/usr/lib/python3/dist-packages/plainbox/vendor/extcmd/glibc.py is in python3-plainbox 0.25-1.
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# Copyright (c) 2010-2012 Linaro Limited
# Copyright (c) 2013 Canonical Ltd.
#
# Author: Zygmunt Krynicki <zygmunt.krynicki@linaro.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
:mod:`plainbox.vendor.extcmd.glibc` - glibc-based extcmd
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
"""
import contextlib
import errno
import fcntl
import logging
import os
import signal
import sys
from plainbox.vendor.glibc import CLD_EXITED
from plainbox.vendor.glibc import CLD_KILLED
from plainbox.vendor.glibc import O_CLOEXEC
from plainbox.vendor.glibc import O_NONBLOCK
from plainbox.vendor.glibc import SFD_CLOEXEC
from plainbox.vendor.glibc import SFD_NONBLOCK
from plainbox.vendor.glibc import F_GETPIPE_SZ
from plainbox.vendor.glibc import dup3
from plainbox.vendor.pyglibc import pipe2
from plainbox.vendor.pyglibc import pthread_sigmask
from plainbox.vendor.pyglibc import signalfd
from plainbox.vendor.pyglibc.selectors import EVENT_READ
from plainbox.vendor.pyglibc.selectors import EpollSelector
from plainbox.vendor.extcmd import ExternalCommand
from plainbox.vendor.extcmd import SafeDelegate
from plainbox.vendor.extcmd import CHUNKED_IO
_logger = logging.getLogger("plainbox.vendor.extcmd")
_bug_logger = logging.getLogger("plainbox.bug")
@contextlib.contextmanager
def close_fd(fd):
"""
A context manager that ensures a file descriptor is closed in the end
:param fd:
The descriptor to close
"""
try:
yield fd
finally:
try:
os.close(fd)
except OSError as exc:
if exc.errno != errno.EBADF:
raise
_PLATFORM_DEFAULT_CLOSE_FDS = object()
class GlibcExternalCommandWithDelegate(ExternalCommand):
"""
A non-portable implementation of ExternalCommandWithDelegate using certain
glibc features. This version is *probably* unsafe to run from within a
multi-threaded application.
"""
def __init__(self, delegate, killsig=signal.SIGINT, flags=0):
self._delegate = SafeDelegate.wrap_if_needed(delegate)
self._killsig = killsig
self._flags = flags
def call(self, args, bufsize=-1, executable=None,
stdin=None, stdout=None, stderr=None,
preexec_fn=None, close_fds=_PLATFORM_DEFAULT_CLOSE_FDS,
shell=False, cwd=None, env=None, universal_newlines=False,
startupinfo=None, creationflags=0,
restore_signals=True, start_new_session=False,
pass_fds=()):
# A few of the things are either not implemented or explicitly
# unsupported, check for those and raise NotImplementedError or
# ValueError respectively
if universal_newlines is True:
raise NotImplementedError(
"universal_newlines=True is not implemented")
if stdout is not None:
raise ValueError("redirecting stdout is not supported")
if stderr is not None:
raise ValueError("redirecting stderr is not supported")
if stdin is not None:
raise ValueError("redirecting stdin is not supported")
if close_fds is _PLATFORM_DEFAULT_CLOSE_FDS:
close_fds = True
selector = EpollSelector()
signal_list = [signal.SIGCHLD, signal.SIGINT, signal.SIGQUIT]
_logger.debug("Obtained: %r", selector)
sfd = signalfd(signal_list, SFD_CLOEXEC | SFD_NONBLOCK)
_logger.debug("Obtained: %r", sfd)
sigmask = pthread_sigmask(signal_list)
_logger.debug("Obtained: %r", sigmask)
stdout_pair = pipe2(O_CLOEXEC)
_logger.debug("Obtained: %r", stdout_pair)
stderr_pair = pipe2(O_CLOEXEC)
_logger.debug("Obtained: %r", stderr_pair)
key = selector.register(stdout_pair[0], EVENT_READ, 'stdout')
_logger.debug("Registered key with selector: %r", key)
key = selector.register(stderr_pair[0], EVENT_READ, 'stderr')
_logger.debug("Registered key with selector: %r", key)
key = selector.register(sfd, EVENT_READ, 'sfd')
_logger.debug("Registered key with selector: %r", key)
with sigmask, sfd, selector, close_fd(stdout_pair[0]),\
close_fd(stderr_pair[0]):
# TODO: create fake args, kwargs
self._delegate.on_begin(None, None)
pid = os.fork()
if pid == 0:
# Undo signal blocking as those are inherited
sigmask.unblock()
# Close stdout and stderr, this will also flush the buffers
sys.stdout.close()
sys.stderr.close()
