143 lines
4.9 KiB
Python
143 lines
4.9 KiB
Python
# Copyright (c) 2012, 2013, 2014 Ilya Otyutskiy <ilya.otyutskiy@icloud.com>
|
|
# Copyright 2020 The Matrix.org Foundation C.I.C.
|
|
#
|
|
# 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 atexit
|
|
import fcntl
|
|
import logging
|
|
import os
|
|
import signal
|
|
import sys
|
|
from types import FrameType, TracebackType
|
|
from typing import NoReturn, Optional, Type
|
|
|
|
|
|
def daemonize_process(pid_file: str, logger: logging.Logger, chdir: str = "/") -> None:
|
|
"""daemonize the current process
|
|
|
|
This calls fork(), and has the main process exit. When it returns we will be
|
|
running in the child process.
|
|
"""
|
|
|
|
# If pidfile already exists, we should read pid from there; to overwrite it, if
|
|
# locking will fail, because locking attempt somehow purges the file contents.
|
|
if os.path.isfile(pid_file):
|
|
with open(pid_file) as pid_fh:
|
|
old_pid = pid_fh.read()
|
|
|
|
# Create a lockfile so that only one instance of this daemon is running at any time.
|
|
try:
|
|
lock_fh = open(pid_file, "w")
|
|
except OSError:
|
|
print("Unable to create the pidfile.")
|
|
sys.exit(1)
|
|
|
|
try:
|
|
# Try to get an exclusive lock on the file. This will fail if another process
|
|
# has the file locked.
|
|
fcntl.flock(lock_fh, fcntl.LOCK_EX | fcntl.LOCK_NB)
|
|
except OSError:
|
|
print("Unable to lock on the pidfile.")
|
|
# We need to overwrite the pidfile if we got here.
|
|
#
|
|
# XXX better to avoid overwriting it, surely. this looks racey as the pid file
|
|
# could be created between us trying to read it and us trying to lock it.
|
|
with open(pid_file, "w") as pid_fh:
|
|
pid_fh.write(old_pid)
|
|
sys.exit(1)
|
|
|
|
# Fork, creating a new process for the child.
|
|
process_id = os.fork()
|
|
|
|
if process_id != 0:
|
|
# parent process: exit.
|
|
|
|
# we use os._exit to avoid running the atexit handlers. In particular, that
|
|
# means we don't flush the logs. This is important because if we are using
|
|
# a MemoryHandler, we could have logs buffered which are now buffered in both
|
|
# the main and the child process, so if we let the main process flush the logs,
|
|
# we'll get two copies.
|
|
os._exit(0)
|
|
|
|
# This is the child process. Continue.
|
|
|
|
# Stop listening for signals that the parent process receives.
|
|
# This is done by getting a new process id.
|
|
# setpgrp() is an alternative to setsid().
|
|
# setsid puts the process in a new parent group and detaches its controlling
|
|
# terminal.
|
|
|
|
os.setsid()
|
|
|
|
# point stdin, stdout, stderr at /dev/null
|
|
devnull = "/dev/null"
|
|
if hasattr(os, "devnull"):
|
|
# Python has set os.devnull on this system, use it instead as it might be
|
|
# different than /dev/null.
|
|
devnull = os.devnull
|
|
|
|
devnull_fd = os.open(devnull, os.O_RDWR)
|
|
os.dup2(devnull_fd, 0)
|
|
os.dup2(devnull_fd, 1)
|
|
os.dup2(devnull_fd, 2)
|
|
os.close(devnull_fd)
|
|
|
|
# now that we have redirected stderr to /dev/null, any uncaught exceptions will
|
|
# get sent to /dev/null, so make sure we log them.
|
|
#
|
|
# (we don't normally expect reactor.run to raise any exceptions, but this will
|
|
# also catch any other uncaught exceptions before we get that far.)
|
|
|
|
def excepthook(
|
|
type_: Type[BaseException],
|
|
value: BaseException,
|
|
traceback: Optional[TracebackType],
|
|
) -> None:
|
|
logger.critical("Unhanded exception", exc_info=(type_, value, traceback))
|
|
|
|
sys.excepthook = excepthook
|
|
|
|
# Set umask to default to safe file permissions when running as a root daemon. 027
|
|
# is an octal number which we are typing as 0o27 for Python3 compatibility.
|
|
os.umask(0o27)
|
|
|
|
# Change to a known directory. If this isn't done, starting a daemon in a
|
|
# subdirectory that needs to be deleted results in "directory busy" errors.
|
|
os.chdir(chdir)
|
|
|
|
try:
|
|
lock_fh.write("%s" % (os.getpid()))
|
|
lock_fh.flush()
|
|
except OSError:
|
|
logger.error("Unable to write pid to the pidfile.")
|
|
print("Unable to write pid to the pidfile.")
|
|
sys.exit(1)
|
|
|
|
# write a log line on SIGTERM.
|
|
def sigterm(signum: int, frame: Optional[FrameType]) -> NoReturn:
|
|
logger.warning("Caught signal %s. Stopping daemon." % signum)
|
|
sys.exit(0)
|
|
|
|
signal.signal(signal.SIGTERM, sigterm)
|
|
|
|
# Cleanup pid file at exit.
|
|
def exit() -> None:
|
|
logger.warning("Stopping daemon.")
|
|
os.remove(pid_file)
|
|
sys.exit(0)
|
|
|
|
atexit.register(exit)
|
|
|
|
logger.warning("Starting daemon.")
|