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
# Global lock for creating global IOLoop instance
_instance_lock = threading.Lock()
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"):
with IOLoop._instance_lock:
if not hasattr(IOLoop, "_instance"):
# New instance after double check
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).
Many applications will only use a single IOLoop that runs for the
entire lifetime of the process. In that case closing the IOLoop
is not necessary since everything will be cleaned up when the
process exits. `IOLoop.close` is provided mainly for scenarios
such as unit tests, which create and destroy a large number of
IOLoops.
An IOLoop must be completely stopped before it can be closed. This
means that `IOLoop.stop()` must be called *and* `IOLoop.start()` must
be allowed to return before attempting to call `IOLoop.close()`.
Therefore the call to `close` will usually appear just after
the call to `start` rather than near the call to `stop`.
"""
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:
poll_timeout = 3600.0
# 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 as e:
# 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) as e:
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.
Note that even after `stop` has been called, the IOLoop is not
completely stopped until `IOLoop.start` has also returned.
"""
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.
Note that it is not safe to call `add_timeout` from other threads.
Instead, you must use `add_callback` to transfer control to the
IOLoop's thread, and then call `add_timeout` from there.
"""
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 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).
Many applications will only use a single IOLoop that runs for the
entire lifetime of the process. In that case closing the IOLoop
is not necessary since everything will be cleaned up when the
process exits. `IOLoop.close` is provided mainly for scenarios
such as unit tests, which create and destroy a large number of
IOLoops.
An IOLoop must be completely stopped before it can be closed. This
means that `IOLoop.stop()` must be called *and* `IOLoop.start()` must
be allowed to return before attempting to call `IOLoop.close()`.
Therefore the call to `close` will usually appear just after
the call to `start` rather than near the call to `stop`.
"""
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:
poll_timeout = 3600.0
# 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 as e:
# 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) as e:
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.
Note that even after `stop` has been called, the IOLoop is not
completely stopped until `IOLoop.start` has also returned.
"""
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.
Note that it is not safe to call `add_timeout` from other threads.
Instead, you must use `add_callback` to transfer control to the
IOLoop's thread, and then call `add_timeout` from there.
"""
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)