A periodic cache warmer. Queries all Sites from Postgres, every interval and pre-populates the cache. After each run the process is hibernated, triggering garbage collection.

Currently Cachex is used, but the underlying implementation can be transparently swapped.

Child specification options available:

• interval - the number of milliseconds for each warm-up cycle, defaults to :sites_by_domain_cache_refresh_interval application env value with random jitter added, for which the maximum is stored under :sites_by_domain_cache_refresh_interval_max_jitter key.
• cache_name - defaults to Cache.name() but can be overriden for testing
• force_start? - enforcess process startup for testing, even if it's barred by Cache.enabled?. This is useful for avoiding issues with DB ownership and async tests.
• warmer_fn - used for testing, a custom function to retrieve the items meant to be cached during the warm-up cycle.

See tests for more comprehensive examples.