/usr/share/pyshared/ClusterShell/Engine/Engine.py is in clustershell 1.6-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# Copyright CEA/DAM/DIF (2007, 2008, 2009, 2010, 2011)
# Contributor: Stephane THIELL <stephane.thiell@cea.fr>
#
# This file is part of the ClusterShell library.
#
# This software is governed by the CeCILL-C license under French law and
# abiding by the rules of distribution of free software. You can use,
# modify and/ or redistribute the software under the terms of the CeCILL-C
# license as circulated by CEA, CNRS and INRIA at the following URL
# "http://www.cecill.info".
#
# As a counterpart to the access to the source code and rights to copy,
# modify and redistribute granted by the license, users are provided only
# with a limited warranty and the software's author, the holder of the
# economic rights, and the successive licensors have only limited
# liability.
#
# In this respect, the user's attention is drawn to the risks associated
# with loading, using, modifying and/or developing or reproducing the
# software by the user in light of its specific status of free software,
# that may mean that it is complicated to manipulate, and that also
# therefore means that it is reserved for developers and experienced
# professionals having in-depth computer knowledge. Users are therefore
# encouraged to load and test the software's suitability as regards their
# requirements in conditions enabling the security of their systems and/or
# data to be ensured and, more generally, to use and operate it in the
# same conditions as regards security.
#
# The fact that you are presently reading this means that you have had
# knowledge of the CeCILL-C license and that you accept its terms.
"""
Interface of underlying Task's Engine.
An Engine implements a loop your thread enters and uses to call event handlers
in response to incoming events (from workers, timers, etc.).
"""
import errno
import heapq
import logging
import time
class EngineException(Exception):
"""
Base engine exception.
"""
class EngineAbortException(EngineException):
"""
Raised on user abort.
"""
def __init__(self, kill):
EngineException.__init__(self)
self.kill = kill
class EngineTimeoutException(EngineException):
"""
Raised when a timeout is encountered.
"""
class EngineIllegalOperationError(EngineException):
"""
Error raised when an illegal operation has been performed.
"""
class EngineAlreadyRunningError(EngineIllegalOperationError):
"""
Error raised when the engine is already running.
"""
class EngineNotSupportedError(EngineException):
"""
Error raised when the engine mechanism is not supported.
"""
def __init__(self, engineid):
EngineException.__init__(self)
self.engineid = engineid
class EngineBaseTimer:
"""
Abstract class for ClusterShell's engine timer. Such a timer
requires a relative fire time (delay) in seconds (as float), and
supports an optional repeating interval in seconds (as float too).
See EngineTimer for more information about ClusterShell timers.
"""
def __init__(self, fire_delay, interval=-1.0, autoclose=False):
"""
Create a base timer.
"""
self.fire_delay = fire_delay
self.interval = interval
self.autoclose = autoclose
self._engine = None
self._timercase = None
def _set_engine(self, engine):
"""
Bind to engine, called by Engine.
"""
if self._engine:
# A timer can be registered to only one engine at a time.
raise EngineIllegalOperationError("Already bound to engine.")
self._engine = engine
def invalidate(self):
"""
Invalidates a timer object, stopping it from ever firing again.
"""
if self._engine:
self._engine.timerq.invalidate(self)
self._engine = None
def is_valid(self):
"""
Returns a boolean value that indicates whether an EngineTimer
object is valid and able to fire.
"""
return self._engine != None
def set_nextfire(self, fire_delay, interval=-1):
"""
Set the next firing delay in seconds for an EngineTimer object.
The optional paramater `interval' sets the firing interval
of the timer. If not specified, the timer fires once and then
is automatically invalidated.
Time values are expressed in second using floating point
values. Precision is implementation (and system) dependent.
It is safe to call this method from the task owning this
timer object, in any event handlers, anywhere.
However, resetting a timer's next firing time may be a
relatively expensive operation. It is more efficient to let
timers autorepeat or to use this method from the timer's own
event handler callback (ie. from its ev_timer).
