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Add remote actor error handling and parent re-raising 

Command requests are sent out and responses are handled in a "message
loop" where each command is associated with a "caller id" and multiple
cmds and results are multiplexed on the came inter-actor channel. When
a cmd result arrives it is pushed into a local queue and delivered to the
appropriate calling actor's task. Errors from a remote actor are always shipped
in an "error" packet back to their spawning-parent actor such that any error
in a subactor is always raised directly in the parent. Based on the
first response to a cmd (either a 'return' or 'yield' packet) the caller
side portal will retrieve values by wrapping the local response queue in
either of an async function or generator as appropriate.
kivy_mainline_and_py3.8
Tyler Goodlet 2018-06-19 15:30:50 -04:00
parent 75996fed0d
commit ef90d7f106
1 changed files with 248 additions and 143 deletions
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365
piker/tractor.py
View File

@ -1,13 +1,14 @@
"""
tracor: An actor model micro-framework.
"""
import uuid
import inspect
import importlib
from functools import partial
import multiprocessing as mp
from typing import Coroutine
from collections import defaultdict
from functools import partial
from typing import Coroutine
import importlib
import inspect
import multiprocessing as mp
import traceback
import uuid
import trio
from async_generator import asynccontextmanager
@ -19,6 +20,9 @@ from .log import get_console_log, get_logger
ctx = mp.get_context("forkserver")
log = get_logger('tractor')
# set at startup and after forks
_current_actor = None
# for debugging
log = get_console_log('debug')
@ -27,8 +31,8 @@ class ActorFailure(Exception):
"General actor failure"
# set at startup and after forks
_current_actor = None
class RemoteActorError(ActorFailure):
"Remote actor exception bundled locally"
@asynccontextmanager
@ -44,6 +48,58 @@ async def maybe_open_nursery(nursery=None):
yield nursery
async def _invoke(
cid, chan, func, kwargs,
treat_as_gen=False, raise_errs=False):
"""Invoke local func and return results over provided channel.
"""
try:
is_async_func = False
if isinstance(func, partial):
is_async_func = inspect.iscoroutinefunction(func.func)
if not inspect.iscoroutinefunction(func) and not is_async_func:
await chan.send({'return': func(**kwargs), 'cid': cid})
else:
coro = func(**kwargs)
if inspect.isasyncgen(coro):
# await chan.send('gen')
async for item in coro:
# TODO: can we send values back in here?
# How do we do it, spawn another task?
# to_send = await chan.recv()
# if to_send is not None:
# await coro.send(to_send)
await chan.send({'yield': item, 'cid': cid})
else:
if treat_as_gen:
# XXX: the async-func may spawn further tasks which push
# back values like an async-generator would but must
# manualy construct the response dict-packet-responses as above
await coro
else:
await chan.send({'return': await coro, 'cid': cid})
except Exception:
if not raise_errs:
await chan.send({'error': traceback.format_exc(), 'cid': cid})
else:
raise
async def get_result(q):
"""Process a msg from a remote actor.
"""
first_msg = await q.get()
if 'return' in first_msg:
return 'return', first_msg, q
elif 'yield' in first_msg:
return 'yield', first_msg, q
elif 'error' in first_msg:
raise RemoteActorError(first_msg['error'])
else:
raise ValueError(f"{first_msg} is an invalid response packet?")
class Actor:
"""The fundamental concurrency primitive.
@ -56,14 +112,14 @@ class Actor:
def __init__(
self,
name: str,
namespaces: [str],
main: Coroutine,
statespace: dict,
main: Coroutine = None,
rpc_module_paths: [str] = [],
statespace: dict = {},
uid: str = None,
allow_rpc: bool = True,
):
self.uid = (name, uid or str(uuid.uuid1()))
self.namespaces = namespaces
self.rpc_module_paths = rpc_module_paths
self._mods = {}
self.main = main
# TODO: consider making this a dynamically defined
@ -73,6 +129,7 @@ class Actor:
# filled in by `_async_main` after fork
self._peers = {}
self._actors2calls = {} # map {uids -> {callids -> waiter queues}}
self._listeners = []
self._parent_chan = None
self._accept_host = None
@ -91,33 +148,29 @@ class Actor:
# be spawned on a different machine from the original nursery
# and we need to try and load the local module code (if it
# exists)
for path in self.namespaces:
for path in self.rpc_module_paths:
self._mods[path] = importlib.import_module(path)
async def _stream_handler(
self,
stream: trio.SocketStream,
):
"""Receive requests and deliver responses spinning up new
channels where necessary.
