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mitogen/mitogen/fork.py

221 lines
7.5 KiB
Python

# Copyright 2017, David Wilson
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# 3. Neither the name of the copyright holder nor the names of its contributors
# may be used to endorse or promote products derived from this software without
# specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
import logging
import os
import random
import sys
import threading
import traceback
import mitogen.core
import mitogen.parent
LOG = logging.getLogger('mitogen')
# Python 2.4/2.5 cannot support fork+threads whatsoever, it doesn't even fix up
# interpreter state. So 2.4/2.5 interpreters start .local() contexts for
# isolation instead. Since we don't have any crazy memory sharing problems to
# avoid, there is no virginal fork parent either. The child is started directly
# from the login/become process. In future this will be default everywhere,
# fork is brainwrong from the stone age.
FORK_SUPPORTED = sys.version_info >= (2, 6)
class Error(mitogen.core.StreamError):
pass
def fixup_prngs():
"""
Add 256 bits of /dev/urandom to OpenSSL's PRNG in the child, and re-seed
the random package with the same data.
"""
s = os.urandom(256 // 8)
random.seed(s)
if 'ssl' in sys.modules:
sys.modules['ssl'].RAND_add(s, 75.0)
def reset_logging_framework():
"""
After fork, ensure any logging.Handler locks are recreated, as a variety of
threads in the parent may have been using the logging package at the moment
of fork.
It is not possible to solve this problem in general; see
https://github.com/dw/mitogen/issues/150 for a full discussion.
"""
logging._lock = threading.RLock()
# The root logger does not appear in the loggerDict.
for name in [None] + list(logging.Logger.manager.loggerDict):
for handler in logging.getLogger(name).handlers:
handler.createLock()
root = logging.getLogger()
root.handlers = [
handler
for handler in root.handlers
if not isinstance(handler, mitogen.core.LogHandler)
]
def on_fork():
"""
Should be called by any program integrating Mitogen each time the process
is forked, in the context of the new child.
"""
reset_logging_framework() # Must be first!
fixup_prngs()
mitogen.core.Latch._on_fork()
mitogen.core.Side._on_fork()
mitogen__service = sys.modules.get('mitogen.service')
if mitogen__service:
mitogen__service._pool_lock = threading.Lock()
def handle_child_crash():
"""
Respond to _child_main() crashing by ensuring the relevant exception is
logged to /dev/tty.
"""
tty = open('/dev/tty', 'wb')
tty.write('\n\nFORKED CHILD PID %d CRASHED\n%s\n\n' % (
os.getpid(),
traceback.format_exc(),
))
tty.close()
os._exit(1)
class Stream(mitogen.parent.Stream):
child_is_immediate_subprocess = True
#: Reference to the importer, if any, recovered from the parent.
importer = None
#: User-supplied function for cleaning up child process state.
on_fork = None
python_version_msg = (
"The mitogen.fork method is not supported on Python versions "
"prior to 2.6, since those versions made no attempt to repair "
"critical interpreter state following a fork. Please use the "
"local() method instead."
)
def construct(self, old_router, max_message_size, on_fork=None,
debug=False, profiling=False, unidirectional=False,
on_start=None):
if not FORK_SUPPORTED:
raise Error(self.python_version_msg)
# fork method only supports a tiny subset of options.
super(Stream, self).construct(max_message_size=max_message_size,
debug=debug, profiling=profiling,
unidirectional=False)
self.on_fork = on_fork
self.on_start = on_start
responder = getattr(old_router, 'responder', None)
if isinstance(responder, mitogen.parent.ModuleForwarder):
self.importer = responder.importer
name_prefix = u'fork'
def start_child(self):
parentfp, childfp = mitogen.parent.create_socketpair()
self.pid = os.fork()
if self.pid:
childfp.close()
# Decouple the socket from the lifetime of the Python socket object.
fd = os.dup(parentfp.fileno())
parentfp.close()
return self.pid, fd, None
else:
parentfp.close()
self._wrap_child_main(childfp)
def _wrap_child_main(self, childfp):
try:
self._child_main(childfp)
except BaseException:
handle_child_crash()
def _child_main(self, childfp):
on_fork()
if self.on_fork:
self.on_fork()
mitogen.core.set_block(childfp.fileno())
# Expected by the ExternalContext.main().
os.dup2(childfp.fileno(), 1)
os.dup2(childfp.fileno(), 100)
# Overwritten by ExternalContext.main(); we must replace the
# parent-inherited descriptors that were closed by Side._on_fork() to
# avoid ExternalContext.main() accidentally allocating new files over
# the standard handles.
os.dup2(childfp.fileno(), 0)
# Avoid corrupting the stream on fork crash by dupping /dev/null over
# stderr. Instead, handle_child_crash() uses /dev/tty to log errors.
devnull = os.open('/dev/null', os.O_WRONLY)
if devnull != 2:
os.dup2(devnull, 2)
os.close(devnull)
# If we're unlucky, childfp.fileno() may coincidentally be one of our
# desired FDs. In that case closing it breaks ExternalContext.main().
if childfp.fileno() not in (0, 1, 100):
childfp.close()
config = self.get_econtext_config()
config['core_src_fd'] = None
config['importer'] = self.importer
config['setup_package'] = False
if self.on_start:
config['on_start'] = self.on_start
try:
try:
mitogen.core.ExternalContext(config).main()
except Exception:
# TODO: report exception somehow.
os._exit(72)
finally:
# Don't trigger atexit handlers, they were copied from the parent.
os._exit(0)
def _connect_bootstrap(self):
# None required.
pass