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Source code for torch.distributed.elastic.rendezvous.dynamic_rendezvous

# Copyright (c) Facebook, Inc. and its affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD-style license found in the
# LICENSE file in the root directory of this source tree.

import inspect
import logging
import os
import pickle
import socket
import threading
import time
import weakref
from abc import ABC, abstractmethod
from dataclasses import dataclass
from datetime import datetime, timedelta
from enum import Enum
from typing import Any, Callable, cast, Dict, List, Optional, Set, Tuple

from torch.distributed import PrefixStore, Store
from torch.distributed.elastic.events import construct_and_record_rdzv_event, NodeState

from .api import (
    RendezvousClosedError,
    RendezvousError,
    RendezvousGracefulExitError,
    RendezvousHandler,
    RendezvousParameters,
    RendezvousStateError,
    RendezvousTimeoutError,
)
from .utils import _delay, _PeriodicTimer

__all__ = ['RendezvousBackend', 'RendezvousTimeout', 'RendezvousSettings', 'DynamicRendezvousHandler', 'create_handler']

logger = logging.getLogger(__name__)


def get_method_name(depth=2):
    if len(inspect.stack()) > depth:
        return inspect.stack()[depth].function
    return "no_method_name"


Token = Any
"""Represent an opaque fencing token used by the rendezvous backend."""

[docs]class RendezvousBackend(ABC): """Represent a backend that holds the rendezvous state.""" @property @abstractmethod def name(self) -> str: """Get the name of the backend."""
[docs] @abstractmethod def get_state(self) -> Optional[Tuple[bytes, Token]]: """Get the rendezvous state. Returns: A tuple of the encoded rendezvous state and its fencing token or ``None`` if no state is found in the backend. Raises: RendezvousConnectionError: The connection to the backend has failed. RendezvousStateError: The rendezvous state is corrupt. """
[docs] @abstractmethod def set_state( self, state: bytes, token: Optional[Token] = None ) -> Optional[Tuple[bytes, Token, bool]]: """Set the rendezvous state. The new rendezvous state is set conditionally: - If the specified ``token`` matches the fencing token stored in the backend, the state will be updated. The new state will be returned to the caller along with its fencing token. - If the specified ``token`` does not match the fencing token stored in the backend, the state won't be updated; instead the existing state along with its fencing token will be returned to the caller. - If the specified ``token`` is ``None``, the new state will be set only if there is no existing state in the backend. Either the new state or the existing state along with its fencing token will be returned to the caller. Args: state: The encoded rendezvous state. token: An optional fencing token that was retrieved by a previous call to :py:meth:`get_state` or ``set_state()``. Returns: A tuple of the serialized rendezvous state, its fencing token, and a boolean value indicating whether our set attempt succeeded. Raises: RendezvousConnectionError: The connection to the backend has failed. RendezvousStateError: The rendezvous state is corrupt. """
[docs]class RendezvousTimeout: """Hold the timeout configuration of a rendezvous. Args: join: The time within which the rendezvous is expected to complete. last_call: An additional wait amount before completing the rendezvous once the rendezvous has the minimum number of required participants. close: The time within which the rendezvous is expected to close after a call to :py:meth:`RendezvousHandler.set_closed` or :py:meth:`RendezvousHandler.shutdown`. keep_alive: The time within which a keep-alive heartbeat is expected to complete. """ _ZERO = timedelta(0) _DEFAULT_TIMEOUTS = { "join": timedelta(seconds=600), "last_call": timedelta(seconds=30), "close": timedelta(seconds=30), "heartbeat": timedelta(seconds=5), } _join: timedelta _last_call: timedelta _close: timedelta _heartbeat: timedelta def __init__( self, join: Optional[timedelta] = None, last_call: Optional[timedelta] = None, close: Optional[timedelta] = None, heartbeat: Optional[timedelta] = None, ) -> None: self._set_timeouts(join=join, last_call=last_call, close=close, heartbeat=heartbeat) @property def join(self) -> timedelta: """Get the join timeout.""" return self._join @property def last_call(self) -> timedelta: """Get the last call timeout.""" return self._last_call @property def close(self) -> timedelta: """Get the close timeout.""" return self._close @property def heartbeat(self) -> timedelta: """Get the keep-alive heartbeat timeout.""" return self._heartbeat def _set_timeouts(self, **timeouts: Optional[timedelta]): for name, timeout in timeouts.items(): if timeout is None: timeout = self._DEFAULT_TIMEOUTS[name] if timeout <= self._ZERO: raise ValueError(f"The {name} timeout ({timeout}) must be positive.") setattr(self, "_" + name, timeout)
