292 lines
9.1 KiB
Python
292 lines
9.1 KiB
Python
# util/queue.py
|
|
# Copyright (C) 2005-2021 the SQLAlchemy authors and contributors
|
|
# <see AUTHORS file>
|
|
#
|
|
# This module is part of SQLAlchemy and is released under
|
|
# the MIT License: http://www.opensource.org/licenses/mit-license.php
|
|
|
|
"""An adaptation of Py2.3/2.4's Queue module which supports reentrant
|
|
behavior, using RLock instead of Lock for its mutex object. The
|
|
Queue object is used exclusively by the sqlalchemy.pool.QueuePool
|
|
class.
|
|
|
|
This is to support the connection pool's usage of weakref callbacks to return
|
|
connections to the underlying Queue, which can in extremely
|
|
rare cases be invoked within the ``get()`` method of the Queue itself,
|
|
producing a ``put()`` inside the ``get()`` and therefore a reentrant
|
|
condition.
|
|
|
|
"""
|
|
|
|
from collections import deque
|
|
from time import time as _time
|
|
|
|
from . import compat
|
|
from .compat import threading
|
|
from .concurrency import asyncio
|
|
from .concurrency import await_fallback
|
|
from .concurrency import await_only
|
|
from .langhelpers import memoized_property
|
|
|
|
|
|
__all__ = ["Empty", "Full", "Queue"]
|
|
|
|
|
|
class Empty(Exception):
|
|
"Exception raised by Queue.get(block=0)/get_nowait()."
|
|
|
|
pass
|
|
|
|
|
|
class Full(Exception):
|
|
"Exception raised by Queue.put(block=0)/put_nowait()."
|
|
|
|
pass
|
|
|
|
|
|
class Queue:
|
|
def __init__(self, maxsize=0, use_lifo=False):
|
|
"""Initialize a queue object with a given maximum size.
|
|
|
|
If `maxsize` is <= 0, the queue size is infinite.
|
|
|
|
If `use_lifo` is True, this Queue acts like a Stack (LIFO).
|
|
"""
|
|
|
|
self._init(maxsize)
|
|
# mutex must be held whenever the queue is mutating. All methods
|
|
# that acquire mutex must release it before returning. mutex
|
|
# is shared between the two conditions, so acquiring and
|
|
# releasing the conditions also acquires and releases mutex.
|
|
self.mutex = threading.RLock()
|
|
# Notify not_empty whenever an item is added to the queue; a
|
|
# thread waiting to get is notified then.
|
|
self.not_empty = threading.Condition(self.mutex)
|
|
# Notify not_full whenever an item is removed from the queue;
|
|
# a thread waiting to put is notified then.
|
|
self.not_full = threading.Condition(self.mutex)
|
|
# If this queue uses LIFO or FIFO
|
|
self.use_lifo = use_lifo
|
|
|
|
def qsize(self):
|
|
"""Return the approximate size of the queue (not reliable!)."""
|
|
|
|
with self.mutex:
|
|
return self._qsize()
|
|
|
|
def empty(self):
|
|
"""Return True if the queue is empty, False otherwise (not
|
|
reliable!)."""
|
|
|
|
with self.mutex:
|
|
return self._empty()
|
|
|
|
def full(self):
|
|
"""Return True if the queue is full, False otherwise (not
|
|
reliable!)."""
|
|
|
|
with self.mutex:
|
|
return self._full()
|
|
|
|
def put(self, item, block=True, timeout=None):
|
|
"""Put an item into the queue.
|
|
|
|
If optional args `block` is True and `timeout` is None (the
|
|
default), block if necessary until a free slot is
|
|
available. If `timeout` is a positive number, it blocks at
|
|
most `timeout` seconds and raises the ``Full`` exception if no
|
|
free slot was available within that time. Otherwise (`block`
|
|
is false), put an item on the queue if a free slot is
|
|
immediately available, else raise the ``Full`` exception
|
|
(`timeout` is ignored in that case).
|
|
"""
|
|
|
|
with self.not_full:
|
|
if not block:
|
|
if self._full():
|
|
raise Full
|
|
elif timeout is None:
|
|
while self._full():
|
|
self.not_full.wait()
|
|
else:
|
|
if timeout < 0:
|
|
raise ValueError("'timeout' must be a positive number")
|
|
endtime = _time() + timeout
|
|
while self._full():
|
|
remaining = endtime - _time()
|
|
if remaining <= 0.0:
|
|
raise Full
|
|
self.not_full.wait(remaining)
|
|
self._put(item)
|
|
self.not_empty.notify()
|
|
|
|
def put_nowait(self, item):
|
|
"""Put an item into the queue without blocking.
|
|
|
|
Only enqueue the item if a free slot is immediately available.
|
|
Otherwise raise the ``Full`` exception.
|
|
"""
|
|
return self.put(item, False)
|
|
|
|
def get(self, block=True, timeout=None):
|
|
"""Remove and return an item from the queue.
