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#!/usr/bin/env python
"""client module for memcached (memory cache daemon)
Overview
========
See U{the MemCached homepage<http://www.danga.com/memcached>} for more
about memcached.
Usage summary
=============
This should give you a feel for how this module operates::
import memcache
mc = memcache.Client(['127.0.0.1:11211'], debug=0)
mc.set("some_key", "Some value")
value = mc.get("some_key")
mc.set("another_key", 3)
mc.delete("another_key")
mc.set("key", "1") # note that the key used for incr/decr must be
# a string.
mc.incr("key")
mc.decr("key")
The standard way to use memcache with a database is like this:
key = derive_key(obj)
obj = mc.get(key)
if not obj:
obj = backend_api.get(...)
mc.set(key, obj)
# we now have obj, and future passes through this code
# will use the object from the cache.
Detailed Documentation
======================
More detailed documentation is available in the L{Client} class.
"""
from __future__ import print_function
import binascii
from io import BytesIO
import re
import socket
import sys
import threading
import time
import zlib
import six
if six.PY2:
# With Python 2, the faster C implementation has to be imported explicitly.
import cPickle as pickle
else:
import pickle
def cmemcache_hash(key):
return (((binascii.crc32(key) & 0xffffffff) >> 16) & 0x7fff) or 1
serverHashFunction = cmemcache_hash
def useOldServerHashFunction():
"""Use the old python-memcache server hash function."""
global serverHashFunction
serverHashFunction = binascii.crc32
valid_key_chars_re = re.compile(b'[\x21-\x7e\x80-\xff]+$')
# Original author: Evan Martin of Danga Interactive
__author__ = "Sean Reifschneider <jafo00@gmail.com>"
__version__ = "1.59"
__copyright__ = "Copyright (C) 2003 Danga Interactive"
# http://en.wikipedia.org/wiki/Python_Software_Foundation_License
__license__ = "Python Software Foundation License"
SERVER_MAX_KEY_LENGTH = 250
# Storing values larger than 1MB requires starting memcached with -I <size> for
# memcached >= 1.4.2 or recompiling for < 1.4.2. If you do, this value can be
# changed by doing "memcache.SERVER_MAX_VALUE_LENGTH = N" after importing this
# module.
SERVER_MAX_VALUE_LENGTH = 1024 * 1024
class _Error(Exception):
pass
class _ConnectionDeadError(Exception):
pass
_DEAD_RETRY = 30 # number of seconds before retrying a dead server.
_SOCKET_TIMEOUT = 3 # number of seconds before sockets timeout.
class Client(threading.local):
"""Object representing a pool of memcache servers.
See L{memcache} for an overview.
In all cases where a key is used, the key can be either:
1. A simple hashable type (string, integer, etc.).
2. A tuple of C{(hashvalue, key)}. This is useful if you want
to avoid making this module calculate a hash value. You may
prefer, for example, to keep all of a given user's objects on
the same memcache server, so you could use the user's unique
id as the hash value.
@group Setup: __init__, set_servers, forget_dead_hosts,
disconnect_all, debuglog
@group Insertion: set, add, replace, set_multi
@group Retrieval: get, get_multi
@group Integers: incr, decr
@group Removal: delete, delete_multi
@sort: __init__, set_servers, forget_dead_hosts, disconnect_all,
debuglog,\ set, set_multi, add, replace, get, get_multi,
incr, decr, delete, delete_multi
"""
_FLAG_PICKLE = 1 << 0
_FLAG_INTEGER = 1 << 1
_FLAG_LONG = 1 << 2
_FLAG_COMPRESSED = 1 << 3
_FLAG_TEXT = 1 << 4
_SERVER_RETRIES = 10 # how many times to try finding a free server.
# exceptions for Client
class MemcachedKeyError(Exception):
pass
class MemcachedKeyLengthError(MemcachedKeyError):
pass
class MemcachedKeyCharacterError(MemcachedKeyError):
pass
class MemcachedKeyNoneError(MemcachedKeyError):
pass
class MemcachedKeyTypeError(MemcachedKeyError):
pass
class MemcachedStringEncodingError(Exception):
pass
def __init__(self, servers, debug=0, pickleProtocol=0,
pickler=pickle.Pickler, unpickler=pickle.Unpickler,
compressor=zlib.compress, decompressor=zlib.decompress,
pload=None, pid=None,
server_max_key_length=None, server_max_value_length=None,
dead_retry=_DEAD_RETRY, socket_timeout=_SOCKET_TIMEOUT,
cache_cas=False, flush_on_reconnect=0, check_keys=True):
"""Create a new Client object with the given list of servers.
@param servers: C{servers} is passed to L{set_servers}.
@param debug: whether to display error messages when a server
can't be contacted.
@param pickleProtocol: number to mandate protocol used by
(c)Pickle.
@param pickler: optional override of default Pickler to allow
subclassing.
@param unpickler: optional override of default Unpickler to
allow subclassing.
@param pload: optional persistent_load function to call on
pickle loading. Useful for cPickle since subclassing isn't
allowed.
@param pid: optional persistent_id function to call on pickle
storing. Useful for cPickle since subclassing isn't allowed.
@param dead_retry: number of seconds before retrying a
blacklisted server. Default to 30 s.
@param socket_timeout: timeout in seconds for all calls to a
server. Defaults to 3 seconds.
