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Merge pull request #73 from goodboy/stream_functions 

Stream functions
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goodboy 2019-03-29 19:41:50 -04:00 committed by GitHub
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277
README.rst
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@ -280,8 +280,60 @@ to all others with ease over standard network protocols).
.. _Executor: https://docs.python.org/3/library/concurrent.futures.html#concurrent.futures.Executor
Async IPC using *portals*
*************************
Cancellation
************
``tractor`` supports ``trio``'s cancellation_ system verbatim.
Cancelling a nursery block cancels all actors spawned by it.
Eventually ``tractor`` plans to support different `supervision strategies`_ like ``erlang``.
.. _supervision strategies: http://erlang.org/doc/man/supervisor.html#sup_flags
Remote error propagation
************************
Any task invoked in a remote actor should ship any error(s) back to the calling
actor where it is raised and expected to be dealt with. This way remote actors
are never cancelled unless explicitly asked or there's a bug in ``tractor`` itself.
.. code:: python
async def assert_err():
assert 0
async def main():
async with tractor.open_nursery() as n:
real_actors = []
for i in range(3):
real_actors.append(await n.start_actor(
f'actor_{i}',
rpc_module_paths=[__name__],
))
# start one actor that will fail immediately
await n.run_in_actor('extra', assert_err)
# should error here with a ``RemoteActorError`` containing
# an ``AssertionError`` and all the other actors have been cancelled
try:
# also raises
tractor.run(main)
except tractor.RemoteActorError:
print("Look Maa that actor failed hard, hehhh!")
You'll notice the nursery cancellation conducts a *one-cancels-all*
supervisory strategy `exactly like trio`_. The plan is to add more
`erlang strategies`_ in the near future by allowing nurseries to accept
a ``Supervisor`` type.
.. _exactly like trio: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-semantics
.. _erlang strategies: http://learnyousomeerlang.com/supervisors
IPC using *portals*
*******************
``tractor`` introduces the concept of a *portal* which is an API
borrowed_ from ``trio``. A portal may seem similar to the idea of
a RPC future_ except a *portal* allows invoking remote *async* functions and
@ -305,10 +357,26 @@ channels_ system or shipping code over the network.
This *portal* approach turns out to be paricularly exciting with the
introduction of `asynchronous generators`_ in Python 3.6! It means that
actors can compose nicely in a data processing pipeline.
actors can compose nicely in a data streaming pipeline.
As an example here's an actor that streams for 1 second from a remote async
generator function running in a separate actor:
Streaming
*********
By now you've figured out that ``tractor`` lets you spawn process based
*actors* that can invoke cross-process (async) functions and all with
structured concurrency built in. But the **real cool stuff** is the
native support for cross-process *streaming*.
Asynchronous generators
+++++++++++++++++++++++
The default streaming function is simply an async generator definition.
Every value *yielded* from the generator is delivered to the calling
portal exactly like if you had invoked the function in-process meaning
you can ``async for`` to receive each value on the calling side.
As an example here's a parent actor that streams for 1 second from a
spawned subactor:
.. code:: python
@ -346,10 +414,87 @@ generator function running in a separate actor:
tractor.run(main)
By default async generator functions are treated as inter-actor
*streams* when invoked via a portal (how else could you really interface
with them anyway) so no special syntax to denote the streaming *service*
is necessary.
Channels and Contexts
+++++++++++++++++++++
If you aren't fond of having to write an async generator to stream data
between actors (or need something more flexible) you can instead use
a ``Context``. A context wraps an actor-local spawned task and
a ``Channel`` so that tasks executing across multiple processes can
stream data to one another using a low level, request oriented API.
A ``Channel`` wraps an underlying *transport* and *interchange* format
to enable *inter-actor-communication*. In its present state ``tractor``
uses TCP and msgpack_.
As an example if you wanted to create a streaming server without writing
an async generator that *yields* values you instead define a decorated
async function:
.. code:: python
@tractor.stream
async def streamer(ctx: tractor.Context, rate: int = 2) -> None:
"""A simple web response streaming server.
"""
while True:
val = await web_request('http://data.feed.com')
# this is the same as ``yield`` in the async gen case
await ctx.send_yield(val)
await trio.sleep(1 / rate)
You must decorate the function with ``@tractor.stream`` and declare
a ``ctx`` argument as the first in your function signature and then
``tractor`` will treat the async function like an async generator - as
a stream from the calling/client side.
This turns out to be handy particularly if you have multiple tasks
pushing responses concurrently:
.. code:: python
async def streamer(
ctx: tractor.Context,
rate: int = 2
) -> None:
"""A simple web response streaming server.
"""
while True:
val = await web_request(url)