@dataclass(repr=False, eq=False, frozen=True) class RendezvousSettings: """Hold the settings of the rendezvous. Attributes: run_id: The run id of the rendezvous. min_nodes: The minimum number of nodes to admit to the rendezvous. max_nodes: The maximum number of nodes to admit to the rendezvous. timeout: The timeout configuration of the rendezvous. keep_alive_interval: The amount of time a node waits before sending a heartbeat to keep it alive in the rendezvous. keep_alive_max_attempt: The maximum number of failed heartbeat attempts after which a node is considered dead. """ run_id: str min_nodes: int max_nodes: int timeout: RendezvousTimeout keep_alive_interval: timedelta keep_alive_max_attempt: int @dataclass(eq=True, order=True, frozen=True) class _NodeDesc: """Describe a node in the rendezvous. Attributes: addr: The FQDN of the node or user specified local node address. pid: The id of the process in which the rendezvous handler runs. local_id: A process-wide unique id. """ addr: str pid: int local_id: int def __repr__(self) -> str: return f"{self.addr}_{self.pid}_{self.local_id}" class _NodeDescGenerator: """Generate node descriptors. A node descriptor is a combination of an FQDN, a process id, and an auto- incremented integer that uniquely identifies a node in the rendezvous. """ _lock: threading.Lock _local_id: int def __init__(self) -> None: self._lock = threading.Lock() # An integer that is incremented with each call to generate(). self._local_id = 0 def generate(self, local_addr: Optional[str] = None) -> _NodeDesc: # This method can be called by multiple threads concurrently; therefore, # we must increment the integer atomically. with self._lock: local_id = self._local_id self._local_id += 1 return _NodeDesc(local_addr or socket.getfqdn(), os.getpid(), local_id) class _RendezvousState: """Hold the state of a rendezvous. Attributes: round: The current round of the rendezvous. complete: A boolean value indicating whether the current round of the rendezvous is complete. deadline: The time at which the current round of the rendezvous will be considered complete if it is still waiting for nodes to join. closed: A boolean value indicating whether the rendezvous is closed. participants: A dictionary of the participants and their corresponding ranks. wait_list: A set of nodes that are waiting to participate in the next round of the rendezvous. redundancy_list: A set of nodes that are redundant in the current round and can join the next rendezvous without triggering re-rendezvous. last_heartbeats: A dictionary containing each node's last heartbeat time. """ round: int complete: bool deadline: Optional[datetime] closed: bool participants: Dict[_NodeDesc, int] wait_list: Set[_NodeDesc] redundancy_list: Set[_NodeDesc] last_heartbeats: Dict[_NodeDesc, datetime] def __init__(self) -> None: self.round = 0 self.complete = False self.deadline = None self.closed = False self.participants = {} self.wait_list = set() self.redundancy_list = set() self.last_heartbeats = {} def _remove_participant_epilogue(state: _RendezvousState, settings: RendezvousSettings) -> None: if state.complete: # If we do not have any participants left, move to the next round. if not state.participants: msg = "No participants left in the rendezvous, marking rendezvous as incomplete" logger.debug(msg) state.complete = False state.round += 1 else: if len(state.participants) < settings.min_nodes: msg = ( f"Number of participants {len(state.participants)}) less than" f"min_nodes {settings.min_nodes}, clearning deadline in state" ) logger.debug(msg) state.deadline = None class _RendezvousStateHolder(ABC): """Hold the shared rendezvous state synced with other nodes.""" @property @abstractmethod def state(self) -> _RendezvousState: """Get the local state.""" @abstractmethod def sync(self) -> Optional[bool]: """Read or writes the latest state. Returns: A boolean value