class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None):
super(PollIOLoop, self).initialize()
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = False
self._thread_ident = None
self._blocking_signal_threshold = None
self._timeout_counter = itertools.count()
# 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)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in self._handlers.values():
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
def add_handler(self, fd, handler, events):
fd, obj = self.split_fd(fd)
self._handlers[fd] = (obj, stack_context.wrap(handler))
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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 start(self):
if self._running:
raise RuntimeError("IOLoop is already running")
self._setup_logging()
if self._stopped:
self._stopped = False
return
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident()
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# a signal may arrive at the beginning of select/poll/etc
# before it goes into its interruptible sleep, so the signal
# will be consumed without waking the select. The solution is
# for the (C, synchronous) signal handler to write to a pipe,
# which will then be seen by select.
#
# In python's signal handling semantics, this only matters on the
# main thread (fortunately, set_wakeup_fd only works on the main
# thread and will raise a ValueError otherwise).
#
# If someone has already set a wakeup fd, we don't want to
# disturb it. This is an issue for twisted, which does its
# SIGCHILD processing in response to its own wakeup fd being
# written to. As long as the wakeup fd is registered on the IOLoop,
# the loop will still wake up and everything should work.
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# the python process on windows.
try:
old_wakeup_fd = signal.set_wakeup_fd(self._waker.write_fileno())
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy,
# but there's no clean get_wakeup_fd and in real use the
# IOLoop is just started once at the beginning.
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError: # non-main thread
pass
try:
while True:
# 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 = []
# Add any timeouts that have come due to the callback list.
# Do not run anything until we have determined which ones
# are ready, so timeouts that call add_timeout cannot
# schedule anything in this iteration.
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
# the timeout was cancelled
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
timeout = heapq.heappop(self._timeouts)
callbacks.append(timeout.callback)
del timeout
else:
break
if (self._cancellations > 512
and self._cancellations > (len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's
# more than half cancellations.
self._cancellations = 0
self._timeouts = [x for x in self._timeouts
if x.callback is not None]
heapq.heapify(self._timeouts)
for callback in callbacks:
self._run_callback(callback)
# Closures may be holding on to a lot of memory, so allow
# them to be freed before we go into our poll wait.
callbacks = callback = None
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
elif self._timeouts:
# If there are any timeouts, schedule the first one.
# Use self.time() instead of 'now' to account for time
# spent running callbacks.
poll_timeout = self._timeouts[0].deadline - self.time()
poll_timeout = max(0, min(poll_timeout, _POLL_TIMEOUT))
else:
# No timeouts and no callbacks, so use the default.
poll_timeout = _POLL_TIMEOUT
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 errno_from_exception(e) == 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:
fd_obj, handler_func = self._handlers[fd]
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
self.handle_callback_exception(self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
# 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)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def call_at(self, deadline, callback, *args, **kwargs):
timeout = _Timeout(
deadline,
functools.partial(stack_context.wrap(callback), *args, **kwargs),
self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
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 add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
# if the signal is handled on another thread, we can add
# it normally (modulo the NullContext)
self.add_callback(callback, *args, **kwargs)
else:
# If we're on the IOLoop's thread, we cannot use
# the regular add_callback because it may deadlock on
# _callback_lock. Blindly insert into self._callbacks.
# This is safe because the GIL makes list.append atomic.
# One subtlety is that if the signal interrupted the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks,
# but either way will work.
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None, **kwargs):
super(PollIOLoop, self).initialize(**kwargs)
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = collections.deque()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = False
self._thread_ident = None
self._pid = os.getpid()
self._blocking_signal_threshold = None
self._timeout_counter = itertools.count()
# 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)
@classmethod
def configurable_base(cls):
return PollIOLoop
@classmethod
def configurable_default(cls):
if hasattr(select, "epoll"):
from tornado.platform.epoll import EPollIOLoop
return EPollIOLoop
if hasattr(select, "kqueue"):
# Python 2.6+ on BSD or Mac
from tornado.platform.kqueue import KQueueIOLoop
return KQueueIOLoop
from tornado.platform.select import SelectIOLoop
return SelectIOLoop
def close(self, all_fds=False):
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in list(self._handlers.values()):
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
if hasattr(self, '_executor'):
self._executor.shutdown()
def add_handler(self, fd, handler, events):
fd, obj = self.split_fd(fd)
self._handlers[fd] = (obj, stack_context.wrap(handler))
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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 start(self):
if self._running:
raise RuntimeError("IOLoop is already running")
if os.getpid() != self._pid:
raise RuntimeError("Cannot share PollIOLoops across processes")
self._setup_logging()
if self._stopped:
self._stopped = False
return
old_current = IOLoop.current(instance=False)
if old_current is not self:
self.make_current()
self._thread_ident = thread.get_ident()
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# a signal may arrive at the beginning of select/poll/etc
# before it goes into its interruptible sleep, so the signal
# will be consumed without waking the select. The solution is
# for the (C, synchronous) signal handler to write to a pipe,
# which will then be seen by select.
#
# In python's signal handling semantics, this only matters on the
# main thread (fortunately, set_wakeup_fd only works on the main
# thread and will raise a ValueError otherwise).
#
# If someone has already set a wakeup fd, we don't want to
# disturb it. This is an issue for twisted, which does its
# SIGCHLD processing in response to its own wakeup fd being
# written to. As long as the wakeup fd is registered on the IOLoop,
# the loop will still wake up and everything should work.
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# the python process on windows.
try:
old_wakeup_fd = signal.set_wakeup_fd(
self._waker.write_fileno())
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy,
# but there's no clean get_wakeup_fd and in real use the
# IOLoop is just started once at the beginning.
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError:
# Non-main thread, or the previous value of wakeup_fd
# is no longer valid.
old_wakeup_fd = None
try:
while True:
# Prevent IO event starvation by delaying new callbacks
# to the next iteration of the event loop.
ncallbacks = len(self._callbacks)
# Add any timeouts that have come due to the callback list.
# Do not run anything until we have determined which ones
# are ready, so timeouts that call add_timeout cannot
# schedule anything in this iteration.
due_timeouts = []
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
# The timeout was cancelled. Note that the
# cancellation check is repeated below for timeouts
# that are cancelled by another timeout or callback.
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
due_timeouts.append(heapq.heappop(self._timeouts))
else:
break
if (self._cancellations > 512 and self._cancellations >
(len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's
# more than half cancellations.
self._cancellations = 0
self._timeouts = [
x for x in self._timeouts if x.callback is not None
]
heapq.heapify(self._timeouts)
for i in range(ncallbacks):
self._run_callback(self._callbacks.popleft())
for timeout in due_timeouts:
if timeout.callback is not None:
self._run_callback(timeout.callback)
# Closures may be holding on to a lot of memory, so allow
# them to be freed before we go into our poll wait.
due_timeouts = timeout = None
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
elif self._timeouts:
# If there are any timeouts, schedule the first one.
# Use self.time() instead of 'now' to account for time
# spent running callbacks.
poll_timeout = self._timeouts[0].deadline - self.time()
poll_timeout = max(0, min(poll_timeout, _POLL_TIMEOUT))
else:
# No timeouts and no callbacks, so use the default.
poll_timeout = _POLL_TIMEOUT
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 errno_from_exception(e) == 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 modify self._events
self._events.update(event_pairs)
while self._events:
fd, events = self._events.popitem()
try:
fd_obj, handler_func = self._handlers[fd]
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
self.handle_callback_exception(
self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
# 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)
if old_current is None:
IOLoop.clear_current()
elif old_current is not self:
old_current.make_current()
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def call_at(self, deadline, callback, *args, **kwargs):
timeout = _Timeout(
deadline,
functools.partial(stack_context.wrap(callback), *args, **kwargs),
self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
if self._closing:
return
# Blindly insert into self._callbacks. This is safe even
# from signal handlers because deque.append is atomic.
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args, **kwargs))
if thread.get_ident() != self._thread_ident:
# This will write one byte but Waker.consume() reads many
# at once, so it's ok to write even when not strictly
# necessary.
self._waker.wake()
else:
# If we're on the IOLoop's thread, we don't need to wake anyone.
pass
def add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
self.add_callback(callback, *args, **kwargs)
class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None):
super(PollIOLoop, self).initialize()
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._running = False
self._stopped = False
self._closing = 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)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd in self._handlers.keys():
try:
close_method = getattr(fd, 'close', None)
if close_method is not None:
close_method()
else:
os.close(fd)
except Exception:
gen_log.debug("error closing fd %s", fd, exc_info=True)
self._waker.close()
self._impl.close()
def add_handler(self, fd, handler, events):
self._handlers[fd] = stack_context.wrap(handler)
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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 start(self):
if not logging.getLogger().handlers:
# The IOLoop catches and logs exceptions, so it's
# important that log output be visible. However, python's
# default behavior for non-root loggers (prior to python
# 3.2) is to print an unhelpful "no handlers could be
# found" message rather than the actual log entry, so we
# must explicitly configure logging if we've made it this
# far without anything.
logging.basicConfig()
if self._stopped:
self._stopped = False
return
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident()
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# a signal may arrive at the beginning of select/poll/etc
# before it goes into its interruptible sleep, so the signal
# will be consumed without waking the select. The solution is
# for the (C, synchronous) signal handler to write to a pipe,
# which will then be seen by select.
#
# In python's signal handling semantics, this only matters on the
# main thread (fortunately, set_wakeup_fd only works on the main
# thread and will raise a ValueError otherwise).
#
# If someone has already set a wakeup fd, we don't want to
# disturb it. This is an issue for twisted, which does its
# SIGCHILD processing in response to its own wakeup fd being
# written to. As long as the wakeup fd is registered on the IOLoop,
# the loop will still wake up and everything should work.
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# the python process on windows.
