/usr/share/pyshared/swift/common/memcached.py is in python-swift 1.4.8-0ubuntu2.5.
This file is owned by root:root, with mode 0o644.
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#
# 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.
"""
Lucid comes with memcached: v1.4.2. Protocol documentation for that
version is at:
http://github.com/memcached/memcached/blob/1.4.2/doc/protocol.txt
"""
import cPickle as pickle
import logging
import socket
import time
from bisect import bisect
from hashlib import md5
try:
import simplejson as json
except ImportError:
import json
DEFAULT_MEMCACHED_PORT = 11211
CONN_TIMEOUT = 0.3
IO_TIMEOUT = 2.0
PICKLE_FLAG = 1
JSON_FLAG = 2
NODE_WEIGHT = 50
PICKLE_PROTOCOL = 2
TRY_COUNT = 3
# if ERROR_LIMIT_COUNT errors occur in ERROR_LIMIT_TIME seconds, the server
# will be considered failed for ERROR_LIMIT_DURATION seconds.
ERROR_LIMIT_COUNT = 10
ERROR_LIMIT_TIME = 60
ERROR_LIMIT_DURATION = 60
def md5hash(key):
return md5(key).hexdigest()
class MemcacheConnectionError(Exception):
pass
class MemcacheRing(object):
"""
Simple, consistent-hashed memcache client.
"""
def __init__(self, servers, connect_timeout=CONN_TIMEOUT,
io_timeout=IO_TIMEOUT, tries=TRY_COUNT,
allow_pickle=False, allow_unpickle=False):
self._ring = {}
self._errors = dict(((serv, []) for serv in servers))
self._error_limited = dict(((serv, 0) for serv in servers))
for server in sorted(servers):
for i in xrange(NODE_WEIGHT):
self._ring[md5hash('%s-%s' % (server, i))] = server
self._tries = tries if tries <= len(servers) else len(servers)
self._sorted = sorted(self._ring.keys())
self._client_cache = dict(((server, []) for server in servers))
self._connect_timeout = connect_timeout
self._io_timeout = io_timeout
self._allow_pickle = allow_pickle
self._allow_unpickle = allow_unpickle or allow_pickle
def _exception_occurred(self, server, e, action='talking'):
if isinstance(e, socket.timeout):
logging.error(_("Timeout %(action)s to memcached: %(server)s"),
{'action': action, 'server': server})
else:
logging.exception(_("Error %(action)s to memcached: %(server)s"),
{'action': action, 'server': server})
now = time.time()
self._errors[server].append(time.time())
if len(self._errors[server]) > ERROR_LIMIT_COUNT:
self._errors[server] = [err for err in self._errors[server]
if err > now - ERROR_LIMIT_TIME]
if len(self._errors[server]) > ERROR_LIMIT_COUNT:
self._error_limited[server] = now + ERROR_LIMIT_DURATION
logging.error(_('Error limiting server %s'), server)
def _get_conns(self, key):
"""
Retrieves a server conn from the pool, or connects a new one.
Chooses the server based on a consistent hash of "key".
"""
pos = bisect(self._sorted, key)
served = []
while len(served) < self._tries:
pos = (pos + 1) % len(self._sorted)
server = self._ring[self._sorted[pos]]
if server in served:
continue
served.append(server)
if self._error_limited[server] > time.time():
continue
try:
fp, sock = self._client_cache[server].pop()
yield server, fp, sock
except IndexError:
try:
if ':' in server:
host, port = server.split(':')
else:
host = server
port = DEFAULT_MEMCACHED_PORT
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
sock.settimeout(self._connect_timeout)
sock.connect((host, int(port)))
sock.settimeout(self._io_timeout)
yield server, sock.makefile(), sock
except Exception, e:
self._exception_occurred(server, e, 'connecting')
def _return_conn(self, server, fp, sock):
""" Returns a server connection to the pool """
self._client_cache[server].append((fp, sock))
def set(self, key, value, serialize=True, timeout=0):
"""
Set a key/value pair in memcache
:param key: key
:param value: value
:param serialize: if True, value is serialized with JSON before sending
to memcache, or with pickle if configured to use
pickle instead of JSON (to avoid cache poisoning)
:param timeout: ttl in memcache
"""
key = md5hash(key)
if timeout > 0:
timeout += time.time()
flags = 0
if serialize and self._allow_pickle:
value = pickle.dumps(value, PICKLE_PROTOCOL)
flags |= PICKLE_FLAG
elif serialize:
value = json.dumps(value)
flags |= JSON_FLAG
for (server, fp, sock) in self._get_conns(key):
try:
sock.sendall('set %s %d %d %s noreply\r\n%s\r\n' % \
(key, flags, timeout, len(value), value))
self._return_conn(server, fp, sock)
return
except Exception, e:
self._exception_occurred(server, e)
def get(self, key):
"""
Gets the object specified by key. It will also unserialize the object
before returning if it is serialized in memcache with JSON, or if it
is pickled and unpickling is allowed.
