513 lines
15 KiB
Python
513 lines
15 KiB
Python
|
# Copyright 2015 The Tornado Authors
|
||
|
|
#
|
||
|
|
# Licensed under the Apache License, Version 2.0 (the "License"); you may
|
||
|
|
# not use this file except in compliance with the License. You may obtain
|
||
|
|
# a copy of the License at
|
||
|
|
#
|
||
|
|
# http://www.apache.org/licenses/LICENSE-2.0
|
||
|
|
#
|
||
|
|
# Unless required by applicable law or agreed to in writing, software
|
||
|
|
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
|
||
|
|
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
|
||
|
|
# License for the specific language governing permissions and limitations
|
||
|
|
# under the License.
|
||
|
|
|
||
|
|
from __future__ import absolute_import, division, print_function, with_statement
|
||
|
|
|
||
|
|
__all__ = ['Condition', 'Event', 'Semaphore', 'BoundedSemaphore', 'Lock']
|
||
|
|
|
||
|
|
import collections
|
||
|
|
|
||
|
|
from tornado import gen, ioloop
|
||
|
|
from tornado.concurrent import Future
|
||
|
|
|
||
|
|
|
||
|
|
class _TimeoutGarbageCollector(object):
|
||
|
|
"""Base class for objects that periodically clean up timed-out waiters.
|
||
|
|
|
||
|
|
Avoids memory leak in a common pattern like:
|
||
|
|
|
||
|
|
while True:
|
||
|
|
yield condition.wait(short_timeout)
|
||
|
|
print('looping....')
|
||
|
|
"""
|
||
|
|
def __init__(self):
|
||
|
|
self._waiters = collections.deque() # Futures.
|
||
|
|
self._timeouts = 0
|
||
|
|
|
||
|
|
def _garbage_collect(self):
|
||
|
|
# Occasionally clear timed-out waiters.
|
||
|
|
self._timeouts += 1
|
||
|
|
if self._timeouts > 100:
|
||
|
|
self._timeouts = 0
|
||
|
|
self._waiters = collections.deque(
|
||
|
|
w for w in self._waiters if not w.done())
|
||
|
|
|
||
|
|
|
||
|
|
class Condition(_TimeoutGarbageCollector):
|
||
|
|
"""A condition allows one or more coroutines to wait until notified.
|
||
|
|
|
||
|
|
Like a standard `threading.Condition`, but does not need an underlying lock
|
||
|
|
that is acquired and released.
|
||
|
|
|
||
|
|
With a `Condition`, coroutines can wait to be notified by other coroutines:
|
||
|
|
|
||
|
|
.. testcode::
|
||
|
|
|
||
|
|
from tornado import gen
|
||
|
|
from tornado.ioloop import IOLoop
|
||
|
|
from tornado.locks import Condition
|
||
|
|
|
||
|
|
condition = Condition()
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def waiter():
|
||
|
|
print("I'll wait right here")
|
||
|
|
yield condition.wait() # Yield a Future.
|
||
|
|
print("I'm done waiting")
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def notifier():
|
||
|
|
print("About to notify")
|
||
|
|
condition.notify()
|
||
|
|
print("Done notifying")
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def runner():
|
||
|
|
# Yield two Futures; wait for waiter() and notifier() to finish.
|
||
|
|
yield [waiter(), notifier()]
|
||
|
|
|
||
|
|
IOLoop.current().run_sync(runner)
|
||
|
|
|
||
|
|
.. testoutput::
|
||
|
|
|
||
|
|
I'll wait right here
|
||
|
|
About to notify
|
||
|
|
Done notifying
|
||
|
|
I'm done waiting
|
||
|
|
|
||
|
|
`wait` takes an optional ``timeout`` argument, which is either an absolute
|
||
|
|
timestamp::
|
||
|
|
|
||
|
|
io_loop = IOLoop.current()
|
||
|
|
|
||
|
|
# Wait up to 1 second for a notification.
|
||
|
|
yield condition.wait(timeout=io_loop.time() + 1)
|
||
|
|
|
||
|
|
...or a `datetime.timedelta` for a timeout relative to the current time::
|
||
|
|
|
||
|
|
# Wait up to 1 second.
|
||
|
|
yield condition.wait(timeout=datetime.timedelta(seconds=1))
|
||
|
|
|
||
|
|
The method raises `tornado.gen.TimeoutError` if there's no notification
|
||
|
|
before the deadline.