try:
old_wakeup_fd = signal.set_wakeup_fd(self._waker.write_fileno())
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy,
# but there's no clean get_wakeup_fd and in real use the
# IOLoop is just started once at the beginning.
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError: # non-main thread
pass
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 = self.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
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:
app_log.error("Exception in I/O handler for fd %s",
fd, exc_info=True)
except Exception:
app_log.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)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def add_timeout(self, deadline, callback):
timeout = _Timeout(deadline, stack_context.wrap(callback), self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
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 add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
# if the signal is handled on another thread, we can add
# it normally (modulo the NullContext)
self.add_callback(callback, *args, **kwargs)
else:
# If we're on the IOLoop's thread, we cannot use
# the regular add_callback because it may deadlock on
# _callback_lock. Blindly insert into self._callbacks.
# This is safe because the GIL makes list.append atomic.
# One subtlety is that if the signal interrupted the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks,
# but either way will work.
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
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 as 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:
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
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 PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None):
super(PollIOLoop, self).initialize()
# 使用的模型，使用的哪一个 select epoll kqueue
# ubuntu系统使用的epoll
self._impl = impl
# 不明白
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
# 设置获取时间的函数
self.time_func = time_func or time.time
# self._handlers[fd] = (obj, stack_context.wrap(handler))
# fd这个时候是一个数字，一般的时候是一个fd的对象
self._handlers = {}
# 保存每一次循环所得到的fd和事件对
self._events = {}
# 所有的callback函数的集合
self._callbacks = []
self._callback_lock = threading.Lock()
# 所有需要延时执行的函数的集合
self._timeouts = []
self._cancellations = 0
self._running = False # IOLoop是不是已经运行了
self._stopped = False # IOLoop是不是已经停止了，为什么有两个
self._closing = 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
# 这个真心不懂，以后研究
self._waker = Waker()
# 初始化的时候添加self._waker的一个读得socket到IOLoop里面
self.add_handler(self._waker.fileno(),
lambda fd, events: self._waker.consume(),
self.READ)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in self._handlers.values():
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
# 添加一个fd（数字）和事件绑定
def add_handler(self, fd, handler, events):
# 添加一个注册事件 fd是文件描述符
fd, obj = self.split_fd(fd) # 通过fd对象，返回数字和fd对象
# 需要监听的fd整数和fd对象与handler的对应
self._handlers[fd] = (obj, stack_context.wrap(handler))
# 注册相关的事件，加入通知
self._impl.register(fd, events | self.ERROR)
# 这里只是更新，没有检查是不是已经存在
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
# 移除事件绑定
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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)
# 初始化的最后一步就是到这个地方了，已经把监听的accept添加进去了，同时添加了一个额外的fd，不知道干嘛的
def start(self):
if self._running:
raise RuntimeError("IOLoop is already running")
self._setup_logging()
if self._stopped:
self._stopped = False
return # 如果两个都是False，好像不知道在做什么
# 保存老的IOLoop._current.instance
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident() # 子线程标记
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# a signal may arrive at the beginning of select/poll/etc
# before it goes into its interruptible sleep, so the signal
# will be consumed without waking the select. The solution is
# for the (C, synchronous) signal handler to write to a pipe,
# which will then be seen by select.
#
# In python's signal handling semantics, this only matters on the
# main thread (fortunately, set_wakeup_fd only works on the main
# thread and will raise a ValueError otherwise).
#
# If someone has already set a wakeup fd, we don't want to
# disturb it. This is an issue for twisted, which does its
# SIGCHILD processing in response to its own wakeup fd being
# written to. As long as the wakeup fd is registered on the IOLoop,
# the loop will still wake up and everything should work.
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# the python process on windows.
try:
old_wakeup_fd = signal.set_wakeup_fd(self._waker.write_fileno())
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy,
# but there's no clean get_wakeup_fd and in real use the
# IOLoop is just started once at the beginning.
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError: # non-main thread
pass
try:
while True: # 这里是循环的精髓部分，单线程和单进程就是在这里循环和阻塞的
poll_timeout = _POLL_TIMEOUT
# 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)
# Closures may be holding on to a lot of memory, so allow
# them to be freed before we go into our poll wait.
callbacks = callback = None
# 有些函数需要延时运行，就是在这里检查的
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
# the timeout was cancelled
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
timeout = heapq.heappop(self._timeouts)
self._run_callback(timeout.callback)
del timeout
else:
seconds = self._timeouts[0].deadline - now
poll_timeout = min(seconds, poll_timeout)
break
if (self._cancellations > 512
and self._cancellations > (len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's
# more than half cancellations.
self._cancellations = 0
self._timeouts = [x for x in self._timeouts
if x.callback is not None]
heapq.heapify(self._timeouts)
# 如果还有回调，那么accept不能阻塞
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:
# 返回值 [(fd, events), (4, 1)] 基本都是数字
# 初始化到这里之后，后面的基本就是如何处理请求进来的连接了，起码一个部分的任务搞定了
event_pairs = self._impl.poll(poll_timeout) # 阻塞在这里
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 errno_from_exception(e) == 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
# 一个连接刚刚进来的时候，event pairs是[(5, 1)] = 此时的事件需要accept
self._events.update(event_pairs)
# 开始处理的地方
while self._events:
fd, events = self._events.popitem()
try:
# 获取socket对应的处理函数
fd_obj, handler_func = self._handlers[fd]
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
self.handle_callback_exception(self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
# 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)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def add_timeout(self, deadline, callback):
timeout = _Timeout(deadline, stack_context.wrap(callback), self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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
self._cancellations += 1
# 有时间就执行： callback(*args, **kwargs)
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
# 给self._callbacks添加回调函数
# 这里把args和kwargs的消息封装到了callback的属性里面了，然后可以直接运行了
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
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 add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
# if the signal is handled on another thread, we can add
# it normally (modulo the NullContext)
self.add_callback(callback, *args, **kwargs)
else:
# If we're on the IOLoop's thread, we cannot use
# the regular add_callback because it may deadlock on
# _callback_lock. Blindly insert into self._callbacks.
# This is safe because the GIL makes list.append atomic.
# One subtlety is that if the signal interrupted the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks,
# but either way will work.
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
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.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 list(self._handlers.keys())[:]:
try:
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
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 PollIOLoop(IOLoop):
def initialize(self, impl, time_func=None, **kwargs):
super(PollIOLoop, self).initialize(**kwargs)
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = False
self._thread_ident = None
self._blocking_signal_threshold = None
self._timeout_counter = itertools.count()
self._waker = Waker()
self.add_handler(self._waker.fileno(),
lambda fd, events: self._waker.consume(),
self.READ)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in self._handlers.values():
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
def add_handler(self, fd, handler, events):
fd, obj = self.split_fd(fd)
self._handlers[fd] = (obj, stack_context.wrap(handler))
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
print("Error deleting fd from IOLoop")
def set_blocking_signal_threshold(self, seconds, action):
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 start(self):
if self._running:
raise RuntimeError("IOLoop is already running")
if self._stopped:
self._stopped = False
return
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident()
self._running = True
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
try:
old_wakeup_fd = signal.set_wakeup_fd(self._waker.write_fileno())
if old_wakeup_fd != -1:
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError:
old_wakeup_fd = None
try:
while True:
with self._callback_lock:
callbacks = self._callbacks
self._callbacks = []
due_timeouts = []
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
due_timeouts.append(heapq.heappop(self._timeouts))
else:
break
if (self._cancellations > 512
and self._cancellations > (len(self._timeouts) >> 1)):
self._cancellations = 0
self._timeouts = [x for x in self._timeouts
if x.callback is not None]
heapq.heapify(self._timeouts)
for callback in callbacks:
self._run_callback(callback)
for timeout in due_timeouts:
if timeout.callback is not None:
self._run_callback(timeout.callback)
callbacks = callback = due_timeouts = timeout = None
if self._callbacks:
poll_timeout = 0.0
elif self._timeouts:
poll_timeout = self._timeouts[0].deadline - self.time()
poll_timeout = max(0, min(poll_timeout, _POLL_TIMEOUT))
else:
poll_timeout = _POLL_TIMEOUT
if not self._running:
break
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL, 0, 0)
try:
event_pairs = self._impl.poll(poll_timeout)
except Exception as e:
if errno_from_exception(e) == errno.EINTR:
continue
else:
raise
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL,
self._blocking_signal_threshold, 0)
self._events.update(event_pairs)
while self._events:
fd, events = self._events.popitem()
try:
fd_obj, handler_func = self._handlers[fd]
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
pass
else:
self.handle_callback_exception(self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
self._stopped = False
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL, 0, 0)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def call_at(self, deadline, callback, *args, **kwargs):
timeout = _Timeout(
deadline,
functools.partial(stack_context.wrap(callback), *args, **kwargs),
self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, timeout):
timeout.callback = None
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
if list_empty and thread.get_ident() != self._thread_ident:
self._waker.wake()
def add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
self.add_callback(callback, *args, **kwargs)
else:
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None):
super(PollIOLoop, self).initialize()
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = 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)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd in self._handlers.keys():
try:
close_method = getattr(fd, 'close', None)
if close_method is not None:
close_method()
else:
os.close(fd)
except Exception:
gen_log.debug("error closing fd %s", fd, exc_info=True)
self._waker.close()
self._impl.close()
# 关键点！！
# 这里应该就是注册到大的事件循环里面的入口了
# 看看地方会调用这个add_handler
def add_handler(self, fd, handler, events):
self._handlers[fd] = stack_context.wrap(handler)
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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) # 采用默认的系统信号处理方法，对于SIGALRM来说，默认是结束掉当前进程
def start(self):
if not logging.getLogger().handlers:
