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

Note

This add-on doesn't do anything by itself. It needs to be integrated by a developer within your own products. For reference you can check the eea.app.visualization package.

Contents

Contents

• Introduction
• Contents
• Main features
• Install
• Dependencies
• Source code
• Cache decorator
• Cache lifetime
  • Cache lifetime override per key
• Invalidate cache
  • memcache.invalidate
  • varnish.invalidate
  • cache.invalidate
  • cache.settings
• Copyright and license
• Funding and project management

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)