Welcome to pymemcache’s documentation!

Contents:

Getting started!

A comprehensive, fast, pure-Python memcached client library.

Basic Usage

from pymemcache.client.base import Client

client = Client('localhost')
client.set('some_key', 'some_value')
result = client.get('some_key')

The server to connect to can be specified in a number of ways.

If using TCP connections over IPv4 or IPv6, the server parameter can be passed a host string, a host:port string, or a (host, port) 2-tuple. The host part may be a domain name, an IPv4 address, or an IPv6 address. The port may be omitted, in which case it will default to 11211.

ipv4_client = Client('127.0.0.1')
ipv4_client_with_port = Client('127.0.0.1:11211')
ipv4_client_using_tuple = Client(('127.0.0.1', 11211))

ipv6_client = Client('[::1]')
ipv6_client_with_port = Client('[::1]:11211')
ipv6_client_using_tuple = Client(('::1', 11211))

domain_client = Client('localhost')
domain_client_with_port = Client('localhost:11211')
domain_client_using_tuple = Client(('localhost', 11211))

Note that IPv6 may be used in preference to IPv4 when passing a domain name as the host if an IPv6 address can be resolved for that domain.

You can also connect to a local memcached server over a UNIX domain socket by passing the socket’s path to the client’s server parameter. An optional unix: prefix may be used for compatibility in code that uses other client libraries that require it.

client = Client('/run/memcached/memcached.sock')
client_with_prefix = Client('unix:/run/memcached/memcached.sock')

Using a client pool

pymemcache.client.base.PooledClient is a thread-safe client pool that provides the same API as pymemcache.client.base.Client. It’s useful in for cases when you want to maintain a pool of already-connected clients for improved performance.

from pymemcache.client.base import PooledClient

client = PooledClient('127.0.0.1', max_pool_size=4)

Using a memcached cluster

This will use a consistent hashing algorithm to choose which server to set/get the values from. It will also automatically rebalance depending on if a server goes down.

from pymemcache.client.hash import HashClient

client = HashClient([
    '127.0.0.1:11211',
    '127.0.0.1:11212',
])
client.set('some_key', 'some value')
result = client.get('some_key')

Using the built-in retrying mechanism

The library comes with retry mechanisms that can be used to wrap all kind of pymemcache clients. The wrapper allow you to define the exceptions that you want to handle with retries, which exceptions to exclude, how many attempts to make and how long to wait between attempts.

The RetryingClient wraps around any of the other included clients and will have the same methods. For this example we’re just using the base Client.

from pymemcache.client.base import Client
from pymemcache.client.retrying import RetryingClient
from pymemcache.exceptions import MemcacheUnexpectedCloseError

base_client = Client(("localhost", 11211))
client = RetryingClient(
    base_client,
    attempts=3,
    retry_delay=0.01,
    retry_for=[MemcacheUnexpectedCloseError]
)
client.set('some_key', 'some value')
result = client.get('some_key')

The above client will attempt each call three times with a wait of 10ms between each attempt, as long as the exception is a MemcacheUnexpectedCloseError.

Using TLS

Memcached supports authentication and encryption via TLS since version 1.5.13.

A Memcached server running with TLS enabled will only accept TLS connections.

To enable TLS in pymemcache, pass a valid TLS context to the client’s tls_context parameter:

import ssl
from pymemcache.client.base import Client

context = ssl.create_default_context(
    cafile="my-ca-root.crt",
)

client = Client('localhost', tls_context=context)
client.set('some_key', 'some_value')
result = client.get('some_key')

Serialization

import json
from pymemcache.client.base import Client

class JsonSerde(object):
    def serialize(self, key, value):
        if isinstance(value, str):
            return value, 1
        return json.dumps(value), 2

    def deserialize(self, key, value, flags):
       if flags == 1:
           return value
       if flags == 2:
           return json.loads(value)
       raise Exception("Unknown serialization format")

client = Client('localhost', serde=JsonSerde())
client.set('key', {'a':'b', 'c':'d'})
result = client.get('key')

pymemcache provides a default pickle-based serializer:

from pymemcache.client.base import Client
from pymemcache import serde

class Foo(object):
  pass

client = Client('localhost', serde=serde.pickle_serde)
client.set('key', Foo())
result = client.get('key')

