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# Copyright 2015 Yahoo.com
#
# 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.
import collections
import contextlib
import threading
import time
from typing import Callable, Optional, TypeVar, Deque, List, Generic, Iterator
T = TypeVar("T")
class ObjectPool(Generic[T]):
"""A pool of objects that release/creates/destroys as needed."""
def __init__(
self,
obj_creator: Callable[[], T],
after_remove: Optional[Callable] = None,
max_size: Optional[int] = None,
idle_timeout: int = 0,
lock_generator: Optional[Callable] = None,
):
self._used_objs: Deque[T] = collections.deque()
self._free_objs: Deque[T] = collections.deque()
self._obj_creator = obj_creator
if lock_generator is None:
self._lock = threading.Lock()
else:
self._lock = lock_generator()
self._after_remove = after_remove
max_size = max_size or 2**31
if not isinstance(max_size, int) or max_size < 0:
raise ValueError('"max_size" must be a positive integer')
self.max_size = max_size
self.idle_timeout = idle_timeout
if idle_timeout:
self._idle_clock = time.time
else:
self._idle_clock = float
@property
def used(self):
return tuple(self._used_objs)
@property
def free(self):
return tuple(self._free_objs)
@contextlib.contextmanager
def get_and_release(self, destroy_on_fail=False) -> Iterator[T]:
obj = self.get()
try:
yield obj
except Exception:
if not destroy_on_fail:
self.release(obj)
else:
self.destroy(obj)
raise
self.release(obj)
def get(self):
with self._lock:
# Find a free object, removing any that have idled for too long.
now = self._idle_clock()
while self._free_objs:
obj = self._free_objs.popleft()
if now - obj._last_used <= self.idle_timeout:
break
if self._after_remove is not None:
self._after_remove(obj)
else:
# No free objects, create a new one.
curr_count = len(self._used_objs)
if curr_count >= self.max_size:
raise RuntimeError(
"Too many objects," " %s >= %s" % (curr_count, self.max_size)
)
obj = self._obj_creator()
self._used_objs.append(obj)
obj._last_used = now
return obj
def destroy(self, obj, silent=True) -> None:
was_dropped = False
with self._lock:
try:
self._used_objs.remove(obj)
was_dropped = True
except ValueError:
if not silent:
raise
if was_dropped and self._after_remove is not None:
self._after_remove(obj)
def release(self, obj, silent=True) -> None:
with self._lock:
try:
self._used_objs.remove(obj)
self._free_objs.append(obj)
obj._last_used = self._idle_clock()
except ValueError:
if not silent:
raise
def clear(self) -> None:
if self._after_remove is not None:
needs_destroy: List[T] = []
with self._lock:
needs_destroy.extend(self._used_objs)
needs_destroy.extend(self._free_objs)
self._free_objs.clear()
self._used_objs.clear()
for obj in needs_destroy:
self._after_remove(obj)
else:
with self._lock:
self._free_objs.clear()
self._used_objs.clear()
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