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#!/usr/bin/env python3
# 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 datetime
import socket
from contextlib import closing
import torch.distributed as dist
from torch.distributed.elastic.utils.logging import get_logger
log = get_logger(__name__)
_ADDRESS_IN_USE = "Address already in use"
_SOCKET_TIMEOUT = "Socket Timeout"
_MEMBER_CHECKIN = "_tcp_store/num_members"
_LAST_MEMBER_CHECKIN = "_tcp_store/last_member"
def create_c10d_store(
is_server: bool,
server_addr: str,
server_port: int = -1,
world_size: int = 1,
timeout: float = (60 * 10), # 10 min
wait_for_workers: bool = True,
retries=3,
):
if server_port == -1 and world_size > 1:
raise ValueError(
f"server_port must be specified when world_size > 1, got server_port={server_port}, world_size={world_size}"
)
if server_port != -1:
log.info("sever_port: %s, specified, ignoring retries", server_port)
# only retry when server_port is NOT static
attempt = retries if server_port == -1 else 1
while True:
if server_port != -1:
port = server_port
else:
port = get_free_port()
log.info(
"Creating c10d store on %s:%s\n"
" world_size : %s\n"
" is_server : %s\n"
" timeout(sec): %s\n",
server_addr, port, world_size, is_server, timeout
)
try:
store = dist.TCPStore(
host_name=server_addr,
port=port,
world_size=world_size,
is_master=is_server,
timeout=datetime.timedelta(seconds=timeout),
wait_for_workers=wait_for_workers,
)
# skips full rank check when we don't have to wait for all workers
if wait_for_workers:
_check_full_rank(store, world_size)
log.info("Successfully created c10d store")
return store
except RuntimeError as e:
# this is brittle, but the underlying exception type is not properly pybinded
# so we parse the error msg for now, interestingly this is how torch itself
# detects timeouts and port conflicts in their own unittests
# see - caffe2/torch/testing/_internal/common_utils.py
# TODO properly map the exceptions in pybind (c10d/init.cpp)
if str(e) == _ADDRESS_IN_USE: # this will only happen on the server
if attempt < retries:
log.warning(
"port: %s already in use, attempt: [%s/%s]", port, attempt, retries
)
attempt += 1
else:
raise RuntimeError(
f"on {server_addr}, port: {port} already in use"
) from e
else:
raise
def _check_full_rank(store, world_size):
idx = store.add(_MEMBER_CHECKIN, 1)
if idx == world_size:
store.set(_LAST_MEMBER_CHECKIN, "<val_ignored>")
try:
store.get(_LAST_MEMBER_CHECKIN)
except RuntimeError as e:
if str(e) == _SOCKET_TIMEOUT:
raise TimeoutError(
f"timed out waiting for all {world_size} members to join"
) from e
else:
raise
def get_free_port():
sock = get_socket_with_port()
with closing(sock):
return sock.getsockname()[1]
def get_socket_with_port() -> socket.socket:
"""
Returns a free port on localhost that is "reserved" by binding a temporary
socket on it. Close the socket before passing the port to the entity
that requires it. Usage example
::
sock = _get_socket_with_port()
with closing(sock):
port = sock.getsockname()[1]
sock.close()
# there is still a race-condition that some other process
# may grab this port before func() runs
func(port)
"""
addrs = socket.getaddrinfo(
host="localhost", port=None, family=socket.AF_UNSPEC, type=socket.SOCK_STREAM
)
for addr in addrs:
family, type, proto, _, _ = addr
s = socket.socket(family, type, proto)
try:
s.bind(("localhost", 0))
s.listen(0)
return s
except OSError as e:
s.close()
log.info("Socket creation attempt failed.", exc_info=e)
raise RuntimeError("Failed to create a socket")
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