/usr/lib/python3/dist-packages/ClusterShell/Engine/Select.py is in python3-clustershell 1.8-1.
This file is owned by root:root, with mode 0o644.
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# Copyright (C) 2009-2016 CEA/DAM
# Copyright (C) 2009-2012 Henri Doreau <henri.doreau@cea.fr>
# Copyright (C) 2009-2012 Aurelien Degremont <aurelien.degremont@cea.fr>
# Copyright (C) 2016 Stephane Thiell <sthiell@stanford.edu>
#
# This file is part of ClusterShell.
#
# ClusterShell is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# ClusterShell 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with ClusterShell; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
"""
A select() based ClusterShell Engine.
The select() system call is available on almost every UNIX-like systems.
"""
import errno
import select
import sys
import time
from ClusterShell.Engine.Engine import Engine, E_READ, E_WRITE
from ClusterShell.Engine.Engine import EngineTimeoutException
from ClusterShell.Worker.EngineClient import EngineClientEOF
class EngineSelect(Engine):
"""
Select Engine
ClusterShell engine using the select.select mechanism
"""
identifier = "select"
def __init__(self, info):
"""
Initialize Engine.
"""
Engine.__init__(self, info)
self._fds_r = []
self._fds_w = []
def _register_specific(self, fd, event):
"""
Engine-specific fd registering. Called by Engine register.
"""
if event & E_READ:
self._fds_r.append(fd)
else:
assert event & E_WRITE
self._fds_w.append(fd)
def _unregister_specific(self, fd, ev_is_set):
"""
Engine-specific fd unregistering. Called by Engine unregister.
"""
if ev_is_set or True:
if fd in self._fds_r:
self._fds_r.remove(fd)
if fd in self._fds_w:
self._fds_w.remove(fd)
def _modify_specific(self, fd, event, setvalue):
"""
Engine-specific modifications after a interesting event change
for a file descriptor. Called automatically by Engine
register/unregister and set_events(). For the select() engine,
it appends/remove the fd to/from the concerned fd_sets.
"""
self._debug("MODSPEC fd=%d event=%x setvalue=%d" % (fd, event,
setvalue))
if setvalue:
self._register_specific(fd, event)
else:
self._unregister_specific(fd, True)
def runloop(self, timeout):
"""
Select engine run(): start clients and properly get replies
"""
if not timeout:
timeout = -1
start_time = time.time()
# run main event loop...
while self.evlooprefcnt > 0:
self._debug("LOOP evlooprefcnt=%d (reg_clifds=%s) (timers=%d)" %
(self.evlooprefcnt, self.reg_clifds.keys(), len(self.timerq)))
try:
timeo = self.timerq.nextfire_delay()
if timeout > 0 and timeo >= timeout:
# task timeout may invalidate clients timeout
self.timerq.clear()
timeo = timeout
elif timeo == -1:
timeo = timeout
self._current_loopcnt += 1
if timeo >= 0:
r_ready, w_ready, x_ready = \
select.select(self._fds_r, self._fds_w, [], timeo)
else:
# no timeout specified, do not supply the timeout argument
r_ready, w_ready, x_ready = \
select.select(self._fds_r, self._fds_w, [])
except select.error as ex:
# might get interrupted by a signal
if ex.args[0] == errno.EINTR:
continue
elif ex.args[0] in (errno.EINVAL, errno.EBADF, errno.ENOMEM):
msg = "Increase RLIMIT_NOFILE?"
logging.getLogger(__name__).error(msg)
raise
# iterate over fd on which events occured
for fd in set(r_ready) | set(w_ready):
# get client instance
client, stream = self._fd2client(fd)
if client is None:
continue
fdev = stream.evmask
sname = stream.name
# process this stream
self._current_stream = stream
# check for possible unblocking read on this fd
if fd in r_ready:
self._debug("R_READY fd=%d %s (%s)" % (fd,
client.__class__.__name__, client.streams))
assert fdev & E_READ
assert stream.events & fdev
self.modify(client, sname, 0, fdev)
try:
client._handle_read(sname)
except EngineClientEOF:
self._debug("EngineClientEOF %s" % client)
self.remove_stream(client, stream)
# check for writing
if fd in w_ready:
self._debug("W_READY fd=%d %s (%s)" % (fd,
client.__class__.__name__, client.streams))
assert fdev == E_WRITE
assert stream.events & fdev
self.modify(client, sname, 0, fdev)
client._handle_write(sname)
# post processing
self._current_stream = None
# apply any changes occured during processing
if client.registered:
self.set_events(client, stream)
# check for task runloop timeout
if timeout > 0 and time.time() >= start_time + timeout:
raise EngineTimeoutException()
# process clients timeout
self.fire_timers()
self._debug("LOOP EXIT evlooprefcnt=%d (reg_clifds=%s) (timers=%d)" %
(self.evlooprefcnt, self.reg_clifds, len(self.timerq)))
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