@param cache_cas: (default False) If true, cas operations will
be cached. WARNING: This cache is not expired internally, if
you have a long-running process you will need to expire it
manually via client.reset_cas(), or the cache can grow
unlimited.
@param server_max_key_length: (default SERVER_MAX_KEY_LENGTH)
Data that is larger than this will not be sent to the server.
@param server_max_value_length: (default
SERVER_MAX_VALUE_LENGTH) Data that is larger than this will
not be sent to the server.
@param flush_on_reconnect: optional flag which prevents a
scenario that can cause stale data to be read: If there's more
than one memcached server and the connection to one is
interrupted, keys that mapped to that server will get
reassigned to another. If the first server comes back, those
keys will map to it again. If it still has its data, get()s
can read stale data that was overwritten on another
server. This flag is off by default for backwards
compatibility.
@param check_keys: (default True) If True, the key is checked
to ensure it is the correct length and composed of the right
characters.
"""
super(Client, self).__init__()
self.debug = debug
self.dead_retry = dead_retry
self.socket_timeout = socket_timeout
self.flush_on_reconnect = flush_on_reconnect
self.set_servers(servers)
self.stats = {}
self.cache_cas = cache_cas
self.reset_cas()
self.do_check_key = check_keys
# Allow users to modify pickling/unpickling behavior
self.pickleProtocol = pickleProtocol
self.pickler = pickler
self.unpickler = unpickler
self.compressor = compressor
self.decompressor = decompressor
self.persistent_load = pload
self.persistent_id = pid
self.server_max_key_length = server_max_key_length
if self.server_max_key_length is None:
self.server_max_key_length = SERVER_MAX_KEY_LENGTH
self.server_max_value_length = server_max_value_length
if self.server_max_value_length is None:
self.server_max_value_length = SERVER_MAX_VALUE_LENGTH
# figure out the pickler style
file = BytesIO()
try:
pickler = self.pickler(file, protocol=self.pickleProtocol)
self.picklerIsKeyword = True
except TypeError:
self.picklerIsKeyword = False
def _encode_key(self, key):
if isinstance(key, tuple):
if isinstance(key[1], six.text_type):
return (key[0], key[1].encode('utf8'))
elif isinstance(key, six.text_type):
return key.encode('utf8')
return key
def _encode_cmd(self, cmd, key, headers, noreply, *args):
cmd_bytes = cmd.encode('utf-8') if six.PY3 else cmd
fullcmd = [cmd_bytes, b' ', key]
if headers:
if six.PY3:
headers = headers.encode('utf-8')
fullcmd.append(b' ')
fullcmd.append(headers)
if noreply:
fullcmd.append(b' noreply')
if args:
fullcmd.append(b' ')
fullcmd.extend(args)
return b''.join(fullcmd)
def reset_cas(self):
"""Reset the cas cache.
This is only used if the Client() object was created with
"cache_cas=True". If used, this cache does not expire
internally, so it can grow unbounded if you do not clear it
yourself.
"""
self.cas_ids = {}
def set_servers(self, servers):
"""Set the pool of servers used by this client.
@param servers: an array of servers.
Servers can be passed in two forms:
1. Strings of the form C{"host:port"}, which implies a
default weight of 1.
2. Tuples of the form C{("host:port", weight)}, where
C{weight} is an integer weight value.
"""
self.servers = [_Host(s, self.debug, dead_retry=self.dead_retry,
socket_timeout=self.socket_timeout,
flush_on_reconnect=self.flush_on_reconnect)
for s in servers]
self._init_buckets()
def get_stats(self, stat_args=None):
"""Get statistics from each of the servers.
@param stat_args: Additional arguments to pass to the memcache
"stats" command.
@return: A list of tuples ( server_identifier,
stats_dictionary ). The dictionary contains a number of
name/value pairs specifying the name of the status field
and the string value associated with it. The values are
not converted from strings.
"""
data = []
for s in self.servers:
if not s.connect():
continue
if s.family == socket.AF_INET:
name = '%s:%s (%s)' % (s.ip, s.port, s.weight)
elif s.family == socket.AF_INET6:
name = '[%s]:%s (%s)' % (s.ip, s.port, s.weight)
else:
name = 'unix:%s (%s)' % (s.address, s.weight)
if not stat_args:
s.send_cmd('stats')
else:
s.send_cmd('stats ' + stat_args)
serverData = {}
data.append((name, serverData))
readline = s.readline
while 1:
line = readline()
if not line or line.decode('ascii').strip() == 'END':
break
stats = line.decode('ascii').split(' ', 2)
serverData[stats[1]] = stats[2]
return data
def get_slab_stats(self):
data = []
for s in self.servers:
if not s.connect():
continue
if s.family == socket.AF_INET:
name = '%s:%s (%s)' % (s.ip, s.port, s.weight)
elif s.family == socket.AF_INET6:
name = '[%s]:%s (%s)' % (s.ip, s.port, s.weight)
else:
name = 'unix:%s (%s)' % (s.address, s.weight)
serverData = {}
data.append((name, serverData))
s.send_cmd('stats slabs')
readline = s.readline
while 1:
line = readline()
if not line or line.strip() == 'END':
break
item = line.split(' ', 2)
if line.startswith('STAT active_slabs') or line.startswith('STAT total_malloced'):
serverData[item[1]] = item[2]
else:
# 0 = STAT, 1 = ITEM, 2 = Value
slab = item[1].split(':', 2)
# 0 = Slab #, 1 = Name
if slab[0] not in serverData:
serverData[slab[0]] = {}
serverData[slab[0]][slab[1]] = item[2]
return data
def get_slabs(self):
data = []
for s in self.servers:
if not s.connect():
continue
if s.family == socket.AF_INET:
name = '%s:%s (%s)' % (s.ip, s.port, s.weight)
elif s.family == socket.AF_INET6:
name = '[%s]:%s (%s)' % (s.ip, s.port, s.weight)
else:
name = 'unix:%s (%s)' % (s.address, s.weight)
serverData = {}
data.append((name, serverData))
s.send_cmd('stats items')
readline = s.readline
while 1:
line = readline()
if not line or line.strip() == 'END':
break
item = line.split(' ', 2)
# 0 = STAT, 1 = ITEM, 2 = Value
slab = item[1].split(':', 2)
# 0 = items, 1 = Slab #, 2 = Name
if slab[1] not in serverData:
serverData[slab[1]] = {}
serverData[slab[1]][slab[2]] = item[2]
return data
def flush_all(self):
"""Expire all data in memcache servers that are reachable."""
