Cache hit rate per URL

[SimenB]

Right now I can get the hitrate per client created, but I'd like to see how the cacherate is per URL as well, kinda like a label in prometheus (which is what we'd use it for). Would that be possible to add?

We query this thing: https://github.com/httpcache4j/httpcache4j/blob/4b26a55286b851ac124c20c8167a78aad860b30b/httpcache4j-core/src/main/java/org/codehaus/httpcache4j/cache/CacheStatistics.java

[hamnis]

Sure, but to avoid having a major memory impact is has to be limited somehow.
It should probably be based on a concurrent LRU map and not introduce external dependencies.

PR ?

[hamnis]

Another possibility is to add a callback handler that deals with different states of cache.
Then the memory impact is not handled in the library, but by clients.

Use of the callback must be optional, so there must be a Noop handler.