The serializer uses the highest pickle protocol available. In order to make sure multiple versions of Python can read the protocol version, you can specify the version by explicitly instantiating pymemcache.serde.PickleSerde:

client = Client('localhost', serde=serde.PickleSerde(pickle_version=2))

Deserialization with Python 3

Values passed to the serde.deserialize() method will be bytestrings. It is therefore necessary to encode and decode them correctly. Here’s a version of the JsonSerde from above which is more careful with encodings:

class JsonSerde(object):
    def serialize(self, key, value):
        if isinstance(value, str):
            return value.encode('utf-8'), 1
        return json.dumps(value).encode('utf-8'), 2

    def deserialize(self, key, value, flags):
       if flags == 1:
           return value.decode('utf-8')
       if flags == 2:
           return json.loads(value.decode('utf-8'))
       raise Exception("Unknown serialization format")

Interacting with pymemcache

For testing purpose pymemcache can be used in an interactive mode by using the python interpreter or again ipython and tools like tox.

One main advantage of using tox to interact with pymemcache is that it comes with it’s own virtual environments. It will automatically install pymemcache and fetch all the needed requirements at run. See the example below:

$ podman run --publish 11211:11211 -it --rm --name memcached memcached
$ tox -e venv -- python
>>> from pymemcache.client.base import Client
>>> client = Client('127.0.0.1')
>>> client.set('some_key', 'some_value')
True
>>> client.get('some_key')
b'some_value'
>>> print(client.get.__doc__)
     The memcached "get" command, but only for one key, as a convenience.
     Args:
       key: str, see class docs for details.
       default: value that will be returned if the key was not found.
     Returns:
       The value for the key, or default if the key wasn't found.

You can instantiate all the classes and clients offered by pymemcache.

Your client will remain open until you decide to close it or until you decide to quit your interpreter. It can allow you to see what’s happen if your server is abruptly closed. Below is an by example.

Starting your server:

$ podman run --publish 11211:11211 -it --name memcached memcached

Starting your client and set some keys:

$ tox -e venv -- python
>>> from pymemcache.client.base import Client
>>> client = Client('127.0.0.1')
>>> client.set('some_key', 'some_value')
True

Restarting the server:

$ podman restart memcached

The previous client is still opened, now try to retrieve some keys:

>>> print(client.get('some_key'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/user/pymemcache/pymemcache/client/base.py", line 535, in get
    return self._fetch_cmd(b'get', [key], False).get(key, default)
  File "/home/user/pymemcache/pymemcache/client/base.py", line 910, in _fetch_cmd
    buf, line = _readline(self.sock, buf)
  File "/home/user/pymemcache/pymemcache/client/base.py", line 1305, in _readline
    raise MemcacheUnexpectedCloseError()
pymemcache.exceptions.MemcacheUnexpectedCloseError

We can see that the connection has been closed.

You can also pass a command directly from CLI parameters and get output directly:

$ tox -e venv -- python -c "from pymemcache.client.base import Client; client = Client('127.0.01'); print(client.get('some_key'))"
b'some_value'

This kind of usage is useful for debug sessions or to dig manually into your server.

Key Constraints

This client implements the ASCII protocol of memcached. This means keys should not contain any of the following illegal characters:

Keys cannot have spaces, new lines, carriage returns, or null characters. We suggest that if you have unicode characters, or long keys, you use an effective hashing mechanism before calling this client.

At Pinterest, we have found that murmur3 hash is a great candidate for this. Alternatively you can set allow_unicode_keys to support unicode keys, but beware of what unicode encoding you use to make sure multiple clients can find the same key.

Best Practices

  • Always set the connect_timeout and timeout arguments in the pymemcache.client.base.Client constructor to avoid blocking your process when memcached is slow. You might also want to enable the no_delay option, which sets the TCP_NODELAY flag on the connection’s socket.

  • Use the noreply flag for a significant performance boost. The noreply flag is enabled by default for “set”, “add”, “replace”, “append”, “prepend”, and “delete”. It is disabled by default for “cas”, “incr” and “decr”. It obviously doesn’t apply to any get calls.