# The IOLoop catches and logs exceptions, so it's
# important that log output be visible. However, python's
# default behavior for non-root loggers (prior to python
# 3.2) is to print an unhelpful "no handlers could be
# found" message rather than the actual log entry, so we
# must explicitly configure logging if we've made it this
# far without anything.
logging.basicConfig()
if self._stopped:
self._stopped = False
return
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident() # 获取当前启动线程的id
self._running = True
# 为什么要在这里设置wakeup_fd这个东东??
# signal.set_wakeup_fd closes a race condition in event loops:
# a signal may arrive at the beginning of select/poll/etc
# before it goes into its interruptible sleep, so the signal
# will be consumed without waking the select. The solution is
# for the (C, synchronous) signal handler to write to a pipe,
# which will then be seen by select.
#
# In python's signal handling semantics, this only matters on the
# main thread (fortunately, set_wakeup_fd only works on the main
# thread and will raise a ValueError otherwise).
#
# If someone has already set a wakeup fd, we don't want to
# disturb it. This is an issue for twisted, which does its
# SIGCHILD processing in response to its own wakeup fd being
# written to. As long as the wakeup fd is registered on the IOLoop,
# the loop will still wake up and everything should work.
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# the python process on windows.
try:
# a '\0' is write to the fd when a signal is received.
old_wakeup_fd = signal.set_wakeup_fd(self._waker.write_fileno()) # 是想在epoll这样的事件轮询里面，捕获到signal进行处理
# TODO 如何响应信号 ??
# epoll这样的事件机制下，信号是如何被处理的？
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy,
# but there's no clean get_wakeup_fd and in real use the
# IOLoop is just started once at the beginning.
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError: # non-main thread
pass
while True:
poll_timeout = _POLL_TIMEOUT
# 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)
# Closures may be holding on to a lot of memory, so allow
# them to be freed before we go into our poll wait.
callbacks = callback = None
# 保持_timeout堆尽量小，减掉没用的timeout事件
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
# the timeout was cancelled
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
timeout = heapq.heappop(self._timeouts)
self._run_callback(timeout.callback)
del timeout
else:
seconds = self._timeouts[0].deadline - now
poll_timeout = min(seconds, poll_timeout)
break
if (self._cancellations > 512
and self._cancellations > (len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's
# more than half cancellations.
self._cancellations = 0
self._timeouts = [x for x in self._timeouts
if x.callback is not None]
heapq.heapify(self._timeouts)
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) # stop sending SIGALRM
# 这里跑的这些event_pairs就是实打实的socket方面的了??
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')
# EINTR means "This call did not succeed because it was interrupted. However, if you try again, it will probably work."
# In other words, EINTR is not a fatal error -- it just means you should retry whatever you were attempting.
# EINTR的错误有很多种情况，比如说，如果在信号来到的情况下，而线程这个时候在跑的话，就会发生OSError，而且errno就是是EINTR，这种情况我们是允许事件轮训再来一次的
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 (OSError, IOError) as e:
if e.args[0] == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
self.handle_callback_exception(self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
# reset the stopped flag so another start/stop pair can be issued 什么是another start/stop pair?
# 把一些状态恢复到运行初期
self._stopped = False
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL, 0, 0) # 去掉这个ITIMER_REAL信号
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def add_timeout(self, deadline, callback):
timeout = _Timeout(deadline, stack_context.wrap(callback), self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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.
# 这样说来，heap就是空间换时间的一个算法
timeout.callback = None
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
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() # 如果当前loop里面没有callbacks，就唤醒一次
def add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
# if the signal is handled on another thread, we can add
# it normally (modulo the NullContext)
self.add_callback(callback, *args, **kwargs)
else:
# If we're on the IOLoop's thread, we cannot use
# the regular add_callback because it may deadlock on
# _callback_lock. Blindly insert into self._callbacks.
# This is safe because the GIL makes list.append atomic.
# One subtlety is that if the signal interrupted the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks,
# but either way will work.
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None):
super(PollIOLoop, self).initialize()
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = 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
# 在 PollIOLoop(IOLoop) 初始化的过程中创建了一个 Waker 对象，
# 将 Waker 对象 fd 的【读】端注册到事件循环中并设定相应的回调函数
# （这样做的好处是当事件循环阻塞而没有响应描述符出现，需要在最大 timeout 时间之前返回，
# 就可以向这个管道发送一个字符）。
# Waker 的使用：
# 一种是在其他线程向 IOLoop 添加 callback 时使用，
# 唤醒 IOLoop 同时会将控制权转移给 IOLoop 线程并完成特定请求。
# 唤醒的方法向管道中写入一个字符'x'。
# 另外，在 IOLoop的stop 函数中会调用self._waker.wake()，通过向管道写入'x'停止事件循环
self._waker = Waker()
self.add_handler(self._waker.fileno(),
lambda fd, events: self._waker.consume(), self.READ)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd in self._handlers.keys():
try:
close_method = getattr(fd, 'close', None)
if close_method is not None:
close_method()
else:
os.close(fd)
except Exception:
gen_log.debug("error closing fd %s", fd, exc_info=True)
self._waker.close()
self._impl.close()
def add_handler(self, fd, handler, events):
#add_handler(self, fd, handler, events)
# HttpServer的Start方法中会调用该方法(待考证)
# add_handler 函数使用了stack_context 提供的 wrap 方法。
# wrap 返回了一个可以直接调用的对象并且保存了传入之前的【堆栈】信息，
# 在执行时可以恢复，这样就保证了函数的异步调用时具有正确的运行环境。
#
self._handlers[fd] = stack_context.wrap(handler)
# self._impl 就是epoll 对象；向epoll中注册、监听socket对象
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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 start(self):
# IOLoop的start方法
# IOLoop 的【核心调度】集中在 start() 方法中，
# IOLoop 实例对象调用 start 后开始 【epoll 事件循环机制】，
# 该方法会一直运行直到 IOLoop 对象调用 stop 函数、当前所有事件循环完成。
# start 方法中主要分三个部分：
# 一个部分是对【超时】的相关处理；
# 一部分是 epoll 事件通知阻塞、接收；
# 一部分是对 epoll 返回I/O事件的处理;
#
# 为防止 IO event starvation（挨饿，哈哈），将回调函数【延迟到下一轮事件循环中执行。
# 超时的处理 heapq 维护一个最小堆，记录每个回调函数的超时时间（deadline）。
# 每次取出 deadline 最早的回调函数，如果callback标志位为 True 并且已经超时，
# 通过 _run_callback 调用函数；如果没有超时需要重新设定 poll_timeout 的值。
# 通过 self._impl.poll(poll_timeout) 进行事件阻塞，
# 当有事件通知或超时时 poll 返回【特定】的 event_pairs。
# epoll 返回通知事件后将新事件加入待处理队列，将就绪事件逐个【弹出】，
# 通过stack_context.wrap(handler)保存的可执行对象调用事件处理。
if not logging.getLogger().handlers:
# The IOLoop catches and logs exceptions, so it's
# important that log output be visible. However, python's
# default behavior for non-root loggers (prior to python
# 3.2) is to print an unhelpful "no handlers could be
# found" message rather than the actual log entry, so we
# must explicitly configure logging(我们必须显式配置日志记录) if we've made it this
# far without anything.
logging.basicConfig()
if self._stopped:
self._stopped = False
return
# 待研究【18-3.6】
# instance 是实例的意思
# 判断是不是有上一次的（或者剩余的IOLoop实例）
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident()
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# a signal may arrive at the beginning of select/poll/etc
# before it goes into its interruptible sleep, so the signal
# will be consumed without waking the select. The solution is
# for the (C, synchronous) signal handler to write to a pipe,
# which will then be seen by select.
#
# In python's signal handling semantics, this only matters on the
# main thread (fortunately, set_wakeup_fd only works on the main
# thread and will raise a ValueError otherwise).
#
# If someone has already set a wakeup fd, we don't want to
# disturb it. This is an issue for twisted, which does its
# SIGCHILD processing in response to its own wakeup fd being
# written to. As long as the wakeup fd is registered on the IOLoop,
# the loop will still wake up and everything should work.
old_wakeup_fd = None
# 旧的被唤醒的 fd
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# the python process on windows.
