Repair startup sequence around parent state transfer
In order to have reliable subactor startup we need the following sequence to take place: - connect to the parent actor, handshake and receive runtime state - load exposed modules into memory - start the channel server up fully using the provided bind address - finally, start processing new messages from the parent Add a bunch more comments to clarify all this.start_up_sequence_trickery
Tyler Goodlet
parent
0a5691e0a8
commit
9a40291d4a
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@ -543,6 +543,13 @@ class Actor:
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async def _async_main(
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self,
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accept_addr: Optional[Tuple[str, int]] = None,
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# XXX: currently ``parent_addr`` is only needed for the
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# ``multiprocessing`` backend (which pickles state sent to
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# the child instead of relaying it over the connect-back
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# channel). Once that backend is removed we can likely just
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# change this so a simple ``is_subactor: bool`` which will
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# be False when running as root actor and True when as
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# a subactor.
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parent_addr: Optional[Tuple[str, int]] = None,
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task_status: TaskStatus[None] = trio.TASK_STATUS_IGNORED,
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) -> None:
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@ -557,26 +564,34 @@ class Actor:
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async with trio.open_nursery() as nursery:
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self._root_nursery = nursery
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# TODO: just make `parent_addr` a bool system (see above)?
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if parent_addr is not None:
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try:
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# Connect back to the parent actor and conduct initial
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# handshake (From this point on if we error, ship the
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# exception back to the parent actor)
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# handshake. From this point on if we error, we
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# attempt to ship the exception back to the parent.
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chan = self._parent_chan = Channel(
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destaddr=parent_addr,
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)
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await chan.connect()
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# initial handshake, report who we are, who they are
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# Initial handshake: swap names.
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await self._do_handshake(chan)
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if self._spawn_method == "trio":
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# recieve additional init params
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# Receive runtime state from our parent
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parent_data = await chan.recv()
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log.debug(
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"Recieved state from parent:\n"
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f"{parent_data}"
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)
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accept_addr = (
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parent_data.pop('bind_host'),
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parent_data.pop('bind_port'),
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)
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for attr, value in parent_data.items():
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setattr(self, attr, value)
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accept_addr = self.bind_host, self.bind_port
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except OSError: # failed to connect
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log.warning(
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f"Failed to connect to parent @ {parent_addr},"
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@ -584,24 +599,36 @@ class Actor:
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await self.cancel()
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self._parent_chan = None
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raise
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else:
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# handle new connection back to parent
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assert self._parent_chan
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nursery.start_soon(
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self._process_messages, self._parent_chan)
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# Startup up channel server
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host, port = accept_addr
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await nursery.start(partial(
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self._serve_forever, accept_host=host, accept_port=port)
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)
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# load exposed/allowed RPC modules
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# XXX: do this **after** establishing connection to parent
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# so that import errors are properly propagated upwards
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# XXX: do this **after** establishing a channel to the parent
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# but **before** starting the message loop for that channel
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# such that import errors are properly propagated upwards
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self.load_modules()
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# register with the arbiter if we're told its addr
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# Startup up channel server with,
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# - subactor: the bind address sent to us by our parent
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# over our established channel
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# - root actor: the ``accept_addr`` passed to this method
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assert accept_addr
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host, port = accept_addr
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await nursery.start(
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partial(
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self._serve_forever,
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accept_host=host,
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accept_port=port
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)
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)
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# Begin handling our new connection back to parent.
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# This is done here since we don't want to start
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# processing parent requests until our server is
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# 100% up and running.
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if self._parent_chan:
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nursery.start_soon(
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self._process_messages, self._parent_chan)
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# Register with the arbiter if we're told its addr
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log.debug(f"Registering {self} for role `{self.name}`")
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assert isinstance(self._arb_addr, tuple)
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async with get_arbiter(*self._arb_addr) as arb_portal:
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@ -613,7 +640,7 @@ class Actor:
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task_status.started()
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log.debug("Waiting on root nursery to complete")
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# blocks here as expected until the channel server is
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# Blocks here as expected until the channel server is
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# killed (i.e. this actor is cancelled or signalled by the parent)
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except Exception as err:
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if not registered_with_arbiter:
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@ -3,11 +3,9 @@ Machinery for actor process spawning using multiple backends.
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"""
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import sys
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import inspect
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import subprocess
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import multiprocessing as mp
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import platform
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from typing import Any, Dict, Optional
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from functools import partial
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import trio
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from trio_typing import TaskStatus
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@ -29,7 +27,7 @@ from ._state import current_actor
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from .log import get_logger
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from ._portal import Portal
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from ._actor import Actor, ActorFailure
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from ._entry import _mp_main, _trio_main
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from ._entry import _mp_main
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log = get_logger('tractor')
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@ -160,7 +158,7 @@ async def cancel_on_completion(
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async def spawn_subactor(
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subactor: 'Actor',
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accept_addr: Tuple[str, int],
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parent_addr: Optional[Tuple[str, int]] = None
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parent_addr: Tuple[str, int],
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):
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spawn_cmd = [
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@ -232,6 +230,7 @@ async def new_proc(
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"bind_port": bind_addr[1]
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})
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# resume caller at next checkpoint now that child is up
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task_status.started(portal)
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# wait for ActorNursery.wait() to be called
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