  • Use pymemcache.client.base.Client.get_many() and pymemcache.client.base.Client.gets_many() whenever possible, as they result in fewer round trip times for fetching multiple keys.

  • Use the ignore_exc flag to treat memcache/network errors as cache misses on calls to the get* methods. This prevents failures in memcache, or network errors, from killing your web requests. Do not use this flag if you need to know about errors from memcache, and make sure you have some other way to detect memcache server failures.

  • Unless you have a known reason to do otherwise, use the provided serializer in pymemcache.serde.pickle_serde for any de/serialization of objects.

Warning

noreply will not read errors returned from the memcached server.

If a function with noreply=True causes an error on the server, it will still succeed and your next call which reads a response from memcached may fail unexpectedly.

pymemcached will try to catch and stop you from sending malformed inputs to memcached, but if you are having unexplained errors, setting noreply=False may help you troubleshoot the issue.

pymemcache

pymemcache package

Subpackages

pymemcache.client package
Submodules
pymemcache.client.base module
class pymemcache.client.base.Client(server, serde=None, serializer=None, deserializer=None, connect_timeout=None, timeout=None, no_delay=False, ignore_exc=False, socket_module=<module 'socket' from '/home/docs/.pyenv/versions/3.7.9/lib/python3.7/socket.py'>, socket_keepalive=None, key_prefix=b'', default_noreply=True, allow_unicode_keys=False, encoding='ascii', tls_context=None)

Bases: object

A client for a single memcached server.

Server Connection

The server parameter controls how the client connects to the memcached server. You can either use a (host, port) tuple for a TCP connection or a string containing the path to a UNIX domain socket.

The connect_timeout and timeout parameters can be used to set socket timeout values. By default, timeouts are disabled.

When the no_delay flag is set, the TCP_NODELAY socket option will also be set. This only applies to TCP-based connections.

Lastly, the socket_module allows you to specify an alternate socket implementation (such as gevent.socket).

Keys and Values

Keys must have a __str__() method which should return a str with no more than 250 ASCII characters and no whitespace or control characters. Unicode strings must be encoded (as UTF-8, for example) unless they consist only of ASCII characters that are neither whitespace nor control characters.

Values must have a __str__() method to convert themselves to a byte string. Unicode objects can be a problem since str() on a Unicode object will attempt to encode it as ASCII (which will fail if the value contains code points larger than U+127). You can fix this with a serializer or by just calling encode on the string (using UTF-8, for instance).

If you intend to use anything but str as a value, it is a good idea to use a serializer. The pymemcache.serde library has an already implemented serializer which pickles and unpickles data.

Serialization and Deserialization

The constructor takes an optional object, the “serializer/deserializer” (“serde”), which is responsible for both serialization and deserialization of objects. That object must satisfy the serializer interface by providing two methods: serialize and deserialize. serialize takes two arguments, a key and a value, and returns a tuple of two elements, the serialized value, and an integer in the range 0-65535 (the “flags”). deserialize takes three parameters, a key, value, and flags, and returns the deserialized value.

Here is an example using JSON for non-str values:

class JSONSerde(object):
    def serialize(self, key, value):
        if isinstance(value, str):
            return value, 1
        return json.dumps(value), 2

    def deserialize(self, key, value, flags):
        if flags == 1:
            return value

        if flags == 2:
            return json.loads(value)

        raise Exception("Unknown flags for value: {1}".format(flags))

Note

Most write operations allow the caller to provide a flags value to support advanced interaction with the server. This will override the “flags” value returned by the serializer and should therefore only be used when you have a complete understanding of how the value should be serialized, stored, and deserialized.

Error Handling

All of the methods in this class that talk to memcached can throw one of the following exceptions:

Instances of this class maintain a persistent connection to memcached which is terminated when any of these exceptions are raised. The next call to a method on the object will result in a new connection being made to memcached.

add(key, value, expire=0, noreply=None, flags=None)

The memcached “add” command.

Parameters

  • key – str, see class docs for details.

  • value – str, see class docs for details.

  • expire – optional int, number of seconds until the item is expired from the cache, or zero for no expiry (the default).