for s in self.servers:
if not s.connect():
continue
s.flush()
def debuglog(self, str):
if self.debug:
sys.stderr.write("MemCached: %s\n" % str)
def _statlog(self, func):
if func not in self.stats:
self.stats[func] = 1
else:
self.stats[func] += 1
def forget_dead_hosts(self):
"""Reset every host in the pool to an "alive" state."""
for s in self.servers:
s.deaduntil = 0
def _init_buckets(self):
self.buckets = []
for server in self.servers:
for i in range(server.weight):
self.buckets.append(server)
def _get_server(self, key):
if isinstance(key, tuple):
serverhash, key = key
else:
serverhash = serverHashFunction(key)
if not self.buckets:
return None, None
for i in range(Client._SERVER_RETRIES):
server = self.buckets[serverhash % len(self.buckets)]
if server.connect():
# print("(using server %s)" % server,)
return server, key
serverhash = str(serverhash) + str(i)
if isinstance(serverhash, six.text_type):
serverhash = serverhash.encode('ascii')
serverhash = serverHashFunction(serverhash)
return None, None
def disconnect_all(self):
for s in self.servers:
s.close_socket()
def delete_multi(self, keys, time=None, key_prefix='', noreply=False):
"""Delete multiple keys in the memcache doing just one query.
>>> notset_keys = mc.set_multi({'a1' : 'val1', 'a2' : 'val2'})
>>> mc.get_multi(['a1', 'a2']) == {'a1' : 'val1','a2' : 'val2'}
1
>>> mc.delete_multi(['key1', 'key2'])
1
>>> mc.get_multi(['key1', 'key2']) == {}
1
This method is recommended over iterated regular L{delete}s as
it reduces total latency, since your app doesn't have to wait
for each round-trip of L{delete} before sending the next one.
@param keys: An iterable of keys to clear
@param time: number of seconds any subsequent set / update
commands should fail. Defaults to 0 for no delay.
@param key_prefix: Optional string to prepend to each key when
sending to memcache. See docs for L{get_multi} and
L{set_multi}.
@param noreply: optional parameter instructs the server to not send the
reply.
@return: 1 if no failure in communication with any memcacheds.
@rtype: int
"""
self._statlog('delete_multi')
server_keys, prefixed_to_orig_key = self._map_and_prefix_keys(
keys, key_prefix)
# send out all requests on each server before reading anything
dead_servers = []
rc = 1
for server in six.iterkeys(server_keys):
bigcmd = []
write = bigcmd.append
if time is not None:
headers = str(time)
else:
headers = None
for key in server_keys[server]: # These are mangled keys
cmd = self._encode_cmd('delete', key, headers, noreply, b'\r\n')
write(cmd)
try:
server.send_cmds(b''.join(bigcmd))
except socket.error as msg:
rc = 0
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
dead_servers.append(server)
# if noreply, just return
if noreply:
return rc
# if any servers died on the way, don't expect them to respond.
for server in dead_servers:
del server_keys[server]
for server, keys in six.iteritems(server_keys):
try:
for key in keys:
server.expect(b"DELETED")
except socket.error as msg:
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
rc = 0
return rc
def delete(self, key, time=None, noreply=False):
'''Deletes a key from the memcache.
@return: Nonzero on success.
@param time: number of seconds any subsequent set / update commands
should fail. Defaults to None for no delay.
@param noreply: optional parameter instructs the server to not send the
reply.
@rtype: int
'''
return self._deletetouch([b'DELETED', b'NOT_FOUND'], "delete", key,
time, noreply)
def touch(self, key, time=0, noreply=False):
'''Updates the expiration time of a key in memcache.
@return: Nonzero on success.
@param time: Tells memcached the time which this value should
expire, either as a delta number of seconds, or an absolute
unix time-since-the-epoch value. See the memcached protocol
docs section "Storage Commands" for more info on <exptime>. We
default to 0 == cache forever.
@param noreply: optional parameter instructs the server to not send the
reply.
