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#
# Copyright (C) 2007-2016 CEA/DAM
# 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 poll() based ClusterShell Engine.
The poll() system call is available on Linux and BSD.
"""
import errno
import logging
import select
import time
from ClusterShell.Engine.Engine import Engine, E_READ, E_WRITE
from ClusterShell.Engine.Engine import EngineException
from ClusterShell.Engine.Engine import EngineNotSupportedError
from ClusterShell.Engine.Engine import EngineTimeoutException
from ClusterShell.Worker.EngineClient import EngineClientEOF
class EnginePoll(Engine):
"""
Poll Engine
ClusterShell engine using the select.poll mechanism (Linux poll()
syscall).
"""
identifier = "poll"
def __init__(self, info):
"""
Initialize Engine.
"""
Engine.__init__(self, info)
try:
# get a polling object
self.polling = select.poll()
except AttributeError:
raise EngineNotSupportedError(EnginePoll.identifier)
def _register_specific(self, fd, event):
"""Engine-specific fd registering. Called by Engine register."""
if event & E_READ:
eventmask = select.POLLIN
else:
assert event & E_WRITE
eventmask = select.POLLOUT
self.polling.register(fd, eventmask)
def _unregister_specific(self, fd, ev_is_set):
if ev_is_set:
self.polling.unregister(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 poll() engine, it reg/unreg or modifies the
event mask associated to a file descriptor.
"""
self._debug("MODSPEC fd=%d event=%x setvalue=%d" % (fd, event,
setvalue))
if setvalue:
self._register_specific(fd, event)
else:
self.polling.unregister(fd)
def runloop(self, timeout):
"""
Poll 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:
poll_timeo = -1
else:
poll_timeo = timeo * 1000.0
evlist = self.polling.poll(poll_timeo)
except select.error as ex:
# might get interrupted by a signal
if ex.args[0] == errno.EINTR:
continue
elif ex.args[0] == errno.EINVAL:
msg = "Increase RLIMIT_NOFILE?"
logging.getLogger(__name__).error(msg)
raise
for fd, event in evlist:
if event & select.POLLNVAL:
raise EngineException("Caught POLLNVAL on fd %d" % fd)
# 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 poll error condition of some sort
if event & select.POLLERR:
self._debug("POLLERR %s" % client)
assert fdev & E_WRITE
self._debug("POLLERR: remove_stream sname %s fdev 0x%x"
% (sname, fdev))
self.remove_stream(client, stream)
self._current_stream = None
continue
# check for data to read
if event & select.POLLIN:
assert fdev & E_READ
assert stream.events & fdev, (stream.events, fdev)
self.modify(client, sname, 0, fdev)
try:
client._handle_read(sname)
except EngineClientEOF:
self._debug("EngineClientEOF %s %s" % (client, sname))
self.remove_stream(client, stream)
self._current_stream = None
continue
# or check for end of stream (do not handle both at the same
# time because handle_read() may perform a partial read)
elif event & select.POLLHUP:
self._debug("POLLHUP fd=%d %s (%s)" %
(fd, client.__class__.__name__, client.streams))
self.remove_stream(client, stream)
self._current_stream = None
continue
# check for writing
if event & select.POLLOUT:
self._debug("POLLOUT 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)
self._current_stream = None
# apply any changes occurred 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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