try:
old_wakeup_fd = signal.set_wakeup_fd(
self._waker.write_fileno())
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy,
# but there's no clean get_wakeup_fd and in real use the
# IOLoop is just started once at the beginning.
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError: # non-main thread
pass
# 循环体(重点)
while True:
# 首先是设定超时时间为3600秒
poll_timeout = 3600.0
# Prevent IO event starvation by delaying new callbacks
# to the next iteration of the event loop.
# (防止[保护]饥饿的IO事件是通过推迟新的回调事件循环的下一次迭代)
# 加上一把线程锁
# 然后在互斥锁下取出上次循环【遗留】下的回调列表（在add_callback添加对象），
# 把这次列表置空；
# 然后依次执行列表里的回调。
with self._callback_lock:
# self._callbacks 回到列表中数据
callbacks = self._callbacks
self._callbacks = []
for callback in callbacks:
# 这里的_run_callback就没什么好分析的了；就是执行剩下的回调函数
self._run_callback(callback)
# 紧接着是检查上次循环遗留的超时列表，
# 如果列表里的项目有回调而且过了截止时间，那肯定超时了，就执行对应的超时回调。
# 然后检查是否又有了事件回调（因为很多回调函数里可能会再添加回调），
# 如果是，则不在poll循环里等待，如注释所述
if self._timeouts:
now = self.time()
while self._timeouts:
# 这种情况是没有回调函数
if self._timeouts[0].callback is None:
# the timeout was cancelled（取消超时时间）
heapq.heappop(self._timeouts)
self._cancellations -= 1
# 有回调且过了截至时间；此时就要执行【过时的回调函数】
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._cancellations > 512 and self._cancellations >
(len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's
# more than half cancellations.
self._cancellations = 0
self._timeouts = [
x for x in self._timeouts if x.callback is not None
]
heapq.heapify(self._timeouts)
# 检查是否有事件回调
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:
# 这句里的【_impl是epoll】，在platform/epoll.py里定义，
# 总之就是一个【等待函数】，当有事件（超时也算）发生就返回。
# 然后把【事件集】保存下来，对于每个事件，self._handlers[fd](fd, events)
# 根据fd找到回调，并把fd和事件做参数回传。
# 如果fd是监听的fd，那么这个回调handler就是accept_handler函数，
# 详见上节代码。如果是新fd可读，一般就是_on_headers 或者 _on_requet_body了，
# 详见前几节。我好像没看到可写时的回调？以上，就是循环的流程了。
# 可能还是看的糊里糊涂的，因为很多对象怎么来的都不清楚，
# configurable也还没有看。看完下面的分析，应该就可以了。
# Configurable类在util.py里被定义
# epoll中轮询
event_pairs = self._impl.poll(poll_timeout)
except Exception as e:
# Depending on python version and IOLoop implementation(实施),
# 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
# 如果有读可用信息，则把【该socket对象句柄和Event Code序列】添加到self._events中
self._events.update(event_pairs)
# 遍历self._events，【处理每个请求】
while self._events:
fd, events = self._events.popitem()
try:
# 以socket为句柄为key，取出self._handlers中的stack_context.wrap(handler)，并执行
# stack_context.wrap(handler)包装了HTTPServer类的_handle_events函数的一个函数
# 是在上一步中执行【add_handler方法时候】，添加到self._handlers中的数据。
# 跳转到了stack_context.wrap(handler)中
# self._handlers[fd] = stack_context.wrap(handler)
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:
app_log.error("Exception in I/O handler for fd %s",
fd,
exc_info=True)
except Exception:
app_log.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)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def add_timeout(self, deadline, callback):
timeout = _Timeout(deadline, stack_context.wrap(callback), self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
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 add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
# if the signal is handled on another thread, we can add
# it normally (modulo the NullContext)
self.add_callback(callback, *args, **kwargs)
else:
# If we're on the IOLoop's thread, we cannot use
# the regular add_callback because it may deadlock on
# _callback_lock. Blindly insert into self._callbacks.
# This is safe because the GIL makes list.append atomic.
# One subtlety is that if the signal interrupted the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks,
# but either way will work.
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None):
super(PollIOLoop, self).initialize()
# 使用的模型，使用的哪一个 select epoll kqueue
# ubuntu系统使用的epoll
self._impl = impl
# 不明白
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
# 设置获取时间的函数
self.time_func = time_func or time.time
# self._handlers[fd] = (obj, stack_context.wrap(handler))
# fd这个时候是一个数字，一般的时候是一个fd的对象
self._handlers = {}
# 保存每一次循环所得到的fd和事件对
self._events = {}
# 所有的callback函数的集合
self._callbacks = []
self._callback_lock = threading.Lock()
# 所有需要延时执行的函数的集合
self._timeouts = []
self._cancellations = 0
self._running = False # IOLoop是不是已经运行了
self._stopped = False # IOLoop是不是已经停止了，为什么有两个
self._closing = 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
# 这个真心不懂，以后研究
self._waker = Waker()
# 初始化的时候添加self._waker的一个读得socket到IOLoop里面
self.add_handler(self._waker.fileno(),
lambda fd, events: self._waker.consume(), self.READ)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in self._handlers.values():
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
# 添加一个fd（数字）和事件绑定
def add_handler(self, fd, handler, events):
# 添加一个注册事件 fd是文件描述符
fd, obj = self.split_fd(fd) # 通过fd对象，返回数字和fd对象
# 需要监听的fd整数和fd对象与handler的对应
self._handlers[fd] = (obj, stack_context.wrap(handler))
# 注册相关的事件，加入通知
self._impl.register(fd, events | self.ERROR)
# 这里只是更新，没有检查是不是已经存在
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
# 移除事件绑定
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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)
# 初始化的最后一步就是到这个地方了，已经把监听的accept添加进去了，同时添加了一个额外的fd，不知道干嘛的
def start(self):
if self._running:
raise RuntimeError("IOLoop is already running")
self._setup_logging()
if self._stopped:
self._stopped = False
return # 如果两个都是False，好像不知道在做什么
# 保存老的IOLoop._current.instance
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident() # 子线程标记
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# a signal may arrive at the beginning of select/poll/etc
# before it goes into its interruptible sleep, so the signal
# will be consumed without waking the select. The solution is
# for the (C, synchronous) signal handler to write to a pipe,
# which will then be seen by select.
#
# In python's signal handling semantics, this only matters on the
# main thread (fortunately, set_wakeup_fd only works on the main
# thread and will raise a ValueError otherwise).
#
# If someone has already set a wakeup fd, we don't want to
# disturb it. This is an issue for twisted, which does its
# SIGCHILD processing in response to its own wakeup fd being
# written to. As long as the wakeup fd is registered on the IOLoop,
# the loop will still wake up and everything should work.
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# the python process on windows.
try:
old_wakeup_fd = signal.set_wakeup_fd(
self._waker.write_fileno())
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy,
# but there's no clean get_wakeup_fd and in real use the
# IOLoop is just started once at the beginning.
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError: # non-main thread
pass
try:
while True: # 这里是循环的精髓部分，单线程和单进程就是在这里循环和阻塞的
poll_timeout = _POLL_TIMEOUT
# 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)
# Closures may be holding on to a lot of memory, so allow
# them to be freed before we go into our poll wait.
callbacks = callback = None
# 有些函数需要延时运行，就是在这里检查的
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
# the timeout was cancelled
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
timeout = heapq.heappop(self._timeouts)
self._run_callback(timeout.callback)
del timeout
else:
seconds = self._timeouts[0].deadline - now
poll_timeout = min(seconds, poll_timeout)
break
if (self._cancellations > 512 and self._cancellations >
(len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's
# more than half cancellations.
self._cancellations = 0
self._timeouts = [
x for x in self._timeouts if x.callback is not None
]
heapq.heapify(self._timeouts)
# 如果还有回调，那么accept不能阻塞
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:
# 返回值 [(fd, events), (4, 1)] 基本都是数字
# 初始化到这里之后，后面的基本就是如何处理请求进来的连接了，起码一个部分的任务搞定了
event_pairs = self._impl.poll(poll_timeout) # 阻塞在这里
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 errno_from_exception(e) == 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
# 一个连接刚刚进来的时候，event pairs是[(5, 1)] = 此时的事件需要accept
self._events.update(event_pairs)
# 开始处理的地方
while self._events:
fd, events = self._events.popitem()
try:
# 获取socket对应的处理函数
fd_obj, handler_func = self._handlers[fd]
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
self.handle_callback_exception(
self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
# 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)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def add_timeout(self, deadline, callback):
timeout = _Timeout(deadline, stack_context.wrap(callback), self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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
self._cancellations += 1
# 有时间就执行： callback(*args, **kwargs)
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
# 给self._callbacks添加回调函数
# 这里把args和kwargs的消息封装到了callback的属性里面了，然后可以直接运行了
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
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 add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
# if the signal is handled on another thread, we can add
# it normally (modulo the NullContext)
self.add_callback(callback, *args, **kwargs)
else:
