This document describes the current stable version of Celery (3.1). For development docs, go here.
Source code for celery.platforms
# -*- coding: utf-8 -*-
"""
celery.platforms
~~~~~~~~~~~~~~~~
Utilities dealing with platform specifics: signals, daemonization,
users, groups, and so on.
"""
from __future__ import absolute_import, print_function
import atexit
import errno
import math
import numbers
import os
import platform as _platform
import signal as _signal
import sys
import warnings
from collections import namedtuple
from billiard import current_process
# fileno used to be in this module
from kombu.utils import maybe_fileno
from kombu.utils.compat import get_errno
from kombu.utils.encoding import safe_str
from contextlib import contextmanager
from .local import try_import
from .five import items, range, reraise, string_t, zip_longest
from .utils.functional import uniq
_setproctitle = try_import('setproctitle')
resource = try_import('resource')
pwd = try_import('pwd')
grp = try_import('grp')
mputil = try_import('multiprocessing.util')
__all__ = ['EX_OK', 'EX_FAILURE', 'EX_UNAVAILABLE', 'EX_USAGE', 'SYSTEM',
'IS_OSX', 'IS_WINDOWS', 'pyimplementation', 'LockFailed',
'get_fdmax', 'Pidfile', 'create_pidlock',
'close_open_fds', 'DaemonContext', 'detached', 'parse_uid',
'parse_gid', 'setgroups', 'initgroups', 'setgid', 'setuid',
'maybe_drop_privileges', 'signals', 'set_process_title',
'set_mp_process_title', 'get_errno_name', 'ignore_errno',
'fd_by_path']
# exitcodes
EX_OK = getattr(os, 'EX_OK', 0)
EX_FAILURE = 1
EX_UNAVAILABLE = getattr(os, 'EX_UNAVAILABLE', 69)
EX_USAGE = getattr(os, 'EX_USAGE', 64)
EX_CANTCREAT = getattr(os, 'EX_CANTCREAT', 73)
SYSTEM = _platform.system()
IS_OSX = SYSTEM == 'Darwin'
IS_WINDOWS = SYSTEM == 'Windows'
DAEMON_WORKDIR = '/'
PIDFILE_FLAGS = os.O_CREAT | os.O_EXCL | os.O_WRONLY
PIDFILE_MODE = ((os.R_OK | os.W_OK) << 6) | ((os.R_OK) << 3) | ((os.R_OK))
PIDLOCKED = """ERROR: Pidfile ({0}) already exists.
Seems we're already running? (pid: {1})"""
_range = namedtuple('_range', ('start', 'stop'))
C_FORCE_ROOT = os.environ.get('C_FORCE_ROOT', False)
ROOT_DISALLOWED = """\
Running a worker with superuser privileges when the
worker accepts messages serialized with pickle is a very bad idea!
If you really want to continue then you have to set the C_FORCE_ROOT
environment variable (but please think about this before you do).
User information: uid={uid} euid={euid} gid={gid} egid={egid}
"""
ROOT_DISCOURAGED = """\
You are running the worker with superuser privileges, which is
absolutely not recommended!
Please specify a different user using the -u option.
User information: uid={uid} euid={euid} gid={gid} egid={egid}
"""
[docs]def pyimplementation():
"""Return string identifying the current Python implementation."""
if hasattr(_platform, 'python_implementation'):
return _platform.python_implementation()
elif sys.platform.startswith('java'):
return 'Jython ' + sys.platform
elif hasattr(sys, 'pypy_version_info'):
v = '.'.join(str(p) for p in sys.pypy_version_info[:3])
if sys.pypy_version_info[3:]:
v += '-' + ''.join(str(p) for p in sys.pypy_version_info[3:])
return 'PyPy ' + v
else:
return 'CPython'
[docs]def get_fdmax(default=None):
"""Return the maximum number of open file descriptors
on this system.
:keyword default: Value returned if there's no file
descriptor limit.
"""
try:
return os.sysconf('SC_OPEN_MAX')
except:
pass
if resource is None: # Windows
return default
fdmax = resource.getrlimit(resource.RLIMIT_NOFILE)[1]
if fdmax == resource.RLIM_INFINITY:
return default
return fdmax
[docs]class Pidfile(object):
"""Pidfile
This is the type returned by :func:`create_pidlock`.
TIP: Use the :func:`create_pidlock` function instead,
which is more convenient and also removes stale pidfiles (when
the process holding the lock is no longer running).
