
@ -379,19 +381,19 @@ class Actor:
self._no_more_peers.set()
self._ongoing_rpc_tasks = trio.Event()
self._ongoing_rpc_tasks.set()
# (chan, cid) -> (cancel_scope, func)
self._rpc_tasks: dict[
Tuple[Channel, str],
Tuple[trio.CancelScope, typing.Callable, trio.Event]
] = {}
# map {uids -> {callids -> waiter queues}}
self._cids2qs: dict[
# map {actor uids -> Context}
self._contexts: dict[
Tuple[Tuple[str, str], str],
Tuple[
trio.abc.SendChannel[Any],
trio.abc.ReceiveChannel[Any]
]
Context
] = {}
self._listeners: List[trio.abc.Listener] = []
self._parent_chan: Optional[Channel] = None
self._forkserver_info: Optional[
@ -567,17 +569,7 @@ class Actor:
await local_nursery.exited.wait()
# channel cleanup sequence
# for (channel, cid) in self._rpc_tasks.copy():
# if channel is chan:
# with trio.CancelScope(shield=True):
# await self._cancel_task(cid, channel)
# # close all consumer side task mem chans
# send_chan, _ = self._cids2qs[(chan.uid, cid)]
# assert send_chan.cid == cid # type: ignore
# await send_chan.aclose()
# ``Channel`` teardown and closure sequence
# Drop ref to channel so it can be gc-ed and disconnected
log.runtime(f"Releasing channel {chan} from {chan.uid}")
@ -621,19 +613,15 @@ class Actor:
) -> None:
"""Push an RPC result to the local consumer's queue.
"""
# actorid = chan.uid
assert chan.uid, f"`chan.uid` can't be {chan.uid}"
send_chan, recv_chan = self._cids2qs[(chan.uid, cid)]
assert send_chan.cid == cid # type: ignore
ctx = self._contexts[(chan.uid, cid)]
send_chan = ctx._send_chan
# TODO: relaying far end context errors to the local
# context through nursery raising?
# if 'error' in msg:
# ctx = getattr(recv_chan, '_ctx', None)
# if ctx:
# ctx._error_from_remote_msg(msg)
# ctx._error_from_remote_msg(msg)
# log.runtime(f"{send_chan} was terminated at remote end")
# # indicate to consumer that far end has stopped
# return await send_chan.aclose()
try:
log.runtime(f"Delivering {msg} from {chan.uid} to caller {cid}")
@ -651,23 +639,35 @@ class Actor:
# so cancel the far end streaming task
log.warning(f"{send_chan} consumer is already closed")
def get_memchans(
def get_context(
self,
actorid: Tuple[str, str],
cid: str
chan: Channel,
cid: str,
max_buffer_size: int = 2**6,
) -> Tuple[trio.abc.SendChannel, trio.abc.ReceiveChannel]:
) -> Context:
'''
Look up or create a new inter-actor-task-IPC-linked task
"context" which encapsulates the local task's scheduling
enviroment including a ``trio`` cancel scope, a pair of IPC
messaging "feeder" channels, and an RPC id unique to the
task-as-function invocation.
log.runtime(f"Getting result queue for {actorid} cid {cid}")
'''
log.runtime(f"Getting result queue for {chan.uid} cid {cid}")
try:
send_chan, recv_chan = self._cids2qs[(actorid, cid)]
ctx = self._contexts[(chan.uid, cid)]
except KeyError:
send_chan, recv_chan = trio.open_memory_channel(2**6)
send_chan.cid = cid # type: ignore
recv_chan.cid = cid # type: ignore
self._cids2qs[(actorid, cid)] = send_chan, recv_chan
send_chan, recv_chan = trio.open_memory_channel(max_buffer_size)
ctx = Context(
chan,
cid,
_send_chan=send_chan,
_recv_chan=recv_chan,
)
self._contexts[(chan.uid, cid)] = ctx
return send_chan, recv_chan
return ctx
async def send_cmd(
self,
@ -675,19 +675,21 @@ class Actor:
ns: str,
func: str,
kwargs: dict
) -> Tuple[str, trio.abc.ReceiveChannel]:
) -> Tuple[str, trio.abc.MemoryReceiveChannel]:
'''
Send a ``'cmd'`` message to a remote actor and return a
caller id and a ``trio.Queue`` that can be used to wait for
responses delivered by the local message processing loop.
Send a ``'cmd'`` message to a remote actor and return a caller
id and a ``trio.MemoryReceiveChannel`` message "feeder" channel
that can be used to wait for responses delivered by the local
runtime's message processing loop.
'''
cid = str(uuid.uuid4())
assert chan.uid
send_chan, recv_chan = self.get_memchans(chan.uid, cid)
ctx = self.get_context(chan, cid)
log.runtime(f"Sending cmd to {chan.uid}: {ns}.{func}({kwargs})")
await chan.send({'cmd': (ns, func, kwargs, self.uid, cid)})
return cid, recv_chan
return ctx.cid, ctx._recv_chan
async def _process_messages(
self,