"""
if not self.is_valid():
raise EngineIllegalOperationError("Operation on invalid timer.")
self.fire_delay = fire_delay
self.interval = interval
self._engine.timerq.reschedule(self)
def _fire(self):
raise NotImplementedError("Derived classes must implement.")
class EngineTimer(EngineBaseTimer):
"""
Concrete class EngineTimer
An EngineTimer object represents a timer bound to an engine that
fires at a preset time in the future. Timers can fire either only
once or repeatedly at fixed time intervals. Repeating timers can
also have their next firing time manually adjusted.
A timer is not a real-time mechanism; it fires when the task's
underlying engine to which the timer has been added is running and
able to check if the timer's firing time has passed.
"""
def __init__(self, fire_delay, interval, autoclose, handler):
EngineBaseTimer.__init__(self, fire_delay, interval, autoclose)
self.eh = handler
assert self.eh != None, "An event handler is needed for timer."
def _fire(self):
self.eh.ev_timer(self)
class _EngineTimerQ:
class _EngineTimerCase:
"""
Helper class that allows comparisons of fire times, to be easily used
in an heapq.
"""
def __init__(self, client):
self.client = client
self.client._timercase = self
# arm timer (first time)
assert self.client.fire_delay > 0
self.fire_date = self.client.fire_delay + time.time()
def __cmp__(self, other):
return cmp(self.fire_date, other.fire_date)
def arm(self, client):
assert client != None
self.client = client
self.client._timercase = self
# setup next firing date
time_current = time.time()
if self.client.fire_delay > 0:
self.fire_date = self.client.fire_delay + time_current
else:
interval = float(self.client.interval)
assert interval > 0
self.fire_date += interval
# If the firing time is delayed so far that it passes one
# or more of the scheduled firing times, reschedule the
# timer for the next scheduled firing time in the future.
while self.fire_date < time_current:
self.fire_date += interval
def disarm(self):
client = self.client
client._timercase = None
self.client = None
return client
def armed(self):
return self.client != None
def __init__(self, engine):
"""
Initializer.
"""
self._engine = engine
self.timers = []
self.armed_count = 0
def __len__(self):
"""
Return the number of active timers.
"""
return self.armed_count
def schedule(self, client):
"""
Insert and arm a client's timer.
"""
# arm only if fire is set
if client.fire_delay > 0:
heapq.heappush(self.timers, _EngineTimerQ._EngineTimerCase(client))
self.armed_count += 1
if not client.autoclose:
self._engine.evlooprefcnt += 1
def reschedule(self, client):
"""
Re-insert client's timer.
"""
if client._timercase:
self.invalidate(client)
self._dequeue_disarmed()
self.schedule(client)
def invalidate(self, client):
"""
Invalidate client's timer. Current implementation doesn't really remove
the timer, but simply flags it as disarmed.
"""
if not client._timercase:
# if timer is being fire, invalidate its values
client.fire_delay = 0
client.interval = 0
return
if self.armed_count <= 0:
raise ValueError, "Engine client timer not found in timer queue"
client._timercase.disarm()
self.armed_count -= 1
if not client.autoclose:
self._engine.evlooprefcnt -= 1
def _dequeue_disarmed(self):
"""
Dequeue disarmed timers (sort of garbage collection).
"""
while len(self.timers) > 0 and not self.timers[0].armed():
heapq.heappop(self.timers)
def fire(self):
"""
Remove the smallest timer from the queue and fire its associated client.
Raise IndexError if the queue is empty.
"""
self._dequeue_disarmed()
timercase = heapq.heappop(self.timers)
client = timercase.disarm()
client.fire_delay = 0
client._fire()
if client.fire_delay > 0 or client.interval > 0:
timercase.arm(client)
heapq.heappush(self.timers, timercase)
else:
self.armed_count -= 1
if not client.autoclose:
self._engine.evlooprefcnt -= 1
def nextfire_delay(self):
"""
Return next timer fire delay (relative time).