indicating whether the local state, in case marked as dirty, was successfully synced with other nodes. """ @abstractmethod def mark_dirty(self) -> None: """Mark the local state as dirty.""" class _BackendRendezvousStateHolder(_RendezvousStateHolder): """Hold the rendezvous state synced with other nodes via a backend. Args: backend: The rendezvous backend to use. settings: The rendezvous settings. cache_duration: The amount of time, in seconds, to cache the last rendezvous state before requesting it from the backend again. """ _backend: RendezvousBackend _state: _RendezvousState _settings: RendezvousSettings _cache_duration: int _token: Token _dirty: bool _last_sync_time: float _dead_nodes: List[_NodeDesc] def __init__( self, backend: RendezvousBackend, settings: RendezvousSettings, cache_duration: int = 1, ) -> None: self._backend = backend self._state = _RendezvousState() self._settings = settings self._cache_duration = cache_duration self._token = None self._dirty = False self._last_sync_time = -1 self._dead_nodes = [] def _record(self, message: str, node_state: NodeState = NodeState.RUNNING): construct_and_record_rdzv_event( name=f"{self.__class__.__name__}.{get_method_name()}", run_id=self._settings.run_id, message=message, node_state=node_state, ) @property def state(self) -> _RendezvousState: """See base class.""" return self._state def sync(self) -> Optional[bool]: """See base class.""" state_bits: Optional[bytes] = None token = None has_set: Optional[bool] if self._dirty: has_set = False state_bits = pickle.dumps(self._state) set_response = self._backend.set_state(state_bits, self._token) if set_response is not None: state_bits, token, has_set = set_response else: has_set = None if self._cache_duration > 0: # Avoid overloading the backend if we are asked to retrieve the # state repeatedly. Try to serve the cached state. if self._last_sync_time >= max(time.monotonic() - self._cache_duration, 0): return None get_response = self._backend.get_state() if get_response is not None: state_bits, token = get_response if state_bits is not None: try: self._state = pickle.loads(state_bits) except pickle.PickleError as exc: raise RendezvousStateError( "The rendezvous state is corrupt. See inner exception for details." ) from exc else: self._state = _RendezvousState() if has_set and self._dead_nodes and logger.isEnabledFor(logging.DEBUG): node_list = ", ".join(f"'{dead_node}'" for dead_node in self._dead_nodes) msg = ( f"As part of the sync operation the node(s) {node_list} have been removed from the " f"rendezvous '{self._settings.run_id}' since they had no heartbeat." ) self._record(message=msg) logger.debug(msg) self._token = token self._dirty = False self._last_sync_time = time.monotonic() self._sanitize() return has_set def _sanitize(self) -> None: state = self._state expire_time = datetime.utcnow() - ( self._settings.keep_alive_interval * self._settings.keep_alive_max_attempt ) # Filter out the dead nodes. self._dead_nodes = [ node for node, last_heartbeat in state.last_heartbeats.items() if last_heartbeat < expire_time ] participant_removed = False for dead_node in self._dead_nodes: msg = f"Detected dead node '{dead_node}', removing it from the rendezvous" logger.debug(msg) del state.last_heartbeats[dead_node] try: del state.participants[dead_node] participant_removed = True except KeyError: pass try: state.wait_list.remove(dead_node) except KeyError: pass try: state.redundancy_list.remove(dead_node) except KeyError: pass if participant_removed: # Common epilogue shared with the _remove_from_participants() # function of _DistributedRendezvousOpExecutor. _remove_participant_epilogue(state, self._settings) def mark_dirty(self) -> None: """See base class. If the local rendezvous state is dirty, the next sync call will try to write the changes back to the backend. However this attempt might fail if another node, which had the same state, also made changes and wrote them before us. """ self._dirty = True class _Action(Enum): """Specifies the possible actions based on the state of the rendezvous.""" KEEP_ALIVE = 1 ADD_TO_PARTICIPANTS = 2 ADD_TO_WAIT_LIST = 3 ADD_TO_REDUNDANCY_LIST = 4 REMOVE_FROM_PARTICIPANTS = 5 REMOVE_FROM_WAIT_LIST = 6 REMOVE_FROM_REDUNDANCY_LIST = 7 MARK_RENDEZVOUS_COMPLETE = 8 MARK_RENDEZVOUS_CLOSED = 9 SYNC = 10 ERROR_CLOSED = 11 ERROR_TIMEOUT = 12 FINISH = 13 class _RendezvousContext: """Holds the context of the