cement.ext.ext_memcached

The Memcached Extension provides application caching and key/value store support via Memcache.

Requirements

  • pylibmc (pip install pylibmc)
    • Note: There are known issues installing pylibmc on OSX/Homebrew via PIP. This post might be helpful.

Configuration

This extension honors the following config settings under a [cache.memcached] section in any configuration file:

  • expire_time - The default time in second to expire items in the cache. Default: 0 (does not expire).
  • hosts - List of Memcached servers.

Configurations can be passed as defaults to a CementApp:

from cement.core.foundation import CementApp
from cement.utils.misc import init_defaults

defaults = init_defaults('myapp', 'cache.memcached')
defaults['cache.memcached']['expire_time'] = 0
defaults['cache.memcached']['hosts'] = ['127.0.0.1']

class MyApp(CementApp):
    class Meta:
        label = 'myapp'
        config_defaults = defaults
        extensions = ['memcached']
        cache_handler = 'memcached'

Additionally, an application configuration file might have a section like the following:

[myapp]

# set the cache handler to use
cache_handler = memcached


[cache.memcached]

# time in seconds that an item in the cache will expire
expire_time = 3600

# comma seperated list of memcached servers
hosts = 127.0.0.1, cache.example.com

Usage

from cement.core import foundation
from cement.utils.misc import init_defaults

defaults = init_defaults('myapp', 'memcached')
defaults['cache.memcached']['expire_time'] = 300 # seconds
defaults['cache.memcached']['hosts'] = ['127.0.0.1']

class MyApp(foundation.CementApp):
    class Meta:
        label = 'myapp'
        config_defaults = defaults
        extensions = ['memcached']
        cache_handler = 'memcached'

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()
class cement.ext.ext_memcached.MemcachedCacheHandler(*args, **kw)

Bases: cement.core.cache.CementCacheHandler

This class implements the ICache interface. It provides a caching interface using the pylibmc library.

Note This extension has an external dependency on pylibmc. You must include pylibmc in your applications dependencies as Cement explicitly does not include external dependencies for optional extensions.

class Meta

Handler meta-data.

interface

alias of cement.core.cache.ICache

_config(key)

This is a simple wrapper, and is equivalent to: self.app.config.get('cache.memcached', <key>).

Parameters:key – The key to get a config value from the ‘cache.memcached’ config section.
Returns:The value of the given key.
_fix_hosts()

Useful to fix up the hosts configuration (i.e. convert a comma-separated string into a list). This function does not return anything, however it is expected to set the hosts value of the [cache.memcached] section (which is what this extension reads for it’s host configution).

Returns:None
_setup(*args, **kw)

The _setup function is called during application initialization and must setup the handler object making it ready for the framework or the application to make further calls to it.

Parameters:app_obj – The application object.
Returns:None
delete(key, **kw)

Delete an item from the cache for the given key. Any additional keyword arguments will be passed directly to the pylibmc delete function.

Parameters:key – The key to delete from the cache.
Returns:None
get(key, fallback=None, **kw)

Get a value from the cache. Any additional keyword arguments will be passed directly to pylibmc get function.

Parameters:
  • key – The key of the item in the cache to get.
  • 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.
purge(**kw)

Purge the entire cache, all keys and values will be lost. Any additional keyword arguments will be passed directly to the pylibmc flush_all() function.

Returns:None
set(key, value, time=None, **kw)

Set a value in the cache for the given key. Any additional keyword arguments will be passed directly to the pylibmc set function.

Parameters:
  • key – The key of the item in the cache to set.
  • value – The value of the item to set.
  • time – The expiration time (in seconds) to keep the item cached. Defaults to expire_time as defined in the applications configuration.
Returns:

None