a437b219ac
Param flush_on_reconnect is very risky to use on production deployments. It can cause exponential raising of connections to memcached servers. Moreover this option makes sense only in keystone's oslo.cache config. This patch is moving flush_on_reconnect from code to oslo.cache config block to be configurable. Co-Authored-By: Hervé Beraud <hberaud@redhat.com> Change-Id: I8e6826bfb2c85e7ceed03e1667bd6a06b3dff469 Closes-Bug: #1888394
267 lines
9.7 KiB
Python
267 lines
9.7 KiB
Python
# Copyright 2014 Mirantis Inc
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# 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, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""Thread-safe connection pool for python-memcached."""
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import collections
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import contextlib
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import itertools
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import queue
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import threading
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import time
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try:
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import eventlet
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except ImportError:
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eventlet = None
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import memcache
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from oslo_log import log
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from oslo_cache._i18n import _
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from oslo_cache import exception
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LOG = log.getLogger(__name__)
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class _MemcacheClient(memcache.Client):
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"""Thread global memcache client
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As client is inherited from threading.local we have to restore object
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methods overloaded by threading.local so we can reuse clients in
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different threads
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"""
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__delattr__ = object.__delattr__
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__getattribute__ = object.__getattribute__
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__setattr__ = object.__setattr__
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# Hack for lp 1812935
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if eventlet and eventlet.patcher.is_monkey_patched('thread'):
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# NOTE(bnemec): I'm not entirely sure why this works in a
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# monkey-patched environment and not with vanilla stdlib, but it does.
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def __new__(cls, *args, **kwargs):
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return object.__new__(cls)
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else:
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__new__ = object.__new__
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def __del__(self):
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pass
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_PoolItem = collections.namedtuple('_PoolItem', ['ttl', 'connection'])
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class ConnectionPool(queue.Queue):
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"""Base connection pool class
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This class implements the basic connection pool logic as an abstract base
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class.
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"""
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def __init__(self, maxsize, unused_timeout, conn_get_timeout=None):
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"""Initialize the connection pool.
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:param maxsize: maximum number of client connections for the pool
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:type maxsize: int
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:param unused_timeout: idle time to live for unused clients (in
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seconds). If a client connection object has been
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in the pool and idle for longer than the
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unused_timeout, it will be reaped. This is to
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ensure resources are released as utilization
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goes down.
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:type unused_timeout: int
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:param conn_get_timeout: maximum time in seconds to wait for a
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connection. If set to `None` timeout is
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indefinite.
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:type conn_get_timeout: int
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"""
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# super() cannot be used here because Queue in stdlib is an
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# old-style class
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queue.Queue.__init__(self, maxsize)
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self._unused_timeout = unused_timeout
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self._connection_get_timeout = conn_get_timeout
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self._acquired = 0
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def _create_connection(self):
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"""Returns a connection instance.
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This is called when the pool needs another instance created.
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:returns: a new connection instance
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"""
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raise NotImplementedError
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def _destroy_connection(self, conn):
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"""Destroy and cleanup a connection instance.
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This is called when the pool wishes to get rid of an existing
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connection. This is the opportunity for a subclass to free up
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resources and cleanup after itself.
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:param conn: the connection object to destroy
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"""
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raise NotImplementedError
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def _do_log(self, level, msg, *args, **kwargs):
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if LOG.isEnabledFor(level):
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thread_id = threading.current_thread().ident
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args = (id(self), thread_id) + args
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prefix = 'Memcached pool %s, thread %s: '
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LOG.log(level, prefix + msg, *args, **kwargs)
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def _debug_logger(self, msg, *args, **kwargs):
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self._do_log(log.DEBUG, msg, *args, **kwargs)
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def _trace_logger(self, msg, *args, **kwargs):
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self._do_log(log.TRACE, msg, *args, **kwargs)
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@contextlib.contextmanager
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def acquire(self):
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self._trace_logger('Acquiring connection')
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self._drop_expired_connections()
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try:
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conn = self.get(timeout=self._connection_get_timeout)
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except queue.Empty:
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raise exception.QueueEmpty(
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_('Unable to get a connection from pool id %(id)s after '
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'%(seconds)s seconds.') %
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{'id': id(self), 'seconds': self._connection_get_timeout})
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self._trace_logger('Acquired connection %s', id(conn))
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try:
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yield conn
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finally:
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self._trace_logger('Releasing connection %s', id(conn))
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try:
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# super() cannot be used here because Queue in stdlib is an
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# old-style class
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queue.Queue.put(self, conn, block=False)
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except queue.Full:
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self._trace_logger('Reaping exceeding connection %s', id(conn))
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self._destroy_connection(conn)
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def _qsize(self):
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if self.maxsize:
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return self.maxsize - self._acquired
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else:
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# A value indicating there is always a free connection
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# if maxsize is None or 0
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return 1
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# NOTE(dstanek): stdlib and eventlet Queue implementations
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# have different names for the qsize method. This ensures
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# that we override both of them.