rendezvous. Attributes: node: The node descriptor associated with the current rendezvous handler instance. state: The current state of the rendezvous. settings: The rendezvous settings. """ node: _NodeDesc state: _RendezvousState settings: RendezvousSettings def __init__( self, node: _NodeDesc, state: _RendezvousState, settings: RendezvousSettings ) -> None: self.node = node self.state = state self.settings = settings class _RendezvousOpExecutor(ABC): """Execute rendezvous operations.""" @abstractmethod def run( self, state_handler: Callable[[_RendezvousContext, float], _Action], deadline: float, update_deadline: Optional[Callable[[timedelta], float]] = None, ) -> None: """Execute a rendezvous operation. An operation is run inside a state machine and is expected to transition the rendezvous from one state to another. Args: state_handler: A callable that is expected to return the next state transition action based on the current state of the rendezvous. deadline: The time, in seconds, at which the operation will be considered timed-out. update_deadline: Function to generate a new operation deadline if the current node may participate in the next rendezvous. """ class _DistributedRendezvousOpExecutor(_RendezvousOpExecutor): """Execute rendezvous operations using a shared state. Args: node: The node descriptor associated with the current rendezvous handler instance. state_holder: The ``RendezvousStateHolder`` to use to sync the rendezvous state with other nodes. settings: The rendezvous settings. """ _node: _NodeDesc _state: _RendezvousState _state_holder: _RendezvousStateHolder _settings: RendezvousSettings def __init__( self, node: _NodeDesc, state_holder: _RendezvousStateHolder, settings: RendezvousSettings, ) -> None: self._node = node self._state_holder = state_holder self._settings = settings def _record(self, message: str, node_state: NodeState = NodeState.RUNNING) -> None: construct_and_record_rdzv_event( name=f"{self.__class__.__name__}.{get_method_name()}", run_id=self._settings.run_id, message=message, node_state=node_state, hostname=self._node.addr, pid=self._node.pid, local_id=self._node.local_id, ) def run( self, state_handler: Callable[[_RendezvousContext, float], _Action], deadline: float, update_deadline: Optional[Callable[[timedelta], float]] = None, ) -> None: """See base class.""" action = None while action != _Action.FINISH: # Reads or writes the latest rendezvous state shared by all nodes in # the rendezvous. Note that our local changes might get overridden # by another node if that node synced its changes before us. has_set = self._state_holder.sync() if has_set is not None: if has_set: msg = ( f"The node '{self._node}' has successfully synced its local changes with " f"other nodes in the rendezvous '{self._settings.run_id}'." ) else: msg = ( f"The node '{self._node}' has a stale state and failed to sync its local " f"changes with other nodes in the rendezvous '{self._settings.run_id}'." ) self._record(message=msg) logger.debug(msg) self._state = self._state_holder.state ctx = _RendezvousContext(self._node, self._state, self._settings) # Determine the next action to take based on the current state of # the rendezvous. action = state_handler(ctx, deadline) if action == _Action.FINISH: continue if action == _Action.ERROR_CLOSED: raise RendezvousClosedError() if action == _Action.ERROR_TIMEOUT: raise RendezvousTimeoutError() if action == _Action.SYNC: # Delay the execution by one second to avoid overloading the # backend if we are asked to poll for state changes. _delay(seconds=1) else: if action == _Action.KEEP_ALIVE: self._keep_alive() elif action == _Action.ADD_TO_PARTICIPANTS: self._add_to_participants() elif action == _Action.ADD_TO_WAIT_LIST: self._add_to_wait_list() elif action == _Action.ADD_TO_REDUNDANCY_LIST: self._add_to_redundancy_list() elif action == _Action.REMOVE_FROM_PARTICIPANTS: self._remove_from_participants() elif action == _Action.REMOVE_FROM_WAIT_LIST: self._remove_from_wait_list() elif action == _Action.REMOVE_FROM_REDUNDANCY_LIST: self._remove_from_redundancy_list() # update deadline since the node may participate in rendezvous process if update_deadline: deadline = update_deadline(self._settings.timeout.join) elif action == _Action.MARK_RENDEZVOUS_COMPLETE: self._mark_rendezvous_complete() elif action == _Action.MARK_RENDEZVOUS_CLOSED: self._mark_rendezvous_closed() # Attempt to sync