135 lines
4.3 KiB
Python
135 lines
4.3 KiB
Python
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# Copyright 2015 Yahoo.com
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import collections
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import contextlib
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import threading
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import time
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from typing import Callable, Optional, TypeVar, Deque, List, Generic, Iterator
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T = TypeVar("T")
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class ObjectPool(Generic[T]):
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"""A pool of objects that release/creates/destroys as needed."""
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def __init__(
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self,
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obj_creator: Callable[[], T],
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after_remove: Optional[Callable] = None,
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max_size: Optional[int] = None,
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idle_timeout: int = 0,
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lock_generator: Optional[Callable] = None,
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):
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self._used_objs: Deque[T] = collections.deque()
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self._free_objs: Deque[T] = collections.deque()
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self._obj_creator = obj_creator
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if lock_generator is None:
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self._lock = threading.Lock()
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else:
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self._lock = lock_generator()
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self._after_remove = after_remove
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max_size = max_size or 2**31
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if not isinstance(max_size, int) or max_size < 0:
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raise ValueError('"max_size" must be a positive integer')
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self.max_size = max_size
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self.idle_timeout = idle_timeout
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if idle_timeout:
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self._idle_clock = time.time
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else:
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self._idle_clock = float
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@property
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def used(self):
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return tuple(self._used_objs)
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@property
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def free(self):
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return tuple(self._free_objs)
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@contextlib.contextmanager
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def get_and_release(self, destroy_on_fail=False) -> Iterator[T]:
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obj = self.get()
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try:
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yield obj
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except Exception:
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if not destroy_on_fail:
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self.release(obj)
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else:
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self.destroy(obj)
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raise
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self.release(obj)
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def get(self):
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with self._lock:
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# Find a free object, removing any that have idled for too long.
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now = self._idle_clock()
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while self._free_objs:
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obj = self._free_objs.popleft()
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if now - obj._last_used <= self.idle_timeout:
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break
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if self._after_remove is not None:
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self._after_remove(obj)
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else:
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# No free objects, create a new one.
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curr_count = len(self._used_objs)
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if curr_count >= self.max_size:
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raise RuntimeError(
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"Too many objects," " %s >= %s" % (curr_count, self.max_size)
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)
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obj = self._obj_creator()
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self._used_objs.append(obj)
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obj._last_used = now
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return obj
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def destroy(self, obj, silent=True) -> None:
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was_dropped = False
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with self._lock:
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try:
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self._used_objs.remove(obj)
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was_dropped = True
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except ValueError:
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if not silent:
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raise
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if was_dropped and self._after_remove is not None:
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self._after_remove(obj)
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def release(self, obj, silent=True) -> None:
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with self._lock:
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try:
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self._used_objs.remove(obj)
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self._free_objs.append(obj)
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obj._last_used = self._idle_clock()
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except ValueError:
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if not silent:
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raise
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def clear(self) -> None:
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if self._after_remove is not None:
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needs_destroy: List[T] = []
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with self._lock:
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needs_destroy.extend(self._used_objs)
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needs_destroy.extend(self._free_objs)
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self._free_objs.clear()
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self._used_objs.clear()
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for obj in needs_destroy:
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self._after_remove(obj)
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else:
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with self._lock:
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self._free_objs.clear()
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self._used_objs.clear()
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