# this is the same as ``yield`` in the async gen case
await ctx.send_yield(val)
await trio.sleep(1 / rate)
@tractor.stream
async def stream_multiple_sources(
ctx: tractor.Context,
sources: List[str]
) -> None:
async with trio.open_nursery() as n:
for url in sources:
n.start_soon(streamer, ctx, url)
The context notion comes from the context_ in nanomsg_.
.. _context: https://nanomsg.github.io/nng/man/tip/nng_ctx.5
.. _msgpack: https://en.wikipedia.org/wiki/MessagePack
A full fledged streaming service
********************************
++++++++++++++++++++++++++++++++
Alright, let's get fancy.
Say you wanted to spawn two actors which each pull data feeds from
@ -471,58 +616,6 @@ as ``multiprocessing`` calls it) which is running ``main()``.
.. _remote function execution: https://codespeak.net/execnet/example/test_info.html#remote-exec-a-function-avoiding-inlined-source-part-i
Cancellation
************
``tractor`` supports ``trio``'s cancellation_ system verbatim.
Cancelling a nursery block cancels all actors spawned by it.
Eventually ``tractor`` plans to support different `supervision strategies`_ like ``erlang``.
.. _supervision strategies: http://erlang.org/doc/man/supervisor.html#sup_flags
Remote error propagation
************************
Any task invoked in a remote actor should ship any error(s) back to the calling
actor where it is raised and expected to be dealt with. This way remote actors
are never cancelled unless explicitly asked or there's a bug in ``tractor`` itself.
.. code:: python
async def assert_err():
assert 0
async def main():
async with tractor.open_nursery() as n:
real_actors = []
for i in range(3):
real_actors.append(await n.start_actor(
f'actor_{i}',
rpc_module_paths=[__name__],
))
# start one actor that will fail immediately
await n.run_in_actor('extra', assert_err)
# should error here with a ``RemoteActorError`` containing
# an ``AssertionError`` and all the other actors have been cancelled
try:
# also raises
tractor.run(main)
except tractor.RemoteActorError:
print("Look Maa that actor failed hard, hehhh!")
You'll notice the nursery cancellation conducts a *one-cancels-all*
supervisory strategy `exactly like trio`_. The plan is to add more
`erlang strategies`_ in the near future by allowing nurseries to accept
a ``Supervisor`` type.
.. _exactly like trio: https://trio.readthedocs.io/en/latest/reference-core.html#cancellation-semantics
.. _erlang strategies: http://learnyousomeerlang.com/supervisors
Actor local variables
*********************
Although ``tractor`` uses a *shared-nothing* architecture between processes
@ -556,8 +649,8 @@ a convenience for passing simple data to newly spawned actors); building
out a state sharing system per-actor is totally up to you.
How do actors find each other (a poor man's *service discovery*)?
*****************************************************************
Service Discovery
*****************
Though it will be built out much more in the near future, ``tractor``
currently keeps track of actors by ``(name: str, id: str)`` using a
special actor called the *arbiter*. Currently the *arbiter* must exist
@ -590,70 +683,6 @@ The ``name`` value you should pass to ``find_actor()`` is the one you passed as
*first* argument to either ``tractor.run()`` or ``ActorNursery.start_actor()``.
Streaming using channels and contexts
*************************************
``Channel`` is the API which wraps an underlying *transport* and *interchange*
format to enable *inter-actor-communication*. In its present state ``tractor``
uses TCP and msgpack_.
If you aren't fond of having to write an async generator to stream data
between actors (or need something more flexible) you can instead use a
``Context``. A context wraps an actor-local spawned task and a ``Channel``
so that tasks executing across multiple processes can stream data
to one another using a low level, request oriented API.
As an example if you wanted to create a streaming server without writing
an async generator that *yields* values you instead define an async
function:
.. code:: python
async def streamer(ctx: tractor.Context, rate: int = 2) -> None:
"""A simple web response streaming server.
"""
while True:
val = await web_request('http://data.feed.com')
# this is the same as ``yield`` in the async gen case
await ctx.send_yield(val)
await trio.sleep(1 / rate)
All that's required is declaring a ``ctx`` argument name somewhere in
your function signature and ``tractor`` will treat the async function
like an async generator - as a streaming function from the client side.
This turns out to be handy particularly if you have
multiple tasks streaming responses concurrently:
.. code:: python
async def streamer(ctx: tractor.Context, rate: int = 2) -> None:
"""A simple web response streaming server.
"""
while True:
val = await web_request(url)
# this is the same as ``yield`` in the async gen case
await ctx.send_yield(val)
await trio.sleep(1 / rate)
async def stream_multiple_sources(
ctx: tractor.Context, sources: List[str]
) -> None:
async with trio.open_nursery() as n:
for url in sources:
n.start_soon(streamer, ctx, url)
The context notion comes from the context_ in nanomsg_.
.. _context: https://nanomsg.github.io/nng/man/tip/nng_ctx.5
.. _msgpack: https://en.wikipedia.org/wiki/MessagePack
Running actors standalone
*************************
You don't have to spawn any actors using ``open_nursery()`` if you just

