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#!/usr/bin/env python
# Copyright 2025 The HuggingFace Inc. team.
# All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
import os
import signal
import sys
class ProcessSignalHandler:
"""Utility class to attach graceful shutdown signal handlers.
The class exposes a shutdown_event attribute that is set when a shutdown
signal is received. A counter tracks how many shutdown signals have been
caught. On the second signal the process exits with status 1.
"""
_SUPPORTED_SIGNALS = ("SIGINT", "SIGTERM", "SIGHUP", "SIGQUIT")
def __init__(self, use_threads: bool, display_pid: bool = False):
# TODO: Check if we can use Event from threading since Event from
# multiprocessing is the a clone of threading.Event.
# https://docs.python.org/3/library/multiprocessing.html#multiprocessing.Event
if use_threads:
from threading import Event
else:
from multiprocessing import Event
self.shutdown_event = Event()
self._counter: int = 0
self._display_pid = display_pid
self._register_handlers()
@property
def counter(self) -> int: # pragma: no cover – simple accessor
"""Number of shutdown signals that have been intercepted."""
return self._counter
def _register_handlers(self):
"""Attach the internal _signal_handler to a subset of POSIX signals."""
def _signal_handler(signum, frame):
pid_str = ""
if self._display_pid:
pid_str = f"[PID: {os.getpid()}]"
logging.info(f"{pid_str} Shutdown signal {signum} received. Cleaning up…")
self.shutdown_event.set()
self._counter += 1
# On a second Ctrl-C (or any supported signal) force the exit to
# mimic the previous behaviour while giving the caller one chance to
# shutdown gracefully.
# TODO: Investigate if we need it later
if self._counter > 1:
logging.info("Force shutdown")
sys.exit(1)
for sig_name in self._SUPPORTED_SIGNALS:
sig = getattr(signal, sig_name, None)
if sig is None:
# The signal is not available on this platform (Windows for
# instance does not provide SIGHUP, SIGQUIT…). Skip it.
continue
try:
signal.signal(sig, _signal_handler)
except (ValueError, OSError): # pragma: no cover – unlikely but safe
# Signal not supported or we are in a non-main thread.
continue
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