our changes back to other nodes. self._state_holder.mark_dirty() def _keep_alive(self) -> None: msg = ( f"The node '{self._node}' updated its keep-alive heartbeat time for the rendezvous " f"'{self._settings.run_id}'. Pending sync." ) self._record(message=msg) logger.debug(msg) self._state.last_heartbeats[self._node] = datetime.utcnow() def _add_to_participants(self) -> None: msg = ( f"The node '{self._node}' added itself to the participants of round " f"{self._state.round} of the rendezvous '{self._settings.run_id}'. Pending sync." ) self._record(message=msg) logger.debug(msg) state = self._state try: state.wait_list.remove(self._node) except KeyError: pass # The ranks of the participants will be set once the rendezvous is # complete. state.participants[self._node] = 0 self._keep_alive() if len(state.participants) == self._settings.min_nodes: state.deadline = datetime.utcnow() + self._settings.timeout.last_call if len(state.participants) == self._settings.max_nodes: self._mark_rendezvous_complete() def _add_to_wait_list(self) -> None: msg = ( f"The node '{self._node}' added itself to the wait list of round " f"{self._state.round + 1} of the rendezvous '{self._settings.run_id}'. Pending sync." ) self._record(message=msg) logger.debug(msg) if self._node in self._state.redundancy_list: self._state.redundancy_list.remove(self._node) self._state.wait_list.add(self._node) self._keep_alive() def _add_to_redundancy_list(self) -> None: msg = ( f"The node '{self._node}' added itself to the redundancy list of round " f"{self._state.round + 1} of the rendezvous '{self._settings.run_id}'. Pending sync." ) self._record(message=msg) logger.debug(msg) self._state.redundancy_list.add(self._node) self._keep_alive() def _remove_from_participants(self) -> None: msg = ( f"The node '{self._node}' removed itself from the participants of round " f"{self._state.round} of the rendezvous '{self._settings.run_id}'. Pending sync." ) self._record(message=msg) logger.debug(msg) state = self._state del state.participants[self._node] del state.last_heartbeats[self._node] # Common epilogue shared with the sanitizer() function of # _BackendRendezvousStateHolder. _remove_participant_epilogue(state, self._settings) def _remove_from_wait_list(self) -> None: msg = ( f"The node '{self._node}' removed itself from the wait list of round " f"{self._state.round + 1} of the rendezvous '{self._settings.run_id}'. Pending sync." ) self._record(message=msg) logger.debug(msg) self._state.wait_list.remove(self._node) del self._state.last_heartbeats[self._node] def _remove_from_redundancy_list(self) -> None: msg = ( f"The node '{self._node}' removed itself from the redunant list of round " f"{self._state.round + 1} of the rendezvous '{self._settings.run_id}'. Pending sync." ) self._record(message=msg) logger.debug(msg) self._state.redundancy_list.remove(self._node) del self._state.last_heartbeats[self._node] def _mark_rendezvous_complete(self) -> None: msg = ( f"The node '{self._node}' marked round {self._state.round} of the rendezvous " f"'{self._settings.run_id}' as complete. Pending sync." ) self._record(message=msg, node_state=NodeState.SUCCEEDED) logger.debug(msg) state = self._state state.complete = True state.deadline = None # Assign the ranks. for rank, node in enumerate(sorted(state.participants)): state.participants[node] = rank def _mark_rendezvous_closed(self) -> None: msg = ( f"The node '{self._node}' marked the rendezvous '{self._settings.run_id}' as closed. " "Pending sync." ) self._record(message=msg, node_state=NodeState.SUCCEEDED) logger.debug(msg) self._state.closed = True def _should_keep_alive(ctx: _RendezvousContext) -> bool: """Determine whether a keep-alive heartbeat should be sent.""" try: last_heartbeat = ctx.state.last_heartbeats[ctx.node] except KeyError: return False return last_heartbeat <= datetime.utcnow() - ctx.settings.keep_alive_interval class _RendezvousExitOp: """Represent a rendezvous exit operation.""" def __call__(self, ctx: _RendezvousContext, deadline: float) -> _Action: if ctx.node in ctx.state.participants: if time.monotonic() > deadline: return _Action.ERROR_TIMEOUT return _Action.REMOVE_FROM_PARTICIPANTS return _Action.FINISH class _RendezvousJoinOp: """Represent a rendezvous join operation.""" def __call__(self, ctx: _RendezvousContext, deadline: float) -> _Action: state = ctx.state # A closed rendezvous means that it no longer accepts