55
tests/test_streaming.py
View File

@ -2,13 +2,29 @@
Streaming via async gen api
"""
import time
from functools import partial
import trio
import tractor
import pytest
async def stream_seq(sequence):
def test_must_define_ctx():
with pytest.raises(TypeError) as err:
@tractor.stream
async def no_ctx():
pass
assert "no_ctx must be `ctx: tractor.Context" in str(err.value)
@tractor.stream
async def no_ctx(ctx):
pass
async def async_gen_stream(sequence):
for i in sequence:
yield i
await trio.sleep(0.1)
@ -20,10 +36,23 @@ async def stream_seq(sequence):
assert cs.cancelled_caught
async def stream_from_single_subactor():
@tractor.stream
async def context_stream(ctx, sequence):
for i in sequence:
await ctx.send_yield(i)
await trio.sleep(0.1)
# block indefinitely waiting to be cancelled by ``aclose()`` call
with trio.CancelScope() as cs:
await trio.sleep(float('inf'))
assert 0
assert cs.cancelled_caught
async def stream_from_single_subactor(stream_func_name):
"""Verify we can spawn a daemon actor and retrieve streamed data.
"""
async with tractor.find_actor('brokerd') as portals:
async with tractor.find_actor('streamerd') as portals:
if not portals:
# only one per host address, spawns an actor if None
async with tractor.open_nursery() as nursery:
@ -36,37 +65,43 @@ async def stream_from_single_subactor():
seq = range(10)
agen = await portal.run(
stream = await portal.run(
__name__,
'stream_seq', # the func above
stream_func_name, # one of the funcs above
sequence=list(seq), # has to be msgpack serializable
)
# it'd sure be nice to have an asyncitertools here...
iseq = iter(seq)
ival = next(iseq)
async for val in agen:
async for val in stream:
assert val == ival
try:
ival = next(iseq)
except StopIteration:
# should cancel far end task which will be
# caught and no error is raised
await agen.aclose()
await stream.aclose()
await trio.sleep(0.3)
try:
await agen.__anext__()
await stream.__anext__()
except StopAsyncIteration:
# stop all spawned subactors
await portal.cancel_actor()
# await nursery.cancel()
def test_stream_from_single_subactor(arb_addr, start_method):
@pytest.mark.parametrize(
'stream_func', ['async_gen_stream', 'context_stream']
)
def test_stream_from_single_subactor(arb_addr, start_method, stream_func):
"""Verify streaming from a spawned async generator.
"""
tractor.run(
stream_from_single_subactor,
partial(
stream_from_single_subactor,
stream_func_name=stream_func,
),
arbiter_addr=arb_addr,
start_method=start_method,
)

9
tractor/__init__.py
View File

@ -11,10 +11,10 @@ import trio # type: ignore
from trio import MultiError
from . import log
from ._ipc import _connect_chan, Channel, Context
from ._actor import (
Actor, _start_actor, Arbiter, get_arbiter, find_actor, wait_for_actor
)
from ._ipc import _connect_chan, Channel
from ._streaming import Context, stream
from ._discovery import get_arbiter, find_actor, wait_for_actor
from ._actor import Actor, _start_actor, Arbiter
from ._trionics import open_nursery
from ._state import current_actor
from ._exceptions import RemoteActorError, ModuleNotExposed
@ -30,6 +30,7 @@ __all__ = [
'wait_for_actor',
'Channel',
'Context',
'stream',
'MultiError',
'RemoteActorError',
'ModuleNotExposed',

