/usr/share/pyshared/zmq/eventloop/ioloop.py is in python-zmq 2.1.11-1.
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# Copyright 2009 Facebook
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""An I/O event loop for non-blocking sockets.
Typical applications will use a single `IOLoop` object, in the
`IOLoop.instance` singleton. The `IOLoop.start` method should usually
be called at the end of the ``main()`` function. Atypical applications may
use more than one `IOLoop`, such as one `IOLoop` per thread, or per `unittest`
case.
In addition to I/O events, the `IOLoop` can also schedule time-based events.
`IOLoop.add_timeout` is a non-blocking alternative to `time.sleep`.
"""
from __future__ import with_statement
import datetime
import errno
import heapq
import os
import sys
import logging
import threading
import time
import traceback
try:
import thread
except ImportError:
# py3k removed thread
thread_get_ident = lambda : threading.current_thread().ident
else:
thread_get_ident = thread.get_ident
from zmq.eventloop import stack_context
from zmq.utils.strtypes import b
try:
import signal
except ImportError:
signal = None
from zmq.eventloop.platform.auto import set_close_exec, Waker
from zmq import (
Poller,
POLLIN, POLLOUT, POLLERR,
ZMQError, ETERM,
)
if sys.version_info[0] >= 3:
# all ints are long in py3k
long = int
class IOLoop(object):
"""A level-triggered I/O loop.
We use the zmq Poller for polling events.
Example usage for a simple TCP server::
import errno
import functools
import ioloop
import socket
def connection_ready(sock, fd, events):
while True:
try:
connection, address = sock.accept()
except socket.error, e:
if e.args[0] not in (errno.EWOULDBLOCK, errno.EAGAIN):
raise
return
connection.setblocking(0)
handle_connection(connection, address)
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.setblocking(0)
sock.bind(("", port))
sock.listen(128)
io_loop = ioloop.IOLoop.instance()
callback = functools.partial(connection_ready, sock)
io_loop.add_handler(sock.fileno(), callback, io_loop.READ)
io_loop.start()
"""
# Constants from the epoll module
_EPOLLIN = 0x001
_EPOLLPRI = 0x002
_EPOLLOUT = 0x004
_EPOLLERR = 0x008
_EPOLLHUP = 0x010
_EPOLLRDHUP = 0x2000
_EPOLLONESHOT = (1 << 30)
_EPOLLET = (1 << 31)
# Our events map exactly to the epoll events
NONE = 0
READ = _EPOLLIN
WRITE = _EPOLLOUT
ERROR = _EPOLLERR | _EPOLLHUP
def __init__(self, impl=None):
self._impl = impl or _poll()
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._running = False
self._stopped = False
self._thread_ident = None
self._blocking_signal_threshold = None
# Create a pipe that we send bogus data to when we want to wake
# the I/O loop when it is idle
self._waker = Waker()
self.add_handler(self._waker.fileno(),
lambda fd, events: self._waker.consume(),
self.READ)
@staticmethod
def instance():
"""Returns a global IOLoop instance.
Most single-threaded applications have a single, global IOLoop.
Use this method instead of passing around IOLoop instances
throughout your code.
A common pattern for classes that depend on IOLoops is to use
a default argument to enable programs with multiple IOLoops
but not require the argument for simpler applications::
class MyClass(object):
def __init__(self, io_loop=None):
self.io_loop = io_loop or IOLoop.instance()
"""
if not hasattr(IOLoop, "_instance"):
IOLoop._instance = IOLoop()
return IOLoop._instance
@staticmethod
def initialized():
"""Returns true if the singleton instance has been created."""
return hasattr(IOLoop, "_instance")
def install(self):
"""Installs this IOloop object as the singleton instance.
This is normally not necessary as `instance()` will create
an IOLoop on demand, but you may want to call `install` to use
a custom subclass of IOLoop.
"""
assert not IOLoop.initialized()
IOLoop._instance = self
def close(self, all_fds=False):
"""Closes the IOLoop, freeing any resources used.
If ``all_fds`` is true, all file descriptors registered on the
IOLoop will be closed (not just the ones created by the IOLoop itself.