new nodes. if state.closed: if ctx.node in state.redundancy_list: msg = f"The rendezvous '{ctx.settings.run_id}' is closed, terminating pending rendezvous." raise RendezvousGracefulExitError(msg) return _Action.ERROR_CLOSED if ctx.node in state.redundancy_list: msg = f"The node {ctx.node} is in redunancy list" logger.debug(msg) # don't apply the timeout logic here, since we want to allow the node to rejoin if len(state.participants) == ctx.settings.max_nodes: if _should_keep_alive(ctx): return _Action.KEEP_ALIVE else: return _Action.SYNC else: # transition to waiting state that will respect timeouts. msg = f"The node {ctx.node} is removed from redunancy list" logger.debug(msg) return _Action.REMOVE_FROM_REDUNDANCY_LIST is_participant = ctx.node in state.participants # If we are part of the rendezvous and it is already complete there is # no further action to take. if state.complete and is_participant: return _Action.FINISH now = time.monotonic() if now > deadline: rollback_period = 5 # 5 seconds # If we still have time to rollback (a short period on top of the # operation deadline), try to remove ourself from the rendezvous. # It is okay if we can't though as our keep-alive will eventually # expire. if now <= deadline + rollback_period: # If we are part of the rendezvous, it means we couldn't find # enough participants to complete it on time. if is_participant: return _Action.REMOVE_FROM_PARTICIPANTS # If we are in the wait list, it means we couldn't wait till the # next round of the rendezvous. if ctx.node in state.wait_list: return _Action.REMOVE_FROM_WAIT_LIST return _Action.ERROR_TIMEOUT if state.complete: # If we are here, it means we are not part of the rendezvous. In # case the rendezvous has capacity for additional participants add # ourself to the wait list for the next round. if len(state.participants) < ctx.settings.max_nodes: if ctx.node not in state.wait_list: return _Action.ADD_TO_WAIT_LIST elif len(state.participants) >= ctx.settings.max_nodes: if ctx.node not in state.redundancy_list and ctx.node not in state.wait_list: return _Action.ADD_TO_REDUNDANCY_LIST elif is_participant: # If the rendezvous has enough number of participants including us, # check whether we have passed the rendezvous deadline. If yes, # complete it. if len(state.participants) >= ctx.settings.min_nodes and \ len(state.participants) <= ctx.settings.max_nodes: if cast(datetime, state.deadline) < datetime.utcnow(): msg = ( f"The node '{ctx.node}' marking the rendezvous complete, " f"quorum established within deadline" ) logger.debug(msg) return _Action.MARK_RENDEZVOUS_COMPLETE else: msg = f"The node '{ctx.node}' can't complete rendezvous: deadline reached" logger.debug(msg) else: msg = f"The node '{ctx.node}' can't complete rendezvous: not enough participants" logger.debug(msg) else: # The rendezvous is not complete yet and we are not part of it. Try # to join. return _Action.ADD_TO_PARTICIPANTS if _should_keep_alive(ctx): return _Action.KEEP_ALIVE # At this point either the rendezvous is not complete, but we are part # of it, which means we have to wait for other participants to join; or # the rendezvous is complete, but we are not part of it, which means we # have to wait for the next round. return _Action.SYNC class _RendezvousCloseOp: """Represent a rendezvous close operation.""" def __call__(self, ctx: _RendezvousContext, deadline: float) -> _Action: if ctx.state.closed: return _Action.FINISH if time.monotonic() > deadline: return _Action.ERROR_TIMEOUT return _Action.MARK_RENDEZVOUS_CLOSED class _RendezvousKeepAliveOp: """Represent a rendezvous keep-alive update operation.""" def __call__(self, ctx: _RendezvousContext, deadline: float) -> _Action: if _should_keep_alive(ctx): if time.monotonic() > deadline: return _Action.ERROR_TIMEOUT return _Action.KEEP_ALIVE return _Action.FINISH
[docs]class DynamicRendezvousHandler(RendezvousHandler): """Represent a handler that sets up a rendezvous among a set of nodes.""" # Static _node_desc_generator = _NodeDescGenerator() _this_node: _NodeDesc _settings: RendezvousSettings _backend_name: str _store: Store _state_holder: _RendezvousStateHolder _op_executor: _RendezvousOpExecutor _heartbeat_lock: threading.Lock _keep_alive_timer: Optional[_PeriodicTimer]