163
tractor/_actor.py
View File

@ -8,26 +8,22 @@ import importlib
import inspect
import uuid
import typing
from typing import Dict, List, Tuple, Any, Optional, Union
from typing import Dict, List, Tuple, Any, Optional
import trio # type: ignore
from async_generator import asynccontextmanager, aclosing
from async_generator import aclosing
from ._ipc import Channel, _connect_chan, Context
from ._ipc import Channel
from ._streaming import Context, _context
from .log import get_console_log, get_logger
from ._exceptions import (
pack_error,
unpack_error,
ModuleNotExposed
)
from ._portal import (
Portal,
open_portal,
_do_handshake,
LocalPortal,
)
from ._discovery import get_arbiter
from ._portal import Portal
from . import _state
from ._state import current_actor
log = get_logger('tractor')
@ -45,19 +41,16 @@ async def _invoke(
kwargs: Dict[str, Any],
task_status=trio.TASK_STATUS_IGNORED
):
"""Invoke local func and return results over provided channel.
"""Invoke local func and deliver result(s) over provided channel.
"""
sig = inspect.signature(func)
treat_as_gen = False
cs = None
ctx = Context(chan, cid)
if 'ctx' in sig.parameters:
cancel_scope = trio.CancelScope()
ctx = Context(chan, cid, cancel_scope)
_context.set(ctx)
if getattr(func, '_tractor_stream_function', False):
# handle decorated ``@tractor.stream`` async functions
kwargs['ctx'] = ctx
# TODO: eventually we want to be more stringent
# about what is considered a far-end async-generator.
# Right now both actual async gens and any async
# function which declares a `ctx` kwarg in its
# signature will be treated as one.
treat_as_gen = True
try:
is_async_partial = False
@ -73,7 +66,7 @@ async def _invoke(
not is_async_gen_partial
):
await chan.send({'functype': 'function', 'cid': cid})
with trio.CancelScope() as cs:
with cancel_scope as cs:
task_status.started(cs)
await chan.send({'return': func(**kwargs), 'cid': cid})
else:
@ -88,7 +81,7 @@ async def _invoke(
# have to properly handle the closing (aclosing)
# of the async gen in order to be sure the cancel
# is propagated!
with trio.CancelScope() as cs:
with cancel_scope as cs:
task_status.started(cs)
async with aclosing(coro) as agen:
async for item in agen:
@ -113,7 +106,7 @@ async def _invoke(
# back values like an async-generator would but must
# manualy construct the response dict-packet-responses as
# above
with trio.CancelScope() as cs:
with cancel_scope as cs:
task_status.started(cs)
await coro
if not cs.cancelled_caught:
@ -122,7 +115,7 @@ async def _invoke(
await chan.send({'stop': True, 'cid': cid})
else:
await chan.send({'functype': 'asyncfunction', 'cid': cid})
with trio.CancelScope() as cs:
with cancel_scope as cs:
task_status.started(cs)
await chan.send({'return': await coro, 'cid': cid})
except Exception as err:
@ -174,7 +167,7 @@ class Actor:
arbiter_addr: Optional[Tuple[str, int]] = None,
) -> None:
self.name = name
self.uid = (name, uid or str(uuid.uuid1()))
self.uid = (name, uid or str(uuid.uuid4()))
self.rpc_module_paths = rpc_module_paths
self._mods: dict = {}
# TODO: consider making this a dynamically defined
@ -247,7 +240,7 @@ class Actor:
# send/receive initial handshake response
try:
uid = await _do_handshake(self, chan)
uid = await self._do_handshake(chan)
except StopAsyncIteration:
log.warning(f"Channel {chan} failed to handshake")
return
@ -351,7 +344,7 @@ class Actor:
caller id and a ``trio.Queue`` that can be used to wait for
responses delivered by the local message processing loop.
"""
cid = str(uuid.uuid1())
cid = str(uuid.uuid4())
assert chan.uid
recv_chan = self.get_memchans(chan.uid, cid)
log.debug(f"Sending cmd to {chan.uid}: {ns}.{func}({kwargs})")
@ -373,11 +366,12 @@ class Actor:
msg = None
log.debug(f"Entering msg loop for {chan} from {chan.uid}")
try:
# internal scope allows for keeping this message
# loop running despite the current task having been
# cancelled (eg. `open_portal()` may call this method from
# a locally spawned task)
with trio.CancelScope(shield=shield) as cs:
# this internal scope allows for keeping this message
# loop running despite the current task having been
# cancelled (eg. `open_portal()` may call this method from
# a locally spawned task) and recieve this scope using
# ``scope = Nursery.start()``
task_status.started(cs)
async for msg in chan:
if msg is None: # loop terminate sentinel
@ -385,7 +379,7 @@ class Actor:
f"Cancelling all tasks for {chan} from {chan.uid}")
for (channel, cid) in self._rpc_tasks:
if channel is chan:
self.cancel_task(cid, Context(channel, cid))
self._cancel_task(cid, channel)
log.debug(
f"Msg loop signalled to terminate for"
f" {chan} from {chan.uid}")
@ -419,6 +413,16 @@ class Actor:
f"{ns}.{funcname}({kwargs})")
if ns == 'self':
func = getattr(self, funcname)