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

  • flags – optional int, arbitrary bit field used for server-specific flags

Returns

If noreply is True (or if it is unset and self.default_noreply is True), the return value is always True. Otherwise the return value is True if the value was stored, and False if it was not (because the key already existed).

append(key, value, expire=0, noreply=None, flags=None)

The memcached “append” command.

Parameters

  • key – str, see class docs for details.

  • value – str, see class docs for details.

  • expire – optional int, number of seconds until the item is expired from the cache, or zero for no expiry (the default).

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

  • flags – optional int, arbitrary bit field used for server-specific flags

Returns

True.

cache_memlimit(memlimit)

The memcached “cache_memlimit” command.

Parameters

memlimit – int, the number of megabytes to set as the new cache memory limit.

Returns

If no exception is raised, always returns True.

cas(key, value, cas, expire=0, noreply=False, flags=None)

The memcached “cas” command.

Parameters

  • key – str, see class docs for details.

  • value – str, see class docs for details.

  • cas – int or str that only contains the characters ‘0’-‘9’.

  • expire – optional int, number of seconds until the item is expired from the cache, or zero for no expiry (the default).

  • noreply – optional bool, False to wait for the reply (the default).

  • flags – optional int, arbitrary bit field used for server-specific flags

Returns

If noreply is True (or if it is unset and self.default_noreply is True), the return value is always True. Otherwise returns None if the key didn’t exist, False if it existed but had a different cas value and True if it existed and was changed.

check_key(key)

Checks key and add key_prefix.

close()

Close the connection to memcached, if it is open. The next call to a method that requires a connection will re-open it.

decr(key, value, noreply=False)

The memcached “decr” command.

Parameters

  • key – str, see class docs for details.

  • value – int, the amount by which to decrement the value.

  • noreply – optional bool, False to wait for the reply (the default).

Returns

If noreply is True, always returns None. Otherwise returns the new value of the key, or None if the key wasn’t found.

delete(key, noreply=None)

The memcached “delete” command.

Parameters

  • key – str, see class docs for details.

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

Returns

If noreply is True (or if it is unset and self.default_noreply is True), the return value is always True. Otherwise returns True if the key was deleted, and False if it wasn’t found.

delete_many(keys, noreply=None)

A convenience function to delete multiple keys.

Parameters

  • keys – list(str), the list of keys to delete.

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

Returns

True. If an exception is raised then all, some or none of the keys may have been deleted. Otherwise all the keys have been sent to memcache for deletion and if noreply is False, they have been acknowledged by memcache.

delete_multi(keys, noreply=None)

A convenience function to delete multiple keys.

Parameters

  • keys – list(str), the list of keys to delete.

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

Returns

True. If an exception is raised then all, some or none of the keys may have been deleted. Otherwise all the keys have been sent to memcache for deletion and if noreply is False, they have been acknowledged by memcache.

disconnect_all()

Close the connection to memcached, if it is open. The next call to a method that requires a connection will re-open it.

flush_all(delay=0, noreply=None)

The memcached “flush_all” command.

Parameters

  • delay – optional int, the number of seconds to wait before flushing, or zero to flush immediately (the default).

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

Returns

True.

get(key, default=None)

The memcached “get” command, but only for one key, as a convenience.

Parameters

  • key – str, see class docs for details.

  • default – value that will be returned if the key was not found.

Returns

The value for the key, or default if the key wasn’t found.

get_many(keys)

The memcached “get” command.

Parameters

keys – list(str), see class docs for details.

Returns

A dict in which the keys are elements of the “keys” argument list and the values are values from the cache. The dict may contain all, some or none of the given keys.

get_multi(keys)

The memcached “get” command.

Parameters

keys – list(str), see class docs for details.

Returns

A dict in which the keys are elements of the “keys” argument list and the values are values from the cache. The dict may contain all, some or none of the given keys.

gets(key, default=None, cas_default=None)

The memcached “gets” command for one key, as a convenience.

Parameters

  • key – str, see class docs for details.

  • default – value that will be returned if the key was not found.

  • cas_default – same behaviour as default argument.

Returns

A tuple of (value, cas) or (default, cas_defaults) if the key was not found.

gets_many(keys)

The memcached “gets” command.