[docs] @classmethod def from_backend( cls, run_id: str, store: Store, backend: RendezvousBackend, min_nodes: int, max_nodes: int, local_addr: Optional[str] = None, timeout: Optional[RendezvousTimeout] = None, ): """Create a new :py:class:`DynamicRendezvousHandler`. Args: run_id: The run id of the rendezvous. store: The C10d store to return as part of the rendezvous. backend: The backend to use to hold the rendezvous state. min_nodes: The minimum number of nodes to admit to the rendezvous. max_nodes: The maximum number of nodes to admit to the rendezvous. local_addr: The local node address. timeout: The timeout configuration of the rendezvous. """ # We associate each handler instance with a unique node descriptor. node = cls._node_desc_generator.generate(local_addr) settings = RendezvousSettings( run_id, min_nodes, max_nodes, timeout or RendezvousTimeout(), keep_alive_interval=timedelta(seconds=5), keep_alive_max_attempt=3, ) state_holder = _BackendRendezvousStateHolder(backend, settings) return cls(node, settings, backend.name, store, state_holder)
def __init__( self, node: _NodeDesc, settings: RendezvousSettings, backend_name: str, store: Store, state_holder: _RendezvousStateHolder, ) -> None: if not settings.run_id: raise ValueError("The run id must be a non-empty string.") if settings.min_nodes < 1: raise ValueError( f"The minimum number of nodes ({settings.min_nodes}) must be greater than zero." ) if settings.max_nodes < settings.min_nodes: raise ValueError( f"The maximum number of nodes ({settings.max_nodes}) must be greater than or equal " f"to the minimum number of nodes ({settings.min_nodes})." ) self._this_node = node self._settings = settings self._backend_name = backend_name self._store = store self._state_holder = state_holder self._op_executor = _DistributedRendezvousOpExecutor( self._this_node, self._state_holder, self._settings ) self._heartbeat_lock = threading.Lock() self._keep_alive_timer = None def _record( self, message: str, node_state: NodeState = NodeState.RUNNING, rank: Optional[int] = None, ) -> None: construct_and_record_rdzv_event( name=f"{self.__class__.__name__}.{get_method_name()}", run_id=self._settings.run_id, message=message, node_state=node_state, hostname=self._this_node.addr, pid=self._this_node.pid, local_id=self._this_node.local_id, rank=rank, ) @property def settings(self) -> RendezvousSettings: """Get the settings of the rendezvous.""" return self._settings def get_backend(self) -> str: """See base class.""" return self._backend_name def next_rendezvous(self) -> Tuple[Store, int, int]: """See base class.""" msg = ( f"The node '{self._this_node}' attempts to join the next round of the rendezvous " f"'{self._settings.run_id}'." ) self._record(message=msg) logger.info(msg) try: self._stop_heartbeats() # Delay the execution for a small random amount of time if this is our # first run. This will slightly skew the rendezvous attempts across the # nodes and reduce the load on the backend. if self._state_holder.state.round == 0: _delay(seconds=(0, 0.3)) exit_op = _RendezvousExitOp() join_op = _RendezvousJoinOp() deadline = self._get_deadline(self._settings.timeout.join) self._op_executor.run(exit_op, deadline) self._op_executor.run( join_op, deadline, self._get_deadline) self._start_heartbeats() rank, world_size = self._get_world() store = self._get_store() except Exception as e: self._record( message=f"{type(e).__name__}: {str(e)}", node_state=NodeState.FAILED, ) raise msg = ( f"The node '{self._this_node}' has joined round {self._state_holder.state.round} of " f"the rendezvous '{self._settings.run_id}' as rank {rank} in a world of size " f"{world_size}." ) self._record(message=msg, rank=rank) logger.info(msg) return store, rank, world_size def is_closed(self) -> bool: """See base class.""" try: with self._heartbeat_lock: self._state_holder.sync() return self._state_holder.state.closed except Exception as e: self._record( message=f"{type(e).__name__}: {str(e)}", node_state=NodeState.FAILED, ) raise def set_closed(self) -> None: """See base class.""" try: with self._heartbeat_lock: self._close() except Exception as e: self._record( message=f"{type(e).__name__}: {str(e)}", node_state=NodeState.FAILED, ) raise def num_nodes_waiting(self) -> int: """See base class.""" try: with self._heartbeat_lock: self._state_holder.sync() return len(self._state_holder.state.wait_list) except Exception as e: self._record( message=f"{type(e).