"""
#: Path to the pid lock file.
path = None
def __init__(self, path):
self.path = os.path.abspath(path)
[docs] def acquire(self):
"""Acquire lock."""
try:
self.write_pid()
except OSError as exc:
reraise(LockFailed, LockFailed(str(exc)), sys.exc_info()[2])
return self
__enter__ = acquire
[docs] def is_locked(self):
"""Return true if the pid lock exists."""
return os.path.exists(self.path)
__exit__ = release
[docs] def read_pid(self):
"""Read and return the current pid."""
with ignore_errno('ENOENT'):
with open(self.path, 'r') as fh:
line = fh.readline()
if line.strip() == line: # must contain '\n'
raise ValueError(
'Partial or invalid pidfile {0.path}'.format(self))
try:
return int(line.strip())
except ValueError:
raise ValueError(
'pidfile {0.path} contents invalid.'.format(self))
[docs] def remove(self):
"""Remove the lock."""
with ignore_errno(errno.ENOENT, errno.EACCES):
os.unlink(self.path)
[docs] def remove_if_stale(self):
"""Remove the lock if the process is not running.
(does not respond to signals)."""
try:
pid = self.read_pid()
except ValueError as exc:
print('Broken pidfile found. Removing it.', file=sys.stderr)
self.remove()
return True
if not pid:
self.remove()
return True
try:
os.kill(pid, 0)
except os.error as exc:
if exc.errno == errno.ESRCH:
print('Stale pidfile exists. Removing it.', file=sys.stderr)
self.remove()
return True
return False
[docs] def write_pid(self):
pid = os.getpid()
content = '{0}\n'.format(pid)
pidfile_fd = os.open(self.path, PIDFILE_FLAGS, PIDFILE_MODE)
pidfile = os.fdopen(pidfile_fd, 'w')
try:
pidfile.write(content)
# flush and sync so that the re-read below works.
pidfile.flush()
try:
os.fsync(pidfile_fd)
except AttributeError: # pragma: no cover
pass
finally:
pidfile.close()
rfh = open(self.path)
try:
if rfh.read() != content:
raise LockFailed(
"Inconsistency: Pidfile content doesn't match at re-read")
finally:
rfh.close()
PIDFile = Pidfile # compat alias
[docs]def create_pidlock(pidfile):
"""Create and verify pidfile.
If the pidfile already exists the program exits with an error message,
however if the process it refers to is not running anymore, the pidfile
is deleted and the program continues.
This function will automatically install an :mod:`atexit` handler
to release the lock at exit, you can skip this by calling
:func:`_create_pidlock` instead.
:returns: :class:`Pidfile`.
**Example**:
.. code-block:: python
pidlock = create_pidlock('/var/run/app.pid')
"""
pidlock = _create_pidlock(pidfile)
atexit.register(pidlock.release)
return pidlock
def _create_pidlock(pidfile):
pidlock = Pidfile(pidfile)
if pidlock.is_locked() and not pidlock.remove_if_stale():
print(PIDLOCKED.format(pidfile, pidlock.read_pid()), file=sys.stderr)
raise SystemExit(EX_CANTCREAT)
pidlock.acquire()
return pidlock
[docs]def fd_by_path(paths):
"""Return a list of fds.
This method returns list of fds corresponding to
file paths passed in paths variable.
:keyword paths: List of file paths go get fd for.
:returns: :list:.
**Example**:
.. code-block:: python
keep = fd_by_path(['/dev/urandom',
'/my/precious/'])
"""
stats = set()
for path in paths:
try:
fd = os.open(path, os.O_RDONLY)
except OSError:
continue
try:
stats.add(os.fstat(fd)[1:3])
finally:
os.close(fd)
def fd_in_stats(fd):
try:
return os.fstat(fd)[1:3] in stats
except OSError:
return False
return [_fd for _fd in range(get_fdmax(2048)) if fd_in_stats(_fd)]
if hasattr(os, 'closerange'):
def close_open_fds(keep=None):
# must make sure this is 0-inclusive (Issue #1882)
keep = list(uniq(sorted(
f for f in map(maybe_fileno, keep or []) if f is not None
)))
maxfd = get_fdmax(default=2048)
kL, kH = iter([-1] + keep), iter(keep + [maxfd])
for low, high in zip_longest(kL, kH):
if low + 1 != high:
os.closerange(low + 1, high)
else:
[docs] def close_open_fds(keep=None): # noqa
keep = [maybe_fileno(f)
for f in (keep or []) if maybe_fileno(f) is not None]
for fd in reversed(range(get_fdmax(default=2048))):
if fd not in keep:
with ignore_errno(errno.EBADF):
os.close(fd)
[docs]class DaemonContext(object):
_is_open = False
def __init__(self, pidfile=None, workdir=None, umask=None,
fake=False, after_chdir=None, after_forkers=True,
**kwargs):
if isinstance(umask, string_t):
