Source code for distributed.comm.core

import asyncio
import inspect
import logging
import random
import sys
import weakref
from abc import ABC, abstractmethod, abstractproperty
from contextlib import suppress

import dask
from dask.utils import parse_timedelta

from ..metrics import time
from ..protocol import pickle
from ..protocol.compression import get_default_compression
from ..utils import TimeoutError
from . import registry
from .addressing import parse_address

logger = logging.getLogger(__name__)


class CommClosedError(IOError):
    pass


class FatalCommClosedError(CommClosedError):
    pass


[docs]class Comm(ABC): """ A message-oriented communication object, representing an established communication channel. There should be only one reader and one writer at a time: to manage current communications, even with a single peer, you must create distinct ``Comm`` objects. Messages are arbitrary Python objects. Concrete implementations of this class can implement different serialization mechanisms depending on the underlying transport's characteristics. """ _instances = weakref.WeakSet() def __init__(self): self._instances.add(self) self.allow_offload = True # for deserialization in utils.from_frames self.name = None self.local_info = {} self.remote_info = {} self.handshake_options = {} # XXX add set_close_callback()?
[docs] @abstractmethod async def read(self, deserializers=None): """ Read and return a message (a Python object). This method returns a coroutine. Parameters ---------- deserializers : dict[str, tuple[Callable, Callable, bool]] | None An optional dict appropriate for distributed.protocol.deserialize. See :ref:`serialization` for more. """
[docs] @abstractmethod async def write(self, msg, serializers=None, on_error=None): """ Write a message (a Python object). This method returns a coroutine. Parameters ---------- msg on_error : str | None The behavior when serialization fails. See ``distributed.protocol.core.dumps`` for valid values. """
[docs] @abstractmethod async def close(self): """ Close the communication cleanly. This will attempt to flush outgoing buffers before actually closing the underlying transport. This method returns a coroutine. """
[docs] @abstractmethod def abort(self): """ Close the communication immediately and abruptly. Useful in destructors or generators' ``finally`` blocks. """
[docs] @abstractmethod def closed(self): """ Return whether the stream is closed. """
@abstractproperty def local_address(self): """ The local address. For logging and debugging purposes only. """ @abstractproperty def peer_address(self): """ The peer's address. For logging and debugging purposes only. """ @property def extra_info(self): """ Return backend-specific information about the communication, as a dict. Typically, this is information which is initialized when the communication is established and doesn't vary afterwards. """ return {} @staticmethod def handshake_info(): return { "compression": get_default_compression(), "python": tuple(sys.version_info)[:3], "pickle-protocol": pickle.HIGHEST_PROTOCOL, } @staticmethod def handshake_configuration(local, remote): try: out = { "pickle-protocol": min( local["pickle-protocol"], remote["pickle-protocol"] ) } except KeyError as e: raise ValueError( "Your Dask versions may not be in sync. " "Please ensure that you have the same version of dask " "and distributed on your client, scheduler, and worker machines" ) from e if local["compression"] == remote["compression"]: out["compression"] = local["compression"] else: out["compression"] = None return out def __repr__(self): return "<{}{} {} local={} remote={}>".format( self.__class__.__name__, " (closed)" if self.closed() else "", self.name or "", self.local_address, self.peer_address, )
[docs]class Listener(ABC):
[docs] @abstractmethod async def start(self): """ Start listening for incoming connections. """
[docs] @abstractmethod def stop(self): """ Stop listening. This does not shutdown already established communications, but prevents accepting new ones. """
