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WebfactoryWfdMetaBundle

What is this cruft?

This bundle provides services and tools to work with content metadata as tracked by the wfDynamic Content Management System. This data is kept in a database table named wfd_meta. Among other things, it holds timestamps for creation, last update and possibly deletion of all managed records.

We have open-sourced it less for direct usage: You probably don't have the necessary information readily available in the format required by this bundle.

We rather found it might be useful for others thinking about a similar solution. Especially using a custom ConfigCacheFactory implementation, custom database-aware resources and the annotation to make Controller results cacheable might be interesting examples how you can hook into details of the Symfony Framework to implement more specialized features.

Services and APIs exposed by this bundle

The following sections try to describe those parts of the bundle meant to serve as the public API. Everything else should be considered the moving parts you are not supposed to interfere with.

webfactory_wfd_meta.provider service

An instance of \Webfactory\Bundle\WfdMetaBundle\Provider that can be used to query the timestamp of the last change (change or deletion) in one or several tables identified by their table names or wfDynamic table IDs. Can also be used to query this information for a single database row.

The special table name * denotes "any change/table".

The \Webfactory\Bundle\WfdMetaBundle\MetaQuery class

Use a MetaQuery to separate concerns when the code that knows what changes to track is distributed and/or different from the code acting upon that information. More precisely, one or several clients can call the MetaQuery to add the Doctrine entity instance, entity class, database table name or wfDynamic table IDs to track for changes. Then, the query can be passed along and eventually be executed. Again, the special tablename * denotes "any table".

Either create a MetaQuery instance for a particular purpose as a DIC service; you can inherit from the abstract webfactory_wfd_meta.meta_query service to do so. Alternatively, call the create() method on the webfactory_wfd_meta.meta_query_factory service.

HTTP cache validation based on wfd_meta data

The Send304IfNotModified annotation is deprecated as we wanted to allow the combination of multiple "ressource watchers" - e.g. one watching wfdMeta data, one watching non-wfd-meta-tracked data and one watching e.g. the date (for resetting at a certain date).

Additionally, we wanted to inverse the dependency direction: a caching bundle should be able to make use of the wfdMetaBundle (and many others), but the wfdMetaBundle should not take care about caching.

This resulted in the concept of "Last Modified Determinators" in the new WebfactoryHttpCacheBundle.

You can quickly convert deprecated Send304IfNotModified annotations to a LastModifiedDeterminator by using WfdMetaQueries . This conversion does not fully embrace the concept of LastModifiedDeterminators (especially not when using resetInterval; see the bundle's readme), but if you're in a hurry, maybe you don't want to be bothered with that.

Using a resetInterval

The annotation features an additional setting named resetInterval with defaults to 2419200 seconds (28 days).

The Last-Modified header added by the annotation will be shifted to the nearest (past) multiple of this value. This effectively makes the response never seem older than the given interval and has the net effect of expiring the cache (and re-running the controller once) after this interval has expired, even when no change has been recorded in wfd_meta.

This can come in handy when you know that your response depends on data that can be tracked via wfd_meta, but it also includes (computed) elements that change over time. For example, set resetInterval to 3600 to regenerate the response every hour, use a cached response as long as possible but also immediately re-generate the response when wfd_meta tracks a change.

webfactory_wfd_meta.controller.template:templateAction controller-as-a-service

Just like the FrameworkBundle:Template-Controller, this can be used to render arbitrary Twig templates that do not need any additional controller for processing. But, in addition to the basic caching properties, wfd_meta settings and change tracking can be added. Here's an example:

The \Webfactory\Bundle\WfdMetaBundle\Util\CriticalSection utility class

This class implements a critical section. Use it whenever two processes (on the same machine/host) do possibly interfering stuff or attempt to do the same thing. The critical section will give one process way and block the others until the first one has finished its task.

A custom ConfigCacheFactory implementation and specialized resource types

In the full-stack Symfony framework, several components use the ConfigCache mechanism to cache expensive-to-generate things. This includes translation catalogues as well as the URL router and matcher components.

This bundle adds two new types of resources, \Webfactory\Bundle\WfdMetaBundle\Config\DoctrineEntityClassResource and \Webfactory\Bundle\WfdMetaBundle\Config\WfdTableResource. Add instances of those resources to classes like the MessageCatalogue (translation component) or the RouteCollection (routing component) when you generate translations or routes based on database content.

This bundle will replace, or more precisely: decorate, the config_cache_factory service implementation. It will include a check for those new resource types and make sure that the cache will be refreshed whenever a relevant change is tracked in wfd_meta. This will also happen in kernel.debug = false, i. e. in production mode!

The CriticalSection will be used to make sure only one process at a time tries to re-create the cache, while others wait and re-use the result.

Configuration

This bundle has a single configuration setting:

With this setting, ConfigCache instances (Symfony Router, Translator, ... maybe?) that include WfdMetaResource instances will expire immediately.

This is helpful e. g. in functional tests, where you have database-backed routes, translations or similar: You can change the database values and no longer need to think about the ConfigCaches or poke wfd_meta to make the changes effective.

Tests

Run the tests with

vendor/bin/phpunit

Credits, Copyright and License

This project was started at webfactory GmbH, Bonn.

• https://www.webfactory.de
• https://twitter.com/webfactory

Copyright 2015-2023 webfactory GmbH, Bonn. Code released under the MIT license.