:param key: key
:returns: value of the key in memcache
"""
key = md5hash(key)
value = None
for (server, fp, sock) in self._get_conns(key):
try:
sock.sendall('get %s\r\n' % key)
line = fp.readline().strip().split()
while line[0].upper() != 'END':
if line[0].upper() == 'VALUE' and line[1] == key:
size = int(line[3])
value = fp.read(size)
if int(line[2]) & PICKLE_FLAG:
if self._allow_unpickle:
value = pickle.loads(value)
else:
value = None
elif int(line[2]) & JSON_FLAG:
value = json.loads(value)
fp.readline()
line = fp.readline().strip().split()
self._return_conn(server, fp, sock)
return value
except Exception, e:
self._exception_occurred(server, e)
def incr(self, key, delta=1, timeout=0):
"""
Increments a key which has a numeric value by delta.
If the key can't be found, it's added as delta or 0 if delta < 0.
If passed a negative number, will use memcached's decr. Returns
the int stored in memcached
Note: The data memcached stores as the result of incr/decr is
an unsigned int. decr's that result in a number below 0 are
stored as 0.
:param key: key
:param delta: amount to add to the value of key (or set as the value
if the key is not found) will be cast to an int
:param timeout: ttl in memcache
:raises MemcacheConnectionError:
"""
key = md5hash(key)
command = 'incr'
if delta < 0:
command = 'decr'
delta = str(abs(int(delta)))
for (server, fp, sock) in self._get_conns(key):
try:
sock.sendall('%s %s %s\r\n' % (command, key, delta))
line = fp.readline().strip().split()
if line[0].upper() == 'NOT_FOUND':
add_val = delta
if command == 'decr':
add_val = '0'
sock.sendall('add %s %d %d %s\r\n%s\r\n' % \
(key, 0, timeout, len(add_val), add_val))
line = fp.readline().strip().split()
if line[0].upper() == 'NOT_STORED':
sock.sendall('%s %s %s\r\n' % (command, key, delta))
line = fp.readline().strip().split()
ret = int(line[0].strip())
else:
ret = int(add_val)
else:
ret = int(line[0].strip())
self._return_conn(server, fp, sock)
return ret
except Exception, e:
self._exception_occurred(server, e)
raise MemcacheConnectionError("No Memcached connections succeeded.")
def decr(self, key, delta=1, timeout=0):
"""
Decrements a key which has a numeric value by delta. Calls incr with
-delta.
:param key: key
:param delta: amount to subtract to the value of key (or set the
value to 0 if the key is not found) will be cast to
an int
:param timeout: ttl in memcache
:raises MemcacheConnectionError:
"""
self.incr(key, delta=-delta, timeout=timeout)
def delete(self, key):
"""
Deletes a key/value pair from memcache.
:param key: key to be deleted
"""
key = md5hash(key)
for (server, fp, sock) in self._get_conns(key):
try:
sock.sendall('delete %s noreply\r\n' % key)
self._return_conn(server, fp, sock)
return
except Exception, e:
self._exception_occurred(server, e)
def set_multi(self, mapping, server_key, serialize=True, timeout=0):
"""
Sets multiple key/value pairs in memcache.
:param mapping: dictonary of keys and values to be set in memcache
:param servery_key: key to use in determining which server in the ring
is used
:param serialize: if True, value is serialized with JSON before sending
to memcache, or with pickle if configured to use
pickle instead of JSON (to avoid cache poisoning)
:param timeout: ttl for memcache
"""
server_key = md5hash(server_key)
if timeout > 0:
timeout += time.time()
msg = ''
for key, value in mapping.iteritems():
key = md5hash(key)
flags = 0
if serialize and self._allow_pickle:
value = pickle.dumps(value, PICKLE_PROTOCOL)
flags |= PICKLE_FLAG
elif serialize:
value = json.dumps(value)
flags |= JSON_FLAG
msg += ('set %s %d %d %s noreply\r\n%s\r\n' %
(key, flags, timeout, len(value), value))
for (server, fp, sock) in self._get_conns(server_key):
try:
sock.sendall(msg)
self._return_conn(server, fp, sock)
return
except Exception, e:
self._exception_occurred(server, e)
def get_multi(self, keys, server_key):
"""
Gets multiple values from memcache for the given keys.
:param keys: keys for values to be retrieved from memcache
:param servery_key: key to use in determining which server in the ring
is used
:returns: list of values
"""
server_key = md5hash(server_key)
keys = [md5hash(key) for key in keys]
for (server, fp, sock) in self._get_conns(server_key):
try:
sock.sendall('get %s\r\n' % ' '.join(keys))
line = fp.readline().strip().split()
responses = {}
while line[0].upper() != 'END':
if line[0].upper() == 'VALUE':
size = int(line[3])
value = fp.read(size)
if int(line[2]) & PICKLE_FLAG:
if self._allow_unpickle:
value = pickle.loads(value)
else:
value = None
elif int(line[2]) & JSON_FLAG:
value = json.loads(value)
responses[line[1]] = value
fp.readline()
line = fp.readline().strip().split()
values = []
for key in keys:
if key in responses:
values.append(responses[key])
else:
values.append(None)
self._return_conn(server, fp, sock)
return values
except Exception, e:
self._exception_occurred(server, e)
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