|
||
|
|
"""
|
||
|
|
|
||
|
|
def __init__(self):
|
||
|
|
super(Condition, self).__init__()
|
||
|
|
self.io_loop = ioloop.IOLoop.current()
|
||
|
|
|
||
|
|
def __repr__(self):
|
||
|
|
result = '<%s' % (self.__class__.__name__, )
|
||
|
|
if self._waiters:
|
||
|
|
result += ' waiters[%s]' % len(self._waiters)
|
||
|
|
return result + '>'
|
||
|
|
|
||
|
|
def wait(self, timeout=None):
|
||
|
|
"""Wait for `.notify`.
|
||
|
|
|
||
|
|
Returns a `.Future` that resolves ``True`` if the condition is notified,
|
||
|
|
or ``False`` after a timeout.
|
||
|
|
"""
|
||
|
|
waiter = Future()
|
||
|
|
self._waiters.append(waiter)
|
||
|
|
if timeout:
|
||
|
|
def on_timeout():
|
||
|
|
waiter.set_result(False)
|
||
|
|
self._garbage_collect()
|
||
|
|
io_loop = ioloop.IOLoop.current()
|
||
|
|
timeout_handle = io_loop.add_timeout(timeout, on_timeout)
|
||
|
|
waiter.add_done_callback(
|
||
|
|
lambda _: io_loop.remove_timeout(timeout_handle))
|
||
|
|
return waiter
|
||
|
|
|
||
|
|
def notify(self, n=1):
|
||
|
|
"""Wake ``n`` waiters."""
|
||
|
|
waiters = [] # Waiters we plan to run right now.
|
||
|
|
while n and self._waiters:
|
||
|
|
waiter = self._waiters.popleft()
|
||
|
|
if not waiter.done(): # Might have timed out.
|
||
|
|
n -= 1
|
||
|
|
waiters.append(waiter)
|
||
|
|
|
||
|
|
for waiter in waiters:
|
||
|
|
waiter.set_result(True)
|
||
|
|
|
||
|
|
def notify_all(self):
|
||
|
|
"""Wake all waiters."""
|
||
|
|
self.notify(len(self._waiters))
|
||
|
|
|
||
|
|
|
||
|
|
class Event(object):
|
||
|
|
"""An event blocks coroutines until its internal flag is set to True.
|
||
|
|
|
||
|
|
Similar to `threading.Event`.
|
||
|
|
|
||
|
|
A coroutine can wait for an event to be set. Once it is set, calls to
|
||
|
|
``yield event.wait()`` will not block unless the event has been cleared:
|
||
|
|
|
||
|
|
.. testcode::
|
||
|
|
|
||
|
|
from tornado import gen
|
||
|
|
from tornado.ioloop import IOLoop
|
||
|
|
from tornado.locks import Event
|
||
|
|
|
||
|
|
event = Event()
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def waiter():
|
||
|
|
print("Waiting for event")
|
||
|
|
yield event.wait()
|
||
|
|
print("Not waiting this time")
|
||
|
|
yield event.wait()
|
||
|
|
print("Done")
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def setter():
|
||
|
|
print("About to set the event")
|
||
|
|
event.set()
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def runner():
|
||
|
|
yield [waiter(), setter()]
|
||
|
|
|
||
|
|
IOLoop.current().run_sync(runner)
|
||
|
|
|
||
|
|
.. testoutput::
|
||
|
|
|
||
|
|
Waiting for event
|
||
|
|
About to set the event
|
||
|
|
Not waiting this time
|
||
|
|
Done
|
||
|
|
"""
|
||
|
|
def __init__(self):
|
||
|
|
self._future = Future()
|
||
|
|
|
||
|
|
def __repr__(self):
|
||
|
|
return '<%s %s>' % (
|
||
|
|
self.__class__.__name__, 'set' if self.is_set() else 'clear')
|
||
|
|
|
||
|
|
def is_set(self):
|
||
|
|
"""Return ``True`` if the internal flag is true."""
|
||
|
|
return self._future.done()
|
||
|
|
|
||
|
|
def set(self):
|
||
|
|
"""Set the internal flag to ``True``. All waiters are awakened.
|
||
|
|
|
||
|
|
Calling `.wait` once the flag is set will not block.