"""
self._dequeue_disarmed()
if len(self.timers) > 0:
return max(0., self.timers[0].fire_date - time.time())
return -1
def expired(self):
"""
Has a timer expired?
"""
self._dequeue_disarmed()
return len(self.timers) > 0 and \
(self.timers[0].fire_date - time.time()) <= 1e-2
def clear(self):
"""
Stop and clear all timers.
"""
for timer in self.timers:
if timer.armed():
timer.client.invalidate()
self.timers = []
self.armed_count = 0
class Engine:
"""
Interface for ClusterShell engine. Subclasses have to implement a runloop
listening for client events.
"""
# Engine client I/O event interest bits
E_READ = 0x1
E_ERROR = 0x2
E_WRITE = 0x4
E_ANY = E_READ | E_ERROR | E_WRITE
identifier = "(none)"
def __init__(self, info):
"""
Initialize base class.
"""
# take a reference on info dict
self.info = info
# and update engine id
self.info['engine'] = self.identifier
# keep track of all clients
self._clients = set()
self._ports = set()
# keep track of the number of registered clients (delayable only)
self.reg_clients = 0
# keep track of registered file descriptors in a dict where keys
# are fileno and values are clients
self.reg_clifds = {}
# Current loop iteration counter. It is the number of performed engine
# loops in order to keep track of client registration epoch, so we can
# safely process FDs by chunk and re-use FDs (see Engine._fd2client).
self._current_loopcnt = 0
# Current client being processed
self._current_client = None
# timer queue to handle both timers and clients timeout
self.timerq = _EngineTimerQ(self)
# reference count to the event loop (must include registered
# clients and timers configured WITHOUT autoclose)
self.evlooprefcnt = 0
# running state
self.running = False
# runloop-has-exited flag
self._exited = False
def clients(self):
"""
Get a copy of clients set.
"""
return self._clients.copy()
def ports(self):
"""
Get a copy of ports set.
"""
return self._ports.copy()
def _fd2client(self, fd):
client, fdev = self.reg_clifds.get(fd, (None, None))
if client:
if client._reg_epoch < self._current_loopcnt:
return client, fdev
else:
self._debug("ENGINE _fd2client: ignoring just re-used FD %d" \
% fd)
return (None, None)
def add(self, client):
"""
Add a client to engine. Subclasses that override this method
should call base class method.
"""
# bind to engine
client._set_engine(self)
if client.delayable:
# add to regular client set
self._clients.add(client)
else:
# add to port set (non-delayable)
self._ports.add(client)
if self.running:
# in-fly add if running
if not client.delayable:
self.register(client)
elif self.info["fanout"] > self.reg_clients:
self.register(client._start())
def _remove(self, client, abort, did_timeout=False, force=False):
"""
Remove a client from engine (subroutine).
"""
# be careful to also remove ports when engine has not started yet
if client.registered or not client.delayable:
if client.registered:
self.unregister(client)
# care should be taken to ensure correct closing flags
client._close(abort=abort, flush=not force, timeout=did_timeout)
def remove(self, client, abort=False, did_timeout=False):
"""
Remove a client from engine. Subclasses that override this
method should call base class method.
"""
self._debug("REMOVE %s" % client)
if client.delayable:
self._clients.remove(client)
else:
self._ports.remove(client)
self._remove(client, abort, did_timeout)
self.start_all()
def clear(self, did_timeout=False, clear_ports=False):
"""
Remove all clients. Subclasses that override this method should
call base class method.
"""
all_clients = [self._clients]
if clear_ports:
all_clients.append(self._ports)
for clients in all_clients:
while len(clients) > 0:
client = clients.pop()
self._remove(client, True, did_timeout, force=True)
def register(self, client):
"""
Register an engine client. Subclasses that override this method
should call base class method.