# XXX: double check the order of actions below with
# subprocess's internal counterpart.
# Make stdout and stderr our pipe
dup3(stdout_pair[1], 1, 0)
dup3(stderr_pair[1], 2, 0)
# Maybe close all open file descriptors
if (close_fds or pass_fds):
pass_fds = frozenset(pass_fds)
max_fd = os.sysconf("SC_OPEN_MAX") or 256
for fd in range(3, max_fd):
# Except for those that are explicitly marked to keep
if fd not in pass_fds:
try:
os.close(fd)
except OSError:
pass
# Maybe modify the environment
if env is not None:
os.environ.clear()
for env_k in env:
os.environ[env_k] = env[env_k]
# Maybe change the current working directory
if cwd is not None:
os.chdir(cwd)
# Maybe restore the signal handlers
if restore_signals:
signal.signal(signal.SIGPIPE, signal.SIG_DFL)
# Maybe start a new session
if start_new_session:
os.setsid()
# Maybe call the preexec function
if preexec_fn is not None:
preexec_fn()
# Execute the child process, maybe using a shell
if shell:
os.execvp(executable or args[0], ['/bin/sh', '-c'] + args)
else:
os.execvp(executable or args[0], args)
# TODO: use a side channel to signal the failure, maybe?
os.exit(-1)
else:
_logger.debug("Forked child process: %r", pid)
# Make all pipes non-blocking as the loop below cannot work
# with any blocking I/O.
flags = fcntl.fcntl(stdout_pair[0], fcntl.F_GETFL)
flags |= O_NONBLOCK
fcntl.fcntl(stdout_pair[0], fcntl.F_SETFL, flags)
flags = fcntl.fcntl(stderr_pair[0], fcntl.F_GETFL)
flags |= O_NONBLOCK
fcntl.fcntl(stderr_pair[0], fcntl.F_SETFL, O_NONBLOCK)
# Close the write sides of the pipes
os.close(stdout_pair[1])
os.close(stderr_pair[1])
return self._loop(selector, pid)
def _handle_SIGCHLD(self, pid):
_logger.debug("calling waitid() on process %d", pid)
waitid_result = os.waitid(
os.P_PID, pid, os.WNOHANG | os.WEXITED)
_logger.debug("waitid() returned %r", waitid_result)
if waitid_result is None:
_logger.warning("waitid() returned nothing?")
return
if waitid_result.si_code == CLD_EXITED:
returncode = waitid_result.si_status
_logger.debug("Saw CLD_EXITED with return code: %r", returncode)
return returncode
elif waitid_result.si_code == CLD_KILLED:
signal_num = waitid_result.si_status
_logger.debug("Saw CLD_KILLED with signal: %r", signal_num)
return -signal_num
else:
_bug_logger.error(
"Unexpected si_code: %d", waitid_result.si_code)
def _handle_SIGINT(self, pid):
_logger.debug("Sending signal %d to process %d", self._killsig, pid)
os.kill(pid, self._killsig)
def _handle_SIGQUIT(self, pid):
_logger.debug("Sending SIGQUIT to process %d", pid)
os.kill(pid, signal.SIGQUIT)
def _read_pipe_chunked(self, fd, name, force_last):
assert name in ('stdout', 'stderr')
pipe_size = fcntl.fcntl(fd, F_GETPIPE_SZ)
_logger.debug("Reading at most %d bytes of data from %s pipe",
pipe_size, name)
data = os.read(fd, pipe_size)
done_reading = force_last or len(data) == 0
_logger.debug("Read %d bytes of data from %s", len(data), name)
self._delegate.on_chunk(name, data)
return done_reading
def _read_pipe_lines(self, fd, name, buffer_map, force_last):
assert name in ('stdout', 'stderr')
pipe_size = fcntl.fcntl(fd, F_GETPIPE_SZ)
_logger.debug("Reading at most %d bytes of data from %s pipe",
pipe_size, name)
data = os.read(fd, pipe_size)
done_reading = force_last or len(data) == 0
_logger.debug("Read %d bytes of data from %s", len(data), name)
buf = buffer_map[name]
if buf is not None:
