Feature Request: Quarkus Caching Hooks

[The-Funk]

Description

I'd like to watch for the expiration of data within a Quarkus Cache. When an entry expires and is ejected from cache, I'd like the key and value being ejected to be passed to a custom hook so that I may perform some action.

Use case: I have an upstream database that provides data to my service. Its caching options are much more simplistic than my Quarkus application's caching options. Via my Quarkus service I can tell that upstream service to cache data for me and I can set an expiration time and that's it. Basically an expire after write. I can also tell this external database to drop cached results. Unfortunately there's no way for me to trigger this external service to drop results without a scheduled method. It would be cool if I could cache a reference to the stored results and when my reference cache expires after access, I could trigger the remote service to drop its cache as well.

Implementation ideas

I'm not great at writing hooks and callbacks but here's a quick idea of how this could look based on what I know about Quarkus.

@CacheExpirationHook(cacheName="my-cache")
void onMyCacheValueEjection(String key, SomeType value) {
    // key and value are passed from the cache's triggered expiration event
    // tell remote service to drop cache
    // do some other things here
}

@CacheHook(cacheName="my-cache")
void onMyCacheValueEjection(@Observes cacheEjectionEvent ejected) {
    ejected.getKey();    // The key ejected from cache
    ejected.getValue(); // The value ejected from cache
    // tell remote service to drop cache
    // do some other things here
}

[quarkus-bot]

/cc @gwenneg (cache)

[geoand]

This sounds interesting, but I am pretty sure it would only be possible in the Caffeine backed cache implementation

[The-Funk]

@geoand I was kind of afraid of that. Looking at Caffeine I knew it was possible there but I know you have several providers you support.