Basically RPC with an async twist ;)
"""
Entry point for new inbound connections to the channel server.
"""
chan = Channel(stream=stream)
log.info(f"New {chan} connected to us")
# send/receive initial handshake response
await chan.send(self.uid)
uid = await chan.recv()
chan.uid = uid
log.info(f"Handshake with actor {uid}@{chan.raddr} complete")
# XXX WTF!?!! THIS BLOCKS RANDOMLY?
# assert tuple(raddr) == chan.laddr
# execute main coroutine provided by spawner
if self.main:
await self.main(actor=self)
event = self._peers.pop(uid, None)
chan.event = event
self._peers[uid] = chan
log.info(f"Registered {chan} for {uid}")
log.debug(f"Retrieved event {event}")
@ -126,59 +179,63 @@ class Actor:
# a recently spawned actor which we'd like to control via
# async-rpc calls.
if event and getattr(event, 'set', None):
log.info(f"Waking waiters of {event.statistics()}")
# Alert any task waiting on this connection to come up
# and don't manage channel messages as some external task is
# waiting to use the channel
# (usually an actor nursery)
event.set()
event.clear()
event.clear() # now consumer can wait on this channel to close
# wait for channel consumer (usually a portal) to be
# done with the channel
await event.wait()
# Drop ref to channel so it can be gc-ed
self._peers.pop(self._uid, None)
# Remote controlled connection, we are likely a subactor
# being told what to do so manage the channel with async-rpc
else:
# Begin channel management - respond to remote requests and
# process received reponses.
try:
await self._process_messages(chan)
finally:
# Drop ref to channel so it can be gc-ed
self._peers.pop(chan.uid, None)
chan.event.set()
log.debug(f"Releasing channel {chan}")
def _push_result(self, actorid, cid, msg):
q = self.get_waitq(actorid, cid)
log.debug(f"Delivering {msg} from {actorid} to caller {cid}")
q.put_nowait(msg)
def get_waitq(self, actorid, cid):
if actorid not in self._actors2calls:
log.warn(f"Caller id {cid} is not yet registered?")
cids2qs = self._actors2calls.setdefault(actorid, {})
if cid not in cids2qs:
log.warn(f"Caller id {cid} is not yet registered?")
return cids2qs.setdefault(cid, trio.Queue(1000))
async def invoke_cmd(self, chan, ns, func, kwargs):
"""Invoke a remote command by sending a `cmd` message and waiting
on the msg processing loop for its response(s).
"""
cid = uuid.uuid1()
q = self.get_waitq(chan.uid, cid)
await chan.send((ns, func, kwargs, self.uid, cid))
return await get_result(q)
async def _process_messages(self, chan, treat_as_gen=False):
"""Process inbound messages async-RPC style.
"""Process messages async-RPC style.
Process rpc requests and deliver retrieved responses from channels.
"""
async def invoke(func, kwargs):
if not inspect.iscoroutinefunction(func):
await chan.send('func')
await chan.send(func(**kwargs))
else:
coro = func(**kwargs)
if inspect.isasyncgen(coro):
await chan.send('gen')
async for item in coro:
# TODO: can we send values back in here?
# How do we do it, spawn another task?
# to_send = await chan.recv()
# if to_send is not None:
# await coro.send(to_send)
await chan.send(item)
else:
if treat_as_gen:
await chan.send('gen')
else:
await chan.send('func')
# XXX: the async-func may spawn further tasks which push
# back values like an async-generator would
await chan.send(await coro)
log.debug(f"Entering async-rpc loop for {chan.laddr}->{chan.raddr}")
log.debug(f"Entering async-rpc loop for {chan}")
async with trio.open_nursery() as nursery:
async for ns, funcname, kwargs, actorid in chan.aiter_recv():
async for msg in chan.aiter_recv():
log.debug(f"Received msg {msg}")
# try:
cid = msg.get('cid')
if cid: # deliver response to local caller/waiter
self._push_result(chan.uid, cid, msg)
continue
else:
ns, funcname, kwargs, actorid, cid = msg['cmd']
# except Exception:
# await chan.send({'error': traceback.format_exc()})
# break
log.debug(
f"Processing request from {actorid}\n"
f"{ns}.{funcname}({kwargs})")
@ -200,7 +257,11 @@ class Actor:
# signature will be treated as one.
treat_as_gen = True
nursery.start_soon(invoke, func, kwargs, name=funcname)
nursery.start_soon(
_invoke, cid, chan, func, kwargs, treat_as_gen,
name=funcname
)
log.debug(f"Exiting msg loop for {chan}")
def _fork_main(self, accept_addr, parent_addr=None):
# after fork routine which invokes a fresh ``trio.run``
@ -220,6 +281,8 @@ class Actor:
A "root-most" (or "top-level") nursery for this actor is opened here
and when cancelled effectively cancels the actor.
