OpenStack Identity (Keystone)
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# Copyright 2014 Mirantis Inc
# All Rights Reserved.
# 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
# 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.
"""Thread-safe connection pool for python-memcached."""
# NOTE(yorik-sar): this file is copied between keystone and keystonemiddleware
# and should be kept in sync until we can use external library for this.
import collections
import contextlib
import itertools
import logging
import threading
import time
import memcache
from six.moves import queue
from keystone import exception
from keystone.i18n import _
from keystone.openstack.common import log
LOG = log.getLogger(__name__)
# This 'class' is taken from
# Don't inherit client from threading.local so that we can reuse clients in
# different threads
_MemcacheClient = type('_MemcacheClient', (object,),
_PoolItem = collections.namedtuple('_PoolItem', ['ttl', 'connection'])
class ConnectionPool(queue.Queue):
"""Base connection pool class
This class implements the basic connection pool logic as an abstract base
def __init__(self, maxsize, unused_timeout, conn_get_timeout=None):
"""Initialize the connection pool.
:param maxsize: maximum number of client connections for the pool
:type maxsize: int
:param unused_timeout: idle time to live for unused clients (in
seconds). If a client connection object has been
in the pool and idle for longer than the
unused_timeout, it will be reaped. This is to
ensure resources are released as utilization
goes down.
:type unused_timeout: int
:param conn_get_timeout: maximum time in seconds to wait for a
connection. If set to `None` timeout is
:type conn_get_timeout: int
queue.Queue.__init__(self, maxsize)
self._unused_timeout = unused_timeout
self._connection_get_timeout = conn_get_timeout
self._acquired = 0
def _create_connection(self):
"""Returns a connection instance.
This is called when the pool needs another instance created.
:returns: a new connection instance
raise NotImplementedError
def _destroy_connection(self, conn):
"""Destroy and cleanup a connection instance.
This is called when the pool wishes to get rid of an existing
connection. This is the opportunity for a subclass to free up
resources and cleaup after itself.
:param conn: the connection object to destroy
raise NotImplementedError
def _debug_logger(self, msg, *args, **kwargs):
if LOG.isEnabledFor(logging.DEBUG):
thread_id = threading.current_thread().ident
args = (id(self), thread_id) + args
prefix = 'Memcached pool %s, thread %s: '
LOG.debug(prefix + msg, *args, **kwargs)
def acquire(self):
self._debug_logger('Acquiring connection')
conn = self.get(timeout=self._connection_get_timeout)
except queue.Empty:
raise exception.UnexpectedError(
_('Unable to get a connection from pool id %(id)s after '
'%(seconds)s seconds.') %
{'id': id(self), 'seconds': self._connection_get_timeout})
self._debug_logger('Acquired connection %s', id(conn))
yield conn
self._debug_logger('Releasing connection %s', id(conn))
def _qsize(self):
return self.maxsize - self._acquired
# NOTE(dstanek): stdlib and eventlet Queue implementations
# have different names for the qsize method. This ensures
# that we override both of them.
if not hasattr(queue.Queue, '_qsize'):
qsize = _qsize
def _get(self):
if self.queue:
conn = self.queue.pop().connection
conn = self._create_connection()
self._acquired += 1
return conn
def _drop_expired_connections(self, conn):
"""Drop all expired connections from the right end of the queue.
:param conn: connection object
now = time.time()
while self.queue and self.queue[0].ttl < now:
conn = self.queue.popleft().connection
self._debug_logger('Reaping connection %s', id(conn))
def _put(self, conn):
ttl=time.time() + self._unused_timeout,
self._acquired -= 1
class MemcacheClientPool(ConnectionPool):
def __init__(self, urls, arguments, **kwargs):
ConnectionPool.__init__(self, **kwargs)
self.urls = urls
self._arguments = arguments
# NOTE(morganfainberg): The host objects expect an int for the
# deaduntil value. Initialize this at 0 for each host with 0 indicating
# the host is not dead.
self._hosts_deaduntil = [0] * len(urls)
def _create_connection(self):
return _MemcacheClient(self.urls, **self._arguments)
def _destroy_connection(self, conn):
def _get(self):
conn = ConnectionPool._get(self)
# Propagate host state known to us to this client's list
now = time.time()
for deaduntil, host in zip(self._hosts_deaduntil, conn.servers):
if deaduntil > now and host.deaduntil <= now:
host.mark_dead('propagating death mark from the pool')
host.deaduntil = deaduntil
except Exception:
# We need to be sure that connection doesn't leak from the pool.
# This code runs before we enter context manager's try-finally
# block, so we need to explicitly release it here
ConnectionPool._put(self, conn)
return conn
def _put(self, conn):
# If this client found that one of the hosts is dead, mark it as
# such in our internal list
now = time.time()
for i, host in zip(itertools.count(), conn.servers):
deaduntil = self._hosts_deaduntil[i]
# Do nothing if we already know this host is dead
if deaduntil <= now:
if host.deaduntil > now:
self._hosts_deaduntil[i] = host.deaduntil
'Marked host %s dead until %s',
self.urls[i], host.deaduntil)
self._hosts_deaduntil[i] = 0
# If all hosts are dead we should forget that they're dead. This
# way we won't get completely shut off until dead_retry seconds
# pass, but will be checking servers as frequent as we can (over
# way smaller socket_timeout)
if all(deaduntil > now for deaduntil in self._hosts_deaduntil):
self._debug_logger('All hosts are dead. Marking them as live.')
self._hosts_deaduntil[:] = [0] * len(self._hosts_deaduntil)
ConnectionPool._put(self, conn)