|
||
|
|
"""
|
||
|
|
if not self._future.done():
|
||
|
|
self._future.set_result(None)
|
||
|
|
|
||
|
|
def clear(self):
|
||
|
|
"""Reset the internal flag to ``False``.
|
||
|
|
|
||
|
|
Calls to `.wait` will block until `.set` is called.
|
||
|
|
"""
|
||
|
|
if self._future.done():
|
||
|
|
self._future = Future()
|
||
|
|
|
||
|
|
def wait(self, timeout=None):
|
||
|
|
"""Block until the internal flag is true.
|
||
|
|
|
||
|
|
Returns a Future, which raises `tornado.gen.TimeoutError` after a
|
||
|
|
timeout.
|
||
|
|
"""
|
||
|
|
if timeout is None:
|
||
|
|
return self._future
|
||
|
|
else:
|
||
|
|
return gen.with_timeout(timeout, self._future)
|
||
|
|
|
||
|
|
|
||
|
|
class _ReleasingContextManager(object):
|
||
|
|
"""Releases a Lock or Semaphore at the end of a "with" statement.
|
||
|
|
|
||
|
|
with (yield semaphore.acquire()):
|
||
|
|
pass
|
||
|
|
|
||
|
|
# Now semaphore.release() has been called.
|
||
|
|
"""
|
||
|
|
def __init__(self, obj):
|
||
|
|
self._obj = obj
|
||
|
|
|
||
|
|
def __enter__(self):
|
||
|
|
pass
|
||
|
|
|
||
|
|
def __exit__(self, exc_type, exc_val, exc_tb):
|
||
|
|
self._obj.release()
|
||
|
|
|
||
|
|
|
||
|
|
class Semaphore(_TimeoutGarbageCollector):
|
||
|
|
"""A lock that can be acquired a fixed number of times before blocking.
|
||
|
|
|
||
|
|
A Semaphore manages a counter representing the number of `.release` calls
|
||
|
|
minus the number of `.acquire` calls, plus an initial value. The `.acquire`
|
||
|
|
method blocks if necessary until it can return without making the counter
|
||
|
|
negative.
|
||
|
|
|
||
|
|
Semaphores limit access to a shared resource. To allow access for two
|
||
|
|
workers at a time:
|
||
|
|
|
||
|
|
.. testsetup:: semaphore
|
||
|
|
|
||
|
|
from collections import deque
|
||
|
|
|
||
|
|
from tornado import gen
|
||
|
|
from tornado.ioloop import IOLoop
|
||
|
|
from tornado.concurrent import Future
|
||
|
|
|
||
|
|
# Ensure reliable doctest output: resolve Futures one at a time.
|
||
|
|
futures_q = deque([Future() for _ in range(3)])
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def simulator(futures):
|
||
|
|
for f in futures:
|
||
|
|
yield gen.moment
|
||
|
|
f.set_result(None)
|
||
|
|
|
||
|
|
IOLoop.current().add_callback(simulator, list(futures_q))
|
||
|
|
|
||
|
|
def use_some_resource():
|
||
|
|
return futures_q.popleft()
|
||
|
|
|
||
|
|
.. testcode:: semaphore
|
||
|
|
|
||
|
|
from tornado import gen
|
||
|
|
from tornado.ioloop import IOLoop
|
||
|
|
from tornado.locks import Semaphore
|
||
|
|
|
||
|
|
sem = Semaphore(2)
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def worker(worker_id):
|
||
|
|
yield sem.acquire()
|
||
|
|
try:
|
||
|
|
print("Worker %d is working" % worker_id)
|
||
|
|
yield use_some_resource()
|
||
|
|
finally:
|
||
|
|
print("Worker %d is done" % worker_id)
|
||
|
|
sem.release()
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def runner():
|
||
|
|
# Join all workers.
|
||
|
|
yield [worker(i) for i in range(3)]
|
||
|
|
|
||
|
|
IOLoop.current().run_sync(runner)
|
||
|
|
|
||
|
|
.. testoutput:: semaphore
|
||
|
|
|
||
|
|
Worker 0 is working
|
||
|
|
Worker 1 is working
|
||
|
|
Worker 0 is done
|
||
|
|
Worker 2 is working
|
||
|
|
Worker 1 is done
|
||
|
|
Worker 2 is done
|
||
|
|
|
||
|
|
Workers 0 and 1 are allowed to run concurrently, but worker 2 waits until
|
||
|
|
the semaphore has been released once, by worker 0.