# If we're on the IOLoop's thread, we cannot use
# the regular add_callback because it may deadlock on
# _callback_lock. Blindly insert into self._callbacks.
# This is safe because the GIL makes list.append atomic.
# One subtlety is that if the signal interrupted the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks,
# but either way will work.
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
class PollIOLoop(IOLoop):
def initialize(self, impl, time_func=None, **kwargs):
super(PollIOLoop, self).initialize(**kwargs)
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = False
self._thread_ident = None
self._blocking_signal_threshold = None
self._timeout_counter = itertools.count()
self._waker = Waker()
self.add_handler(self._waker.fileno(),
lambda fd, events: self._waker.consume(), self.READ)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in self._handlers.values():
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
def add_handler(self, fd, handler, events):
fd, obj = self.split_fd(fd)
self._handlers[fd] = (obj, stack_context.wrap(handler))
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
print("Error deleting fd from IOLoop")
def set_blocking_signal_threshold(self, seconds, action):
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 start(self):
if self._running:
raise RuntimeError("IOLoop is already running")
if self._stopped:
self._stopped = False
return
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident()
self._running = True
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
try:
old_wakeup_fd = signal.set_wakeup_fd(
self._waker.write_fileno())
if old_wakeup_fd != -1:
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError:
old_wakeup_fd = None
try:
while True:
with self._callback_lock:
callbacks = self._callbacks
self._callbacks = []
due_timeouts = []
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
due_timeouts.append(heapq.heappop(self._timeouts))
else:
break
if (self._cancellations > 512 and self._cancellations >
(len(self._timeouts) >> 1)):
self._cancellations = 0
self._timeouts = [
x for x in self._timeouts if x.callback is not None
]
heapq.heapify(self._timeouts)
for callback in callbacks:
self._run_callback(callback)
for timeout in due_timeouts:
if timeout.callback is not None:
self._run_callback(timeout.callback)
callbacks = callback = due_timeouts = timeout = None
if self._callbacks:
poll_timeout = 0.0
elif self._timeouts:
poll_timeout = self._timeouts[0].deadline - self.time()
poll_timeout = max(0, min(poll_timeout, _POLL_TIMEOUT))
else:
poll_timeout = _POLL_TIMEOUT
if not self._running:
break
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL, 0, 0)
try:
event_pairs = self._impl.poll(poll_timeout)
except Exception as e:
if errno_from_exception(e) == errno.EINTR:
continue
else:
raise
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL,
self._blocking_signal_threshold, 0)
self._events.update(event_pairs)
while self._events:
fd, events = self._events.popitem()
try:
fd_obj, handler_func = self._handlers[fd]
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
pass
else:
self.handle_callback_exception(
self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
self._stopped = False
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL, 0, 0)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def call_at(self, deadline, callback, *args, **kwargs):
timeout = _Timeout(
deadline,
functools.partial(stack_context.wrap(callback), *args, **kwargs),
self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, timeout):
timeout.callback = None
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
if list_empty and thread.get_ident() != self._thread_ident:
self._waker.wake()
def add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
self.add_callback(callback, *args, **kwargs)
else:
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None, **kwargs):
super(PollIOLoop, self).initialize(**kwargs)
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
# key:fd value:(fd_obj, handler)
self._handlers = {}
# key:fd value:events
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = False
self._thread_ident = None
self._blocking_signal_threshold = None
# 计时器id，方便计时器获取自己添加到ioloop的顺序，用于比较超时时间
# 加入超时时间点相同，触发时候根据加入的顺序进行回调
self._timeout_counter = itertools.count()
# Create a pipe that we send bogus data to when we want to wake
# the I/O loop when it is idle
# 当添加fd或者停止ioloop时候用于从多路复用中唤醒
self._waker = Waker()
self.add_handler(self._waker.fileno(),
lambda fd, events: self._waker.consume(), self.READ)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in self._handlers.values():
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
def add_handler(self, fd, handler, events):
fd, obj = self.split_fd(fd)
self._handlers[fd] = (obj, stack_context.wrap(handler))
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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 start(self):
if self._running:
raise RuntimeError("IOLoop is already running")
self._setup_logging()
if self._stopped:
self._stopped = False
return
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident() # 保存当前线程ID
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# a signal may arrive at the beginning of select/poll/etc
# before it goes into its interruptible sleep, so the signal
# will be consumed without waking the select. The solution is
# for the (C, synchronous) signal handler to write to a pipe,
# which will then be seen by select.
#
# In python's signal handling semantics, this only matters on the
# main thread (fortunately, set_wakeup_fd only works on the main
# thread and will raise a ValueError otherwise).
#
# If someone has already set a wakeup fd, we don't want to
# disturb it. This is an issue for twisted, which does its
# SIGCHLD processing in response to its own wakeup fd being
# written to. As long as the wakeup fd is registered on the IOLoop,
# the loop will still wake up and everything should work.
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# the python process on windows.
try:
old_wakeup_fd = signal.set_wakeup_fd(
self._waker.write_fileno())
# 已经设置，还原回去
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy,
# but there's no clean get_wakeup_fd and in real use the
# IOLoop is just started once at the beginning.
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError:
# Non-main thread, or the previous value of wakeup_fd
# is no longer valid.
old_wakeup_fd = None
try:
while True:
# Prevent IO event starvation by delaying new callbacks
# to the next iteration of the event loop.
# self._callbacks为立即事件,每次循环就会马上回调
# 并且只回调一次就清空
with self._callback_lock:
callbacks = self._callbacks
self._callbacks = []
# Add any timeouts that have come due to the callback list.
# Do not run anything until we have determined which ones
# are ready, so timeouts that call add_timeout cannot
# schedule anything in this iteration.
due_timeouts = []
# self._timeouts为二叉堆,用于管理定时器
if self._timeouts:
now = self.time()
while self._timeouts:
# 定时器的回调函数有可能为None的情况,因为用户删除定时器,内部并不会
# 立即从二叉堆中删除,而是直接将其回调标记为None,因为
# 从二叉堆中删除会造成不必要的开销
# 国内科学软件Shadowsocks源码tcprelay.py中的class TCPRelay借鉴了此方法
# 在_sweep_timeout方法中可以找到,只是在此基础上修改，使用sorted list进行存储
# 通过map存储每个callback在sorted list的下标
if self._timeouts[0].callback is None:
# The timeout was cancelled. Note that the
# cancellation check is repeated below for timeouts
# that are cancelled by another timeout or callback.
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
# 已经超时的定时器暂时放到due_timeouts当中
due_timeouts.append(heapq.heappop(self._timeouts))
else:
break
# 二叉堆中已被删除的定时器数目超过512或者大于二叉堆总数的一半
# 那么重新整理二叉堆,将删除的定时器从二叉堆移除,然后重新构建二叉堆
if (self._cancellations > 512 and self._cancellations >
(len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's
# more than half cancellations.
self._cancellations = 0
self._timeouts = [
x for x in self._timeouts if x.callback is not None
]
# 重新构建二叉堆
heapq.heapify(self._timeouts)
# 先运行callback
for callback in callbacks:
self._run_callback(callback)
# 再运行callback_timeout
for timeout in due_timeouts:
if timeout.callback is not None:
self._run_callback(timeout.callback)
# Closures may be holding on to a lot of memory, so allow
# them to be freed before we go into our poll wait.
callbacks = callback = due_timeouts = timeout = None
# 这里获取下次循环超时的时间
# 1. 有立即回调的函数即self._callbacks非空,poll_timeout为0（有可能在上面回调的时候添加）
# 2. 如果有定时器存在,从二叉堆顶获取最短触发的定时器的超时时间
# 3. ioloop中没有任何事件,默认使用_POLL_TIMEOUT，3600秒
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
elif self._timeouts:
# If there are any timeouts, schedule the first one.
# Use self.time() instead of 'now' to account for time
# spent running callbacks.
poll_timeout = self._timeouts[0].deadline - self.time()
poll_timeout = max(0, min(poll_timeout, _POLL_TIMEOUT))
else:
# No timeouts and no callbacks, so use the default.
poll_timeout = _POLL_TIMEOUT
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:
# self._impl从外部传递进来,底层操作系统IO多路复用API
# 返回发生的事件列表以及对应的事件类型
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 errno_from_exception(e) == 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 modify self._events
self._events.update(event_pairs)
while self._events:
fd, events = self._events.popitem()
try:
fd_obj, handler_func = self._handlers[fd]
# 这里调用与文件描述符对应的回调函数
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
self.handle_callback_exception(
self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
# 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)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def call_at(self, deadline, callback, *args, **kwargs):
# 继承实现IOLoop call_at
timeout = _Timeout(
deadline,
functools.partial(stack_context.wrap(callback), *args, **kwargs),
self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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.