@rtype: int
'''
return self._deletetouch([b'TOUCHED'], "touch", key, time, noreply)
def _deletetouch(self, expected, cmd, key, time=0, noreply=False):
key = self._encode_key(key)
if self.do_check_key:
self.check_key(key)
server, key = self._get_server(key)
if not server:
return 0
self._statlog(cmd)
if time is not None:
headers = str(time)
else:
headers = None
fullcmd = self._encode_cmd(cmd, key, headers, noreply)
try:
server.send_cmd(fullcmd)
if noreply:
return 1
line = server.readline()
if line and line.strip() in expected:
return 1
self.debuglog('%s expected %s, got: %r'
% (cmd, b' or '.join(expected), line))
except socket.error as msg:
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
return 0
def incr(self, key, delta=1, noreply=False):
"""Increment value for C{key} by C{delta}
Sends a command to the server to atomically increment the
value for C{key} by C{delta}, or by 1 if C{delta} is
unspecified. Returns None if C{key} doesn't exist on server,
otherwise it returns the new value after incrementing.
Note that the value for C{key} must already exist in the
memcache, and it must be the string representation of an
integer.
>>> mc.set("counter", "20") # returns 1, indicating success
1
>>> mc.incr("counter")
21
>>> mc.incr("counter")
22
Overflow on server is not checked. Be aware of values
approaching 2**32. See L{decr}.
@param delta: Integer amount to increment by (should be zero
or greater).
@param noreply: optional parameter instructs the server to not send the
reply.
@return: New value after incrementing, no None for noreply or error.
@rtype: int
"""
return self._incrdecr("incr", key, delta, noreply)
def decr(self, key, delta=1, noreply=False):
"""Decrement value for C{key} by C{delta}
Like L{incr}, but decrements. Unlike L{incr}, underflow is
checked and new values are capped at 0. If server value is 1,
a decrement of 2 returns 0, not -1.
@param delta: Integer amount to decrement by (should be zero
or greater).
@param noreply: optional parameter instructs the server to not send the
reply.
@return: New value after decrementing, or None for noreply or error.
@rtype: int
"""
return self._incrdecr("decr", key, delta, noreply)
def _incrdecr(self, cmd, key, delta, noreply=False):
key = self._encode_key(key)
if self.do_check_key:
self.check_key(key)
server, key = self._get_server(key)
if not server:
return None
self._statlog(cmd)
fullcmd = self._encode_cmd(cmd, key, str(delta), noreply)
try:
server.send_cmd(fullcmd)
if noreply:
return
line = server.readline()
if line is None or line.strip() == b'NOT_FOUND':
return None
return int(line)
except socket.error as msg:
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
return None
def add(self, key, val, time=0, min_compress_len=0, noreply=False):
'''Add new key with value.
Like L{set}, but only stores in memcache if the key doesn't
already exist.
@return: Nonzero on success.
@rtype: int
'''
return self._set("add", key, val, time, min_compress_len, noreply)
def append(self, key, val, time=0, min_compress_len=0, noreply=False):
'''Append the value to the end of the existing key's value.
Only stores in memcache if key already exists.
Also see L{prepend}.
@return: Nonzero on success.
@rtype: int
'''
return self._set("append", key, val, time, min_compress_len, noreply)
def prepend(self, key, val, time=0, min_compress_len=0, noreply=False):
'''Prepend the value to the beginning of the existing key's value.
Only stores in memcache if key already exists.
Also see L{append}.
@return: Nonzero on success.
@rtype: int
'''
return self._set("prepend", key, val, time, min_compress_len, noreply)
def replace(self, key, val, time=0, min_compress_len=0, noreply=False):
'''Replace existing key with value.
Like L{set}, but only stores in memcache if the key already exists.
The opposite of L{add}.
@return: Nonzero on success.
@rtype: int
'''
return self._set("replace", key, val, time, min_compress_len, noreply)
def set(self, key, val, time=0, min_compress_len=0, noreply=False):
'''Unconditionally sets a key to a given value in the memcache.
The C{key} can optionally be an tuple, with the first element
being the server hash value and the second being the key. If
you want to avoid making this module calculate a hash value.
You may prefer, for example, to keep all of a given user's
objects on the same memcache server, so you could use the
user's unique id as the hash value.
@return: Nonzero on success.
@rtype: int
@param time: Tells memcached the time which this value should
expire, either as a delta number of seconds, or an absolute
unix time-since-the-epoch value. See the memcached protocol
docs section "Storage Commands" for more info on <exptime>. We
default to 0 == cache forever.
@param min_compress_len: The threshold length to kick in
auto-compression of the value using the compressor
routine. If the value being cached is a string, then the
length of the string is measured, else if the value is an
object, then the length of the pickle result is measured. If
the resulting attempt at compression yields a larger string
than the input, then it is discarded. For backwards
compatibility, this parameter defaults to 0, indicating don't
ever try to compress.
@param noreply: optional parameter instructs the server to not
send the reply.
'''
return self._set("set", key, val, time, min_compress_len, noreply)
def cas(self, key, val, time=0, min_compress_len=0, noreply=False):
'''Check and set (CAS)
Sets a key to a given value in the memcache if it hasn't been
altered since last fetched. (See L{gets}).
The C{key} can optionally be an tuple, with the first element
being the server hash value and the second being the key. If
you want to avoid making this module calculate a hash value.
You may prefer, for example, to keep all of a given user's
objects on the same memcache server, so you could use the
user's unique id as the hash value.
@return: Nonzero on success.
@rtype: int
@param time: Tells memcached the time which this value should
expire, either as a delta number of seconds, or an absolute
unix time-since-the-epoch value. See the memcached protocol
docs section "Storage Commands" for more info on <exptime>. We
default to 0 == cache forever.
