Introduction

Caching of web pages is a complicated process: there are many possible policies to choose from, and the right policy can depend on factors such as who is making the request, the URL is being retrieved and resource negotiation settings such as accepted languages and encodings,

Hardcoding caching logic in an application is not desirable, especially for reusable code. It is also not possible to allow an administrator to manually configure the caching headers for every resource in an application. This packages tries to address this problem by providing a cache ruleset framework: it allows implementors to specify a ruleset for every component. Administrators can then define a policy which dictates the correct caching behaviour for each ruleset.

Depending on your environment there are different options for turning the ruleset into HTTP caching headers. If you are using Plone you can use five.caching to integrate with CacheSetup. In a WSGI environment you could set the ruleset in environ or a response header and add a piece of middleware which acts on those hints.

Usage

You can register rulesets using either zcml or direct python. If you use zcml you can use the cache:ruleset directive:

<configure
    xmlns="http://namespaces.zope.org/zope"
    xmlns:browser="http://namespaces.zope.org/browser"
    xmlns:cache="http://namespaces.zope.org/cache"/>

  <cache:ruleset
      for=".frontpage.FrontpageView"
      ruleset="plone-content-types"
      />

  <browser:page
      for="..interfaces.IFrontpage"
      class=".frontpage.FrontpageView"
      name="frontpage_view"
      template="templates/frontpage_view.pt"
      permission="zope2.View" />
</configure>

This example sets up a browser view called frontpage_view and associates it with the plone-content-types ruleset.

If you prefer to use python directly you can do so:

from z3c.caching.registry import register
from frontpage import FrontpageView

register(FrontpageView, "plone-content-types")

You can register a ruleset for objects, their interfaces or a base class.

To find the ruleset for an object use the lookup method:

from z3c.caching.registry import lookup

lookup(FrontpageView)

Changelog