"""
assert client in self._clients or client in self._ports
assert not client.registered
efd = client.fd_error
rfd = client.fd_reader
wfd = client.fd_writer
assert rfd is not None or wfd is not None
self._debug("REG %s(e%s,r%s,w%s)(autoclose=%s)" % \
(client.__class__.__name__, efd, rfd, wfd,
client.autoclose))
client._events = 0
client.registered = True
client._reg_epoch = self._current_loopcnt
if client.delayable:
self.reg_clients += 1
if client.autoclose:
refcnt_inc = 0
else:
refcnt_inc = 1
if efd != None:
self.reg_clifds[efd] = client, Engine.E_ERROR
client._events |= Engine.E_ERROR
self.evlooprefcnt += refcnt_inc
self._register_specific(efd, Engine.E_ERROR)
if rfd != None:
self.reg_clifds[rfd] = client, Engine.E_READ
client._events |= Engine.E_READ
self.evlooprefcnt += refcnt_inc
self._register_specific(rfd, Engine.E_READ)
if wfd != None:
self.reg_clifds[wfd] = client, Engine.E_WRITE
client._events |= Engine.E_WRITE
self.evlooprefcnt += refcnt_inc
self._register_specific(wfd, Engine.E_WRITE)
client._new_events = client._events
# start timeout timer
self.timerq.schedule(client)
def unregister_writer(self, client):
self._debug("UNREG WRITER r%s,w%s" % (client.reader_fileno(), \
client.writer_fileno()))
if client.autoclose:
refcnt_inc = 0
else:
refcnt_inc = 1
wfd = client.fd_writer
if wfd != None:
self._unregister_specific(wfd, client._events & Engine.E_WRITE)
client._events &= ~Engine.E_WRITE
del self.reg_clifds[wfd]
self.evlooprefcnt -= refcnt_inc
def unregister(self, client):
"""
Unregister a client. Subclasses that override this method should
call base class method.
"""
# sanity check
assert client.registered
self._debug("UNREG %s (r%s,e%s,w%s)" % (client.__class__.__name__,
client.reader_fileno(), client.error_fileno(),
client.writer_fileno()))
# remove timeout timer
self.timerq.invalidate(client)
if client.autoclose:
refcnt_inc = 0
else:
refcnt_inc = 1
# clear interest events
efd = client.fd_error
if efd is not None:
self._unregister_specific(efd, client._events & Engine.E_ERROR)
client._events &= ~Engine.E_ERROR
del self.reg_clifds[efd]
self.evlooprefcnt -= refcnt_inc
rfd = client.fd_reader
if rfd is not None:
self._unregister_specific(rfd, client._events & Engine.E_READ)
client._events &= ~Engine.E_READ
del self.reg_clifds[rfd]
self.evlooprefcnt -= refcnt_inc
wfd = client.fd_writer
if wfd is not None:
self._unregister_specific(wfd, client._events & Engine.E_WRITE)
client._events &= ~Engine.E_WRITE
del self.reg_clifds[wfd]
self.evlooprefcnt -= refcnt_inc
client._new_events = 0
client.registered = False
if client.delayable:
self.reg_clients -= 1
def modify(self, client, setmask, clearmask):
"""
Modify the next loop interest events bitset for a client.
"""
self._debug("MODEV set:0x%x clear:0x%x %s" % (setmask, clearmask,
client))
client._new_events &= ~clearmask
client._new_events |= setmask
if self._current_client is not client:
# modifying a non processing client, apply new_events now
self.set_events(client, client._new_events)
def _register_specific(self, fd, event):
"""Engine-specific register fd for event method."""
raise NotImplementedError("Derived classes must implement.")
def _unregister_specific(self, fd, ev_is_set):
"""Engine-specific unregister fd method."""
raise NotImplementedError("Derived classes must implement.")
def _modify_specific(self, fd, event, setvalue):
"""Engine-specific modify fd for event method."""
raise NotImplementedError("Derived classes must implement.")
def set_events(self, client, new_events):
"""
Set the active interest events bitset for a client.