38
tractor/_portal.py
View File

@ -109,16 +109,20 @@ class Portal:
async def _submit(
self,
ns: str,
func: str,
kwargs,
) -> Tuple[str, trio.MemoryReceiveChannel, str, Dict[str, Any]]:
"""Submit a function to be scheduled and run by actor, return the
associated caller id, response queue, response type str,
first message packet as a tuple.
'''
Submit a function to be scheduled and run by actor, return the
associated caller id, response queue, response type str, first
message packet as a tuple.
This is an async call.
"""
'''
# ship a function call request to the remote actor
cid, recv_chan = await self.actor.send_cmd(
self.channel, ns, func, kwargs)
@ -244,7 +248,8 @@ class Portal:
trio.BrokenResourceError,
):
log.cancel(
f"{self.channel} for {self.channel.uid} was already closed or broken?")
f"{self.channel} for {self.channel.uid} was already "
"closed or broken?")
return False
async def run_from_ns(
@ -392,7 +397,8 @@ class Portal:
**kwargs,
) -> AsyncGenerator[Tuple[Context, Any], None]:
'''Open an inter-actor task context.
'''
Open an inter-actor task context.
This is a synchronous API which allows for deterministic
setup/teardown of a remote task. The yielded ``Context`` further
@ -433,19 +439,20 @@ class Portal:
raise
_err: Optional[BaseException] = None
# this should already have been created from the
# ``._submit()`` call above.
ctx = self.actor.get_context(self.channel, cid)
# pairs with handling in ``Actor._push_result()``
assert ctx._recv_chan is recv_chan
ctx._portal = self
# deliver context instance and .started() msg value in open tuple.
try:
async with trio.open_nursery() as scope_nursery:
ctx = Context(
self.channel,
cid,
_portal=self,
_recv_chan=recv_chan,
_scope_nursery=scope_nursery,
)
ctx._scope_nursery = scope_nursery
# pairs with handling in ``Actor._push_result()``
# recv_chan._ctx = ctx
# do we need this?
# await trio.lowlevel.checkpoint()
yield ctx, first
@ -496,6 +503,7 @@ class Portal:
# we tear down the runtime feeder chan last
# to avoid premature stream clobbers.
if recv_chan is not None:
# should we encapsulate this in the context api?
await recv_chan.aclose()
if _err:

46
tractor/_streaming.py
View File

@ -32,9 +32,10 @@ log = get_logger(__name__)
class ReceiveMsgStream(trio.abc.ReceiveChannel):
'''A IPC message stream for receiving logically sequenced values
over an inter-actor ``Channel``. This is the type returned to
a local task which entered either ``Portal.open_stream_from()`` or
'''
A IPC message stream for receiving logically sequenced values over
an inter-actor ``Channel``. This is the type returned to a local
task which entered either ``Portal.open_stream_from()`` or
``Context.open_stream()``.
Termination rules:
@ -177,7 +178,7 @@ class ReceiveMsgStream(trio.abc.ReceiveChannel):
# In the bidirectional case, `Context.open_stream()` will create
# the `Actor._cids2qs` entry from a call to
# `Actor.get_memchans()` and will send the stop message in
# `Actor.get_context()` and will send the stop message in
# ``__aexit__()`` on teardown so it **does not** need to be
# called here.
if not self._ctx._portal:
@ -302,29 +303,38 @@ class MsgStream(ReceiveMsgStream, trio.abc.Channel):
@dataclass
class Context:
'''An inter-actor task communication context.
'''
An inter-actor, ``trio`` task communication context.
Allows maintaining task or protocol specific state between
2 communicating actor tasks. A unique context is created on the
callee side/end for every request to a remote actor from a portal.
A context can be cancelled and (possibly eventually restarted) from
either side of the underlying IPC channel.
A context can be used to open task oriented message streams and can
be thought of as an IPC aware inter-actor cancel scope.
either side of the underlying IPC channel, open task oriented
message streams and acts as an IPC aware inter-actor-task cancel
scope.
'''
chan: Channel
cid: str
# these are the "feeder" channels for delivering
# message values to the local task from the runtime
# msg processing loop.
_recv_chan: Optional[trio.MemoryReceiveChannel] = None
_send_chan: Optional[trio.MemorySendChannel] = None
# only set on the caller side
_portal: Optional['Portal'] = None # type: ignore # noqa
_recv_chan: Optional[trio.MemoryReceiveChannel] = None
_result: Optional[Any] = False
_remote_func_type: str = None
# status flags
_cancel_called: bool = False
_started_called: bool = False
_started_received: bool = False
_stream_opened: bool = False
# only set on the callee side
_scope_nursery: Optional[trio.Nursery] = None
@ -424,7 +434,8 @@ class Context:
self,
) -> AsyncGenerator[MsgStream, None]:
'''Open a ``MsgStream``, a bi-directional stream connected to the
'''
Open a ``MsgStream``, a bi-directional stream connected to the
cross-actor (far end) task for this ``Context``.
This context manager must be entered on both the caller and
@ -467,29 +478,32 @@ class Context:
# 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
ctx = actor.get_context(
self.chan,
self.cid,
)
assert ctx is self
# XXX: If the underlying channel feeder receive mem chan has
# been closed then likely client code has already exited
# a ``.open_stream()`` block prior or there was some other
# unanticipated error or cancellation from ``trio``.
if recv_chan._closed:
if ctx._recv_chan._closed:
raise trio.ClosedResourceError(
'The underlying channel for this stream was already closed!?')
async with MsgStream(
ctx=self,
rx_chan=recv_chan,
rx_chan=ctx._recv_chan,
) as rchan:
if self._portal:
self._portal._streams.add(rchan)
try:
self._stream_opened = True
# ensure we aren't cancelled before delivering
# the stream
# await trio.lowlevel.checkpoint()