iframe-proxy | Sunbelt Computer Software

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"""A memcached cache backend."""

import socket

from functools import wraps

from json import (

dumps,

loads,

)

from .entry import CacheEntry

STR_VALUE = 1

JSON_VALUE = 2

def json_serializer(key, value):

if type(value) == str:

return value, STR_VALUE

return dumps(value.to_dict()).encode('utf-8'), JSON_VALUE

def json_deserializer(key, value, flags):

if flags == STR_VALUE:

return value

if flags == JSON_VALUE:

return loads(value.decode('utf-8'))

raise Exception("Unknown serialization format")

def memcache_error_handling(f):

@wraps(f)

def wrapper(self, *args, **kwargs):

try:

ret = f(self, *args, **kwargs)

except Exception:

return None

return ret

return wrapper

class MemcachedStore(object):

"""Caching implementation that uses Memcached as data storage.

:param host: String representation of hostname or IP of the memcached server

:param port: Port number (int) on which the memcached server is listening

:param connect_timeout: optional float, seconds to wait for a connection to

the memcached server. Defaults to "forever" (uses the underlying

default socket timeout, which can be very long)

:param timeout: optional float, seconds to wait for send or recv calls on

the socket connected to memcached. Defaults to "forever" (uses the

underlying default socket timeout, which can be very long).

:param no_delay: optional bool, set the TCP_NODELAY flag, which may help

with performance in some cases. Defaults to False.

:param ignore_exc: optional bool, True to cause the "get", "gets",

"get_many" and "gets_many" calls to treat any errors as cache

misses. Defaults to True. Ie. if the cache is failing use the

Stormpath API.

:param socket_module: socket module to use, e.g. gevent.socket. Defaults to

the standard library's socket module.

:param key_prefix: Prefix of key. You can use this as namespace. Defaults

to b''.

"""

DEFAULT_TTL = 5 * 60 # seconds

def __init__(self, host='localhost', port=11211,

connect_timeout=None, timeout=None,

no_delay=False, ignore_exc=True,

key_prefix=b'', socket_module=socket, ttl=DEFAULT_TTL):

self.ttl = ttl

try:

from pymemcache.client import Client as Memcache

except ImportError:

raise RuntimeError('Memcached support is not available. Run "pip install pymemcache".')

self.memcache = Memcache(

(host, port),

serializer=json_serializer,

deserializer=json_deserializer,

connect_timeout=connect_timeout,

timeout=timeout,

socket_module=socket_module,

no_delay=no_delay,

ignore_exc=ignore_exc,

key_prefix=key_prefix)

@memcache_error_handling

def __getitem__(self, key):

entry = self.memcache.get(key)

if entry is None:

return None

return CacheEntry.parse(entry)

@memcache_error_handling

def __setitem__(self, key, entry):

self.memcache.set(key, entry, expire=self.ttl)

@memcache_error_handling

def __delitem__(self, key):

self.memcache.delete(key)

@memcache_error_handling

def clear(self):

self.memcache.flush_all()

@memcache_error_handling

def __len__(self):

return self.memcache.stats()['curr_items']

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