Eviction listener

Similar to #38, it would be really useful to have an eviction listener.

In my use-case i’m using an in-memory Cache<MyKey, File> to manage an on-disk cache of files, so whenever an entry is expired / removed / evicted from the cache I need to delete the corresponding file.

I’m currently using caffeine but would like to try cache2k to see if it supports our access patterns better.

[cruftex]

Thanks for the detailed thoughts on this. Looks reasonable.

so if it was possible to expose the intrinsic age of each item to the cache

cache2k honors the least recently used aspect. So when you insert the oldest ones first, that will do.

I plan to release 1.0 now with the current feature set. Then I like to start an 1.1 dev version. This allows testing new features, while being able to change and improve the API or even drop features again that didn’t prove. I cannot promise, but probably something testable will pop up the next months. Would be nice when you then take a look at it and test it.

[cr-orilibhaber]

Well, I took 1.3.1 for a test drive and I admit it looks mostly promising, the thing is, I noticed that the eviction Listener invocation was flaky, it either is able to work flawlessly, or not at all. I’ll expand on this: I use a messaging service to deliver events to a SpringBoot based service. I use Cache2K as a read-through cache (LRU) to load results from a DB, it is instantiated lazily, manually (not through Spring’s DI) as this is a multi-tenant service and the key set variations are unknown. I test the LRU capability of the cache by using a maxSize limit of 1 to trigger eviction constantly (I use a key set > 3) When the message queue is empty, and the whole service is given enough time to start (along with Cache2K instance) the eviction Listener is able to intercept evicted events once traffic start coming in. But when I start the service and the queue has already pending messages that start coming in as soon as the consumer thread is ready, it seems like Cache2K instance didn’t had “enough time” to start-up correctly and as a result the eviction Listener doesn’t get invoked at all.