"""
self.remove_handler(self._waker.fileno())
if all_fds:
for fd in self._handlers.keys()[:]:
try:
if hasattr(fd, 'close'):
fd.close()
else:
os.close(fd)
except Exception:
logging.debug("error closing fd %s", fd, exc_info=True)
self._waker.close()
self._impl.close()
def add_handler(self, fd, handler, events):
"""Registers the given handler to receive the given events for fd."""
self._handlers[fd] = stack_context.wrap(handler)
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
"""Changes the events we listen for fd."""
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
"""Stop listening for events on fd."""
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except (OSError, IOError):
logging.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
"""Sends a signal if the ioloop is blocked for more than s seconds.
Pass seconds=None to disable. Requires python 2.6 on a unixy
platform.
The action parameter is a python signal handler. Read the
documentation for the python 'signal' module for more information.
If action is None, the process will be killed if it is blocked for
too long.
"""
if not hasattr(signal, "setitimer"):
logging.error("set_blocking_signal_threshold requires a signal module "
"with the setitimer method")
return
self._blocking_signal_threshold = seconds
if seconds is not None:
signal.signal(signal.SIGALRM,
action if action is not None else signal.SIG_DFL)
def set_blocking_log_threshold(self, seconds):
"""Logs a stack trace if the ioloop is blocked for more than s seconds.
Equivalent to set_blocking_signal_threshold(seconds, self.log_stack)
"""
self.set_blocking_signal_threshold(seconds, self.log_stack)
def log_stack(self, signal, frame):
"""Signal handler to log the stack trace of the current thread.
For use with set_blocking_signal_threshold.
"""
logging.warning('IOLoop blocked for %f seconds in\n%s',
self._blocking_signal_threshold,
''.join(traceback.format_stack(frame)))
def start(self):
"""Starts the I/O loop.
The loop will run until one of the I/O handlers calls stop(), which
will make the loop stop after the current event iteration completes.
"""
if self._stopped:
self._stopped = False
return
self._thread_ident = thread_get_ident()
self._running = True
while True:
# Never use an infinite timeout here - it can stall epoll
poll_timeout = 0.2
# Prevent IO event starvation by delaying new callbacks
# to the next iteration of the event loop.
with self._callback_lock:
callbacks = self._callbacks
self._callbacks = []
for callback in callbacks:
self._run_callback(callback)
if self._timeouts:
now = time.time()
while self._timeouts:
if self._timeouts[0].callback is None:
# the timeout was cancelled
heapq.heappop(self._timeouts)
elif self._timeouts[0].deadline <= now:
timeout = heapq.heappop(self._timeouts)
self._run_callback(timeout.callback)
else:
seconds = self._timeouts[0].deadline - now
poll_timeout = min(seconds, poll_timeout)
break
if self._callbacks:
# If any callbacks or timeouts called add_callback,
# we don't want to wait in poll() before we run them.
poll_timeout = 0.0
if not self._running:
break
if self._blocking_signal_threshold is not None:
# clear alarm so it doesn't fire while poll is waiting for
# events.
signal.setitimer(signal.ITIMER_REAL, 0, 0)
try:
event_pairs = self._impl.poll(poll_timeout)
except Exception:
e = sys.exc_info()[1]
# Depending on python version and IOLoop implementation,
# different exception types may be thrown and there are
# two ways EINTR might be signaled:
# * e.errno == errno.EINTR
# * e.args is like (errno.EINTR, 'Interrupted system call')
if (getattr(e, 'errno', None) == errno.EINTR or
(isinstance(getattr(e, 'args', None), tuple) and
len(e.args) == 2 and e.args[0] == errno.EINTR)):
continue
elif getattr(e, 'errno', None) == ETERM:
# This happens when the zmq Context is closed; we should just exit.
self._running = False
self._stopped = True
break
else:
raise
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL,
self._blocking_signal_threshold, 0)
# Pop one fd at a time from the set of pending fds and run
# its handler. Since that handler may perform actions on
# other file descriptors, there may be reentrant calls to
# this IOLoop that update self._events
self._events.update(event_pairs)
while self._events:
fd, events = self._events.popitem()
try:
self._handlers[fd](fd, events)
except (OSError, IOError):
e = sys.exc_info()[1]
if e.args[0] == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
logging.error("Exception in I/O handler for fd %s",
fd, exc_info=True)
except Exception:
logging.error("Exception in I/O handler for fd %s",
fd, exc_info=True)
# reset the stopped flag so another start/stop pair can be issued
self._stopped = False
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL, 0, 0)
def stop(self):
"""Stop the loop after the current event loop iteration is complete.
