/usr/lib/python3/dist-packages/cement/ext/ext_redis.py is in python3-cement 2.10.0-1.
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The Redis Extension provides application caching and key/value store
support via Redis.
Requirements
------------
* redis (``pip install redis``)
Configuration
-------------
This extension honors the following config settings
under a ``[cache.redis]`` section in any configuration file:
* **expire_time** - The default time in second to expire items in the
cache. Default: 0 (does not expire).
* **host** - Redis server.
* **port** - Redis port.
* **db** - Redis database number.
Configurations can be passed as defaults to a CementApp:
.. code-block:: python
from cement.core.foundation import CementApp
from cement.utils.misc import init_defaults
defaults = init_defaults('myapp', 'cache.redis')
defaults['cache.redis']['expire_time'] = 0
defaults['cache.redis']['host'] = '127.0.0.1'
defaults['cache.redis']['port'] = 6379
defaults['cache.redis']['db'] = 0
class MyApp(CementApp):
class Meta:
label = 'myapp'
config_defaults = defaults
extensions = ['redis']
cache_handler = 'redis'
Additionally, an application configuration file might have a section like
the following:
.. code-block:: text
[myapp]
# set the cache handler to use
cache_handler = redis
[cache.redis]
# time in seconds that an item in the cache will expire
expire_time = 300
# Redis server
host = 127.0.0.1
# Redis port
port = 6379
# Redis database number
db = 0
Usage
-----
.. code-block:: python
from cement.core import foundation
from cement.utils.misc import init_defaults
defaults = init_defaults('myapp', 'redis')
defaults['cache.redis']['expire_time'] = 300 # seconds
defaults['cache.redis']['host'] = '127.0.0.1'
defaults['cache.redis']['port'] = 6379
defaults['cache.redis']['db'] = 0
class MyApp(foundation.CementApp):
class Meta:
label = 'myapp'
config_defaults = defaults
extensions = ['redis']
cache_handler = 'redis'
with MyApp() as app:
# Run the app
app.run()
# Set a cached value
app.cache.set('my_key', 'my value')
# Get a cached value
app.cache.get('my_key')
# Delete a cached value
app.cache.delete('my_key')
# Delete the entire cache
app.cache.purge()
"""
import redis
from ..core import cache
from ..utils.misc import minimal_logger
LOG = minimal_logger(__name__)
class RedisCacheHandler(cache.CementCacheHandler):
"""
This class implements the :ref:`ICache <cement.core.cache>`
interface. It provides a caching interface using the
`redis <http://github.com/andymccurdy/redis-py>`_ library.
**Note** This extension has an external dependency on ``redis``. You
must include ``redis`` in your applications dependencies as Cement
explicitly does *not* include external dependencies for optional
extensions.
"""
class Meta:
"""Handler meta-data."""
interface = cache.ICache
label = 'redis'
config_defaults = dict(
hosts='127.0.0.1',
port=6379,
db=0,
expire_time=0,
)
def __init__(self, *args, **kw):
super(RedisCacheHandler, self).__init__(*args, **kw)
self.mc = None
def _setup(self, *args, **kw):
super(RedisCacheHandler, self)._setup(*args, **kw)
self.r = redis.StrictRedis(
host=self._config('host', default='127.0.0.1'),
port=self._config('port', default=6379),
db=self._config('db', default=0))
def _config(self, key, default=None):
"""
This is a simple wrapper, and is equivalent to:
``self.app.config.get('cache.redis', <key>)``.
:param key: The key to get a config value from the 'cache.redis'
config section.
:returns: The value of the given key.
"""
return self.app.config.get(self._meta.config_section, key)
def get(self, key, fallback=None, **kw):
"""
Get a value from the cache. Additional keyword arguments are ignored.
:param key: The key of the item in the cache to get.
:param fallback: The value to return if the item is not found in the
cache.
:returns: The value of the item in the cache, or the `fallback` value.
"""
LOG.debug("getting cache value using key '%s'" % key)
res = self.r.get(key)
if res is None:
return fallback
else:
return res.decode('utf-8')
def set(self, key, value, time=None, **kw):
"""
Set a value in the cache for the given ``key``. Additional
keyword arguments are ignored.
:param key: The key of the item in the cache to set.
:param value: The value of the item to set.
:param time: The expiration time (in seconds) to keep the item cached.
Defaults to `expire_time` as defined in the applications
configuration.
:returns: ``None``
"""
if time is None:
time = int(self._config('expire_time'))
if time == 0:
self.r.set(key, value)
else:
self.r.setex(key, time, value)
def delete(self, key, **kw):
"""
Delete an item from the cache for the given ``key``. Additional
keyword arguments are ignored.
:param key: The key to delete from the cache.
:returns: ``None``
"""
self.r.delete(key)
def purge(self, **kw):
"""
Purge the entire cache, all keys and values will be lost. Any
additional keyword arguments will be passed directly to the
redis ``flush_all()`` function.
:returns: ``None``
"""
keys = self.r.keys('*')
if keys:
self.r.delete(*keys)
def load(app):
app.handler.register(RedisCacheHandler)
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