# 直接赋值为None，而不是从二叉堆中删除
timeout.callback = None
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
if thread.get_ident() != self._thread_ident:
# If we're not on the IOLoop's thread, we need to synchronize
# with other threads, or waking logic will induce a race.
with self._callback_lock:
if self._closing:
return
list_empty = not self._callbacks
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
if list_empty:
# 在其他线程中添加callback需要唤醒，不然可能会持续睡眠
# If we're not in the IOLoop's thread, 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()
else:
if self._closing:
return
# If we're on the IOLoop's thread, we don't need the lock,
# since we don't need to wake anyone, just add the
# callback. Blindly insert into self._callbacks. This is
# safe even from signal handlers because the GIL makes
# list.append atomic. One subtlety is that if the signal
# is interrupting another thread holding the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks, but
# either way will work.
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
def add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
self.add_callback(callback, *args, **kwargs)
class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None, **kwargs):
super(PollIOLoop, self).initialize(**kwargs)
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = False
self._thread_ident = None
self._blocking_signal_threshold = None
self._timeout_counter = itertools.count()
# 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)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in self._handlers.values():
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
def add_handler(self, fd, handler, events):
fd, obj = self.split_fd(fd)
self._handlers[fd] = (obj, stack_context.wrap(handler))
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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 start(self):
if self._running:
raise RuntimeError("IOLoop is already running")
self._setup_logging()
if self._stopped:
self._stopped = False
return
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
# TODO 这里需要了解一下 python thread
self._thread_ident = thread.get_ident()
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# signal.set_wakeup_fd 在事件循环的时候关闭竞争条件：
# a signal may arrive at the beginning of select/poll/etc before it goes into its interruptible sleep,
# 信号可以可以在select/poll/etc进入可中断休眠之前到达。
# so the signal will be consumed without waking the select.
# 所以信号会被消费掉而避免唤醒select。
# The solution is for the (C, 同步) signal handler to write to a pipe, which will then be seen by select.
# 该解决方案是为(C, 同步)信号处理程序写入管道， 然后会被select接收到。
# In python's signal handling semantics, this only matters on the main thread (fortunately, set_wakeup_fd only works on the main thread and will raise a ValueError otherwise).
# 在Python中的信号处理的逻辑，只会在主线程上（幸运的是，set_wakeup_fd只能工作在主线程，将抛出ValueError异常，otherwise）。
# If someone has already set a wakeup fd, we don't want to disturb it.
# 如果有人已经设置唤醒FD，我们不想中断它。
# This is an issue for twisted, which does its SIGCHLD processing in response to its own wakeup fd being written to.
# 这是twisted的一个问题，它的SIGCHLD处理程序响应自己唤醒FD被写入。
# As long as the wakeup fd is registered on the IOLoop, the loop will still wake up and everything should work.
# 只要唤醒FD是在IOLoop注册，轮询仍然会被唤醒并且执行。
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# 需要python 2.6+, nuix. set_wakeup_fd存在崩溃的情况。
# the python process on windows.
try:
# TODO 这里需要了解一下python signal
old_wakeup_fd = signal.set_wakeup_fd(self._waker.write_fileno())
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy, but there's no clean get_wakeup_fd and in real use the IOLoop is just started once at the beginning.
# 已经设置了恢复以前的值。这有点不好，只因为没有清理get_wakeup_fd然后IOLoop就在开始的时候仅仅实际使用了一次。
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError:
# Non-main thread, or the previous value of wakeup_fd is no longer valid.
# 不是主线程，或者之前的值对wakeup_fd不再有效。
old_wakeup_fd = None
try:
while True:
# Prevent IO event starvation by delaying new callbacks to the next iteration of the event loop.
# 通过延迟一个新的回调事件防止在下一次事件轮询中使IO事件处于饥饿状态。
with self._callback_lock:
callbacks = self._callbacks
self._callbacks = []
# Add any timeouts that have come due to the callback list.
# 把回调列表中所有超时的都记录下来。
# Do not run anything until we have determined which ones are ready, so timeouts that call add_timeout cannot schedule anything in this iteration.
# 不要运行任何东西直到我们确定了哪些东西是准备好了的了，所以在本次迭代中超时的都无法调用add_timeout。
due_timeouts = []
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
# The timeout was cancelled. Note that the cancellation check is repeated below for timeouts that are cancelled by another timeout or callback.
# 取消超时。
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
due_timeouts.append(heapq.heappop(self._timeouts))
else:
break
if (self._cancellations > 512
and self._cancellations > (len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's more than half cancellations.
# 当超时队列变大并且超过一半取消对象的时候清理一下。
self._cancellations = 0
self._timeouts = [x for x in self._timeouts
if x.callback is not None]
heapq.heapify(self._timeouts)
for callback in callbacks:
self._run_callback(callback)
for timeout in due_timeouts:
if timeout.callback is not None:
self._run_callback(timeout.callback)
# Closures may be holding on to a lot of memory, so allow them to be freed before we go into our poll wait.
# 闭包会占用大量内存，所以我们在进入轮寻等待之前先把他们释放了。
callbacks = callback = due_timeouts = timeout = None
if self._callbacks:
# If any callbacks or timeouts called add_callback, we don't want to wait in poll() before we run them.
# 如果任何的回调或超时对象被add_callback调用，我们不想在运行之前在poll()中等待。
poll_timeout = 0.0
elif self._timeouts:
# If there are any timeouts, schedule the first one.
# 如果有任何的超时对象，调用第一个。
# Use self.time() instead of 'now' to account for time spent running callbacks.
# 使用 self.time() 代替 'now' 去占用运行回调的时间。
poll_timeout = self._timeouts[0].deadline - self.time()
poll_timeout = max(0, min(poll_timeout, _POLL_TIMEOUT))
else:
# No timeouts and no callbacks, so use the default.
# 没有超时对象和回调对象，就使用默认值。
poll_timeout = _POLL_TIMEOUT
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 errno_from_exception(e) == 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.
# 弹出一个fd对象从挂起这个文件描述符的时间和他运行的操作对象。
# Since that handler may perform actions on other file descriptors,
# 因为该处理程序可以在其他文件描述符上执行操作
# there may be reentrant calls to this IOLoop that update self._events
# 有可能是重新调用IOLoop然后更新self._events
self._events.update(event_pairs)
while self._events:
fd, events = self._events.popitem()
try:
fd_obj, handler_func = self._handlers[fd]
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
self.handle_callback_exception(self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
# 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)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def call_at(self, deadline, callback, *args, **kwargs):
timeout = _Timeout(
deadline,
functools.partial(stack_context.wrap(callback), *args, **kwargs),
self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
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 add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
# if the signal is handled on another thread, we can add
# it normally (modulo the NullContext)
self.add_callback(callback, *args, **kwargs)
else:
# If we're on the IOLoop's thread, we cannot use
# the regular add_callback because it may deadlock on
# _callback_lock. Blindly insert into self._callbacks.
# This is safe because the GIL makes list.append atomic.
# One subtlety is that if the signal interrupted the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks,
# but either way will work.
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None, **kwargs):
super(PollIOLoop, self).initialize(**kwargs)
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = False
self._thread_ident = None
self._blocking_signal_threshold = None
self._timeout_counter = itertools.count()
# 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)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in self._handlers.values():
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
def add_handler(self, fd, handler, events):
fd, obj = self.split_fd(fd)
self._handlers[fd] = (obj, stack_context.wrap(handler))
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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 start(self):
if self._running:
raise RuntimeError("IOLoop is already running")
self._setup_logging()
if self._stopped:
self._stopped = False
return
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
# TODO 这里需要了解一下 python thread
self._thread_ident = thread.get_ident()
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# signal.set_wakeup_fd 在事件循环的时候关闭竞争条件：
# a signal may arrive at the beginning of select/poll/etc before it goes into its interruptible sleep,
# 信号可以可以在select/poll/etc进入可中断休眠之前到达。
# so the signal will be consumed without waking the select.
# 所以信号会被消费掉而避免唤醒select。
# The solution is for the (C, 同步) signal handler to write to a pipe, which will then be seen by select.
# 该解决方案是为(C, 同步)信号处理程序写入管道， 然后会被select接收到。
# In python's signal handling semantics, this only matters on the main thread (fortunately, set_wakeup_fd only works on the main thread and will raise a ValueError otherwise).