If the event loop is not currently running, the next call to start()
will return immediately.
To use asynchronous methods from otherwise-synchronous code (such as
unit tests), you can start and stop the event loop like this::
ioloop = IOLoop()
async_method(ioloop=ioloop, callback=ioloop.stop)
ioloop.start()
ioloop.start() will return after async_method has run its callback,
whether that callback was invoked before or after ioloop.start.
"""
self._running = False
self._stopped = True
self._waker.wake()
def running(self):
"""Returns true if this IOLoop is currently running."""
return self._running
def add_timeout(self, deadline, callback):
"""Calls the given callback at the time deadline from the I/O loop.
Returns a handle that may be passed to remove_timeout to cancel.
``deadline`` may be a number denoting a unix timestamp (as returned
by ``time.time()`` or a ``datetime.timedelta`` object for a deadline
relative to the current time.
"""
timeout = _Timeout(deadline, stack_context.wrap(callback))
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, timeout):
"""Cancels a pending timeout.
The argument is a handle as returned by add_timeout.
"""
# Removing from a heap is complicated, so just leave the defunct
# timeout object in the queue (see discussion in
# http://docs.python.org/library/heapq.html).
# If this turns out to be a problem, we could add a garbage
# collection pass whenever there are too many dead timeouts.
timeout.callback = None
def add_callback(self, callback):
"""Calls the given callback on the next I/O loop iteration.
It is safe to call this method from any thread at any time.
Note that this is the *only* method in IOLoop that makes this
guarantee; all other interaction with the IOLoop must be done
from that IOLoop's thread. add_callback() may be used to transfer
control from other threads to the IOLoop's thread.
"""
with self._callback_lock:
list_empty = not self._callbacks
self._callbacks.append(stack_context.wrap(callback))
if list_empty and thread_get_ident() != self._thread_ident:
# If we're in the IOLoop's thread, we know it's not currently
# polling. If we're not, and we added the first callback to an
# empty list, we may need to wake it up (it may wake up on its
# own, but an occasional extra wake is harmless). Waking
# up a polling IOLoop is relatively expensive, so we try to
# avoid it when we can.
self._waker.wake()
def _run_callback(self, callback):
try:
callback()
except Exception:
self.handle_callback_exception(callback)
def handle_callback_exception(self, callback):
"""This method is called whenever a callback run by the IOLoop
throws an exception.
By default simply logs the exception as an error. Subclasses
may override this method to customize reporting of exceptions.
The exception itself is not passed explicitly, but is available
in sys.exc_info.
"""
logging.error("Exception in callback %r", callback, exc_info=True)
class _Timeout(object):
"""An IOLoop timeout, a UNIX timestamp and a callback"""
# Reduce memory overhead when there are lots of pending callbacks
__slots__ = ['deadline', 'callback']
def __init__(self, deadline, callback):
if isinstance(deadline, (int, long, float)):
self.deadline = deadline
elif isinstance(deadline, datetime.timedelta):
self.deadline = time.time() + _Timeout.timedelta_to_seconds(deadline)
else:
raise TypeError("Unsupported deadline %r" % deadline)
self.callback = callback
@staticmethod
def timedelta_to_seconds(td):
"""Equivalent to td.total_seconds() (introduced in python 2.7)."""
return (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10**6) / float(10**6)
# Comparison methods to sort by deadline, with object id as a tiebreaker
# to guarantee a consistent ordering. The heapq module uses __le__
# in python2.5, and __lt__ in 2.6+ (sort() and most other comparisons
# use __lt__).
def __lt__(self, other):
return ((self.deadline, id(self)) <
(other.deadline, id(other)))
def __le__(self, other):
return ((self.deadline, id(self)) <=
(other.deadline, id(other)))
class PeriodicCallback(object):
"""Schedules the given callback to be called periodically.