|
||
|
|
|
||
|
|
`.acquire` is a context manager, so ``worker`` could be written as::
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def worker(worker_id):
|
||
|
|
with (yield sem.acquire()):
|
||
|
|
print("Worker %d is working" % worker_id)
|
||
|
|
yield use_some_resource()
|
||
|
|
|
||
|
|
# Now the semaphore has been released.
|
||
|
|
print("Worker %d is done" % worker_id)
|
||
|
|
|
||
|
|
In Python 3.5, the semaphore itself can be used as an async context
|
||
|
|
manager::
|
||
|
|
|
||
|
|
async def worker(worker_id):
|
||
|
|
async with sem:
|
||
|
|
print("Worker %d is working" % worker_id)
|
||
|
|
await use_some_resource()
|
||
|
|
|
||
|
|
# Now the semaphore has been released.
|
||
|
|
print("Worker %d is done" % worker_id)
|
||
|
|
|
||
|
|
.. versionchanged:: 4.3
|
||
|
|
Added ``async with`` support in Python 3.5.
|
||
|
|
"""
|
||
|
|
def __init__(self, value=1):
|
||
|
|
super(Semaphore, self).__init__()
|
||
|
|
if value < 0:
|
||
|
|
raise ValueError('semaphore initial value must be >= 0')
|
||
|
|
|
||
|
|
self._value = value
|
||
|
|
|
||
|
|
def __repr__(self):
|
||
|
|
res = super(Semaphore, self).__repr__()
|
||
|
|
extra = 'locked' if self._value == 0 else 'unlocked,value:{0}'.format(
|
||
|
|
self._value)
|
||
|
|
if self._waiters:
|
||
|
|
extra = '{0},waiters:{1}'.format(extra, len(self._waiters))
|
||
|
|
return '<{0} [{1}]>'.format(res[1:-1], extra)
|
||
|
|
|
||
|
|
def release(self):
|
||
|
|
"""Increment the counter and wake one waiter."""
|
||
|
|
self._value += 1
|
||
|
|
while self._waiters:
|
||
|
|
waiter = self._waiters.popleft()
|
||
|
|
if not waiter.done():
|
||
|
|
self._value -= 1
|
||
|
|
|
||
|
|
# If the waiter is a coroutine paused at
|
||
|
|
#
|
||
|
|
# with (yield semaphore.acquire()):
|
||
|
|
#
|
||
|
|
# then the context manager's __exit__ calls release() at the end
|
||
|
|
# of the "with" block.
|
||
|
|
waiter.set_result(_ReleasingContextManager(self))
|
||
|
|
break
|
||
|
|
|
||
|
|
def acquire(self, timeout=None):
|
||
|
|
"""Decrement the counter. Returns a Future.
|
||
|
|
|
||
|
|
Block if the counter is zero and wait for a `.release`. The Future
|
||
|
|
raises `.TimeoutError` after the deadline.
|
||
|
|
"""
|
||
|
|
waiter = Future()
|
||
|
|
if self._value > 0:
|
||
|
|
self._value -= 1
|
||
|
|
waiter.set_result(_ReleasingContextManager(self))
|
||
|
|
else:
|
||
|
|
self._waiters.append(waiter)
|
||
|
|
if timeout:
|
||
|
|
def on_timeout():
|
||
|
|
waiter.set_exception(gen.TimeoutError())
|
||
|
|
self._garbage_collect()
|
||
|
|
io_loop = ioloop.IOLoop.current()
|
||
|
|
timeout_handle = io_loop.add_timeout(timeout, on_timeout)
|
||
|
|
waiter.add_done_callback(
|
||
|
|
lambda _: io_loop.remove_timeout(timeout_handle))
|
||
|
|
return waiter
|
||
|
|
|
||
|
|
def __enter__(self):
|
||
|
|
raise RuntimeError(
|
||
|
|
"Use Semaphore like 'with (yield semaphore.acquire())', not like"
|
||
|
|
" 'with semaphore'")
|
||
|
|
|
||
|
|
__exit__ = __enter__
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def __aenter__(self):
|
||
|
|
yield self.acquire()
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def __aexit__(self, typ, value, tb):
|
||
|
|
self.release()
|
||
|
|
|
||
|
|
|
||
|
|
class BoundedSemaphore(Semaphore):
|
||
|
|
"""A semaphore that prevents release() being called too many times.