# 在Python中的信号处理的逻辑，只会在主线程上（幸运的是，set_wakeup_fd只能工作在主线程，将抛出ValueError异常，otherwise）。
# If someone has already set a wakeup fd, we don't want to disturb it.
# 如果有人已经设置唤醒FD，我们不想中断它。
# This is an issue for twisted, which does its SIGCHLD processing in response to its own wakeup fd being written to.
# 这是twisted的一个问题，它的SIGCHLD处理程序响应自己唤醒FD被写入。
# As long as the wakeup fd is registered on the IOLoop, the loop will still wake up and everything should work.
# 只要唤醒FD是在IOLoop注册，轮询仍然会被唤醒并且执行。
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# 需要python 2.6+, nuix. set_wakeup_fd存在崩溃的情况。
# the python process on windows.
try:
# TODO 这里需要了解一下python signal
old_wakeup_fd = signal.set_wakeup_fd(
self._waker.write_fileno())
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy, but there's no clean get_wakeup_fd and in real use the IOLoop is just started once at the beginning.
# 已经设置了恢复以前的值。这有点不好，只因为没有清理get_wakeup_fd然后IOLoop就在开始的时候仅仅实际使用了一次。
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError:
# Non-main thread, or the previous value of wakeup_fd is no longer valid.
# 不是主线程，或者之前的值对wakeup_fd不再有效。
old_wakeup_fd = None
try:
while True:
# Prevent IO event starvation by delaying new callbacks to the next iteration of the event loop.
# 通过延迟一个新的回调事件防止在下一次事件轮询中使IO事件处于饥饿状态。
with self._callback_lock:
callbacks = self._callbacks
self._callbacks = []
# Add any timeouts that have come due to the callback list.
# 把回调列表中所有超时的都记录下来。
# Do not run anything until we have determined which ones are ready, so timeouts that call add_timeout cannot schedule anything in this iteration.
# 不要运行任何东西直到我们确定了哪些东西是准备好了的了，所以在本次迭代中超时的都无法调用add_timeout。
due_timeouts = []
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
# The timeout was cancelled. Note that the cancellation check is repeated below for timeouts that are cancelled by another timeout or callback.
# 取消超时。
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
due_timeouts.append(heapq.heappop(self._timeouts))
else:
break
if (self._cancellations > 512 and self._cancellations >
(len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's more than half cancellations.
# 当超时队列变大并且超过一半取消对象的时候清理一下。
self._cancellations = 0
self._timeouts = [
x for x in self._timeouts if x.callback is not None
]
heapq.heapify(self._timeouts)
for callback in callbacks:
self._run_callback(callback)
for timeout in due_timeouts:
if timeout.callback is not None:
self._run_callback(timeout.callback)
# Closures may be holding on to a lot of memory, so allow them to be freed before we go into our poll wait.
# 闭包会占用大量内存，所以我们在进入轮寻等待之前先把他们释放了。
callbacks = callback = due_timeouts = timeout = None
if self._callbacks:
# If any callbacks or timeouts called add_callback, we don't want to wait in poll() before we run them.
# 如果任何的回调或超时对象被add_callback调用，我们不想在运行之前在poll()中等待。
poll_timeout = 0.0
elif self._timeouts:
# If there are any timeouts, schedule the first one.
# 如果有任何的超时对象，调用第一个。
# Use self.time() instead of 'now' to account for time spent running callbacks.
# 使用 self.time() 代替 'now' 去占用运行回调的时间。
poll_timeout = self._timeouts[0].deadline - self.time()
poll_timeout = max(0, min(poll_timeout, _POLL_TIMEOUT))
else:
# No timeouts and no callbacks, so use the default.
# 没有超时对象和回调对象，就使用默认值。
poll_timeout = _POLL_TIMEOUT
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 errno_from_exception(e) == 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.
# 弹出一个fd对象从挂起这个文件描述符的时间和他运行的操作对象。
# Since that handler may perform actions on other file descriptors,
# 因为该处理程序可以在其他文件描述符上执行操作
# there may be reentrant calls to this IOLoop that update self._events
# 有可能是重新调用IOLoop然后更新self._events
self._events.update(event_pairs)
while self._events:
fd, events = self._events.popitem()
try:
fd_obj, handler_func = self._handlers[fd]
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
self.handle_callback_exception(
self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
# 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)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def call_at(self, deadline, callback, *args, **kwargs):
timeout = _Timeout(
deadline,
functools.partial(stack_context.wrap(callback), *args, **kwargs),
self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
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 add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
# if the signal is handled on another thread, we can add
# it normally (modulo the NullContext)
self.add_callback(callback, *args, **kwargs)
else:
# If we're on the IOLoop's thread, we cannot use
# the regular add_callback because it may deadlock on
# _callback_lock. Blindly insert into self._callbacks.
# This is safe because the GIL makes list.append atomic.
# One subtlety is that if the signal interrupted the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks,
# but either way will work.
self._callbacks.append(
functools.partial(stack_context.wrap(callback), *args,
**kwargs))
class PollIOLoop(IOLoop):
"""Base class for IOLoops built around a select-like function.
For concrete implementations, see `tornado.platform.epoll.EPollIOLoop`
(Linux), `tornado.platform.kqueue.KQueueIOLoop` (BSD and Mac), or
`tornado.platform.select.SelectIOLoop` (all platforms).
"""
def initialize(self, impl, time_func=None):
super(PollIOLoop, self).initialize()
self._impl = impl
if hasattr(self._impl, 'fileno'):
set_close_exec(self._impl.fileno())
self.time_func = time_func or time.time
self._handlers = {}
self._events = {}
self._callbacks = []
self._callback_lock = threading.Lock()
self._timeouts = []
self._cancellations = 0
self._running = False
self._stopped = False
self._closing = False
self._thread_ident = None
self._blocking_signal_threshold = None
self._timeout_counter = itertools.count()
# 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)
def close(self, all_fds=False):
with self._callback_lock:
self._closing = True
self.remove_handler(self._waker.fileno())
if all_fds:
for fd, handler in self._handlers.values():
self.close_fd(fd)
self._waker.close()
self._impl.close()
self._callbacks = None
self._timeouts = None
def add_handler(self, fd, handler, events):
fd, obj = self.split_fd(fd)
self._handlers[fd] = (obj, stack_context.wrap(handler))
self._impl.register(fd, events | self.ERROR)
def update_handler(self, fd, events):
fd, obj = self.split_fd(fd)
self._impl.modify(fd, events | self.ERROR)
def remove_handler(self, fd):
fd, obj = self.split_fd(fd)
self._handlers.pop(fd, None)
self._events.pop(fd, None)
try:
self._impl.unregister(fd)
except Exception:
gen_log.debug("Error deleting fd from IOLoop", exc_info=True)
def set_blocking_signal_threshold(self, seconds, action):
if not hasattr(signal, "setitimer"):
gen_log.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 start(self):
# tonardo 使用 _running/_stopped 两个字段组合表示3种状态：
# 1、就绪（初始化完成/已经结束）：_running=False, _stopped=False;
# 2、正在运行：_running=True, _stopped=False;
# 3、正在结束：_running=False, _stopped=True;
if self._running:
raise RuntimeError("IOLoop is already running")
self._setup_logging()
if self._stopped:
self._stopped = False
return
old_current = getattr(IOLoop._current, "instance", None)
IOLoop._current.instance = self
self._thread_ident = thread.get_ident()
self._running = True
# signal.set_wakeup_fd closes a race condition in event loops:
# a signal may arrive at the beginning of select/poll/etc
# before it goes into its interruptible sleep, so the signal
# will be consumed without waking the select. The solution is
# for the (C, synchronous) signal handler to write to a pipe,
# which will then be seen by select.
#
# In python's signal handling semantics, this only matters on the
# main thread (fortunately, set_wakeup_fd only works on the main
# thread and will raise a ValueError otherwise).
#
# If someone has already set a wakeup fd, we don't want to
# disturb it. This is an issue for twisted, which does its
# SIGCHILD processing in response to its own wakeup fd being
# written to. As long as the wakeup fd is registered on the IOLoop,
# the loop will still wake up and everything should work.
#
# signal.set_wakeup_fd(fd) 设置文件描述符 fd , 当接收到信号时会在它上面写入一个 '＼0' 字节。
# 用于唤醒被 poll 或 select 调用阻塞的进程，使进程能够处理信号。方法参数fd必须是以非阻塞
# (non-blocking)方式打开的文件描述符，否则无效。调用该方法返回上一次调用设置的文件描述符（没有
# 设置过则返回-1）。该方法只能在主线程中调用，在其他线程调用时将抛出 ValueError 异常。
#
# 上述原注释中有提到 twisted 自身会设置 wakeup fd 处理 SIGCHILD 信号，所以在结合 twisted 使用时要注
# 意 override PosixReactorBase.installWaker 等与 waker 相关法方法（暂时对 twistd 不了解，猜测）。
#
# self._waker.write_fileno()文件描述符的 READ 事件已经在 initialize 方法中加入 I/O 循环列表。
old_wakeup_fd = None
if hasattr(signal, 'set_wakeup_fd') and os.name == 'posix':
# requires python 2.6+, unix. set_wakeup_fd exists but crashes
# the python process on windows.
try:
old_wakeup_fd = signal.set_wakeup_fd(self._waker.write_fileno())
if old_wakeup_fd != -1:
# Already set, restore previous value. This is a little racy,
# but there's no clean get_wakeup_fd and in real use the
# IOLoop is just started once at the beginning.
signal.set_wakeup_fd(old_wakeup_fd)
old_wakeup_fd = None
except ValueError: # non-main thread
pass
try:
while True:
# 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 = []
# Add any timeouts that have come due to the callback list.
# Do not run anything until we have determined which ones
# are ready, so timeouts that call add_timeout cannot
# schedule anything in this iteration.
#
# self._timeouts 是一个基于 heap 的 priority queue，存放 _Timeout 类型实例，
# 按照到期时间由近到远和加入heap的先后顺序排序（参见 _Timeout 的 __lt__ 和 __le__ ）。
due_timeouts = []
if self._timeouts:
now = self.time()
while self._timeouts:
if self._timeouts[0].callback is None:
# The timeout was cancelled. Note that the
# cancellation check is repeated below for timeouts
# that are cancelled by another timeout or callback.
heapq.heappop(self._timeouts)
self._cancellations -= 1
elif self._timeouts[0].deadline <= now:
due_timeouts.append(heapq.heappop(self._timeouts))
else:
break
# 由于从 heap 中移除一个元素很复杂，所以 tornado 实现 remove_timeout 时将取消的
# timeout 对象保留在 heap 中，这样可能会导致内存问题，所以这里做了一个处理 512 的
# 阈值执行垃圾回收。remove_timeout 方法的注释中有说明。
if (self._cancellations > 512
and self._cancellations > (len(self._timeouts) >> 1)):
# Clean up the timeout queue when it gets large and it's
# more than half cancellations.
self._cancellations = 0
self._timeouts = [x for x in self._timeouts
if x.callback is not None]
heapq.heapify(self._timeouts)
for callback in callbacks:
self._run_callback(callback)
for timeout in due_timeouts:
if timeout.callback is not None:
self._run_callback(timeout.callback)
# Closures may be holding on to a lot of memory, so allow
# them to be freed before we go into our poll wait.
#
# 在进入poll等待之前释放闭包占用的内存，优化系统
callbacks = callback = due_timeouts = timeout = None
# 优化 poll 等待超时时间：
# 1、I/O 循环有 callback 需要处理时，不阻塞 poll 调用，也就是 poll_timeout=0；
# 2、I/O 循环有 timeout 需要处理时，计算第一个 timeout（self._timeouts[0]，
# 最先超时需要处理的 timeout）距离现在的超时间隔，取 poll_timeout 默认值与
# 该间隔之间的最小值（以保证 timeout 一超时就能被I/O循环立即处理，不被 poll
# 等待导致延时；若第一个 timeout 现在已经超时，则最小值<0，故需要与0比较修正）；
# 3、I/O 循环没有 callback 和 timeout 需要处理，则使用默认等待时间。
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
elif self._timeouts:
# If there are any timeouts, schedule the first one.
# Use self.time() instead of 'now' to account for time
# spent running callbacks.
poll_timeout = self._timeouts[0].deadline - self.time()
poll_timeout = max(0, min(poll_timeout, _POLL_TIMEOUT))
else:
# No timeouts and no callbacks, so use the default.
poll_timeout = _POLL_TIMEOUT
if not self._running:
break
# 为了监视 I/O 循环的阻塞状态，tornado 提供了通过定时发送 SIGALRM 信号的方式来异步通知
# 进程 I/O 循环阻塞超过了预期的最大时间（self._blocking_signal_threshold）。
#
# IOLoop.set_blocking_signal_threshold() 方法设置一个 signal.SIGALRM
# 信号处理函数来监视 I/O 循环的阻塞时间。
#
# poll 调用返回后（ poll 等待时间不计入 I/O 循环阻塞时间），通过调用 signal.setitimer(
# signal.ITIMER_REAL, self._blocking_signal_threshold, 0)设置定时器，每间
# 隔 _blocking_signal_threshold 发送一个 SIGALRM 信号，也就是说当 I/O 循环阻塞超
# 过 _blocking_signal_threshold 时会发送一个 SIGALRM 信号。
#
# 进入 poll 之前调用signal.setitimer(signal.ITIMER_REAL, 0, 0)清理定时器，直到
# poll 返回后重新设置定时器。
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')
#
# poll 调用可能会导致进程进入阻塞状态（sleep），这时候进程被信号唤醒后会引发 EINTR 错误（
# 抛出异常的类型取决于 python 的版本和具体的 IOLoop 实现）。通过 signal.set_wakeup_fd()
# 设置 wakeup fd 来捕获信号进行处理，不引发 InterruptedError[Raised when a system call is
# interrupted by an incoming signal. Corresponds to errno EINTR.]）。
#
# 注：这种会导致当前进程（线程）进入阻塞的系统调用被称为慢系统调用(slow system call)，比如 accept 、
# read 、 write 、 select 、和 open 之类的函数。
if errno_from_exception(e) == errno.EINTR:
continue
else:
raise
# 设置定时器以便在I/O循环阻塞超过预期时间时发送 SIGALRM 信号。
#
# signal.setitimer 函数，提供三种定时器，它们相互独立，任意一个定时完成都将发送定时信号到进程，并且自动重新计时。
# 1、ITIMER_REAL，计时器的值实时递减（以系统实时时间来计算 ），超时发送 SIGALRM 信号。
# 2、ITIMER_VIRT，进程执行时递减计时器的值（只计算（用户态）进程的执行时间），超时发送 SIGVTALRM 信号。
# 3、ITIMER_PROF，进程和系统执行时都递减计时器的值。结合 ITIMER_VIRTUAL， 常常被用于分析程序在用户态和内核态
# 花费的时间。超时发送 SIGPROF 信号。
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
#
# 由于一个 handler 可能会操作其他文件描述符与 IOLoop 进行交互，比如调用
# IOLoop.remove_handler 方法等将导致 self._events 被修改。所以使用
# while 循环而不是 for 循环（要求迭代期间 self._events 不能被修改）。
self._events.update(event_pairs)
while self._events:
fd, events = self._events.popitem()
try:
fd_obj, handler_func = self._handlers[fd]
handler_func(fd_obj, events)
except (OSError, IOError) as e:
if errno_from_exception(e) == errno.EPIPE:
# Happens when the client closes the connection
pass
else:
self.handle_callback_exception(self._handlers.get(fd))
except Exception:
self.handle_callback_exception(self._handlers.get(fd))
fd_obj = handler_func = None
finally:
# reset the stopped flag so another start/stop pair can be issued
#
# I/O循环结束重置_stopped状态，清理定时器，将当前 IOLoop 实例从当前线程移除绑定。
self._stopped = False
if self._blocking_signal_threshold is not None:
signal.setitimer(signal.ITIMER_REAL, 0, 0)
IOLoop._current.instance = old_current
if old_wakeup_fd is not None:
signal.set_wakeup_fd(old_wakeup_fd)
def stop(self):
self._running = False
self._stopped = True
self._waker.wake()
def time(self):
return self.time_func()
def call_at(self, deadline, callback, *args, **kwargs):
timeout = _Timeout(
deadline,
functools.partial(stack_context.wrap(callback), *args, **kwargs),
self)
heapq.heappush(self._timeouts, timeout)
return timeout
def remove_timeout(self, 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
self._cancellations += 1
def add_callback(self, callback, *args, **kwargs):
with self._callback_lock:
if self._closing:
raise RuntimeError("IOLoop is closing")
list_empty = not self._callbacks
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))
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.
#
# 如果不是在 IOLoop 线程中加入第1个回调，就手动唤醒一下 IOLoop （当然 IOLoop 可能
# 已经自己唤醒了自己，但是偶尔额外手动唤醒一下并没有什么害处）。由于唤醒一个 IOLoop 是
# 相对比较昂贵的，所以我们要尽可能避免这个操作（注：所以仅在不是在 IOLoop 线程中加入第1
# 个回调时才手动唤醒）。
self._waker.wake()
def add_callback_from_signal(self, callback, *args, **kwargs):
with stack_context.NullContext():
if thread.get_ident() != self._thread_ident:
# if the signal is handled on another thread, we can add
# it normally (modulo the NullContext)
self.add_callback(callback, *args, **kwargs)
else:
# If we're on the IOLoop's thread, we cannot use
# the regular add_callback because it may deadlock on
# _callback_lock. Blindly insert into self._callbacks.
# This is safe because the GIL makes list.append atomic.
# One subtlety is that if the signal interrupted the
# _callback_lock block in IOLoop.start, we may modify
# either the old or new version of self._callbacks,
# but either way will work.
#
# 在 IOLoop 线程中：
# 这个方法是为了避免在 _callback_lock 上发生“死锁”而提供的。这是因为
# 在 start 的 IOLoop 中会通过 _callback_lock 对 self._callbacks
# 加锁，当已经获取锁（未释放）的情况下被信号中断时信号处理器中再通过普通的
# add_callback 方法（需要获取 _callback_lock ）增加回调的话，会导致
# “死锁”。 由于 GIL 保证 list.append 是原子操作，所以直接通过
# self._callbacks.append 增加回调是安全的。
self._callbacks.append(functools.partial(
stack_context.wrap(callback), *args, **kwargs))