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)
class IOLoop(object):
"""A level-triggered I/O loop.
We use epoll (Linux) or kqueue (BSD and Mac OS X; requires python
2.6+) if they are available, or else we fall back on select(). If
you are implementing a system that needs to handle thousands of
simultaneous connections, you should use a system that supports either
epoll or queue.
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.errno 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:
os.close(fd)
except Exception:
logging.debug("error closing fd %d", 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:
milliseconds = self._timeouts[0].deadline - now
poll_timeout = min(milliseconds, 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:
# 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
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 (KeyboardInterrupt, SystemExit):
raise
except (OSError, IOError, EnvironmentError), e:
if e.errno == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
logging.error("Exception in I/O handler for fd %d",
fd, exc_info=True)
except Exception:
logging.error("Exception in I/O handler for fd %d",
fd, exc_info=True)