EEA Cache

Introduction

This package combines the features from lovely.memcached and plone.memoize.ram. It provides a decorator and utility for Memcaches at EEA. The decorator allows you set dependencies known by eea.cache

Contents

Main features

1. Extends and overrides plone.memoize cache adapters to work with memcache
2. Provides an extended @cache decorator that supports:
   • cache lifetime override per method
   • dependencies string in order to bulk invalidate cache
   • auto-invalidation of cache when ObjectModifiedEvent is triggered
3. Possibility to manually invalidate cache via URL.

Install

• Add eea.cache to your eggs and zcml section in your buildout and re-run buildout:

  eggs =
    ...
    eea.cache
  
  zcml =
    ...
    eea.cache
    eea.cache-overrides

• You can download a sample buildout from https://github.com/eea/eea.cache/tree/master/buildouts/plone4
• Install eea.cache within Site Setup > Add-ons

• Start memcache:

  $ bin/memcached start

Dependencies

• python-memcached
• pylibmc (optional, for better performance)
• plone.memoize
• plone.uuid

Source code

Latest source code (Zope 2 compatible):

• Plone Collective on Github
• EEA on Github

Cache decorator

>>> def key(method, self):
...     return method.__name__

>>> from eea.cache import cache
>>> @cache(key, dependencies=["frontpage"])
... def myMethod(num):
...     return num*num

Lets clear any running memcache:

>>> from eea.cache.event import InvalidateMemCacheEvent
>>> from zope.event import notify
>>> notify(InvalidateMemCacheEvent(raw=True, dependencies=['frontpage']))

Our myMethod will now be cached with the key returned from the method 'key' and with dependency 'frontpage':

>>> myMethod(2)
4
>>> myMethod(3)
4

>>> notify(InvalidateMemCacheEvent(raw=True, dependencies=['frontpage']))
>>> myMethod(3)
9

Cache lifetime

By default your content is cached in memcache for one hour (3600 seconds). You can change this by adding an int property within: ZMI > portal_properties > site_properties called memcached_defaultLifetime and set it's value to 86400 (one day) for example.

Cache lifetime override per key

Starting with eea.cache 5.1 you can also pass a lifetime key with the duration in seconds which will override the defaultLifetime either given from the portal property or the default one from lovely.memcached of 3600 seconds:

ex: in order to cache the result only for 4 minutes
>>> @cache(key, dependencies=["frontpage"], lifetime=240)
... def myMethod(num):
...     return num*num

Invalidate cache

If you use cache decorator for BrowserView methods or directly on Zope objects methods cache will be automatically invalidated when object is modified (ObjectModifiedEvent is triggered):

>>> from Products.Five.browser import BrowserView

>>> class XXX(BrowserView):
...     @cache(key)
...     def title(self):
...         return self.context.title_or_id()

You can disable auto invalidation by providing the auto_invalidate param to @cache decorator:

>>> @cache(key, auto_invalidate=False)
... def title(self):
...     return self.context.title_or_id()

memcache.invalidate

In order to manually invalidate memcached cache per object this package provides a browser view called memcache.invalidate. It will invalidate all memcached methods associated with current object's UID:

http://localhost:2020/Plone/front-page/memcache.invalidate

You can also manually invalidate related items and back references:

http://localhost:2020/Plone/front-page/memcache.invalidate/relatedItems

http://localhost:2020/Plone/front-page/memcache.invalidate/backRefs

By default this method can be called by users with these roles:

• Editor
• CommonEditor
• Owner
• Manager

varnish.invalidate

In order to manually invalidate memcached cache per object this package provides a browser view called varnish.invalidate. It will invalidate all memcached methods associated with current object's UID:

http://localhost:2020/Plone/front-page/varnish.invalidate

You can also manually invalidate related items and back references:

http://localhost:2020/Plone/front-page/varnish.invalidate/relatedItems

http://localhost:2020/Plone/front-page/varnish.invalidate/backRefs

By default this method can be called by users with these roles:

• Editor
• CommonEditor
• Owner
• Manager

cache.invalidate

In order to manually invalidate cache (memcached and varnish) per object this package provides a browser view called cache.invalidate. It will call memcache.invalidate and varnish.invalidate:

http://localhost:2020/Plone/front-page/cache.invalidate

You can also manually invalidate related items and back references:

http://localhost:2020/Plone/front-page/cache.invalidate/relatedItems

http://localhost:2020/Plone/front-page/cache.invalidate/backRefs

By default this method can be called by users with these roles:

• Editor
• CommonEditor
• Owner
• Manager

cache.settings

There is also a Cache Tab per object where you can manually select which cache to invalidate. By default, you can invalidate memcache and varnish. You also have the possibility to invalidate memcache and/or varnish for related items and also fo back references.

This form can be extended with more options. For a more detailed example see eea.pdf

configure.zcml:

<adapter
  zcml:condition="installed eea.cache"
  factory=".behavior.ExtraBehavior"
  />

<adapter
  zcml:condition="installed eea.cache"
  factory=".behavior.ExtraSettings"
  name="eea.pdf.cache.extender"
  />

behavior.py:

# Model
class IExtraSettings(model.Schema):
    """ Extra settings
    """
    pdf = schema.Bool(
        title=_(u"PDF"),
        description=_(u"Invalidate latest generated PDF file"),
        required=False,
        default=False
    )


# Behaviour
class ExtraBehavior(object):
    implements(IExtraSettings)
    adapts(IPDFAware)

    def __init__(self, context):
        self.context = context

    @property
    def pdf(self):
        """ PDF
        """
        return False

    @pdf.setter
    def pdf(self, value):
        """ Invalidate last generated PDF?
        """
        if not value:
            return

        removePdfFiles()

# Form
class ExtraSettings(extensible.FormExtender):
    adapts(IPDFAware, ILayer, SettingsForm)

    def __init__(self, context, request, form):
        self.context = context
        self.request = request
        self.form = form

    def update(self):
        """ Extend form
        """
        self.add(IExtraSettings, prefix="extra")
        self.move('pdf', after='varnish', prefix='extra')

Copyright and license

The Initial Owner of the Original Code is European Environment Agency (EEA). All Rights Reserved.

The eea.cache (the Original Code) is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

More details under docs/License.txt

Funding and project management

EEA - European Environment Agency (EU)