@param min_compress_len: The threshold length to kick in
auto-compression of the value using the compressor
routine. If the value being cached is a string, then the
length of the string is measured, else if the value is an
object, then the length of the pickle result is measured. If
the resulting attempt at compression yields a larger string
than the input, then it is discarded. For backwards
compatibility, this parameter defaults to 0, indicating don't
ever try to compress.
@param noreply: optional parameter instructs the server to not
send the reply.
'''
return self._set("cas", key, val, time, min_compress_len, noreply)
def _map_and_prefix_keys(self, key_iterable, key_prefix):
"""Map keys to the servers they will reside on.
Compute the mapping of server (_Host instance) -> list of keys to
stuff onto that server, as well as the mapping of prefixed key
-> original key.
"""
key_prefix = self._encode_key(key_prefix)
# Check it just once ...
key_extra_len = len(key_prefix)
if key_prefix and self.do_check_key:
self.check_key(key_prefix)
# server (_Host) -> list of unprefixed server keys in mapping
server_keys = {}
prefixed_to_orig_key = {}
# build up a list for each server of all the keys we want.
for orig_key in key_iterable:
if isinstance(orig_key, tuple):
# Tuple of hashvalue, key ala _get_server(). Caller is
# essentially telling us what server to stuff this on.
# Ensure call to _get_server gets a Tuple as well.
serverhash, key = orig_key
key = self._encode_key(key)
if not isinstance(key, six.binary_type):
# set_multi supports int / long keys.
key = str(key)
if six.PY3:
key = key.encode('utf8')
bytes_orig_key = key
# Gotta pre-mangle key before hashing to a
# server. Returns the mangled key.
server, key = self._get_server(
(serverhash, key_prefix + key))
orig_key = orig_key[1]
else:
key = self._encode_key(orig_key)
if not isinstance(key, six.binary_type):
# set_multi supports int / long keys.
key = str(key)
if six.PY3:
key = key.encode('utf8')
bytes_orig_key = key
server, key = self._get_server(key_prefix + key)
# alert when passed in key is None
if orig_key is None:
self.check_key(orig_key, key_extra_len=key_extra_len)
# Now check to make sure key length is proper ...
if self.do_check_key:
self.check_key(bytes_orig_key, key_extra_len=key_extra_len)
if not server:
continue
if server not in server_keys:
server_keys[server] = []
server_keys[server].append(key)
prefixed_to_orig_key[key] = orig_key
return (server_keys, prefixed_to_orig_key)
def set_multi(self, mapping, time=0, key_prefix='', min_compress_len=0,
noreply=False):
'''Sets multiple keys in the memcache doing just one query.
>>> notset_keys = mc.set_multi({'key1' : 'val1', 'key2' : 'val2'})
>>> keys = mc.get_multi(['key1', 'key2'])
>>> keys == {'key1': 'val1', 'key2': 'val2'}
True
This method is recommended over regular L{set} as it lowers
the number of total packets flying around your network,
reducing total latency, since your app doesn't have to wait
for each round-trip of L{set} before sending the next one.
@param mapping: A dict of key/value pairs to set.
@param time: Tells memcached the time which this value should
expire, either as a delta number of seconds, or an
absolute unix time-since-the-epoch value. See the
memcached protocol docs section "Storage Commands" for
more info on <exptime>. We default to 0 == cache forever.
@param key_prefix: Optional string to prepend to each key when
sending to memcache. Allows you to efficiently stuff these
keys into a pseudo-namespace in memcache:
>>> notset_keys = mc.set_multi(
... {'key1' : 'val1', 'key2' : 'val2'},
... key_prefix='subspace_')
>>> len(notset_keys) == 0
True
>>> keys = mc.get_multi(['subspace_key1', 'subspace_key2'])
>>> keys == {'subspace_key1': 'val1', 'subspace_key2': 'val2'}
True
Causes key 'subspace_key1' and 'subspace_key2' to be
set. Useful in conjunction with a higher-level layer which
applies namespaces to data in memcache. In this case, the
return result would be the list of notset original keys,
prefix not applied.
@param min_compress_len: The threshold length to kick in
auto-compression of the value using the compressor
routine. If the value being cached is a string, then the
length of the string is measured, else if the value is an
object, then the length of the pickle result is
measured. If the resulting attempt at compression yields a
larger string than the input, then it is discarded. For
backwards compatibility, this parameter defaults to 0,
indicating don't ever try to compress.
@param noreply: optional parameter instructs the server to not
send the reply.
@return: List of keys which failed to be stored [ memcache out
of memory, etc. ].
@rtype: list
'''
self._statlog('set_multi')
server_keys, prefixed_to_orig_key = self._map_and_prefix_keys(
six.iterkeys(mapping), key_prefix)
# send out all requests on each server before reading anything
dead_servers = []
notstored = [] # original keys.
for server in six.iterkeys(server_keys):
bigcmd = []
write = bigcmd.append
try:
for key in server_keys[server]: # These are mangled keys
store_info = self._val_to_store_info(
mapping[prefixed_to_orig_key[key]],
min_compress_len)
if store_info:
flags, len_val, val = store_info
headers = "%d %d %d" % (flags, time, len_val)
fullcmd = self._encode_cmd('set', key, headers,
noreply,
b'\r\n', val, b'\r\n')
write(fullcmd)
else:
notstored.append(prefixed_to_orig_key[key])
server.send_cmds(b''.join(bigcmd))
except socket.error as msg:
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
dead_servers.append(server)
# if noreply, just return early
if noreply:
return notstored
# if any servers died on the way, don't expect them to respond.
for server in dead_servers:
del server_keys[server]
# short-circuit if there are no servers, just return all keys
if not server_keys:
return list(mapping.keys())
for server, keys in six.iteritems(server_keys):
try:
for key in keys:
if server.readline() == b'STORED':
continue
else:
# un-mangle.
notstored.append(prefixed_to_orig_key[key])
except (_Error, socket.error) as msg:
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
return notstored
def _val_to_store_info(self, val, min_compress_len):
"""Transform val to a storable representation.