if funcname == '_cancel_task':
# XXX: a special case is made here for
# remote calls since we don't want the
# remote actor have to know which channel
# the task is associated with and we can't
# pass non-primitive types between actors.
# This means you can use:
# Portal.run('self', '_cancel_task, cid=did)
# without passing the `chan` arg.
kwargs['chan'] = chan
else:
# complain to client about restricted modules
try:
@ -537,7 +541,7 @@ class Actor:
)
await chan.connect()
# initial handshake, report who we are, who they are
await _do_handshake(self, chan)
await self._do_handshake(chan)
except OSError: # failed to connect
log.warning(
f"Failed to connect to parent @ {parent_addr},"
@ -661,21 +665,20 @@ class Actor:
self.cancel_server()
self._root_nursery.cancel_scope.cancel()
async def cancel_task(self, cid, ctx):
"""Cancel a local task.
async def _cancel_task(self, cid, chan):
"""Cancel a local task by call-id / channel.
Note this method will be treated as a streaming funciton
Note this method will be treated as a streaming function
by remote actor-callers due to the declaration of ``ctx``
in the signature (for now).
"""
# right now this is only implicitly called by
# streaming IPC but it should be called
# to cancel any remotely spawned task
chan = ctx.chan
try:
# this ctx based lookup ensures the requested task to
# be cancelled was indeed spawned by a request from this channel
scope, func, is_complete = self._rpc_tasks[(ctx.chan, cid)]
scope, func, is_complete = self._rpc_tasks[(chan, cid)]
except KeyError:
log.warning(f"{cid} has already completed/terminated?")
return
@ -686,7 +689,7 @@ class Actor:
# don't allow cancelling this function mid-execution
# (is this necessary?)
if func is self.cancel_task:
if func is self._cancel_task:
return
scope.cancel()
@ -704,7 +707,7 @@ class Actor:
log.info(f"Cancelling all {len(tasks)} rpc tasks:\n{tasks} ")
for (chan, cid) in tasks.copy():
# TODO: this should really done in a nursery batch
await self.cancel_task(cid, Context(chan, cid))
await self._cancel_task(cid, chan)
# if tasks:
log.info(
f"Waiting for remaining rpc tasks to complete {tasks}")
@ -735,6 +738,25 @@ class Actor:
"""Return all channels to the actor with provided uid."""
return self._peers[uid]
async def _do_handshake(
self,
chan: Channel
) -> Tuple[str, str]:
"""Exchange (name, UUIDs) identifiers as the first communication step.
These are essentially the "mailbox addresses" found in actor model
parlance.
"""
await chan.send(self.uid)
uid: Tuple[str, str] = await chan.recv()
if not isinstance(uid, tuple):
raise ValueError(f"{uid} is not a valid uid?!")
chan.uid = uid
log.info(f"Handshake with actor {uid}@{chan.raddr} complete")
return uid
class Arbiter(Actor):
"""A special actor who knows all the other actors and always has
@ -840,66 +862,3 @@ async def _start_actor(
log.info("Completed async main")
return result
@asynccontextmanager
async def get_arbiter(
host: str, port: int
) -> typing.AsyncGenerator[Union[Portal, LocalPortal], None]:
"""Return a portal instance connected to a local or remote
arbiter.
"""
actor = current_actor()
if not actor:
raise RuntimeError("No actor instance has been defined yet?")
if actor.is_arbiter:
# we're already the arbiter
# (likely a re-entrant call from the arbiter actor)
yield LocalPortal(actor)
else:
async with _connect_chan(host, port) as chan:
async with open_portal(chan) as arb_portal:
yield arb_portal
@asynccontextmanager
async def find_actor(
name: str, arbiter_sockaddr: Tuple[str, int] = None
) -> typing.AsyncGenerator[Optional[Portal], None]:
"""Ask the arbiter to find actor(s) by name.
Returns a connected portal to the last registered matching actor
known to the arbiter.
"""
actor = current_actor()
async with get_arbiter(*arbiter_sockaddr or actor._arb_addr) as arb_portal:
sockaddr = await arb_portal.run('self', 'find_actor', name=name)
# TODO: return portals to all available actors - for now just
# the last one that registered
if name == 'arbiter' and actor.is_arbiter:
raise RuntimeError("The current actor is the arbiter")
elif sockaddr:
async with _connect_chan(*sockaddr) as chan:
async with open_portal(chan) as portal:
yield portal
else:
yield None
@asynccontextmanager
async def wait_for_actor(
name: str,
arbiter_sockaddr: Tuple[str, int] = None
) -> typing.AsyncGenerator[Portal, None]:
"""Wait on an actor to register with the arbiter.
A portal to the first registered actor is returned.
"""
actor = current_actor()
async with get_arbiter(*arbiter_sockaddr or actor._arb_addr) as arb_portal:
sockaddrs = await arb_portal.run('self', 'wait_for_actor', name=name)
sockaddr = sockaddrs[-1]
async with _connect_chan(*sockaddr) as chan:
async with open_portal(chan) as portal:
yield portal