|
|
|
|
If optional args `block` is True and `timeout` is None (the
|
|
default), block if necessary until an item is available. If
|
|
`timeout` is a positive number, it blocks at most `timeout`
|
|
seconds and raises the ``Empty`` exception if no item was
|
|
available within that time. Otherwise (`block` is false),
|
|
return an item if one is immediately available, else raise the
|
|
``Empty`` exception (`timeout` is ignored in that case).
|
|
|
|
"""
|
|
with self.not_empty:
|
|
if not block:
|
|
if self._empty():
|
|
raise Empty
|
|
elif timeout is None:
|
|
while self._empty():
|
|
self.not_empty.wait()
|
|
else:
|
|
if timeout < 0:
|
|
raise ValueError("'timeout' must be a positive number")
|
|
endtime = _time() + timeout
|
|
while self._empty():
|
|
remaining = endtime - _time()
|
|
if remaining <= 0.0:
|
|
raise Empty
|
|
self.not_empty.wait(remaining)
|
|
item = self._get()
|
|
self.not_full.notify()
|
|
return item
|
|
|
|
def get_nowait(self):
|
|
"""Remove and return an item from the queue without blocking.
|
|
|
|
Only get an item if one is immediately available. Otherwise
|
|
raise the ``Empty`` exception.
|
|
"""
|
|
|
|
return self.get(False)
|
|
|
|
# Override these methods to implement other queue organizations
|
|
# (e.g. stack or priority queue).
|
|
# These will only be called with appropriate locks held
|
|
|
|
# Initialize the queue representation
|
|
def _init(self, maxsize):
|
|
self.maxsize = maxsize
|
|
self.queue = deque()
|
|
|
|
def _qsize(self):
|
|
return len(self.queue)
|
|
|
|
# Check whether the queue is empty
|
|
def _empty(self):
|
|
return not self.queue
|
|
|
|
# Check whether the queue is full
|
|
def _full(self):
|
|
return self.maxsize > 0 and len(self.queue) == self.maxsize
|
|
|
|
# Put a new item in the queue
|
|
def _put(self, item):
|
|
self.queue.append(item)
|
|
|
|
# Get an item from the queue
|
|
def _get(self):
|
|
if self.use_lifo:
|
|
# LIFO
|
|
return self.queue.pop()
|
|
else:
|
|
# FIFO
|
|
return self.queue.popleft()
|
|
|
|
|
|
class AsyncAdaptedQueue:
|
|
await_ = staticmethod(await_only)
|
|
|
|
def __init__(self, maxsize=0, use_lifo=False):
|
|
self.use_lifo = use_lifo
|
|
self.maxsize = maxsize
|
|
|
|
def empty(self):
|
|
return self._queue.empty()
|
|
|
|
def full(self):
|
|
return self._queue.full()
|
|
|
|
def qsize(self):
|
|
return self._queue.qsize()
|
|
|
|
@memoized_property
|
|
def _queue(self):
|
|
# Delay creation of the queue until it is first used, to avoid
|
|
# binding it to a possibly wrong event loop.
|
|
# By delaying the creation of the pool we accommodate the common
|
|
# usage pattern of instantiating the engine at module level, where a
|
|
# different event loop is in present compared to when the application
|
|
# is actually run.
|
|
|
|
if self.use_lifo:
|
|
queue = asyncio.LifoQueue(maxsize=self.maxsize)
|
|
else:
|
|
queue = asyncio.Queue(maxsize=self.maxsize)
|
|
return queue
|
|
|
|
def put_nowait(self, item):
|
|
try:
|
|
return self._queue.put_nowait(item)
|
|
except asyncio.QueueFull as err:
|
|
compat.raise_(
|
|
Full(),
|
|
replace_context=err,
|
|
)
|
|
|
|
def put(self, item, block=True, timeout=None):
|
|
if not block:
|
|
return self.put_nowait(item)
|
|
|
|
try:
|
|
if timeout is not None:
|
|
return self.await_(
|
|
asyncio.wait_for(self._queue.put(item), timeout)
|
|
)
|
|
else:
|
|
return self.await_(self._queue.put(item))
|
|
except (asyncio.QueueFull, asyncio.TimeoutError) as err:
|
|
compat.raise_(
|
|
Full(),
|
|
replace_context=err,
|
|
)
|
|
|
|
def get_nowait(self):
|
|
try:
|
|
return self._queue.get_nowait()
|
|
except asyncio.QueueEmpty as err:
|
|
compat.raise_(
|
|
Empty(),
|
|
replace_context=err,
|
|
)
|
|
|
|
def get(self, block=True, timeout=None):
|
|
if not block:
|
|
return self.get_nowait()
|
|
|
|
try:
|
|
if timeout is not None:
|
|
return self.await_(
|
|
asyncio.wait_for(self._queue.get(), timeout)
|
|
)
|
|
else:
|
|
return self.await_(self._queue.get())
|
|
except (asyncio.QueueEmpty, asyncio.TimeoutError) as err:
|
|
compat.raise_(
|
|
Empty(),
|
|
replace_context=err,
|
|
)
|
|
|
|
|
|
class FallbackAsyncAdaptedQueue(AsyncAdaptedQueue):
|
|
await_ = staticmethod(await_fallback)
|