Returns a tuple of the flags, the length of the new value, and
the new value itself.
"""
flags = 0
# Check against the exact type, rather than using isinstance(), so that
# subclasses of native types (such as markup-safe strings) are pickled
# and restored as instances of the correct class.
val_type = type(val)
if val_type == six.binary_type:
pass
elif val_type == six.text_type:
flags |= Client._FLAG_TEXT
val = val.encode('utf-8')
elif val_type == int:
flags |= Client._FLAG_INTEGER
val = '%d' % val
if six.PY3:
val = val.encode('ascii')
# force no attempt to compress this silly string.
min_compress_len = 0
elif six.PY2 and isinstance(val, long): # noqa: F821
flags |= Client._FLAG_LONG
val = str(val)
if six.PY3:
val = val.encode('ascii')
# force no attempt to compress this silly string.
min_compress_len = 0
else:
flags |= Client._FLAG_PICKLE
file = BytesIO()
if self.picklerIsKeyword:
pickler = self.pickler(file, protocol=self.pickleProtocol)
else:
pickler = self.pickler(file, self.pickleProtocol)
if self.persistent_id:
pickler.persistent_id = self.persistent_id
pickler.dump(val)
val = file.getvalue()
lv = len(val)
# We should try to compress if min_compress_len > 0
# and this string is longer than our min threshold.
if min_compress_len and lv > min_compress_len:
comp_val = self.compressor(val)
# Only retain the result if the compression result is smaller
# than the original.
if len(comp_val) < lv:
flags |= Client._FLAG_COMPRESSED
val = comp_val
# silently do not store if value length exceeds maximum
if (self.server_max_value_length != 0 and
len(val) > self.server_max_value_length):
return 0
return (flags, len(val), val)
def _set(self, cmd, key, val, time, min_compress_len=0, noreply=False):
key = self._encode_key(key)
if self.do_check_key:
self.check_key(key)
server, key = self._get_server(key)
if not server:
return 0
def _unsafe_set():
self._statlog(cmd)
if cmd == 'cas' and key not in self.cas_ids:
return self._set('set', key, val, time, min_compress_len,
noreply)
store_info = self._val_to_store_info(val, min_compress_len)
if not store_info:
return 0
flags, len_val, encoded_val = store_info
if cmd == 'cas':
headers = ("%d %d %d %d"
% (flags, time, len_val, self.cas_ids[key]))
else:
headers = "%d %d %d" % (flags, time, len_val)
fullcmd = self._encode_cmd(cmd, key, headers, noreply,
b'\r\n', encoded_val)
try:
server.send_cmd(fullcmd)
if noreply:
return True
return server.expect(b"STORED", raise_exception=True) == b"STORED"
except socket.error as msg:
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
return 0
try:
return _unsafe_set()
except _ConnectionDeadError:
# retry once
try:
if server._get_socket():
return _unsafe_set()
except (_ConnectionDeadError, socket.error) as msg:
server.mark_dead(msg)
return 0
def _get(self, cmd, key):
key = self._encode_key(key)
if self.do_check_key:
self.check_key(key)
server, key = self._get_server(key)
if not server:
return None
def _unsafe_get():
self._statlog(cmd)
try:
cmd_bytes = cmd.encode('utf-8') if six.PY3 else cmd
fullcmd = b''.join((cmd_bytes, b' ', key))
server.send_cmd(fullcmd)
rkey = flags = rlen = cas_id = None
if cmd == 'gets':
rkey, flags, rlen, cas_id, = self._expect_cas_value(
server, raise_exception=True
)
if rkey and self.cache_cas:
self.cas_ids[rkey] = cas_id
else:
rkey, flags, rlen, = self._expectvalue(
server, raise_exception=True
)
if not rkey:
return None
try:
value = self._recv_value(server, flags, rlen)
finally:
server.expect(b"END", raise_exception=True)
except (_Error, socket.error) as msg:
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
return None
return value
try:
return _unsafe_get()
except _ConnectionDeadError:
# retry once
try:
if server.connect():
return _unsafe_get()
return None
except (_ConnectionDeadError, socket.error) as msg:
server.mark_dead(msg)
return None
def get(self, key):
'''Retrieves a key from the memcache.
@return: The value or None.
'''
return self._get('get', key)
def gets(self, key):
'''Retrieves a key from the memcache. Used in conjunction with 'cas'.
@return: The value or None.
'''
return self._get('gets', key)
def get_multi(self, keys, key_prefix=''):
'''Retrieves multiple keys from the memcache doing just one query.
>>> success = mc.set("foo", "bar")
>>> success = mc.set("baz", 42)
>>> mc.get_multi(["foo", "baz", "foobar"]) == {
... "foo": "bar", "baz": 42
... }
1
>>> mc.set_multi({'k1' : 1, 'k2' : 2}, key_prefix='pfx_') == []
1
This looks up keys 'pfx_k1', 'pfx_k2', ... . Returned dict
will just have unprefixed keys 'k1', 'k2'.