"""
self._debug("SETEV new_events:0x%x events:0x%x %s" % (new_events,
client._events, client))
if not client.registered:
logging.getLogger(__name__).debug( \
"set_events: client %s not registered" % self)
return
chgbits = new_events ^ client._events
if chgbits == 0:
return
# configure interest events as appropriate
efd = client.fd_error
if efd is not None:
if chgbits & Engine.E_ERROR:
status = new_events & Engine.E_ERROR
self._modify_specific(efd, Engine.E_ERROR, status)
if status:
client._events |= Engine.E_ERROR
else:
client._events &= ~Engine.E_ERROR
rfd = client.fd_reader
if rfd is not None:
if chgbits & Engine.E_READ:
status = new_events & Engine.E_READ
self._modify_specific(rfd, Engine.E_READ, status)
if status:
client._events |= Engine.E_READ
else:
client._events &= ~Engine.E_READ
wfd = client.fd_writer
if wfd is not None:
if chgbits & Engine.E_WRITE:
status = new_events & Engine.E_WRITE
self._modify_specific(wfd, Engine.E_WRITE, status)
if status:
client._events |= Engine.E_WRITE
else:
client._events &= ~Engine.E_WRITE
client._new_events = client._events
def set_reading(self, client):
"""
Set client reading state.
"""
# listen for readable events
self.modify(client, Engine.E_READ, 0)
def set_reading_error(self, client):
"""
Set client reading error state.
"""
# listen for readable events
self.modify(client, Engine.E_ERROR, 0)
def set_writing(self, client):
"""
Set client writing state.
"""
# listen for writable events
self.modify(client, Engine.E_WRITE, 0)
def add_timer(self, timer):
"""
Add engine timer.
"""
timer._set_engine(self)
self.timerq.schedule(timer)
def remove_timer(self, timer):
"""
Remove engine timer.
"""
self.timerq.invalidate(timer)
def fire_timers(self):
"""
Fire expired timers for processing.
"""
while self.timerq.expired():
self.timerq.fire()
def start_ports(self):
"""
Start and register all port clients.
"""
# Ports are special, non-delayable engine clients
for port in self._ports:
if not port.registered:
self._debug("START PORT %s" % port)
self.register(port)
def start_all(self):
"""
Start and register all other possible clients, in respect of task fanout.
"""
# Get current fanout value
fanout = self.info["fanout"]
assert fanout > 0
if fanout <= self.reg_clients:
return
# Register regular engine clients within the fanout limit
for client in self._clients:
if not client.registered:
self._debug("START CLIENT %s" % client.__class__.__name__)
self.register(client._start())
if fanout <= self.reg_clients:
break
def run(self, timeout):
"""
Run engine in calling thread.
"""
# change to running state
if self.running:
raise EngineAlreadyRunningError()
self.running = True
# start port clients
self.start_ports()
# peek in ports for early pending messages
self.snoop_ports()
# start all other clients
self.start_all()
# note: try-except-finally not supported before python 2.5
try:
try:
self.runloop(timeout)
except Exception, e:
# any exceptions invalidate clients
self.clear(isinstance(e, EngineTimeoutException))
raise
finally:
# cleanup
self.timerq.clear()
self.running = False
def snoop_ports(self):
"""
Peek in ports for possible early pending messages.
This method simply tries to read port pipes in non-
blocking mode.
"""
# make a copy so that early messages on installed ports may
# lead to new ports
ports = self._ports.copy()
for port in ports:
try:
port._handle_read()
except (IOError, OSError), (err, strerr):
if err == errno.EAGAIN or err == errno.EWOULDBLOCK:
# no pending message
return
# raise any other error
raise
def runloop(self, timeout):
"""
Engine specific run loop. Derived classes must implement.
"""
raise NotImplementedError("Derived classes must implement.")
def abort(self, kill):
"""
Abort runloop.
"""
if self.running:
raise EngineAbortException(kill)
self.clear(clear_ports=kill)
def exited(self):
"""
Returns True if the engine has exited the runloop once.
"""
return not self.running and self._exited
def _debug(self, s):
# library engine debugging hook
#import sys
#print >>sys.stderr, s
pass
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