"""
result = None
try:
async with maybe_open_nursery(nursery) as nursery:
self._root_nursery = nursery
@ -228,42 +291,8 @@ class Actor:
host, port = accept_addr
await self._serve_forever(
nursery, accept_host=host, accept_port=port,
parent_addr=parent_addr
)
# start "main" routine in a task
if self.main:
await self.main(self)
# blocks here as expected if no nursery was provided until
# the channel server is killed
async def _serve_forever(
self,
nursery, # spawns main func and channel server
*,
# (host, port) to bind for channel server
accept_host=None,
accept_port=0,
parent_addr=None,
task_status=trio.TASK_STATUS_IGNORED
):
"""Main coroutine: connect back to the parent, spawn main task, begin
listening for new messages.
"""
log.debug(f"Starting tcp server on {accept_host}:{accept_port}")
listeners = await nursery.start(
partial(
trio.serve_tcp,
self._stream_handler,
handler_nursery=nursery,
port=accept_port, host=accept_host,
)
)
self._listeners.extend(listeners)
log.debug(f"Spawned {listeners}")
if parent_addr is not None:
# Connect back to the parent actor and conduct initial
# handshake (From this point on if we error ship the
@ -289,6 +318,56 @@ class Actor:
self.load_namespaces()
nursery.start_soon(self._process_messages, chan)
if self.main:
log.debug(f"Starting main task `{self.main}`")
if self._parent_chan:
# start "main" routine in a task
nursery.start_soon(
_invoke, 'main', self._parent_chan, self.main, {},
False, True # treat_as_gen, raise_errs params
)
else:
# run directly
result = await self.main()
# blocks here as expected if no nursery was provided until
# the channel server is killed (i.e. this actor is
# cancelled or signalled by the parent actor)
except Exception:
if self._parent_chan:
log.exception("Actor errored:")
await self._parent_chan.send(
{'error': traceback.format_exc(), 'cid': 'main'})
else:
raise
return result
async def _serve_forever(
self,
nursery, # spawns main func and channel server
*,
# (host, port) to bind for channel server
accept_host=None,
accept_port=0,
task_status=trio.TASK_STATUS_IGNORED
):
"""Main coroutine: connect back to the parent, spawn main task, begin
listening for new messages.
"""
log.debug(f"Starting tcp server on {accept_host}:{accept_port}")
listeners = await nursery.start(
partial(
trio.serve_tcp,
self._stream_handler,
handler_nursery=nursery,
port=accept_port, host=accept_host,
)
)
self._listeners.extend(listeners)
log.debug(f"Spawned {listeners}")
# when launched in-process, trigger awaiter's completion
task_status.started()
@ -339,7 +418,7 @@ class Portal:
"""
def __init__(self, channel, event=None):
self.channel = channel
self._uid = None
self._uid = channel.uid
self._event = event
async def __aenter__(self):
@ -369,13 +448,26 @@ class Portal:
# (think `yield from`, `gen.send()`, and functional reactive stuff)
chan = self.channel
# ship a function call request to the remote actor
await chan.send((ns, func, kwargs, _current_actor.uid))
# get expected response type
functype = await chan.recv()
if functype == 'gen':
return chan.aiter_recv()
actor = current_actor()
resptype, first_msg, q = await actor.invoke_cmd(chan, ns, func, kwargs)
if resptype == 'yield':
async def yield_from_q():
yield first
for msg in q:
try:
yield msg['yield']
except KeyError:
raise RemoteActorError(msg['error'])
return yield_from_q()
elif resptype == 'return':
return first_msg['return']
else:
return await chan.recv()
raise ValueError(f"Unknown msg response type: {first_msg}")
class LocalPortal:
@ -398,9 +490,9 @@ class LocalPortal:
class ActorNursery:
"""Spawn scoped subprocess actors.
