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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 sys
import threading
import six
class ObjectPool(object):
"""A pool of objects that release/creates/destroys as needed."""
def __init__(self, obj_creator,
after_remove=None, max_size=None):
self._used_objs = collections.deque()
self._free_objs = collections.deque()
self._obj_creator = obj_creator
self._lock = threading.Lock()
self._after_remove = after_remove
max_size = max_size or 2 ** 31
if not isinstance(max_size, six.integer_types) or max_size < 0:
raise ValueError('"max_size" must be a positive integer')
self.max_size = max_size
@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):
obj = self.get()
try:
yield obj
except Exception:
exc_info = sys.exc_info()
if not destroy_on_fail:
self.release(obj)
else:
self.destroy(obj)
six.reraise(exc_info[0], exc_info[1], exc_info[2])
self.release(obj)
def get(self):
with self._lock:
if not self._free_objs:
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)
return obj
else:
obj = self._free_objs.pop()
self._used_objs.append(obj)
return obj
def destroy(self, obj, silent=True):
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):
with self._lock:
try:
self._used_objs.remove(obj)
self._free_objs.append(obj)
except ValueError:
if not silent:
raise
def clear(self):
if self._after_remove is not None:
needs_destroy = []
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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