Parameters

keys – list(str), see class docs for details.

Returns

A dict in which the keys are elements of the “keys” argument list and the values are tuples of (value, cas) from the cache. The dict may contain all, some or none of the given keys.

incr(key, value, noreply=False)

The memcached “incr” command.

Parameters

  • key – str, see class docs for details.

  • value – int, the amount by which to increment the value.

  • noreply – optional bool, False to wait for the reply (the default).

Returns

If noreply is True, always returns None. Otherwise returns the new value of the key, or None if the key wasn’t found.

prepend(key, value, expire=0, noreply=None, flags=None)

The memcached “prepend” command.

Parameters

  • key – str, see class docs for details.

  • value – str, see class docs for details.

  • expire – optional int, number of seconds until the item is expired from the cache, or zero for no expiry (the default).

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

  • flags – optional int, arbitrary bit field used for server-specific flags

Returns

True.

quit()

The memcached “quit” command.

This will close the connection with memcached. Calling any other method on this object will re-open the connection, so this object can be re-used after quit.

replace(key, value, expire=0, noreply=None, flags=None)

The memcached “replace” command.

Parameters

  • key – str, see class docs for details.

  • value – str, see class docs for details.

  • expire – optional int, number of seconds until the item is expired from the cache, or zero for no expiry (the default).

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

  • flags – optional int, arbitrary bit field used for server-specific flags

Returns

If noreply is True (or if it is unset and self.default_noreply is True), the return value is always True. Otherwise returns True if the value was stored and False if it wasn’t (because the key didn’t already exist).

set(key, value, expire=0, noreply=None, flags=None)

The memcached “set” command.

Parameters

  • key – str, see class docs for details.

  • value – str, see class docs for details.

  • expire – optional int, number of seconds until the item is expired from the cache, or zero for no expiry (the default).

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

  • flags – optional int, arbitrary bit field used for server-specific flags

Returns

If no exception is raised, always returns True. If an exception is raised, the set may or may not have occurred. If noreply is True, then a successful return does not guarantee a successful set.

set_many(values, expire=0, noreply=None, flags=None)

A convenience function for setting multiple values.

Parameters

  • values – dict(str, str), a dict of keys and values, see class docs for details.

  • expire – optional int, number of seconds until the item is expired from the cache, or zero for no expiry (the default).

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

  • flags – optional int, arbitrary bit field used for server-specific flags

Returns

Returns a list of keys that failed to be inserted. If noreply is True, always returns empty list.

set_multi(values, expire=0, noreply=None, flags=None)

A convenience function for setting multiple values.

Parameters

  • values – dict(str, str), a dict of keys and values, see class docs for details.

  • expire – optional int, number of seconds until the item is expired from the cache, or zero for no expiry (the default).

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

  • flags – optional int, arbitrary bit field used for server-specific flags

Returns

Returns a list of keys that failed to be inserted. If noreply is True, always returns empty list.

shutdown(graceful=False)

The memcached “shutdown” command.

This will request shutdown and eventual termination of the server, optionally preceded by a graceful stop of memcached’s internal state machine. Note that the server needs to have been started with the shutdown protocol command enabled with the –enable-shutdown flag.

Parameters

graceful – optional bool, True to request a graceful shutdown with SIGUSR1 (defaults to False, i.e. SIGINT shutdown).

stats(*args)

The memcached “stats” command.

The returned keys depend on what the “stats” command returns. A best effort is made to convert values to appropriate Python types, defaulting to strings when a conversion cannot be made.

Parameters

*arg – extra string arguments to the “stats” command. See the memcached protocol documentation for more information.

Returns

A dict of the returned stats.

touch(key, expire=0, noreply=None)

The memcached “touch” command.

Parameters

  • key – str, see class docs for details.

  • expire – optional int, number of seconds until the item is expired from the cache, or zero for no expiry (the default).

  • noreply – optional bool, True to not wait for the reply (defaults to self.default_noreply).

Returns

True if the expiration time was updated, False if the key wasn’t found.

version()

The memcached “version” command.