__name__}: {str(e)}", node_state=NodeState.FAILED, ) raise def get_run_id(self) -> str: """See base class.""" return self._settings.run_id def shutdown(self) -> bool: """See base class.""" self._stop_heartbeats() try: self._close() return True except RendezvousError as ex: msg = ( f"The node '{self._this_node}' has failed to shutdown the rendezvous " f"'{self._settings.run_id}' due to an error of type {type(ex).__name__}." ) self._record(message=msg, node_state=NodeState.FAILED) logger.warning(msg) return False except Exception as e: self._record( message=f"{type(e).__name__}: {str(e)}", node_state=NodeState.FAILED, ) raise def _close(self) -> None: op = _RendezvousCloseOp() deadline = self._get_deadline(self._settings.timeout.close) self._op_executor.run(op, deadline) msg = f"The node '{self._this_node}' has closed the rendezvous '{self._settings.run_id}'." self._record(message=msg, node_state=NodeState.SUCCEEDED) logger.info(msg) @staticmethod def _keep_alive_weak(weak_self) -> None: self = weak_self() if self is not None: self._keep_alive() def _keep_alive(self) -> None: self._heartbeat_lock.acquire() op = _RendezvousKeepAliveOp() deadline = self._get_deadline(self._settings.timeout.heartbeat) try: self._op_executor.run(op, deadline) msg = ( f"The node '{self._this_node}' has sent a keep-alive heartbeat to the rendezvous " f"'{self._settings.run_id}'." ) self._record(message=msg) logger.debug(msg) except RendezvousError as ex: msg = ( f"The node '{self._this_node}' has failed to send a keep-alive heartbeat to the " f"rendezvous '{self._settings.run_id}' due to an error of type {type(ex).__name__}." ) self._record(message=msg, node_state=NodeState.FAILED) logger.warning(msg) finally: self._heartbeat_lock.release() def _start_heartbeats(self) -> None: self._keep_alive_timer = _PeriodicTimer( self._settings.keep_alive_interval, self._keep_alive_weak, weakref.ref(self) ) self._keep_alive_timer.set_name(f"RendezvousKeepAliveTimer_{self._this_node.local_id}") self._keep_alive_timer.start() def _stop_heartbeats(self) -> None: if self._keep_alive_timer is None: return self._keep_alive_timer.cancel() def _get_world(self) -> Tuple[int, int]: state = self._state_holder.state return state.participants[self._this_node], len(state.participants) def _get_store(self) -> Store: key_prefix = f"torch.rendezvous.{self._settings.run_id}.{self._state_holder.state.round}" return PrefixStore(key_prefix, self._store) def _get_deadline(self, timeout: timedelta) -> float: return time.monotonic() + timeout.total_seconds()
def _get_timeout(params: RendezvousParameters, key: str) -> Optional[timedelta]: timeout = params.get_as_int(key + "_timeout") if timeout is None: return None return timedelta(seconds=timeout)
[docs]def create_handler( store: Store, backend: RendezvousBackend, params: RendezvousParameters ) -> DynamicRendezvousHandler: """Create a new :py:class:`DynamicRendezvousHandler` from the specified parameters. Args: store: The C10d store to return as part of the rendezvous. backend: The backend to use to hold the rendezvous state. +-------------------+------------------------------------------------------+ | Parameter | Description | +===================+======================================================+ | join_timeout | The total time, in seconds, within which the | | | rendezvous is expected to complete. Defaults to 600 | | | seconds. | +-------------------+------------------------------------------------------+ | last_call_timeout | An additional wait amount, in seconds, before | | | completing the rendezvous once the minimum number of | | | nodes has been reached. Defaults to 30 seconds. | +-------------------+------------------------------------------------------+ | close_timeout | The time, in seconds, within which the rendezvous is | | | expected to close after a call to | | | :py:meth:`RendezvousHandler.set_closed` or | | | :py:meth:`RendezvousHandler.shutdown`. Defaults to | | | 30 seconds. | +-------------------+------------------------------------------------------+ """ try: timeout = RendezvousTimeout( _get_timeout(params, "join"), _get_timeout(params, "last_call"), _get_timeout(params, "close"), ) return DynamicRendezvousHandler.from_backend( params.run_id, store, backend, params.min_nodes, params.max_nodes, params.local_addr, timeout, ) except Exception as e: construct_and_record_rdzv_event( message=f"{type(e).__name__}: {str(e)}", run_id=params.run_id, node_state=NodeState.FAILED, ) raise

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