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# Copyright 2013 Red Hat, Inc.
#
# 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 abc
import collections
import threading
from oslo_log import log as logging
from oslo_utils import timeutils
from oslo_messaging._drivers import common
LOG = logging.getLogger(__name__)
class Pool(object, metaclass=abc.ABCMeta):
"""A thread-safe object pool.
Modelled after the eventlet.pools.Pool interface, but designed to be safe
when using native threads without the GIL.
Resizing is not supported.
"""
def __init__(self, max_size=4, min_size=2, ttl=1200, on_expire=None):
super(Pool, self).__init__()
self._min_size = min_size
self._max_size = max_size
self._item_ttl = ttl
self._current_size = 0
self._cond = threading.Condition()
self._items = collections.deque()
self._on_expire = on_expire
def expire(self):
"""Remove expired items from left (the oldest item) to
right (the newest item).
"""
with self._cond:
while len(self._items) > self._min_size:
try:
ttl_watch, item = self._items.popleft()
if ttl_watch.expired():
self._on_expire and self._on_expire(item)
self._current_size -= 1
else:
self._items.appendleft((ttl_watch, item))
return
except IndexError:
break
def put(self, item):
"""Return an item to the pool."""
with self._cond:
ttl_watch = timeutils.StopWatch(duration=self._item_ttl)
ttl_watch.start()
self._items.append((ttl_watch, item))
self._cond.notify()
def get(self):
"""Return an item from the pool, when one is available.
This may cause the calling thread to block.
"""
with self._cond:
while True:
try:
ttl_watch, item = self._items.pop()
self.expire()
return item
except IndexError:
pass
if self._current_size < self._max_size:
self._current_size += 1
break
LOG.warning("Connection pool limit exceeded: "
"current size %s surpasses max "
"configured rpc_conn_pool_size %s",
self._current_size, self._max_size)
self._cond.wait()
# We've grabbed a slot and dropped the lock, now do the creation
try:
return self.create()
except Exception:
with self._cond:
self._current_size -= 1
raise
def iter_free(self):
"""Iterate over free items."""
while True:
try:
_, item = self._items.pop()
yield item
except IndexError:
return
@abc.abstractmethod
def create(self):
"""Construct a new item."""
class ConnectionPool(Pool):
"""Class that implements a Pool of Connections."""
def __init__(self, conf, max_size, min_size, ttl, url, connection_cls):
self.connection_cls = connection_cls
self.conf = conf
self.url = url
super(ConnectionPool, self).__init__(max_size, min_size, ttl,
self._on_expire)
def _on_expire(self, connection):
connection.close()
LOG.debug("Idle connection has expired and been closed."
" Pool size: %d" % len(self._items))
def create(self, purpose=common.PURPOSE_SEND):
LOG.debug('Pool creating new connection')
return self.connection_cls(self.conf, self.url, purpose)
def empty(self):
for item in self.iter_free():
item.close()