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

# 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 binascii
from base64 import b64decode, b64encode
from typing import Optional, Tuple, cast

import urllib3.exceptions  # type: ignore[import]
from etcd import Client as EtcdClient  # type: ignore[import]
from etcd import (
    EtcdAlreadyExist,
    EtcdCompareFailed,
    EtcdException,
    EtcdKeyNotFound,
    EtcdResult,
)
from torch.distributed import Store

from .api import RendezvousConnectionError, RendezvousParameters, RendezvousStateError
from .dynamic_rendezvous import RendezvousBackend, Token
from .etcd_store import EtcdStore
from .utils import parse_rendezvous_endpoint


[docs]class EtcdRendezvousBackend(RendezvousBackend): """Represents an etcd-based rendezvous backend. Args: client: The ``etcd.Client`` instance to use to communicate with etcd. run_id: The run id of the rendezvous. key_prefix: The path under which to store the rendezvous state in etcd. ttl: The TTL of the rendezvous state. If not specified, defaults to two hours. """ _DEFAULT_TTL = 7200 # 2 hours _client: EtcdClient _key: str _ttl: int def __init__( self, client: EtcdClient, run_id: str, key_prefix: Optional[str] = None, ttl: Optional[int] = None, ) -> None: if not run_id: raise ValueError("The run id must be a non-empty string.") self._client = client if key_prefix: self._key = key_prefix + "/" + run_id else: self._key = run_id if ttl and ttl > 0: self._ttl = ttl else: self._ttl = self._DEFAULT_TTL @property def name(self) -> str: """See base class.""" return "etcd-v2"
[docs] def get_state(self) -> Optional[Tuple[bytes, Token]]: """See base class.""" try: result = self._client.read(self._key) except EtcdKeyNotFound: return None except (EtcdException, urllib3.exceptions.TimeoutError) as exc: raise RendezvousConnectionError( "The connection to etcd has failed. See inner exception for details." ) from exc return self._decode_state(result)
[docs] def set_state( self, state: bytes, token: Optional[Token] = None ) -> Optional[Tuple[bytes, Token, bool]]: """See base class.""" base64_state = b64encode(state).decode() kwargs = {} def get_state(): result = self.get_state() if result is not None: tmp = *result, False # Python 3.6 does not support tuple unpacking in return # statements. return tmp return None if token: try: token = int(token) except ValueError: return get_state() if token: kwargs["prevIndex"] = token else: kwargs["prevExist"] = False try: result = self._client.write(self._key, base64_state, self._ttl, **kwargs) except (EtcdAlreadyExist, EtcdCompareFailed): result = None except (EtcdException, urllib3.exceptions.TimeoutError) as exc: raise RendezvousConnectionError( "The connection to etcd has failed. See inner exception for details." ) from exc if result is None: return get_state() tmp = *self._decode_state(result), True return tmp
def _decode_state(self, result: EtcdResult) -> Tuple[bytes, Token]: base64_state = result.value.encode() try: state = b64decode(base64_state) except binascii.Error as exc: raise RendezvousStateError( "The state object is corrupt. See inner exception for details." ) from exc return state, result.modifiedIndex
def _create_etcd_client(params: RendezvousParameters) -> EtcdClient: host, port = parse_rendezvous_endpoint(params.endpoint, default_port=2379) # The timeout read_timeout = cast(int, params.get_as_int("read_timeout", 60)) if read_timeout <= 0: raise ValueError("The read timeout must be a positive integer.") # The communication protocol protocol = params.get("protocol", "http").strip().lower() if protocol != "http" and protocol != "https": raise ValueError("The protocol must be HTTP or HTTPS.") # The SSL client certificate ssl_cert = params.get("ssl_cert") if ssl_cert: ssl_cert_key = params.get("ssl_cert_key") if ssl_cert_key: # The etcd client expects the certificate key as the second element # of the `cert` tuple. ssl_cert = (ssl_cert, ssl_cert_key) # The root certificate ca_cert = params.get("ca_cert") try: return EtcdClient( host, port, read_timeout=read_timeout, protocol=protocol, cert=ssl_cert, ca_cert=ca_cert, allow_reconnect=True, ) except (EtcdException, urllib3.exceptions.TimeoutError) as exc: raise RendezvousConnectionError( "The connection to etcd has failed. See inner exception for details." ) from exc
[docs]def create_backend(params: RendezvousParameters) -> Tuple[EtcdRendezvousBackend, Store]: """Creates a new :py:class:`EtcdRendezvousBackend` from the specified parameters. +--------------+-----------------------------------------------------------+ | Parameter | Description | +==============+===========================================================+ | read_timeout | The read timeout, in seconds, for etcd operations. | | | Defaults to 60 seconds. | +--------------+-----------------------------------------------------------+ | protocol | The protocol to use to communicate with etcd. Valid | | | values are "http" and "https". Defaults to "http". | +--------------+-----------------------------------------------------------+ | ssl_cert | The path to the SSL client certificate to use along with | | | HTTPS. Defaults to ``None``. | +--------------+-----------------------------------------------------------+ | ssl_cert_key | The path to the private key of the SSL client certificate | | | to use along with HTTPS. Defaults to ``None``. | +--------------+-----------------------------------------------------------+ | ca_cert | The path to the rool SSL authority certificate. Defaults | | | to ``None``. | +--------------+-----------------------------------------------------------+ """ client = _create_etcd_client(params) backend = EtcdRendezvousBackend(client, params.run_id, key_prefix="/torch/elastic/rendezvous") store = EtcdStore(client, "/torch/elastic/store") return backend, store

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