Refresh¶

cache := otter.Must(&otter.Options[string, string]{
    ExpiryCalculator: otter.ExpiryWriting[string, string](time.Hour),
    RefreshCalculator: otter.RefreshWriting[string, string](30*time.Minute),
})

Refreshing is not quite the same as eviction. As specified in Cache.Refresh, refreshing a key loads a new value for the key asynchronously. The old value (if any) is still returned while the key is being refreshed, in contrast to eviction, which forces retrievals to wait until the value is loaded anew.

In contrast to ExpiryCalculator, RefreshCalculator will make a key eligible for refresh after the returned duration, but a refresh will only be actually initiated when the entry is queried. So, for example, you can specify both ExpiryCalculator, RefreshCalculator on the same cache so that the expiration timer on an entry isn't blindly reset whenever an entry becomes eligible for a refresh. If an entry isn't queried after it comes eligible for refreshing, it is allowed to expire.

A Loader may specify smart behavior to use on a refresh by overriding Loader.Reload which allows you to use the old value in computing the new value. The Loader implementation should always return ErrNotFound if the entry was not found in the data source.

Cache.Refresh can be used to explicitly refresh an entry and will deduplicate requests while they are in-flight.

Refresh operations are executed asynchronously using goroutine by default.

If an error is returned after refresh then the old value is kept and the error is logged (using Logger) and swallowed.