# Combine this buffer with the previous one before attempting
# to detect newlines. This way, on the outside, we always
# return complete lines and no something partial or in the
# middle.
buf.extend(data)
else:
buf = bytearray(data)
assert isinstance(buf, bytearray)
# Split the buffer into lines, the last line (aka line_list[-1])
# may be partial and we have to keep it around for the next time
# we're called.
line_buffer_list = buf.splitlines(True)
for line_buffer in line_buffer_list[0:-1]:
self._delegate.on_line(name, bytes(line_buffer))
if len(line_buffer_list) > 0:
last_line_buffer = line_buffer_list[-1]
if last_line_buffer.endswith(b'\n') or done_reading:
# If the last line is complete (ends with the newline byte)
# or this is the last chunk (we're done reading) then send it
# out immedaitely.
self._delegate.on_line(name, bytes(last_line_buffer))
buffer_map[name] = None
else:
# Otherwise keep the last line around for the next time we're
# called
buffer_map[name] = last_line_buffer
else:
buffer_map[name] = None
return done_reading
def _loop(self, selector, pid):
waiting_for = set(['stdout', 'stderr', 'proc'])
return_code = None
# This buffer holds partial data that was not yet published
buffer_map = {
'stdout': None,
'stderr': None,
}
while waiting_for:
event_list = selector.select()
for key, events in event_list:
if key.data == 'sfd':
if events & EVENT_READ:
for fdsi in key.fileobj.read():
_logger.debug("read signal information: %r", fdsi)
if fdsi.ssi_signo == signal.SIGCHLD:
return_code = self._handle_SIGCHLD(pid)
if return_code is not None:
waiting_for.remove('proc')
elif fdsi.ssi_signo == signal.SIGINT:
self._handle_SIGINT(pid)
elif fdsi.ssi_signo == signal.SIGQUIT:
self._handle_SIGQUIT(pid)
else:
_bug_logger.error(
"read unexpected signal: %r", fdsi)
else:
_bug_logger.error(
"Unexpected event mask for signalfd: %d", events)
else:
if events & EVENT_READ:
# Don't drain the pipe more than once if the process
# has terminated. This way we see everythng the process
# could have written and don't wait forever if the pipe
# has leaked.
force_last = 'proc' not in waiting_for
if self._flags & CHUNKED_IO:
is_done = self._read_pipe_chunked(
key.fd, key.data, force_last)
else:
is_done = self._read_pipe_lines(
key.fd, key.data, buffer_map, force_last)
if is_done:
_logger.debug(
"pipe %s depleted, unregistering and closing",
key.data)
selector.unregister(key.fd)
os.close(key.fd)
# NOTE: since we're cleaning waiting_for above,
# this part is optional
if key.data in waiting_for:
waiting_for.remove(key.data)
else:
_bug_logger.error(
"Unexpected event mask for pipe: %d", events)
if return_code is None:
_bug_logger.error(
"We don't know the real status of the child, faking failure")
return_code = 1
# NOTE: we should defer on_end() / on_abnormal_end() until we deplete
# I/O as delegates might close their files and we still can call
# on_line() after that happens.
if return_code >= 0:
self._delegate.on_end(return_code)
else:
signal_num = -return_code
self._delegate.on_abnormal_end(signal_num)
_logger.debug("Returning from extcmd: %d", return_code)
return return_code
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