|
||
|
|
|
||
|
|
If `.release` would increment the semaphore's value past the initial
|
||
|
|
value, it raises `ValueError`. Semaphores are mostly used to guard
|
||
|
|
resources with limited capacity, so a semaphore released too many times
|
||
|
|
is a sign of a bug.
|
||
|
|
"""
|
||
|
|
def __init__(self, value=1):
|
||
|
|
super(BoundedSemaphore, self).__init__(value=value)
|
||
|
|
self._initial_value = value
|
||
|
|
|
||
|
|
def release(self):
|
||
|
|
"""Increment the counter and wake one waiter."""
|
||
|
|
if self._value >= self._initial_value:
|
||
|
|
raise ValueError("Semaphore released too many times")
|
||
|
|
super(BoundedSemaphore, self).release()
|
||
|
|
|
||
|
|
|
||
|
|
class Lock(object):
|
||
|
|
"""A lock for coroutines.
|
||
|
|
|
||
|
|
A Lock begins unlocked, and `acquire` locks it immediately. While it is
|
||
|
|
locked, a coroutine that yields `acquire` waits until another coroutine
|
||
|
|
calls `release`.
|
||
|
|
|
||
|
|
Releasing an unlocked lock raises `RuntimeError`.
|
||
|
|
|
||
|
|
`acquire` supports the context manager protocol in all Python versions:
|
||
|
|
|
||
|
|
>>> from tornado import gen, locks
|
||
|
|
>>> lock = locks.Lock()
|
||
|
|
>>>
|
||
|
|
>>> @gen.coroutine
|
||
|
|
... def f():
|
||
|
|
... with (yield lock.acquire()):
|
||
|
|
... # Do something holding the lock.
|
||
|
|
... pass
|
||
|
|
...
|
||
|
|
... # Now the lock is released.
|
||
|
|
|
||
|
|
In Python 3.5, `Lock` also supports the async context manager
|
||
|
|
protocol. Note that in this case there is no `acquire`, because
|
||
|
|
``async with`` includes both the ``yield`` and the ``acquire``
|
||
|
|
(just as it does with `threading.Lock`):
|
||
|
|
|
||
|
|
>>> async def f(): # doctest: +SKIP
|
||
|
|
... async with lock:
|
||
|
|
... # Do something holding the lock.
|
||
|
|
... pass
|
||
|
|
...
|
||
|
|
... # Now the lock is released.
|
||
|
|
|
||
|
|
.. versionchanged:: 3.5
|
||
|
|
Added ``async with`` support in Python 3.5.
|
||
|
|
|
||
|
|
"""
|
||
|
|
def __init__(self):
|
||
|
|
self._block = BoundedSemaphore(value=1)
|
||
|
|
|
||
|
|
def __repr__(self):
|
||
|
|
return "<%s _block=%s>" % (
|
||
|
|
self.__class__.__name__,
|
||
|
|
self._block)
|
||
|
|
|
||
|
|
def acquire(self, timeout=None):
|
||
|
|
"""Attempt to lock. Returns a Future.
|
||
|
|
|
||
|
|
Returns a Future, which raises `tornado.gen.TimeoutError` after a
|
||
|
|
timeout.
|
||
|
|
"""
|
||
|
|
return self._block.acquire(timeout)
|
||
|
|
|
||
|
|
def release(self):
|
||
|
|
"""Unlock.
|
||
|
|
|
||
|
|
The first coroutine in line waiting for `acquire` gets the lock.
|
||
|
|
|
||
|
|
If not locked, raise a `RuntimeError`.
|
||
|
|
"""
|
||
|
|
try:
|
||
|
|
self._block.release()
|
||
|
|
except ValueError:
|
||
|
|
raise RuntimeError('release unlocked lock')
|
||
|
|
|
||
|
|
def __enter__(self):
|
||
|
|
raise RuntimeError(
|
||
|
|
"Use Lock like 'with (yield lock)', not like 'with lock'")
|
||
|
|
|
||
|
|
__exit__ = __enter__
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def __aenter__(self):
|
||
|
|
yield self.acquire()
|
||
|
|
|
||
|
|
@gen.coroutine
|
||
|
|
def __aexit__(self, typ, value, tb):
|
||
|
|
self.release()
|