Cached Computed Field

A field that allows to cache computationally expensive computed data in field storage.

Use this field for computed data that is expensive to generate, for example data that is computed using NP-hard algorithms or data that comes from third party sources.

The data will then be updated on a regular basis during cron runs. This
allows to do the processor intensive or time consuming calculations offline
and update the database asynchronously.

A typical use case is to store the result of external REST API calls in field
storage and refreshing these at night when there are few visitors on the site.

Having the data stored in the database in normal field storage has the
advantage that it integrates seamlessly with the rest of Drupal, and the values
can even be exposed in the editor UI for temporary adjustments (e.g. for
adjusting warehouse stock levels on the fly, until the nightly cron run resets
the data).

Usage

This is an API module that is intended for developers. In order to update the
field data an event subscriber needs to be implemented that listens to the
RefreshExpiredFieldEventInterface::EVENT_NAME event. A base class is provided that makes it easy to implement your own event subscriber.

See the README file for an example.