Returns

A string of the memcached version.

class pymemcache.client.base.KeepaliveOpts(idle=1, intvl=1, cnt=5)

Bases: object

A configuration structure to define the socket keepalive.

This structure must be passed to a client. The client will configure its socket keepalive by using the elements of the structure.

Parameters

  • idle – The time (in seconds) the connection needs to remain idle before TCP starts sending keepalive probes. Should be a positive integer most greater than zero.

  • intvl – The time (in seconds) between individual keepalive probes. Should be a positive integer most greater than zero.

  • cnt – The maximum number of keepalive probes TCP should send before dropping the connection. Should be a positive integer most greater than zero.

cnt
idle
intvl
class pymemcache.client.base.PooledClient(server, serde=None, serializer=None, deserializer=None, connect_timeout=None, timeout=None, no_delay=False, ignore_exc=False, socket_module=<module 'socket' from '/home/docs/.pyenv/versions/3.7.9/lib/python3.7/socket.py'>, socket_keepalive=None, key_prefix=b'', max_pool_size=None, pool_idle_timeout=0, lock_generator=None, default_noreply=True, allow_unicode_keys=False, encoding='ascii', tls_context=None)

Bases: object

A thread-safe pool of clients (with the same client api).

Parameters

  • max_pool_size – maximum pool size to use (going above this amount triggers a runtime error), by default this is 2147483648L when not provided (or none).

  • pool_idle_timeout – pooled connections are discarded if they have been unused for this many seconds. A value of 0 indicates that pooled connections are never discarded.

  • lock_generator – a callback/type that takes no arguments that will be called to create a lock or semaphore that can protect the pool from concurrent access (for example a eventlet lock or semaphore could be used instead)

Further arguments are interpreted as for Client constructor.

Note: if serde is given, the same object will be used for all clients in the pool. Your serde object must therefore be thread-safe.

add(key, value, expire=0, noreply=None, flags=None)
append(key, value, expire=0, noreply=None, flags=None)
cas(key, value, cas, expire=0, noreply=False, flags=None)
check_key(key)

Checks key and add key_prefix.

client_class

Client class used to create new clients

alias of Client

close()
decr(key, value, noreply=False)
delete(key, noreply=None)
delete_many(keys, noreply=None)
delete_multi(keys, noreply=None)
disconnect_all()
flush_all(delay=0, noreply=None)
get(key, default=None)
get_many(keys)
get_multi(keys)
gets(key)
gets_many(keys)
incr(key, value, noreply=False)
prepend(key, value, expire=0, noreply=None, flags=None)
quit()
replace(key, value, expire=0, noreply=None, flags=None)
set(key, value, expire=0, noreply=None, flags=None)
set_many(values, expire=0, noreply=None, flags=None)
set_multi(values, expire=0, noreply=None, flags=None)
shutdown(graceful=False)
stats(*args)
touch(key, expire=0, noreply=None)
version()
pymemcache.client.base.check_key_helper(key, allow_unicode_keys, key_prefix=b'')

Checks key and add key_prefix.

pymemcache.client.base.normalize_server_spec(server)
pymemcache.client.hash module
class pymemcache.client.hash.HashClient(servers, hasher=<class 'pymemcache.client.rendezvous.RendezvousHash'>, serde=None, serializer=None, deserializer=None, connect_timeout=None, timeout=None, no_delay=False, socket_module=<module 'socket' from '/home/docs/.pyenv/versions/3.7.9/lib/python3.7/socket.py'>, socket_keepalive=None, key_prefix=b'', max_pool_size=None, pool_idle_timeout=0, lock_generator=None, retry_attempts=2, retry_timeout=1, dead_timeout=60, use_pooling=False, ignore_exc=False, allow_unicode_keys=False, default_noreply=True, encoding='ascii', tls_context=None)