77
tractor/_discovery.py 100644
View File

@ -0,0 +1,77 @@
"""
Actor discovery API.
"""
import typing
from typing import Tuple, Optional, Union
from async_generator import asynccontextmanager
from ._ipc import _connect_chan
from ._portal import (
Portal,
open_portal,
LocalPortal,
)
from ._state import current_actor
@asynccontextmanager
async def get_arbiter(
host: str, port: int
) -> typing.AsyncGenerator[Union[Portal, LocalPortal], None]:
"""Return a portal instance connected to a local or remote
arbiter.
"""
actor = current_actor()
if not actor:
raise RuntimeError("No actor instance has been defined yet?")
if actor.is_arbiter:
# we're already the arbiter
# (likely a re-entrant call from the arbiter actor)
yield LocalPortal(actor)
else:
async with _connect_chan(host, port) as chan:
async with open_portal(chan) as arb_portal:
yield arb_portal
@asynccontextmanager
async def find_actor(
name: str, arbiter_sockaddr: Tuple[str, int] = None
) -> typing.AsyncGenerator[Optional[Portal], None]:
"""Ask the arbiter to find actor(s) by name.
Returns a connected portal to the last registered matching actor
known to the arbiter.
"""
actor = current_actor()
async with get_arbiter(*arbiter_sockaddr or actor._arb_addr) as arb_portal:
sockaddr = await arb_portal.run('self', 'find_actor', name=name)
# TODO: return portals to all available actors - for now just
# the last one that registered
if name == 'arbiter' and actor.is_arbiter:
raise RuntimeError("The current actor is the arbiter")
elif sockaddr:
async with _connect_chan(*sockaddr) as chan:
async with open_portal(chan) as portal:
yield portal
else:
yield None
@asynccontextmanager
async def wait_for_actor(
name: str,
arbiter_sockaddr: Tuple[str, int] = None
) -> typing.AsyncGenerator[Portal, None]:
"""Wait on an actor to register with the arbiter.
A portal to the first registered actor is returned.
"""
actor = current_actor()
async with get_arbiter(*arbiter_sockaddr or actor._arb_addr) as arb_portal:
sockaddrs = await arb_portal.run('self', 'wait_for_actor', name=name)
sockaddr = sockaddrs[-1]
async with _connect_chan(*sockaddr) as chan:
async with open_portal(chan) as portal:
yield portal