# octal or decimal, depending on initial zero.
umask = int(umask, 8 if umask.startswith('0') else 10)
self.workdir = workdir or DAEMON_WORKDIR
self.umask = umask
self.fake = fake
self.after_chdir = after_chdir
self.after_forkers = after_forkers
self.stdfds = (sys.stdin, sys.stdout, sys.stderr)
[docs] def redirect_to_null(self, fd):
if fd is not None:
dest = os.open(os.devnull, os.O_RDWR)
os.dup2(dest, fd)
[docs] def open(self):
if not self._is_open:
if not self.fake:
self._detach()
os.chdir(self.workdir)
if self.umask is not None:
os.umask(self.umask)
if self.after_chdir:
self.after_chdir()
if not self.fake:
# We need to keep /dev/urandom from closing because
# shelve needs it, and Beat needs shelve to start.
keep = list(self.stdfds) + fd_by_path(['/dev/urandom'])
close_open_fds(keep)
for fd in self.stdfds:
self.redirect_to_null(maybe_fileno(fd))
if self.after_forkers and mputil is not None:
mputil._run_after_forkers()
self._is_open = True
__enter__ = open
__exit__ = close
def _detach(self):
if os.fork() == 0: # first child
os.setsid() # create new session
if os.fork() > 0: # second child
os._exit(0)
else:
os._exit(0)
return self
[docs]def detached(logfile=None, pidfile=None, uid=None, gid=None, umask=0,
workdir=None, fake=False, **opts):
"""Detach the current process in the background (daemonize).
:keyword logfile: Optional log file. The ability to write to this file
will be verified before the process is detached.
:keyword pidfile: Optional pidfile. The pidfile will not be created,
as this is the responsibility of the child. But the process will
exit if the pid lock exists and the pid written is still running.
:keyword uid: Optional user id or user name to change
effective privileges to.
:keyword gid: Optional group id or group name to change effective
privileges to.
:keyword umask: Optional umask that will be effective in the child process.
:keyword workdir: Optional new working directory.
:keyword fake: Don't actually detach, intented for debugging purposes.
:keyword \*\*opts: Ignored.
**Example**:
.. code-block:: python
from celery.platforms import detached, create_pidlock
with detached(logfile='/var/log/app.log', pidfile='/var/run/app.pid',
uid='nobody'):
# Now in detached child process with effective user set to nobody,
# and we know that our logfile can be written to, and that
# the pidfile is not locked.
pidlock = create_pidlock('/var/run/app.pid')
# Run the program
program.run(logfile='/var/log/app.log')
"""
if not resource:
raise RuntimeError('This platform does not support detach.')
workdir = os.getcwd() if workdir is None else workdir
signals.reset('SIGCLD') # Make sure SIGCLD is using the default handler.
maybe_drop_privileges(uid=uid, gid=gid)
def after_chdir_do():
# Since without stderr any errors will be silently suppressed,
# we need to know that we have access to the logfile.
logfile and open(logfile, 'a').close()
# Doesn't actually create the pidfile, but makes sure it's not stale.
if pidfile:
_create_pidlock(pidfile).release()
return DaemonContext(
umask=umask, workdir=workdir, fake=fake, after_chdir=after_chdir_do,
)
[docs]def parse_uid(uid):
"""Parse user id.
uid can be an integer (uid) or a string (user name), if a user name
the uid is taken from the system user registry.
"""
try:
return int(uid)
except ValueError:
try:
return pwd.getpwnam(uid).pw_uid
except (AttributeError, KeyError):
raise KeyError('User does not exist: {0}'.format(uid))
[docs]def parse_gid(gid):
"""Parse group id.
gid can be an integer (gid) or a string (group name), if a group name
the gid is taken from the system group registry.