The callback is called every callback_time milliseconds.
`start` must be called after the PeriodicCallback is created.
"""
def __init__(self, callback, callback_time, io_loop=None):
self.callback = callback
self.callback_time = callback_time
self.io_loop = io_loop or IOLoop.instance()
self._running = False
self._timeout = None
def start(self):
"""Starts the timer."""
self._running = True
self._next_timeout = time.time()
self._schedule_next()
def stop(self):
"""Stops the timer."""
self._running = False
if self._timeout is not None:
self.io_loop.remove_timeout(self._timeout)
self._timeout = None
def _run(self):
if not self._running: return
try:
self.callback()
except Exception:
logging.error("Error in periodic callback", exc_info=True)
self._schedule_next()
def _schedule_next(self):
if self._running:
current_time = time.time()
while self._next_timeout <= current_time:
self._next_timeout += self.callback_time / 1000.0
self._timeout = self.io_loop.add_timeout(self._next_timeout, self._run)
class DelayedCallback(PeriodicCallback):
"""Schedules the given callback to be called once.
The callback is called once, after callback_time milliseconds.
`start` must be called after the DelayedCallback is created.
The timeout is calculated from when `start` is called.
"""
def start(self):
"""Starts the timer."""
self._running = True
self._firstrun = True
self._next_timeout = time.time() + self.callback_time / 1000.0
self.io_loop.add_timeout(self._next_timeout, self._run)
def _run(self):
if not self._running: return
self._running = False
try:
self.callback()
except Exception:
logging.error("Error in delayed callback", exc_info=True)
class ZMQPoller(object):
"""A poller that can be used in the tornado IOLoop.
This simply wraps a regular zmq.Poller, scaling the timeout
by 1000, so that it is in seconds rather than milliseconds.
"""
def __init__(self):
self._poller = Poller()
@staticmethod
def _map_events(events):
"""translate IOLoop.READ/WRITE/ERROR event masks into zmq.POLLIN/OUT/ERR"""
z_events = 0
if events & IOLoop.READ:
z_events |= POLLIN
if events & IOLoop.WRITE:
z_events |= POLLOUT
if events & IOLoop.ERROR:
z_events |= POLLERR
return z_events
@staticmethod
def _remap_events(z_events):
"""translate zmq.POLLIN/OUT/ERR event masks into IOLoop.READ/WRITE/ERROR"""
events = 0
if z_events & POLLIN:
events |= IOLoop.READ
if z_events & POLLOUT:
events |= IOLoop.WRITE
if z_events & POLLERR:
events |= IOLoop.ERROR
return events
def register(self, fd, events):
return self._poller.register(fd, self._map_events(events))
def modify(self, fd, events):
return self._poller.modify(fd, self._map_events(events))
def unregister(self, fd):
return self._poller.unregister(fd)
def poll(self, timeout):
"""poll in seconds rather than milliseconds.
Event masks will be IOLoop.READ/WRITE/ERROR
"""
z_events = self._poller.poll(1000*timeout)
return [ (fd,self._remap_events(evt)) for (fd,evt) in z_events ]
def close(self):
pass
_poll = ZMQPoller
def install():
"""set the tornado IOLoop instance with the pyzmq IOLoop.
After calling this function, tornado's IOLoop.instance() and pyzmq's
IOLoop.instance() will return the same object.
An assertion error will be raised if tornado's IOLoop has been initialized
prior to calling this function.
"""
from tornado import ioloop
# check if tornado's IOLoop is already initialized to something other
# than the pyzmq IOLoop instance:
assert (not ioloop.IOLoop.initialized()) or \
ioloop.IOLoop.instance() is IOLoop.instance(), "tornado IOLoop already initialized"
# register as instance with tornado.ioloop
ioloop.IOLoop._instance = IOLoop.instance()
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