23
tractor/_ipc.py
View File

@ -1,7 +1,6 @@
"""
Inter-process comms abstractions
"""
from dataclasses import dataclass
import typing
from typing import Any, Tuple, Optional
@ -205,28 +204,6 @@ class Channel:
return self.msgstream.connected() if self.msgstream else False
@dataclass(frozen=True)
class Context:
"""An IAC (inter-actor communication) context.
Allows maintaining task or protocol specific state between communicating
actors. A unique context is created on the receiving end for every request
to a remote actor.
"""
chan: Channel
cid: str
# TODO: we should probably attach the actor-task
# cancel scope here now that trio is exposing it
# as a public object
async def send_yield(self, data: Any) -> None:
await self.chan.send({'yield': data, 'cid': self.cid})
async def send_stop(self) -> None:
await self.chan.send({'stop': True, 'cid': self.cid})
@asynccontextmanager
async def _connect_chan(
host: str, port: int

37
tractor/_portal.py
View File

@ -33,21 +33,6 @@ async def maybe_open_nursery(nursery: trio._core._run.Nursery = None):
yield nursery
async def _do_handshake(
actor: 'Actor', # type: ignore
chan: Channel
) -> Any:
await chan.send(actor.uid)
uid: Tuple[str, str] = await chan.recv()
if not isinstance(uid, tuple):
raise ValueError(f"{uid} is not a valid uid?!")
chan.uid = uid
log.info(f"Handshake with actor {uid}@{chan.raddr} complete")
return uid
class StreamReceiveChannel(trio.abc.ReceiveChannel):
"""A wrapper around a ``trio._channel.MemoryReceiveChannel`` with
special behaviour for signalling stream termination across an
@ -95,8 +80,8 @@ class StreamReceiveChannel(trio.abc.ReceiveChannel):
raise unpack_error(msg, self._portal.channel)
async def aclose(self):
"""Cancel associate remote actor task on close
as well as the local memory channel.
"""Cancel associated remote actor task and local memory channel
on close.
"""
if self._rx_chan._closed:
log.warning(f"{self} is already closed")
@ -107,15 +92,10 @@ class StreamReceiveChannel(trio.abc.ReceiveChannel):
log.warning(
f"Cancelling stream {cid} to "
f"{self._portal.channel.uid}")
# TODO: yeah.. it'd be nice if this was just an
# async func on the far end. Gotta figure out a
# better way then implicitly feeding the ctx
# to declaring functions; likely a decorator
# system.
rchan = await self._portal.run(
'self', 'cancel_task', cid=cid)
async for _ in rchan:
pass
# 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('self', '_cancel_task', cid=cid)
if cs.cancelled_caught:
# XXX: there's no way to know if the remote task was indeed
@ -153,6 +133,7 @@ class Portal:
Tuple[str, Any, str, Dict[str, Any]]
] = None
self._streams: Set[StreamReceiveChannel] = set()
self.actor = current_actor()
async def _submit(
self,
@ -167,7 +148,7 @@ class Portal:
This is an async call.
"""
# ship a function call request to the remote actor
cid, recv_chan = await current_actor().send_cmd(
cid, recv_chan = await self.actor.send_cmd(
self.channel, ns, func, kwargs)
# wait on first response msg and handle (this should be
@ -345,7 +326,7 @@ async def open_portal(
was_connected = True
if channel.uid is None:
await _do_handshake(actor, channel)
await actor._do_handshake(channel)
msg_loop_cs = await nursery.start(
partial(

49
tractor/_streaming.py 100644
View File

@ -0,0 +1,49 @@
import inspect
from contextvars import ContextVar
from dataclasses import dataclass
from typing import Any
import trio
from ._ipc import Channel
_context: ContextVar['Context'] = ContextVar('context')
@dataclass(frozen=True)
class Context:
"""An IAC (inter-actor communication) context.
Allows maintaining task or protocol specific state between communicating
actors. A unique context is created on the receiving end for every request
to a remote actor.
"""
chan: Channel
cid: str
cancel_scope: trio.CancelScope
async def send_yield(self, data: Any) -> None:
await self.chan.send({'yield': data, 'cid': self.cid})
async def send_stop(self) -> None:
await self.chan.send({'stop': True, 'cid': self.cid})
def current_context():
"""Get the current task's context instance.
"""
return _context.get()
def stream(func):
"""Mark an async function as a streaming routine.
"""
func._tractor_stream_function = True
sig = inspect.signature(func)
if 'ctx' not in sig.parameters:
raise TypeError(
"The first argument to the stream function "
f"{func.__name__} must be `ctx: tractor.Context`"
)
return func