"""
try:
return int(gid)
except ValueError:
try:
return grp.getgrnam(gid).gr_gid
except (AttributeError, KeyError):
raise KeyError('Group does not exist: {0}'.format(gid))
def _setgroups_hack(groups):
""":fun:`setgroups` may have a platform-dependent limit,
and it is not always possible to know in advance what this limit
is, so we use this ugly hack stolen from glibc."""
groups = groups[:]
while 1:
try:
return os.setgroups(groups)
except ValueError: # error from Python's check.
if len(groups) <= 1:
raise
groups[:] = groups[:-1]
except OSError as exc: # error from the OS.
if exc.errno != errno.EINVAL or len(groups) <= 1:
raise
groups[:] = groups[:-1]
[docs]def setgroups(groups):
"""Set active groups from a list of group ids."""
max_groups = None
try:
max_groups = os.sysconf('SC_NGROUPS_MAX')
except Exception:
pass
try:
return _setgroups_hack(groups[:max_groups])
except OSError as exc:
if exc.errno != errno.EPERM:
raise
if any(group not in groups for group in os.getgroups()):
# we shouldn't be allowed to change to this group.
raise
[docs]def initgroups(uid, gid):
"""Compat version of :func:`os.initgroups` which was first
added to Python 2.7."""
if not pwd: # pragma: no cover
return
username = pwd.getpwuid(uid)[0]
if hasattr(os, 'initgroups'): # Python 2.7+
return os.initgroups(username, gid)
groups = [gr.gr_gid for gr in grp.getgrall()
if username in gr.gr_mem]
setgroups(groups)
[docs]def setgid(gid):
"""Version of :func:`os.setgid` supporting group names."""
os.setgid(parse_gid(gid))
[docs]def setuid(uid):
"""Version of :func:`os.setuid` supporting usernames."""
os.setuid(parse_uid(uid))
[docs]def maybe_drop_privileges(uid=None, gid=None):
"""Change process privileges to new user/group.
If UID and GID is specified, the real user/group is changed.
If only UID is specified, the real user is changed, and the group is
changed to the users primary group.
If only GID is specified, only the group is changed.
"""
if sys.platform == 'win32':
return
if os.geteuid():
# no point trying to setuid unless we're root.
if not os.getuid():
raise AssertionError('contact support')
uid = uid and parse_uid(uid)
gid = gid and parse_gid(gid)
if uid:
# If GID isn't defined, get the primary GID of the user.
if not gid and pwd:
gid = pwd.getpwuid(uid).pw_gid
# Must set the GID before initgroups(), as setgid()
# is known to zap the group list on some platforms.
# setgid must happen before setuid (otherwise the setgid operation
# may fail because of insufficient privileges and possibly stay
# in a privileged group).
setgid(gid)
initgroups(uid, gid)
# at last:
setuid(uid)
# ... and make sure privileges cannot be restored:
try:
setuid(0)
except OSError as exc:
if get_errno(exc) != errno.EPERM:
raise
pass # Good: cannot restore privileges.
else:
raise RuntimeError(
'non-root user able to restore privileges after setuid.')
else:
gid and setgid(gid)
if uid and (not os.getuid()) and not (os.geteuid()):
raise AssertionError('Still root uid after drop privileges!')
if gid and (not os.getgid()) and not (os.getegid()):
raise AssertionError('Still root gid after drop privileges!')
class Signals(object):
"""Convenience interface to :mod:`signals`.
If the requested signal is not supported on the current platform,
the operation will be ignored.
**Examples**:
.. code-block:: python
>>> from celery.platforms import signals
>>> from proj.handlers import my_handler
>>> signals['INT'] = my_handler
>>> signals['INT']
my_handler
>>> signals.supported('INT')
True
>>> signals.signum('INT')
2
>>> signals.ignore('USR1')
>>> signals['USR1'] == signals.ignored
True
>>> signals.reset('USR1')
>>> signals['USR1'] == signals.default
True
>>> from proj.handlers import exit_handler, hup_handler
>>> signals.update(INT=exit_handler,
... TERM=exit_handler,
... HUP=hup_handler)
"""
ignored = _signal.SIG_IGN
default = _signal.SIG_DFL
if hasattr(_signal, 'setitimer'):
def arm_alarm(self, seconds):
_signal.setitimer(_signal.ITIMER_REAL, seconds)
else: # pragma: no cover
try:
from itimer import alarm as _itimer_alarm # noqa
except ImportError:
def arm_alarm(self, seconds): # noqa
_signal.alarm(math.ceil(seconds))
else: # pragma: no cover
def arm_alarm(self, seconds): # noqa
return _itimer_alarm(seconds) # noqa
def reset_alarm(self):
return _signal.alarm(0)
def supported(self, signal_name):
"""Return true value if ``signal_name`` exists on this platform."""
try:
return self.signum(signal_name)
except AttributeError:
pass
def signum(self, signal_name):
"""Get signal number from signal name."""
if isinstance(signal_name, numbers.Integral):
return signal_name
if not isinstance(signal_name, string_t) \
or not signal_name.isupper():
raise TypeError('signal name must be uppercase string.')
if not signal_name.startswith('SIG'):
signal_name = 'SIG' + signal_name
return getattr(_signal, signal_name)
def reset(self, *signal_names):
"""Reset signals to the default signal handler.
