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Last updated: 4 Aug 2020

finder-frontend: Registries

The registries module (app/lib/registries) provides datasets from other applications.

These registries are intended to be used when rendering facets. For example, the OrganisationsRegistry provides the data for the organisations facet.

Each registry fetches data from another application (such as search-api or whitehall), and caches it locally.

Motivation for registries

Frontend applications like finder-frontend, according to GOV.UK architecture guidelines, should not have a data store.

We have slightly broken this rule to decrease page load times. If we don't make additional requests for facets, and if our queries request less data, then we can return search results to users faster.


We cache the data for each registry in memcached, using the dalli gem.

There is a separate instance of memcached running on each machine, so the stores can be out of sync.

We refresh the cache using the registries:cache_refresh rake task.

The cached data is refreshed routinely using a cron job, defined in config/schedule.rb and administrated with the whenever gem.

The cache is refreshed during a deploy, too.

Both the deploy time and routine cache refreshes are called in the govuk-app-deployment deploy. The capistrano deploy process supplies data to the cache and sets up the cron job.


We have a healthcheck for the registry caches, so we know when there are empty registries. Poor health will be reported in Icinga. They are defined in app/lib/healthchecks.