@abstractproperty def listen_address(self): """ The listening address as a URI string. """ @abstractproperty def contact_address(self): """ An address this listener can be contacted on. This can be different from `listen_address` if the latter is some wildcard address such as 'tcp://0.0.0.0:123'. """ async def __aenter__(self): await self.start() return self async def __aexit__(self, *exc): future = self.stop() if inspect.isawaitable(future): await future def __await__(self): async def _(): await self.start() return self return _().__await__() async def on_connection(self, comm: Comm, handshake_overrides=None): local_info = {**comm.handshake_info(), **(handshake_overrides or {})} timeout = dask.config.get("distributed.comm.timeouts.connect") timeout = parse_timedelta(timeout, default="seconds") try: # Timeout is to ensure that we'll terminate connections eventually. # Connector side will employ smaller timeouts and we should only # reach this if the comm is dead anyhow. await asyncio.wait_for(comm.write(local_info), timeout=timeout) handshake = await asyncio.wait_for(comm.read(), timeout=timeout) # This would be better, but connections leak if worker is closed quickly # write, handshake = await asyncio.gather(comm.write(local_info), comm.read()) except Exception as e: with suppress(Exception): await comm.close() raise CommClosedError(f"Comm {comm!r} closed.") from e comm.remote_info = handshake comm.remote_info["address"] = comm._peer_addr comm.local_info = local_info comm.local_info["address"] = comm._local_addr comm.handshake_options = comm.handshake_configuration( comm.local_info, comm.remote_info )
class Connector(ABC): @abstractmethod async def connect(self, address, deserialize=True): """ Connect to the given address and return a Comm object. This function returns a coroutine. It may raise EnvironmentError if the other endpoint is unreachable or unavailable. It may raise ValueError if the address is malformed. """
[docs]async def connect( addr, timeout=None, deserialize=True, handshake_overrides=None, **connection_args ): """ Connect to the given address (a URI such as ``tcp://127.0.0.1:1234``) and yield a ``Comm`` object. If the connection attempt fails, it is retried until the *timeout* is expired. """ if timeout is None: timeout = dask.config.get("distributed.comm.timeouts.connect") timeout = parse_timedelta(timeout, default="seconds") scheme, loc = parse_address(addr) backend = registry.get_backend(scheme) connector = backend.get_connector() comm = None start = time() def time_left(): deadline = start + timeout return max(0, deadline - time()) backoff_base = 0.01 attempt = 0 # Prefer multiple small attempts than one long attempt. This should protect # primarily from DNS race conditions # gh3104, gh4176, gh4167 intermediate_cap = timeout / 5 active_exception = None while time_left() > 0: try: comm = await asyncio.wait_for( connector.connect(loc, deserialize=deserialize, **connection_args), timeout=min(intermediate_cap, time_left()), ) break except FatalCommClosedError: raise # CommClosed, EnvironmentError inherit from OSError except (TimeoutError, OSError) as exc: active_exception = exc # The intermediate capping is mostly relevant for the initial # connect. Afterwards we should be more forgiving intermediate_cap = intermediate_cap * 1.5 # FullJitter see https://aws.amazon.com/blogs/architecture/exponential-backoff-and-jitter/ upper_cap = min(time_left(), backoff_base * (2 ** attempt)) backoff = random.uniform(0, upper_cap) attempt += 1 logger.debug( "Could not connect to %s, waiting for %s before retrying", loc, backoff ) await asyncio.sleep(backoff) else: raise OSError( f"Timed out trying to connect to {addr} after {timeout} s" ) from active_exception local_info = { **comm.handshake_info(), **(handshake_overrides or {}), } try: # This would be better, but connections leak if worker is closed quickly # write, handshake = await asyncio.gather(comm.write(local_info), comm.read()) handshake = await asyncio.wait_for(comm.read(), time_left()) await asyncio.wait_for(comm.write(local_info), time_left()) except Exception as exc: with suppress(Exception): await comm.close() raise OSError( f"Timed out during handshake while connecting to {addr} after {timeout} s" ) from exc comm.remote_info = handshake comm.remote_info["address"] = comm._peer_addr comm.local_info = local_info comm.local_info["address"] = comm._local_addr comm.handshake_options = comm.handshake_configuration( comm.local_info, comm.remote_info ) return comm
[docs]def listen(addr, handle_comm, deserialize=True, **kwargs): """ Create a listener object with the given parameters. When its ``start()`` method is called, the listener will listen on the given address (a URI such as ``tcp://0.0.0.0``) and call *handle_comm* with a ``Comm`` object for each incoming connection. *handle_comm* can be a regular function or a coroutine. """ try: scheme, loc = parse_address(addr, strict=True) except ValueError: if kwargs.get("ssl_context"): addr = "tls://" + addr else: addr = "tcp://" + addr scheme, loc = parse_address(addr, strict=True) backend = registry.get_backend(scheme) return backend.get_listener(loc, handle_comm, deserialize, **kwargs)