>>> mc.get_multi(['k1', 'k2', 'nonexist'],
... key_prefix='pfx_') == {'k1' : 1, 'k2' : 2}
1
get_multi [ and L{set_multi} ] can take str()-ables like ints /
longs as keys too. Such as your db pri key fields. They're
rotored through str() before being passed off to memcache,
with or without the use of a key_prefix. In this mode, the
key_prefix could be a table name, and the key itself a db
primary key number.
>>> mc.set_multi({42: 'douglass adams',
... 46: 'and 2 just ahead of me'},
... key_prefix='numkeys_') == []
1
>>> mc.get_multi([46, 42], key_prefix='numkeys_') == {
... 42: 'douglass adams',
... 46: 'and 2 just ahead of me'
... }
1
This method is recommended over regular L{get} as it lowers
the number of total packets flying around your network,
reducing total latency, since your app doesn't have to wait
for each round-trip of L{get} before sending the next one.
See also L{set_multi}.
@param keys: An array of keys.
@param key_prefix: A string to prefix each key when we
communicate with memcache. Facilitates pseudo-namespaces
within memcache. Returned dictionary keys will not have this
prefix.
@return: A dictionary of key/value pairs that were
available. If key_prefix was provided, the keys in the returned
dictionary will not have it present.
'''
self._statlog('get_multi')
server_keys, prefixed_to_orig_key = self._map_and_prefix_keys(
keys, key_prefix)
# send out all requests on each server before reading anything
dead_servers = []
for server in six.iterkeys(server_keys):
try:
fullcmd = b"get " + b" ".join(server_keys[server])
server.send_cmd(fullcmd)
except socket.error as msg:
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
dead_servers.append(server)
# if any servers died on the way, don't expect them to respond.
for server in dead_servers:
del server_keys[server]
retvals = {}
for server in six.iterkeys(server_keys):
try:
line = server.readline()
while line and line != b'END':
rkey, flags, rlen = self._expectvalue(server, line)
# Bo Yang reports that this can sometimes be None
if rkey is not None:
val = self._recv_value(server, flags, rlen)
# un-prefix returned key.
retvals[prefixed_to_orig_key[rkey]] = val
line = server.readline()
except (_Error, socket.error) as msg:
if isinstance(msg, tuple):
msg = msg[1]
server.mark_dead(msg)
return retvals
def _expect_cas_value(self, server, line=None, raise_exception=False):
if not line:
line = server.readline(raise_exception)
if line and line[:5] == b'VALUE':
resp, rkey, flags, len, cas_id = line.split()
return (rkey, int(flags), int(len), int(cas_id))
else:
return (None, None, None, None)
def _expectvalue(self, server, line=None, raise_exception=False):
if not line:
line = server.readline(raise_exception)
if line and line[:5] == b'VALUE':
resp, rkey, flags, len = line.split()
flags = int(flags)
rlen = int(len)
return (rkey, flags, rlen)
else:
return (None, None, None)
def _recv_value(self, server, flags, rlen):
rlen += 2 # include \r\n
buf = server.recv(rlen)
if len(buf) != rlen:
raise _Error("received %d bytes when expecting %d"
% (len(buf), rlen))
if len(buf) == rlen:
buf = buf[:-2] # strip \r\n
if flags & Client._FLAG_COMPRESSED:
buf = self.decompressor(buf)
flags &= ~Client._FLAG_COMPRESSED
if flags == 0:
# Bare bytes
val = buf
elif flags & Client._FLAG_TEXT:
val = buf.decode('utf-8')
elif flags & Client._FLAG_INTEGER:
val = int(buf)
elif flags & Client._FLAG_LONG:
if six.PY3:
val = int(buf)
else:
val = long(buf) # noqa: F821
elif flags & Client._FLAG_PICKLE:
try:
file = BytesIO(buf)
unpickler = self.unpickler(file)
if self.persistent_load:
unpickler.persistent_load = self.persistent_load
val = unpickler.load()
except Exception as e:
self.debuglog('Pickle error: %s\n' % e)
return None
else:
self.debuglog("unknown flags on get: %x\n" % flags)
raise ValueError('Unknown flags on get: %x' % flags)
return val
def check_key(self, key, key_extra_len=0):
"""Checks sanity of key.
Fails if:
Key length is > SERVER_MAX_KEY_LENGTH (Raises MemcachedKeyLength).
Contains control characters (Raises MemcachedKeyCharacterError).