Bases: object

A client for communicating with a cluster of memcached servers

add(key, *args, **kwargs)
add_server(server, port=None)
append(key, *args, **kwargs)
cas(key, *args, **kwargs)
client_class

alias of pymemcache.client.base.Client

close()
decr(key, *args, **kwargs)
delete(key, *args, **kwargs)
delete_many(keys, *args, **kwargs)
delete_multi(keys, *args, **kwargs)
disconnect_all()
flush_all(*args, **kwargs)
get(key, default=None, **kwargs)
get_many(keys, gets=False, *args, **kwargs)
get_multi(keys, gets=False, *args, **kwargs)
gets(key, *args, **kwargs)
gets_many(keys, *args, **kwargs)
gets_multi(keys, *args, **kwargs)
incr(key, *args, **kwargs)
prepend(key, *args, **kwargs)
quit()
remove_server(server, port=None)
replace(key, *args, **kwargs)
set(key, *args, **kwargs)
set_many(values, *args, **kwargs)
set_multi(values, *args, **kwargs)
touch(key, *args, **kwargs)
pymemcache.client.murmur3 module
pymemcache.client.murmur3.murmur3_32(data, seed=0)

MurmurHash3 was written by Austin Appleby, and is placed in the public domain. The author hereby disclaims copyright to this source code.

pymemcache.client.rendezvous module
class pymemcache.client.rendezvous.RendezvousHash(nodes=None, seed=0, hash_function=<function murmur3_32>)

Bases: object

Implements the Highest Random Weight (HRW) hashing algorithm most commonly referred to as rendezvous hashing.

Originally developed as part of python-clandestined.

Copyright (c) 2014 Ernest W. Durbin III

add_node(node)
get_node(key)
remove_node(node)
pymemcache.client.retrying module

Module containing the RetryingClient wrapper class.

class pymemcache.client.retrying.RetryingClient(client, attempts=2, retry_delay=0, retry_for=None, do_not_retry_for=None)

Bases: object

Client that allows retrying calls for the other clients.

Module contents
pymemcache.test package
Submodules
pymemcache.test.conftest module
pymemcache.test.test_benchmark module
pymemcache.test.test_client module
pymemcache.test.test_client_hash module
pymemcache.test.test_client_retry module
pymemcache.test.test_integration module
pymemcache.test.test_rendezvous module
pymemcache.test.test_serde module
pymemcache.test.test_utils module
pymemcache.test.utils module

Useful testing utilities.

This module is considered public API.

class pymemcache.test.utils.MockMemcacheClient(server=None, serde=None, serializer=None, deserializer=None, connect_timeout=None, timeout=None, no_delay=False, ignore_exc=False, socket_module=None, default_noreply=True, allow_unicode_keys=False, encoding='ascii', tls_context=None)

Bases: object

A (partial) in-memory mock for Clients.

add(key, value, expire=0, noreply=True, flags=None)
append(key, value, expire=0, noreply=True, flags=None)
cache_memlimit(memlimit)
cas(key, value, cas, expire=0, noreply=False, flags=None)
check_key(key)

Checks key and add key_prefix.

clear()

Method used to clear/reset mock cache

close()
decr(key, value, noreply=False)
delete(key, noreply=True)
delete_many(keys, noreply=True)
delete_multi(keys, noreply=True)
flush_all(delay=0, noreply=True)
get(key, default=None)
get_many(keys)
get_multi(keys)
incr(key, value, noreply=False)
prepend(key, value, expire=0, noreply=True, flags=None)
quit()
replace(key, value, expire=0, noreply=True, flags=None)
set(key, value, expire=0, noreply=True, flags=None)
set_many(values, expire=0, noreply=True, flags=None)
set_multi(values, expire=0, noreply=True, flags=None)
stats(*_args)
touch(key, expire=0, noreply=True)
version()
Module contents

Submodules

pymemcache.exceptions module
exception pymemcache.exceptions.MemcacheClientError

Bases: pymemcache.exceptions.MemcacheError

Raised when memcached fails to parse the arguments to a request, likely due to a malformed key and/or value, a bug in this library, or a version mismatch with memcached.

exception pymemcache.exceptions.MemcacheError

Bases: Exception

Base exception class

exception pymemcache.exceptions.MemcacheIllegalInputError

Bases: pymemcache.exceptions.MemcacheClientError

Raised when a key or value is not legal for Memcache (see the class docs for Client for more details).

exception pymemcache.exceptions.MemcacheServerError

Bases: pymemcache.exceptions.MemcacheError

Raised when memcached reports a failure while processing a request, likely due to a bug or transient issue in memcached.

