Caching

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Caching
Introduction to the Cache Interface
Cement defines a Cache Interface, but does not implement caching by default.
Cement often includes multiple handler implementations of an interface that may or may not have additional features or functionality than the interface requires. The documentation below only references usage based on the interface and default handler (not the full capabilities of an implementation).
Cement Extensions That Provide Cache Handlers:
​Memcached​
​Redis​
API References:
​Cement Core Cache Module​
Configuration
Application Meta Options
The following options under App.Meta modify configuration handling:
Option
Description
cache_handler
The handler that implements the cache interface.
Working with Caches
The following example uses the Memcached Extension, which requires the pylibmc library to be installed, as well as a Memcached server running on localhost:11211.
Example: Working with Caches
from cement import App
from cement.utils.misc import init_defaults
​
CONFIG = init_defaults('myapp', 'memcached')
CONFIG['cache.memcached']['expire_time'] = 300 # seconds
CONFIG['cache.memcached']['hosts'] = ['127.0.0.1']
​
class MyApp(App):
    class Meta:
        label = 'myapp'
        config_defaults = CONFIG
        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()
Creating a Cache Handler
All interfaces in Cement can be overridden with your own implementation. This can be done either by sub-classing CacheHandler itself, or by sub-classing an existing extension's handlers in order to alter their functionality.
Example: Creating a Cache Handler
myapp.py
from cement import App
from cement.core.cache import CacheHandler
​
class MyCacheHandler(CacheHandler):
    class Meta:
        label = 'my_cache_handler'
​
    # do something to implement the interface
​
class MyApp(App):
    class Meta:
        label = 'myapp'
        cache_handler = 'my_cache_handler'
        handlers = [
            MyCacheHandler,
        ]
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Introduction to the Cache Interface
Configuration
Application Meta Options
Working with Caches
Creating a Cache Handler