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if not hasattr(queue.Queue, '_qsize'):
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qsize = _qsize
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def _get(self):
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try:
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conn = self.queue.pop().connection
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except IndexError:
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conn = self._create_connection()
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self._acquired += 1
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return conn
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def _drop_expired_connections(self):
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"""Drop all expired connections from the left end of the queue."""
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now = time.time()
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try:
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while self.queue[0].ttl < now:
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conn = self.queue.popleft().connection
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self._trace_logger('Reaping connection %s', id(conn))
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self._destroy_connection(conn)
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except IndexError:
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# NOTE(amakarov): This is an expected excepton. so there's no
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# need to react. We have to handle exceptions instead of
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# checking queue length as IndexError is a result of race
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# condition too as well as of mere queue depletio of mere queue
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# depletionn.
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pass
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def _put(self, conn):
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self.queue.append(_PoolItem(
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ttl=time.time() + self._unused_timeout,
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connection=conn,
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))
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self._acquired -= 1
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class MemcacheClientPool(ConnectionPool):
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def __init__(self, urls, arguments, **kwargs):
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# super() cannot be used here because Queue in stdlib is an
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# old-style class
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ConnectionPool.__init__(self, **kwargs)
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self.urls = urls
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self._arguments = arguments
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# NOTE(morganfainberg): The host objects expect an int for the
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# deaduntil value. Initialize this at 0 for each host with 0 indicating
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# the host is not dead.
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self._hosts_deaduntil = [0] * len(urls)
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def _create_connection(self):
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return _MemcacheClient(self.urls, **self._arguments)
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def _destroy_connection(self, conn):
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conn.disconnect_all()
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def _get(self):
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# super() cannot be used here because Queue in stdlib is an
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# old-style class
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conn = ConnectionPool._get(self)
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try:
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# Propagate host state known to us to this client's list
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now = time.time()
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for deaduntil, host in zip(self._hosts_deaduntil, conn.servers):
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if deaduntil > now and host.deaduntil <= now:
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host.mark_dead('propagating death mark from the pool')
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host.deaduntil = deaduntil
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except Exception:
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# We need to be sure that connection doesn't leak from the pool.
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# This code runs before we enter context manager's try-finally
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# block, so we need to explicitly release it here.
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# super() cannot be used here because Queue in stdlib is an
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# old-style class
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ConnectionPool._put(self, conn)
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raise
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return conn
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def _put(self, conn):
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try:
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# If this client found that one of the hosts is dead, mark it as
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# such in our internal list
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now = time.time()
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for i, host in zip(itertools.count(), conn.servers):
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deaduntil = self._hosts_deaduntil[i]
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# Do nothing if we already know this host is dead
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if deaduntil <= now:
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if host.deaduntil > now:
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self._hosts_deaduntil[i] = host.deaduntil
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self._debug_logger(
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'Marked host %s dead until %s',
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self.urls[i], host.deaduntil)
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else:
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self._hosts_deaduntil[i] = 0
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# If all hosts are dead we should forget that they're dead. This
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# way we won't get completely shut off until dead_retry seconds
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# pass, but will be checking servers as frequent as we can (over
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# way smaller socket_timeout)
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if all(deaduntil > now for deaduntil in self._hosts_deaduntil):
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self._debug_logger('All hosts are dead. Marking them as live.')
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self._hosts_deaduntil[:] = [0] * len(self._hosts_deaduntil)
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finally:
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# super() cannot be used here because Queue in stdlib is an
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# old-style class
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ConnectionPool._put(self, conn)
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