Is not a string (Raises MemcachedStringEncodingError)
Is an unicode string (Raises MemcachedStringEncodingError)
Is not a string (Raises MemcachedKeyError)
Is None (Raises MemcachedKeyError)
"""
if isinstance(key, tuple):
key = key[1]
if key is None:
raise Client.MemcachedKeyNoneError("Key is None")
if key is '':
if key_extra_len is 0:
raise Client.MemcachedKeyNoneError("Key is empty")
# key is empty but there is some other component to key
return
if not isinstance(key, six.binary_type):
raise Client.MemcachedKeyTypeError("Key must be a binary string")
if (self.server_max_key_length != 0 and
len(key) + key_extra_len > self.server_max_key_length):
raise Client.MemcachedKeyLengthError(
"Key length is > %s" % self.server_max_key_length
)
if not valid_key_chars_re.match(key):
raise Client.MemcachedKeyCharacterError(
"Control/space characters not allowed (key=%r)" % key)
class _Host(object):
def __init__(self, host, debug=0, dead_retry=_DEAD_RETRY,
socket_timeout=_SOCKET_TIMEOUT, flush_on_reconnect=0):
self.dead_retry = dead_retry
self.socket_timeout = socket_timeout
self.debug = debug
self.flush_on_reconnect = flush_on_reconnect
if isinstance(host, tuple):
host, self.weight = host
else:
self.weight = 1
# parse the connection string
m = re.match(r'^(?P<proto>unix):(?P<path>.*)$', host)
if not m:
m = re.match(r'^(?P<proto>inet6):'
r'\[(?P<host>[^\[\]]+)\](:(?P<port>[0-9]+))?$', host)
if not m:
m = re.match(r'^(?P<proto>inet):'
r'(?P<host>[^:]+)(:(?P<port>[0-9]+))?$', host)
if not m:
m = re.match(r'^(?P<host>[^:]+)(:(?P<port>[0-9]+))?$', host)
if not m:
raise ValueError('Unable to parse connection string: "%s"' % host)
hostData = m.groupdict()
if hostData.get('proto') == 'unix':
self.family = socket.AF_UNIX
self.address = hostData['path']
elif hostData.get('proto') == 'inet6':
self.family = socket.AF_INET6
self.ip = hostData['host']
self.port = int(hostData.get('port') or 11211)
self.address = (self.ip, self.port)
else:
self.family = socket.AF_INET
self.ip = hostData['host']
self.port = int(hostData.get('port') or 11211)
self.address = (self.ip, self.port)
self.deaduntil = 0
self.socket = None
self.flush_on_next_connect = 0
self.buffer = b''
def debuglog(self, str):
if self.debug:
sys.stderr.write("MemCached: %s\n" % str)
def _check_dead(self):
if self.deaduntil and self.deaduntil > time.time():
return 1
self.deaduntil = 0
return 0
def connect(self):
if self._get_socket():
return 1
return 0
def mark_dead(self, reason):
self.debuglog("MemCache: %s: %s. Marking dead." % (self, reason))
self.deaduntil = time.time() + self.dead_retry
if self.flush_on_reconnect:
self.flush_on_next_connect = 1
self.close_socket()
def _get_socket(self):
if self._check_dead():
return None
if self.socket:
return self.socket
s = socket.socket(self.family, socket.SOCK_STREAM)
if hasattr(s, 'settimeout'):
s.settimeout(self.socket_timeout)
try:
s.connect(self.address)
except socket.timeout as msg:
self.mark_dead("connect: %s" % msg)
return None
except socket.error as msg:
if isinstance(msg, tuple):
msg = msg[1]
self.mark_dead("connect: %s" % msg)
return None
self.socket = s
self.buffer = b''
if self.flush_on_next_connect:
self.flush()
self.flush_on_next_connect = 0
return s
def close_socket(self):
if self.socket:
self.socket.close()
self.socket = None
def send_cmd(self, cmd):
if isinstance(cmd, six.text_type):
cmd = cmd.encode('utf8')
self.socket.sendall(cmd + b'\r\n')
def send_cmds(self, cmds):
"""cmds already has trailing \r\n's applied."""
if isinstance(cmds, six.text_type):
cmds = cmds.encode('utf8')
self.socket.sendall(cmds)
def readline(self, raise_exception=False):
"""Read a line and return it.
If "raise_exception" is set, raise _ConnectionDeadError if the
read fails, otherwise return an empty string.
"""
buf = self.buffer
if self.socket:
recv = self.socket.recv
else:
recv = lambda bufsize: b''
while True:
index = buf.find(b'\r\n')
if index >= 0:
break
data = recv(4096)
if not data:
# connection close, let's kill it and raise
self.mark_dead('connection closed in readline()')
if raise_exception:
raise _ConnectionDeadError()
else:
return ''
buf += data
self.buffer = buf[index + 2:]
return buf[:index]
def expect(self, text, raise_exception=False):
line = self.readline(raise_exception)
if self.debug and line != text:
if six.PY3:
text = text.decode('utf8')
log_line = line.decode('utf8', 'replace')
else:
log_line = line
self.debuglog("while expecting %r, got unexpected response %r"
% (text, log_line))
return line
def recv(self, rlen):
self_socket_recv = self.socket.recv
buf = self.buffer
while len(buf) < rlen:
foo = self_socket_recv(max(rlen - len(buf), 4096))
buf += foo
if not foo:
raise _Error('Read %d bytes, expecting %d, '
'read returned 0 length bytes' % (len(buf), rlen))
self.buffer = buf[rlen:]
return buf[:rlen]
def flush(self):
self.send_cmd('flush_all')
self.expect(b'OK')
def __str__(self):
d = ''
if self.deaduntil:
d = " (dead until %d)" % self.deaduntil
if self.family == socket.AF_INET:
return "inet:%s:%d%s" % (self.address[0], self.address[1], d)
elif self.family == socket.AF_INET6:
return "inet6:[%s]:%d%s" % (self.address[0], self.address[1], d)
else:
return "unix:%s%s" % (self.address, d)
def _doctest():
import doctest
import memcache
servers = ["127.0.0.1:11211"]
mc = memcache.Client(servers, debug=1)
globs = {"mc": mc}
results = doctest.testmod(memcache, globs=globs)
mc.disconnect_all()
print("Doctests: %s" % (results,))
if results.failed:
sys.exit(1)
# vim: ts=4 sw=4 et :