Does nothing if the platform doesn't support signals,
or the specified signal in particular.
"""
self.update((sig, self.default) for sig in signal_names)
def ignore(self, *signal_names):
"""Ignore signal using :const:`SIG_IGN`.
Does nothing if the platform doesn't support signals,
or the specified signal in particular.
"""
self.update((sig, self.ignored) for sig in signal_names)
def __getitem__(self, signal_name):
return _signal.getsignal(self.signum(signal_name))
def __setitem__(self, signal_name, handler):
"""Install signal handler.
Does nothing if the current platform doesn't support signals,
or the specified signal in particular.
"""
try:
_signal.signal(self.signum(signal_name), handler)
except (AttributeError, ValueError):
pass
def update(self, _d_=None, **sigmap):
"""Set signal handlers from a mapping."""
for signal_name, handler in items(dict(_d_ or {}, **sigmap)):
self[signal_name] = handler
signals = Signals()
get_signal = signals.signum # compat
install_signal_handler = signals.__setitem__ # compat
reset_signal = signals.reset # compat
ignore_signal = signals.ignore # compat
def strargv(argv):
arg_start = 2 if 'manage' in argv[0] else 1
if len(argv) > arg_start:
return ' '.join(argv[arg_start:])
return ''
[docs]def set_process_title(progname, info=None):
"""Set the ps name for the currently running process.
Only works if :mod:`setproctitle` is installed.
"""
proctitle = '[{0}]'.format(progname)
proctitle = '{0} {1}'.format(proctitle, info) if info else proctitle
if _setproctitle:
_setproctitle.setproctitle(safe_str(proctitle))
return proctitle
if os.environ.get('NOSETPS'): # pragma: no cover
def set_mp_process_title(*a, **k):
pass
else:
[docs] def set_mp_process_title(progname, info=None, hostname=None): # noqa
"""Set the ps name using the multiprocessing process name.
Only works if :mod:`setproctitle` is installed.
"""
if hostname:
progname = '{0}: {1}'.format(progname, hostname)
return set_process_title(
'{0}:{1}'.format(progname, current_process().name), info=info)
[docs]def get_errno_name(n):
"""Get errno for string, e.g. ``ENOENT``."""
if isinstance(n, string_t):
return getattr(errno, n)
return n
@contextmanager
[docs]def ignore_errno(*errnos, **kwargs):
"""Context manager to ignore specific POSIX error codes.
Takes a list of error codes to ignore, which can be either
the name of the code, or the code integer itself::
>>> with ignore_errno('ENOENT'):
... with open('foo', 'r') as fh:
... return fh.read()
>>> with ignore_errno(errno.ENOENT, errno.EPERM):
... pass
:keyword types: A tuple of exceptions to ignore (when the errno matches),
defaults to :exc:`Exception`.
"""
types = kwargs.get('types') or (Exception, )
errnos = [get_errno_name(errno) for errno in errnos]
try:
yield
except types as exc:
if not hasattr(exc, 'errno'):
raise
if exc.errno not in errnos:
raise
def check_privileges(accept_content):
uid = os.getuid() if hasattr(os, 'getuid') else 65535
gid = os.getgid() if hasattr(os, 'getgid') else 65535
euid = os.geteuid() if hasattr(os, 'geteuid') else 65535
egid = os.getegid() if hasattr(os, 'getegid') else 65535
if hasattr(os, 'fchown'):
if not all(hasattr(os, attr)
for attr in ['getuid', 'getgid', 'geteuid', 'getegid']):
raise AssertionError('suspicious platform, contact support')
if not uid or not gid or not euid or not egid:
if ('pickle' in accept_content or
'application/x-python-serialize' in accept_content):
if not C_FORCE_ROOT:
try:
print(ROOT_DISALLOWED.format(
uid=uid, euid=euid, gid=gid, egid=egid,
), file=sys.stderr)
finally:
os._exit(1)
warnings.warn(RuntimeWarning(ROOT_DISCOURAGED.format(
uid=uid, euid=euid, gid=gid, egid=egid,
)))