65
tractor/msg.py
View File

@ -12,7 +12,7 @@ import wrapt
from .log import get_logger
from . import current_actor
from ._ipc import Context
from ._streaming import Context
__all__ = ['pub']
@ -97,29 +97,32 @@ def pub(
):
"""Publisher async generator decorator.
A publisher can be called multiple times from different actors
but will only spawn a finite set of internal tasks to stream values
to each caller. The ``tasks` argument to the decorator (``Set[str]``)
specifies the names of the mutex set of publisher tasks.
When the publisher function is called, an argument ``task_name`` must be
passed to specify which task (of the set named in ``tasks``) should be
used. This allows for using the same publisher with different input
(arguments) without allowing more concurrent tasks then necessary.
A publisher can be called multiple times from different actors but
will only spawn a finite set of internal tasks to stream values to
each caller. The ``tasks: Set[str]`` argument to the decorator
specifies the names of the mutex set of publisher tasks. When the
publisher function is called, an argument ``task_name`` must be
passed to specify which task (of the set named in ``tasks``) should
be used. This allows for using the same publisher with different
input (arguments) without allowing more concurrent tasks then
necessary.
Values yielded from the decorated async generator
must be ``Dict[str, Dict[str, Any]]`` where the fist level key is the
topic string an determines which subscription the packet will be delivered
to and the value is a packet ``Dict[str, Any]`` by default of the form:
Values yielded from the decorated async generator must be
``Dict[str, Dict[str, Any]]`` where the fist level key is the topic
string and determines which subscription the packet will be
delivered to and the value is a packet ``Dict[str, Any]`` by default
of the form:
.. ::python
{topic: value}
{topic: str: value: Any}
The caller can instead opt to pass a ``packetizer`` callback who's return
value will be delivered as the published response.
The caller can instead opt to pass a ``packetizer`` callback who's
return value will be delivered as the published response.
The decorated function must *accept* an argument :func:`get_topics` which
dynamically returns the tuple of current subscriber topics:
The decorated async generator function must accept an argument
:func:`get_topics` which dynamically returns the tuple of current
subscriber topics:
.. code:: python
@ -162,15 +165,15 @@ def pub(
print(f"Subscriber received {value}")
Here, you don't need to provide the ``ctx`` argument since the remote actor
provides it automatically to the spawned task. If you were to call
``pub_service()`` directly from a wrapping function you would need to
provide this explicitly.
Here, you don't need to provide the ``ctx`` argument since the
remote actor provides it automatically to the spawned task. If you
were to call ``pub_service()`` directly from a wrapping function you
would need to provide this explicitly.
Remember you only need this if you need *a finite set of tasks* running in
a single actor to stream data to an arbitrary number of subscribers. If you
are ok to have a new task running for every call to ``pub_service()`` then
probably don't need this.
Remember you only need this if you need *a finite set of tasks*
running in a single actor to stream data to an arbitrary number of
subscribers. If you are ok to have a new task running for every call
to ``pub_service()`` then probably don't need this.
"""
# handle the decorator not called with () case
if wrapped is None:
@ -181,10 +184,7 @@ def pub(
for name in tasks:
task2lock[name] = trio.StrictFIFOLock()
async def takes_ctx(get_topics, ctx=None):
pass
@wrapt.decorator(adapter=takes_ctx)
@wrapt.decorator
async def wrapper(agen, instance, args, kwargs):
# this is used to extract arguments properly as per
# the `wrapt` docs
@ -249,7 +249,6 @@ def pub(
# invoke it
await _execute(*args, **kwargs)
funcname = wrapped.__name__
if not inspect.isasyncgenfunction(wrapped):
raise TypeError(
@ -261,4 +260,8 @@ def pub(
"`get_topics` argument"
)
# XXX: manually monkey the wrapped function since
# ``wrapt.decorator`` doesn't seem to want to play nice with its
# whole "adapter" thing...
wrapped._tractor_stream_function = True # type: ignore
return wrapper(wrapped)