exception pymemcache.exceptions.MemcacheUnexpectedCloseError

Bases: pymemcache.exceptions.MemcacheServerError

Raised when the connection with memcached closes unexpectedly.

exception pymemcache.exceptions.MemcacheUnknownCommandError

Bases: pymemcache.exceptions.MemcacheClientError

Raised when memcached fails to parse a request, likely due to a bug in this library or a version mismatch with memcached.

exception pymemcache.exceptions.MemcacheUnknownError

Bases: pymemcache.exceptions.MemcacheError

Raised when this library receives a response from memcached that it cannot parse, likely due to a bug in this library or a version mismatch with memcached.

pymemcache.fallback module

A client for falling back to older memcached servers when performing reads.

It is sometimes necessary to deploy memcached on new servers, or with a different configuration. In these cases, it is undesirable to start up an empty memcached server and point traffic to it, since the cache will be cold, and the backing store will have a large increase in traffic.

This class attempts to solve that problem by providing an interface identical to the Client interface, but which can fall back to older memcached servers when reads to the primary server fail. The approach for upgrading memcached servers or configuration then becomes:

  1. Deploy a new host (or fleet) with memcached, possibly with a new configuration.

  2. From your application servers, use FallbackClient to write and read from the new cluster, and to read from the old cluster when there is a miss in the new cluster.

  3. Wait until the new cache is warm enough to support the load.

  4. Switch from FallbackClient to a regular Client library for doing all reads and writes to the new cluster.

  5. Take down the old cluster.

Best Practices:

  • Make sure that the old client has “ignore_exc” set to True, so that it treats failures like cache misses. That will allow you to take down the old cluster before you switch away from FallbackClient.

class pymemcache.fallback.FallbackClient(caches)

Bases: object

add(key, value, expire=0, noreply=True)
append(key, value, expire=0, noreply=True)
cas(key, value, cas, expire=0, noreply=True)
close()

Close each of the memcached clients

decr(key, value, noreply=True)
delete(key, noreply=True)
flush_all(delay=0, noreply=True)
get(key)
get_many(keys)
gets(key)
gets_many(keys)
incr(key, value, noreply=True)
prepend(key, value, expire=0, noreply=True)
quit()
replace(key, value, expire=0, noreply=True)
set(key, value, expire=0, noreply=True)
stats()
touch(key, expire=0, noreply=True)
pymemcache.pool module
class pymemcache.pool.ObjectPool(obj_creator, after_remove=None, max_size=None, idle_timeout=0, lock_generator=None)

Bases: object

A pool of objects that release/creates/destroys as needed.

clear()
destroy(obj, silent=True)
property free
get()
get_and_release(destroy_on_fail=False)
release(obj, silent=True)
property used
pymemcache.serde module
class pymemcache.serde.LegacyWrappingSerde(serializer_func, deserializer_func)

Bases: object

This class defines how to wrap legacy de/serialization functions into a ‘serde’ object which implements ‘.serialize’ and ‘.deserialize’ methods. It is used automatically by pymemcache.client.base.Client when the ‘serializer’ or ‘deserializer’ arguments are given.

The serializer_func and deserializer_func are expected to be None in the case that they are missing.

class pymemcache.serde.PickleSerde(pickle_version=4)

Bases: object

An object which implements the serialization/deserialization protocol for pymemcache.client.base.Client and its descendants using the pickle module.

Serialization and deserialization are implemented as methods of this class. To implement a custom serialization/deserialization method for pymemcache, you should implement the same interface as the one provided by this object – pymemcache.serde.PickleSerde.serialize() and pymemcache.serde.PickleSerde.deserialize(). Then, pass your custom object to the pymemcache client object in place of PickleSerde.

For more details on the serialization protocol, see the class documentation for pymemcache.client.base.Client

deserialize(key, value, flags)
serialize(key, value)
pymemcache.serde.get_python_memcache_serializer(pickle_version=4)

Return a serializer using a specific pickle version

pymemcache.serde.python_memcache_deserializer(key, value, flags)
pymemcache.serde.python_memcache_serializer(key, value, *, pickle_version=4)

Module contents

Indices and tables