"""
def __init__(self, parent_actor, supervisor=None):
def __init__(self, actor, supervisor=None):
self.supervisor = supervisor
self._parent_actor = parent_actor
self._actor = actor
# We'll likely want some way to cancel all sub-actors eventually
# self.cancel_scope = cancel_scope
self._children = {}
@ -409,38 +501,43 @@ class ActorNursery:
return self
async def start_actor(
self, name, module_paths,
self, name,
bind_addr=('127.0.0.1', 0),
statespace=None,
rpc_module_paths=None,
main=None,
):
actor = Actor(
name,
module_paths, # modules allowed to invoked funcs from
# modules allowed to invoked funcs from
rpc_module_paths=rpc_module_paths,
statespace=statespace, # global proc state vars
main=main, # main coroutine to be invoked
)
parent_addr = self._parent_actor.accept_addr
parent_addr = self._actor.accept_addr
proc = ctx.Process(
target=actor._fork_main,
args=(bind_addr, parent_addr),
daemon=True,
name=name,
)
self._children[(name, proc.pid)] = (actor, proc)
proc.start()
if not proc.is_alive():
raise ActorFailure("Couldn't start sub-actor?")
# wait for actor to spawn and connect back to us
# channel should have handshake completed by the
# local actor by the time we get a ref to it
if proc.is_alive():
event, chan = await self._parent_actor.wait_for_peer(actor.uid)
else:
raise ActorFailure("Couldn't start sub-actor?")
event, chan = await self._actor.wait_for_peer(actor.uid)
# channel is up, get queue which delivers result from main routine
main_q = self._actor.get_waitq(actor.uid, 'main')
self._children[(name, proc.pid)] = (actor, proc, main_q)
return Portal(chan)
return Portal(chan, event=event)
async def wait(self):
async def cancel(self):
async def wait_for_proc(proc):
# TODO: timeout block here?
if proc.is_alive():
@ -451,6 +548,10 @@ class ActorNursery:
# unblocks when all waiter tasks have completed
async with trio.open_nursery() as nursery:
for actor, proc in self._children.values():
nursery.start_soon(wait_for_proc, proc)
async def cancel(self):
for actor, proc in self._children.values():
if proc is mp.current_process():
actor.cancel()
@ -459,10 +560,15 @@ class ActorNursery:
# sub-actors
proc.terminate()
# os.kill(proc.pid, signal.SIGINT)
nursery.start_soon(wait_for_proc, proc)
await self.wait()
async def __aexit__(self, etype, value, tb):
await self.cancel()
"""Wait on all subactor's main routines to complete.
"""
async with trio.open_nursery() as nursery:
for subactor, proc, q in self._children.values():
nursery.start_soon(get_result, q)
def current_actor() -> Actor:
@ -517,7 +623,7 @@ async def get_arbiter(host='127.0.0.1', port=1616, main=None):
# no arbiter found on this host so start one in-process
arbiter = Arbiter(
'arbiter',
namespaces=[], # the arbiter doesn't allow module rpc
rpc_module_paths=[], # the arbiter doesn't allow module rpc
statespace={}, # global proc state vars
main=main, # main coroutine to be invoked
)
@ -538,7 +644,7 @@ async def get_arbiter(host='127.0.0.1', port=1616, main=None):
# If spawned locally, the arbiter is cancelled when this context
# is complete (i.e the underlying context manager block completes)
nursery.cancel_scope.cancel()
# nursery.cancel_scope.cancel()
@asynccontextmanager
@ -559,27 +665,26 @@ async def find_actor(name):
async def _main(async_fn, args, kwargs, name):
main = partial(async_fn, *args)
# Creates an internal nursery which shouldn't be cancelled even if
# the one opened below is (this is desirable because the arbitter should
# stay up until a re-election process has taken place - which is not
# implemented yet FYI).
async with get_arbiter(
host=kwargs.get('arbiter_host', '127.0.0.1'),
port=kwargs.get('arbiter_port', 1616),
main=partial(async_fn, *args, **kwargs)
host=kwargs.pop('arbiter_host', '127.0.0.1'),
port=kwargs.pop('arbiter_port', 1616),
main=main,
) as portal:
if not current_actor().is_arbiter:
# create a local actor and start it up its main routine
actor = Actor(
name or 'anonymous',
# namespaces=kwargs.get('namespaces'),
# statespace=kwargs.get('statespace'),
# main=async_fn, # main coroutine to be invoked
main=main, # main coroutine to be invoked
**kwargs
)
# this will block and yield control to the `trio` run loop
await serve_local_actor(
actor, accept_addr=kwargs.get('accept_addr', (None, 0)))
actor, accept_addr=kwargs.pop('accept_addr', (None, 0)))
log.info("Completed async main")
else:
# block waiting for the arbiter main task to complete